Biologically active isoquinoline alkaloids covering 2014-2018.

The alkaloids in this classification have the simplest structures and are distributed mainly in the genera Papaver, Corydalis, Thalictrum and others. Eighteen isoquinoline alkaloids were identified and isolated from plants and animals between 2014 and 2018 ( Figure 2 ). In 2016, two new isoquinoline alkaloids 3,8-diolisoquinoline ( 1 ) and 1-methoxy-4,5-diolisoquinoline ( 2 ) were isolated from an ethanol extract of the Chinese redheaded centipede Scolopendra subspinipes mutilans 22 . In another study in the following year, the new isoquinoline alkaloid 1,5-dihydroxy-4-methoxyisoquinoline ( 3 ), also isolated from this centipede species, showed moderate cytotoxicity against five cancer cells 23 . Carnegine ( 4 ) and N -methylisosalsoline ( 5 ), isolated from the plant Hammada scoparia , exhibited antibacterial and antioxidant activities 24 . Also, in 2016, N -methylcorydaldine ( 6 ) was isolated from Fumaria officinalis 25 and 6,7-dimethoxy-1,2,3,4-tetrahydro-isoquinoline-3-carboxylic acid ( 7 ) from Mucuna pruriens seeds 26 . In 2018, the previously reported N -methylcorydaldine ( 6 ) together with two more isoquinoline alkaloids 7-methoxy-1,2,3,4-tetrahydroisoquinolin-1-one ( 8 ) and thalifoline ( 9 ) were isolated from Michelia champaca 27 . Other studies in same year described the isolation as well as hepatoprotective activities of the latter compound ( 9 ), N -methylisosalsoline ( 5 ), corydaldine ( 10 ), oxohydrastinine ( 11 ), 6,7-methylenedioxy-1(2 H )-isoquinolinone ( 12 ) and oxyhydrastinine ( 13 ) from Corydalis tomentella, C. hendersonii and Plumula nelumbinis 28 - 30 . 6,7-Dihydroxy-1-methyl-3,4-dihydroisoquinolone ( 14 ), ( S )-(−)-salsolinol ( 15 ), 6,7-dihydroxy-3,4-dihydroisoquinolone ( 16 ) and ( R )-(+)-1-isobutyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline ( 17 ), were isolated from the medicinal plant Portulaca oleracea 31 . These four simple isoquinoline alkaloids contained 6,7-dihydroxy substitution but different saturation or substituents at C-1. Four “naphthalene-devoid” tetra- and dihydroisoquinolines, named ealaines A–D ( 18-21 ), were isolated from the Congolese plant Ancistrocladus ealaensis 32 . Akihisa et al . 33 isolated noroxyhydrastinine ( 22 ) from the bark of Phellodendron amurense ( Figure 2 ). Reticuline ( 23 ) exhibits significant pharmacological activities, leading to the search for and identification of alternate natural sources, such as Litsea cubeba , Unonopsis genus, Cryptocarya densiflora, C. infectoria, C. griffithiana and Dehaasia longipedicellata , over the past five years 34 - 39 . (+)- N -Methylisococlaurine ( 24 ) also was found in Cryptocarya species 37 and (−)- N -methylcoclaurine ( 25 ) was identified in the rhizomes of Sinomenium acutum in 2014 40 . Berbithine ( 26 ) and 6-([1,3]dioxolo[4,5-g]isoquinoline-5-carbonyl)-2,3-dimethoxybenzoic acid methyl ester ( 27 ) were isolated from the rhizome of Coptis chinensis 41 . In 2018, several benzylisoquinoline alkaloids, including 24 , 25 , norcolaurine-4′- O -glucoside ( 28 ), N -methylhigenamine ( 29 ), norcoclaurine-6- O -glucoside ( 30 ), norcoclaurine ( 31 ), argemexirine ( 32 ), lotusine ( 33 ), isococlaurine ( 34 ), armepavine ( 35 ), 6-demethy-4′-methyl- N -methylcoclaurine ( 36 ), coclaurine ( 37 ), N -nor- O -methylarmepavine ( 38 ), isococlaurine-5′- O -pentoside ( 39 ), and coclaurine-5′- O -pentoside ( 40 ) were identified from Plumula nelumbinis through UPLC-ESI-QTOF-MS 30 . Subsequently, juzirine ( 41 ) was identified from the aerial parts of Leonurus japonicus 42 . ( R )-(+)-1-Benzyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline ( 42 ) from Portulaca oleracea showed anti-inflammatory and β2-adrenergic receptor agonist activities 26 . Laudanosine ( 43 ), pseudolaudanine ( 44 ) and rugosinone ( 45 )were isolated from the whole herb of Thalictrum cirrhosum 43 ( Figure 3 ). Hendersine B methyl ester ( 46 ), bicucullinine ( 47 ) and hendersine B ( 48 ) were isolated from Corydalis tomentella 28 . Bisbenzyl isoquinoline alkaloids are one of the major phytochemicals reported from members of the plant families Menispermacea, Berberidaceae, Lauraceae, and Ranunculaceae, which grow in tropical and subtropical regions. They contain two benzylisoquinolines linked through diphenyl ether, benzyl phenyl ether, or biphenyl bonds 5 , 19 . In 2016, two new bisbenzylisoquinolines, 6,6′,7′,12-tetramethoxy-5′-hydroxy-2,2′-dimethyloxycanthan ( 49 ) and 6,5′,6′,7′,12-pentamethoxy-2,2′-dimethoxyethane ( 50 ), were isolated from the stems of Thalictrum foliolosum 44 . Meanwhile, hernandezine ( 51 ), a known alkaloid, was identified from T. flavum 45 . In 2018, two seco -bisbenzylisoquinolines, 6,7,12-trimethoxy-2-methyl-13-hydroxy-11-(4′-formylphenoxy)benzylisoquinoline ( 52 ) and 5,6-(methylenedioxy)-7,12-dimethoxy-2-methyl-10-(4′-formylphenoxy)benzylisoquinoline ( 53 ), were isolated from T. wangii 46 . Tiliamosine ( 54 ) was found from T. racemosa 47 ( Figure 3 ). Bisbenzylisoquinoline alkaloids are also found in the genus Stephania . In 2014, two new compounds, (−)-pseudocurine ( 55 ) and (−)-pseudoisocurine ( 56 ), were isolated from a leaf extract of Stephania abyssinica 48 . Tetrandrine ( 57 ) and fangchinoline ( 58 ) were isolated from S. tetrandra, which has been used for 2,000 years as an antirheumatic herbal medicine in China 49 . In addition, (−)- O - O -dimethylgrisabine ( 59 ) from Dehaasia longipedicellata exhibited significant antiparasitic and antioxidant activities 38 . Using a 1 H NMR-based metabolomics approach, berbamine ( 60 ), a bisbenzylisoquinoline-type compound, was identified from Mahonia aquifolium 50 ( Figure 4 ). Neferine ( 61 ) is a well-known bisbenzylisoquinoline-type alkaloid due to its wide range of pharmacological activities, including antiarrhythmic, antihypertensive 51 , 52 , relaxant 53 , antidiabetic 54 , cholinesterase inhibitory 55 , antioxidant, anti-inflammatory, anti-amnesic 56 and sedative 57 , 58 effects. In addition to M. aquifolium , it is found in lotus ( Nelumbo nucifera ) seed embryos 59 . In 2018, compound 61 as well as four other bisbenzylisoquinoline alkaloids, liensinine ( 62 ), isoliensinine ( 63 ), norisoliensinine ( 64 ) and 6-hydroxynorisoliensinine ( 65 ) were found in Plumula nelumbinis 30 . Five alkaloids also were isolated from Alseodaphne corneri , including (−)-gyrolidine ( 66 ), (+)- O -methyllimacusine ( 67 ), (+)-2-norobaberine ( 68 ), (+)-norstephasubine ( 69 ) and (+)-stephasubine ( 70 ) 60 ( Figure 4 ). Spirobenzylisoquinoline alkaloids are isoquinoline alkaloids with a unique ‘ spiro ’ structure as shown in Figure 6 . They have been found only within the plant family Fumariaceae, and more specifically within the genera Fumaria and Corydalis. In 2014, coptichic aldehyde ( 71 ) was isolated from the traditional Chinese medicine preparation Coptidis Rhizoma – Euodiae Fructus couple; it showed growth inhibitory activity against NCI-N87 cells with an IC 50 value of 8.92 μM 61 . In 2016, the new isoquinoline alkaloid fumaranine ( 72 ) together with seven other alkaloids, (−)-fumaricine ( 73 ), (+)-dihydrofumariline ( 74 ), (−)-fumaritine ( 75 ), (−)- O -methylfumarophycine ( 76 ), (−)-fumarophycine ( 77 ), (+)-fumariline ( 78 ), (+)-parfumidine ( 79 ), and (+)-parfumine ( 80 ) were found from the aerial parts of F. officinalis 24 . Also, four new spirobenzylisoquinoline N -oxide alkaloids hendersines C-F ( 81-84 ) were identified from Corydalis hendersonii 27 ( Figure 4 ). Aporphine alkaloids are a large group of isoquinolines that generally possess a characteristic tetracyclic ring system (rings A-D) with a nitrogen in ring B 62 . The structures of the aporphine alkaloids can be classified into subtypes, including simple aporphines, their dehydro derivatives, oxoaporphines, miscellaneous aporphinoids, and dimeric aporphinoid alkaloids 63 - 66 . Simple aporphines have a 5,6,6a,7-tetrahydro-4 H -dibenzo[ de,g ]quinoline core substituted primarily with different numbers of hydroxy, methoxy, and methylenedioxy groups at various positions. The nitrogen is substituted most frequently with hydrogen or methyl, although other groups (e.g., formyl, acetyl, and others) are sometimes present. They are 1-benzylisoquinolines with one additional ring closure between the 2′-carbon in the pendant phenyl ring and the 1a-carbon in the isoquinoline ring junction, forming a non-linear tetracyclic (6-6-6-6) system. Boldine ( 85 ), isolated from Litsea cubeba and Dehaasia longipedicellata , showed anti-inflammatory activity and potential synergistic effects in vivo 67 , 60 . Compound 85 and (−)-norboldine ( 86 ), also found in D. longipedicellata , 38 showed moderate antioxidant and antiplasmodial activities 38 . In 2016, (+)-laurotetanine ( 87 ), isolated from Alseodaphne corneri 68 and Bocageopsis pleiosperma 39 , was found to exhibit strong antiplasmodial activity ( Figure 5 ). Compound 87 , (+)-nornantenine ( 88 ) and (+)- N -methyllaurotetanine ( 89 ) were isolated from Cryptocarya densiflora , C. infectoria and C. griffithiana 37 . Corydine ( 90 ) and norisoboldine ( 91 ) were isolated from Croton echinocarpus leaves 69 , while isocorydine ( 92 ) and norisocorydine ( 93 ) were identified from Alseodaphne corneri 60 ( Figure 5 ). The aporphine stephalagine (1,2-methylenedioxy-3-methoxyaporphine) ( 94 ) was isolated from the fruit peel of Annona crassiflora 70 . In 2017, N -formyl-asimilobine-2- O -β- d -glucoside ( 95 ), an amidic aporphine, was obtained from the tubers of Stephania succifera 71 . Four aporphine alkaloids, isoboldine ( 96 ), anonaine ( 97 ), nornuciferine ( 98 ) and actinodaphnine ( 99 ), were isolated from Annona hypoglauca 72 . Magnoflorine ( 100 ) was found in the rhizomes of Mahonia aquifolium, Coptis japonica and Sinomenium acutum 40 , 50 , 73 ( Figure 5 ). Both norpurpureine ( 101 ) and purpureine ( 102 ) were isolated from Annona purpurea leaves 74 . In 2018, eight aporphine alkaloids [anonaine ( 97 ), N -nornuciferine ( 98 ), nornuciferidine ( 103 ), zenkerine ( 104 ), O -nornuciferine ( 105 ), nuciferine ( 106 ), roemerine ( 107 ) and oxidation-nuciferine (5-hydroxynuciferine) ( 108 )] were identified from Plumula nelumbinis 30 . Compounds 93 , 97 and 98 as well as asimilobine ( 109 ), isopiline ( 110 ), O -methylisopiline ( 111 ), glaucine ( 112 ), and norglaucine ( 113 ) were reported for the first time from Unonopsis floribunda 35 , 36 ( Figure 5 ). Compounds 97 , 98 , 109 and 112 also were found from Unonopsis duckei 75 , and compounds 89 , 96 , 97 and 109 also were reported from Bocageopsis pleiosperma 40 . (+)- N -Formylnorglaucine ( 114 ) was reported from Unonopsis stipitata 76 . Four new phenyl-C 1 substituted aporphine alkaloids, 6a R -2′-methoxycarbonylthaliadine ( 115 ), 6a R -2′-carboxylthaliadine ( 116 ), 6a R -3-methoxyhernandalinol ( 117 ), 6a S -1,3,10-trimethoxynatalamine ( 118 ), together with three known isoquinoline alkaloids 89 , predicentrine ( 119 ), and thaliadine ( 120 ) were isolated from the whole herb of Thalictrum cirrhosum 43 . Glaucine ( 121 ) from Corydalis turtschaninovii 77 , as well as three new analogs, (+)-8-(4′-formylphenoxy)glaucine ( 122 ), (+)-8-(4′-hydroxymethylphenoxy)glaucine ( 123 ), (+)-3-methoxy-8-(4′-formylphenoxy)glaucine ( 124 ), and two known alkaloids, 120 and its oxidized derivative 125 , were isolated from the whole plant of Thalictrum wangii 46 ( Figure 5 ). An unprecedented alkaloid, dactyllactone A ( 126 ), which contains a rearranged benzofuran lactone with a gemdimethoxycarbonyl unit and is derived from an 8,9;11,11a- bis -seco-aporphine skeleton, was isolated from Dactylicapnos scandens . It exhibited anti-inflammatory activity 78 ( Figure 5 ). 7-Oxygenated aporphines have a hydroxyl or methoxy group at C-7 or two such groups at C-4 and C-7 66 , 79 . The oxoaporphines (7 H -dibenzo[ de,g ]quinoline-7-one skeleton) and oxoisoaporphines (7 H -dibenzo[ de,h ]quinoline-7-one skeleton) have an aromatic isoquinoline (aromatic ring B in the tetracyclic structure) and a carbonyl group at C-7 80 . Two oxoisoaporphines sallisonine E ( 127 ) and dauriporphine ( 128 ) were isolated from the rhizomes of Sinomenium acutum , in 2014 and 2016, respectively 40 , 81 . Five oxoaporphines isomoschatoline ( 129 ), O-methylmoschatoline ( 130 ), liriodenine ( 131 ), subsessiline ( 132 ) and lysicamine ( 133 ) were identified from Guatteria blepharophylla also in 2016 74 and compounds 131 , 133 were reported from Unonopsis duckei in 2014 75 . One new 4,7-dihydroxy-7-methylaporphine alkaloid (7-hydroxyguatteriopsiscine ( 134 )) and three new 7,7-dimethylaporphinoids [( R )-dihydroguatteriscine ( 135 ), guatterfriesidine ( 136 ), and iso-9-methoxyguatterfriesine ( 137 )] were isolated from the stem bark of G. friesiana in 2018. 75 Compound 136 exhibited antiglycation activity as determined by inhibiting the formation of advanced glycation end-products in both bovine serum albumin (BSA)/methylglyoxal and BSA/fructose assay systems 82 . In 2018, one 7-hydroxyaporphine [norushinsunine ( 138 )] and four oxoaporphines [ 131 , 133 , oxoglaucine ( 139 ), and lanuginosine ( 140 )] were reported for the first time from Unonopsis floribunda 35 ( Figure 6 ). Another new oxoaporphine alkaloid 3-methoxy-2′-methoxycarbonyl-oxohernandalincin ( 141 ) as well as the known 3-methoxy-oxohernandaline ( 142 ), oxopurpureine ( 143 ), and oxophoebine ( 144 ) were isolated from the whole herb of Thalictrum cirrhosum 43 . 1,2,3,9,10-Pentamethoxy-11-(4′-formylphenoxy)-7-oxoaporphine ( 145 ) and 1,2,9,10-tetramethoxy-11-(4′-formylphenoxy)-7-oxoaporphine ( 146 ), two new oxoaporphines that, like 142 , contain an ether-linked formylphenyl moiety were identified from T. wangii 46 ( Figure 6 ). Dehydroaporphines are 5,6-dihydro-4H-dibenzo[de,g]quinolines with a double, rather than single, between C-6a and C-7. In the preceding subtypes, this bond is saturated or C-7 is substituted with hydroxy, methoxy, or methyl groups or part of a carbonyl unit 19 , 83 , 84 . Based on bioassay-guided fractionation against numerous cancer cells, Le et al . 85 isolated one dehydroaporphine [dehydrocrebanine ( 147 )] and three simple aporphines [crebanine ( 148 ), stephanine ( 149 ) and O -methylbulbocapnine ( 150 )] from the tubers of Stephania venosa growing in Vietnam. Compound 149 was the most active among the four compounds with IC 50 values of 3.33 μM, 5.66 μM and 6.49 μM against HeLa, MDA-MB231 and MCF-7 cells, respectively. In 2017, an amidic dehydroapophine ( 151 , 6-formyl-1,2,9,10-tetramethoxy-6α,7-dehydroaporphine) was isolated from the aerial parts of Aconitum carmichaelii 70 ( Figure 6 ). Proaporphine alkaloids are biogenetic precursors to certain aporphine alkaloids. The tetracyclic system (2’,3’,8’,8a’-tetrahydro-1’H-spiro[cyclohexane-1,7’-cyclopenta[ij]isoquinoline) is composed of a bicyclic isoquinoline fused to a five-membered ring that is also connected to a six-membered ring through a spiro carbon. In 2014, glaziovine ( 152 ) was reported from Unonopsis duckei 75 . In 2016, the proaporpine (+)-oridine ( 153 ) was obtained from leaves of Cryptocarya densiflora 37 . In 2018, several proaporphines were identified from various plant species: two new [(−)-10- O -acetylprodensiflorins A ( 154 ) and B ( 155 )] and one known [prodensiflorin B ( 156 )] and from the whole plant of Thalictrum wangii 46 , dihydroglaziovine ( 157 ) and linearisine ( 158 ) from T. cirrhosum , 43 pronuciferine ( 159 ) from Plumula nelumbinis 30 and stepharine ( 160 ) from Unonopsis floribunda for the first time 35 , 36 , and compound 160 also was found Bocageopsis pleiosperma 39 . ( Figure 6 ). Berberine ( 161 ) is a famous isoquinoline alkaloid from the rhizome, roots and stem bark of Berberis sp .; it exhibits various pharmacological effects, such as antitumor, antibacterial, antiviral, antiinflammatory, antidiabetic and myocardial protective activities. Berberine is a quaternary protoberberine alkaloid with a tetracyclic skeleton [5,6-dihydrobenzo[a,g]quinolizinium (C 17 H 14 N + ) salt] with the nitrogen at the junction of the two middle rings (position 7). Structurally, it is a benzylisoquinoline with an additional ring formed between the 2′-carbon of the pendant phenyl ring and a methyl on the isoquinoline nitrogen. Various oxygenated substituents (hydroxy, methoxy, methylenedioxy) are present on the two outer rings, most often, although not exclusively, at positions 2,3,9,10 or 2,3,10,11, which is often designated as ‘pseudo’. Methylation at position 13 is commonly seen as well. Besides the genus Berberis , it has also been isolated from plants of the genera Coptis , Corydalis and Mahonia together with other known structurally related alkaloids, including jatrorrhizine ( 162 ), epiberberine ( 163 ), demethyleneberberine ( 164 ), coptisine ( 165 ) and palmatine ( 166 ) 50 , 73 , 86 - 88 . Compounds 161, 162, 165, 166, pseudodehydrocorydaline ( 167 ), dehydrocorybulbine ( 168 ) and pseudocoptisine ( 169 ) were isolated from the roots of Corydalis turtschaninovii . They showed strong neuraminidase inhibitory activity (IC 50 , 12.8–65.2 μM) 77 . Dehydroisoapocavidine ( 170 ), dehydrocheilanthifoline ( 171 ), isolated from the related species C. tomentella , showed hepatoprotective activity 28 . Corydamine ( 172 ), a B-ring opened 3-phenyl isoquinoline analog of 159 , was isolated from the aerial parts of Fumaria officinalis 19 ( Figure 7 ). Other protoberberines include tetrahydroprotoberberines and dihydroprotoberberines. In 2014, several 8-oxo-protoberberines, including a pair of new enantiomeric isoquinoline alkaloids, (+)- and (−)-5-hydroxyl-8-oxyberberine ( 173 ), 8,13-dioxocoptisine hydroxide ( 174 ), 8-oxyberberine ( 175 ), 8-oxo-epiberberine ( 176 ), 8-oxocoptisine ( 177 ), and 8-oxoberberrubine ( 178 ), together with tetrahydroberberine ( 179 ) and corydaline ( 180 ) as well as the benzylisoquinoline alkaloid 26 were isolated from the rhizoma of Coptis chinensis . C2C12 cells exposed to 176 and 178 showed reduced glucose uptake 41 , 89 . The whole plant of Corydalis pallida also yielded 177 together with four tetrahydroprotoberberines, (−)-corydalidzine ( 181 ), (−)-corybulbine ( 182 ), (−)-yuanhunine ( 183 ) and (−)-ophiocarpine ( 184 ), as well as the quaternary protoberberine alkaloid dehydrocorydaline ( 185 ) 90 . Dihydrocoptisine ( 186 ), trans- protopinium ( 187 ), cis -protopinium ( 188 ), and thalictrifoline ( 189 ) from Corydalis tomentella displayed moderate hepatoprotective activities; the values of relative survival rates were 34.25–47.51% at a concentration of 10 μM 28 . The isomeric 187 and 188 obtained from roots of Fumaria parviflora also showed nematocidal activity 91 ( Figure 7 ). In 2014, compound 180 and tetrahydrocoptisine ( 190 ) were isolated from the roots of Corydalis turtschaninovii 77 . A new compound 13-carboxaldehyde-8-oxocoptisine ( 191 ) together with 177 were isolated from the traditional Chinese preparation Coptidis Rhizoma - Euodiae Fructus couple, used to treat gastrointestinal disorders 61 . Corydalis hendersonii and Coptis japonica were found to contain tetrahydropalmatine ( 192 ) and 8-hydroxy-7,8-dihydrocoptisine ( 1 93 ), respectively 27 , 73 . Cavidine ( 194 ) was isolated from Corydalis impatiens 92 . In 2016, (−)-stylopine ( 195 ), (−)-sinactine ( 196 ) and (−)-cheilanthifoline ( 197 ) were isolated from aerial parts of Fumaria officinalis 24 . The latter compound also was found in Sinomenium acutum 81 . Phellodendrine ( 198 ) was identified from Phellodendri chinensis cortex 93 . In 2017, a new glycoalkaloid, (−)-1- O -β- d -glucoside-8-oxotetrahydropalmatine ( 199 ), isolated from tubers of Stephania succifera , exhibited antimicrobial activity against Staphylococcus aureus 71 . N -Methylcanadine ( 200 ) was isolated from Zanthoxylum tingoassuiba 94 , and demethylalangiside ( 201 ), alangiside ( 202 ) and isoalangiside ( 203 ) were identified and isolated from Ophiorrhiza nutans 95 . Subsequently, in 2018, it was shown that scoulerine ( 204 ) from Corydalis dubia exhibited promising suppression of cancer cell growth 96 . ( Figure 8 ). 2′- O - trans -Sinapoylisoalangiside ( 205 ) was identified from Alangium longiflorum 97 . Four new isoquinoline alkaloids rupestrines A-D ( 206-209 ) and the known 195 were identified from Corydalis rupestris 98 ( Figure 8 ). Compounds from this classification have a 5,6,7,8,13,14-hexahydrodibenzo[c,g]azecine skeleton. They lack the B/C bond and, thus, are tricyclic (6-10-6) with a 10-membered ring between two phenyl rings. Only two compounds of this type were identified during the past five years. Protopine ( 210 ) and cryptopine ( 211 ) were isolated from Fumaria officinalis 24 , and the former compound also was found in Corydalis mucronifera 99 ( Figure 9 ). Naphthylisoquinolines are a group of structurally diverse secondary metabolites containing both naphthalene and isoquinoline bicyclic systems connected by a C,C or C,N biaryl axis. These chiral compounds are mostly found only in two palaeotropic families, Dioncophyllaceae and Ancistrocladaceae. Dioncophyllaceae-type alkaloids have a R-configuration at C-3 and always lack an oxygen function at C-6. The structurally similar Ancistrocladaceae-type alkaloids are found in the closely related Ancistrocladaceae plant family. Among the studies over the past two decades on the isolation and bioactivity evaluation of naphthylisoquinoline alkaloids, extensive work has been published by Bringmann et al . 21 , 100 - 113 . From 2014 to the present, numerous new compounds were isolated in investigations by several research groups on Asian lianas. The approximately 60 structurally divergent monomeric and dimeric naphthylisoquinoline alkaloids exhibit all seven known C,C-coupling types (5,1′, 5,3′, 5,8′, 7,1′, 7,3′, 7,6′, and 7,8′). The twigs and stems of the Chinese liana Ancistrocladus tectorius contained five new 5,8′-coupled naphthylisoquinolines, ancistectorine D ( 212 ), its 6- O -demethyl derivative ( 213 ), ancistrotectoriline A ( 214 ), ancistrotanzanine B ( 215 ), and ancistroealaine A ( 216 ), three new 7,1′-linked alkaloids, 6- O -methylancistectorine B 1 ( 217 ), ancistectorine B 2 ( 218 ), and 6- O -demethyl-8- O -methyl-7-epi-ancistrobrevine D ( 219 ), and twenty 5,1′-linked naphthylisoquinoline alkaloids ancistrobenomines B ( 220 ) and C ( 221 ), 6- O -methylancistectorine A 3 ( 222 ), 4′- O -demethylancistectorine A 2 ( 223 ), ancistectorine A 3 ( 224 ), ancistrocladine ( 225 ), hamatine ( 226 ), 5′- O -demethylhamatine ( 227 ), ancistrocline ( 228 ), ancistrocladinine ( 229 ), hamatinine ( 230 ), ancistectorine A 2 ( 231 ) and its atropo-diastereomer 5- epi -ancistectorine A 2 ( 232 ), ancistrobenomine A ( 233 ), 6- O -methylancistrocladine ( 234 ), 6- O -methylhamatine ( 235 ), 4′- O -demethylancistrocladine ( 236 ), 5′- O -demethylhamatine ( 237 ), 6- O -methylhamatinine ( 238 ) and 5′- O -demethylhamatinine ( 239 ) 105 , 106 . Although some compounds were already known from related Asian and African Ancistrocladus species, they were discovered from A. tectorius for the first time, such as a monomeric alkaloid, korupensamine D ( 240 ) 110 . From this species, two unique pentacyclic N,C -coupled naphthylisoquinolines, ancistrocyclinones A ( 241 ) and B ( 242 ), also were discovered, as well as six known N,C -coupled alkaloids, viz., ancistrocladinium A (a/b) ( 243 ), 4′- O -demethylancistrocladinium A (a/b) ( 244 ), 6,4′- O,O -didemethylancistrocladinium A (a/b) ( 245 ), ancistrotectorine B 1 ( 246 ), shuangancistrotectorine C ( 247 ), ancistrotectoquinone B (a/b) ( 248 ) and compounds 161 and 222 107 ( Figures 10 , 11 ). In 2017, the first 5,8′-coupled Dioncophyllaceous alkaloid, dioncophylline F ( 249 ), together with dioncophyllines C 2 ( 250 ), D 2 ( 251 ), and three known compounds, 5′- O -methyldioncophylline D ( 252 ), dioncophylline A ( 253 ) and 4′- O -demethyldioncophylline A ( 254 ) were isolated from the Congolese liana Ancistrocladus ileboensis 108 . Moreover, the Ancistrocladaceae-type compound ancistrocladisine B ( 255 ) (oxygenated at C-6 and S -configured at C-3), together with four known alkaloids, 225 , ancistrobrevine C ( 256 ), ancistrocladisine A ( 257 ) and ancistrobertsonine D ( 258 ) also were identified. Four new C,C-coupled compounds, ancistroyafungines A-D ( 259-262 ), and eleven known C,C - and N,C -linked analogs, including compounds 214, 235, 236 and 243 , ancistroguineine A ( 263 ), ancistrobertsonine A ( 264 ), ancistrobrevine B ( 265 ), 6,5′- O,O -didemethylancistroealaine A ( 266 ), 6- O -demethylancistroealaine A ( 267 ), 7- epi -ancistrobrevine D ( 268 ) and ancistrocladinium B ( 269 ), were isolated from an unidentified Ancistrocladus plant 109 ( Figure 12 ). In 2016, five new michellamine-type dimeric naphthylisoquinoline alkaloids, named michellamines A 2 , A 3 , A 4 , B 2 , and B 3 ( 270-274 ), were isolated from the root bark of the Central African liana Ancistrocladus congolensis , along with their two known parent compounds, michellamines A ( 275 ) and B ( 276 ) 110 . More recently in 2018, michellamines A 6 (277 ) and A 7 ( 278 ), the first dimeric 5,8′-coupled naphthylisoquinoline alkaloids with cis-configured stereocenters in both tetrahydroisoquinoline subunits, were isolated from the leaves of an unidentified Congolese Ancistrocladus liana together with two new dimeric analogs, michellamines B 4 ( 279 ) and B 5 ( 280 ) 111 ( Figure 13 ). In addition, ancistrobonsolines A 1 ( 281 ) and A 2 ( 282 ), unique naphthyldihydroisoquinolines with an M-configured biaryl axis and R-configuration at C-3, together with five known compounds, ancistroealaine C ( 283 ), korupensamines A ( 284 ) and B ( 285 ), 270 and michellamine E ( 286 ) were reported 111 ( Figure 14 ). In 2017, ealapasamines A-C ( 287-289 ), three unusual new heterodimeric naphthylisoquinoline alkaloids, were obtained from the leaves of the Congolese Ancistrocladus ealaensis 112 ( Figure 14 ). These ‘mixed’, constitutionally unsymmetrical dimers are the first cross-coupled products of a 5,8′- and a 7,8′-coupled naphthylisoquinoline linked via C-6′ in both naphthalene segments. Previously, dimers with a central 6,6″-axis were found only from two African Ancistrocladus species 112 . The following year, four new [(michellamine A 5 ( 290 ), mbandakamines C-E ( 291-293 )] and one known [mbandakamine A ( 294 )] dimeric naphthylisoquinoline alkaloids were isolated in another study on A. ealaensis 32 , 113 . Four new 5,8′-coupled monomeric naphthylisoquinolines, ancistroealaines C-F ( 283, 295-297 ) as well as five known compounds 214, 243, 245, 284 and ancistrolikokine B ( 298 ) were isolated from the same plant 113 ( Figure 14 ). Benzophenanthridine isoquinoline compounds occur only in higher plants and show a wide spectrum of non-specific biological activities as well as multiple pharmacological properties. Sanguinarine ( 299 ) ( Figure 15 ), the most extensively studied alkaloid of this group, exhibits many biological effects, such as antibacterial 114 , antifungal 115 , 116 , anti-inflammatory 117 , antioxidant 118 , antiviral 119 , nematicidal 120 , antitumor 121 , immunomodulatory 122 , and insecticidal 123 , 124 activities. Chelidonine ( 300 ) and homochelidonine ( 301 ), two B/C- cis -11-hydroxyhexahydrobenzo[ c ]phenanthridine alkaloids classified as partially hydrogenated-type congeners, were isolated and described as the main natural constituents of Chelidonium majus 125 . From the same plant, six pairs of 6-monosubstituted dihydrobenzophenanthridine alkaloids were separated as corresponding six scalemic mixtures from the aerial parts. Two scalemic mixtures were assigned as (1′ R ,6 R /1′ S ,6 S )- and (1′ S ,6 R / 1′ R ,6 S )-1-(dihydrochelerythrine-6-yl) ethanol ( 302, 303 ), two as (1′ R ,6 R )/(1′ S ,6 S )- and (1′ S ,6 R )/ (1′ R ,6 S )-1-(dihydrosanguinarine-6-yl)ethanol ( 304, 305 ), one as (±)-ethyl 2-(dihydrosanguinarine-6-yl) acetate ( 306 ), and one as (±)-ethyl dihydrosanguinarine-6-carboxylate ( 307 ) ( Figure 15 ) 126 . Heitziquinone ( 308 ), a new benzophenanthridine alkaloid, together with dihydronitidine ( 309 ), isoarnottianamide ( 310 ), rhoifoline B ( 311 ) were found as minor compounds from a hexane extract of Zanthoxylum heitzii stem bark 127 . Furthermore, dihydrocheleryhtrine ( 312 ) was isolated from Z. tingoassuiba 94 and decarine ( 313) was identified from Z. myriacanthum var. pubescens bark 128 . The genus Corydalis contains many benzophenanthridine alkaloids. Corynoline ( 314 ) from Corydalis bungeana possesses anti-inflammatory and antibacterial activities 129 . Ambinine ( 315 ), the major alkaloid of tuber C. ambigua var. amurensis tuber, produces protective effects on H9C2 myocardial cells 130 . Norsanguinarine ( 316 ), (−)-6-acetonyldihydrisanguinarine ( 317 ) and cavidilinine ( 318 ) were isolated from C. tomentella 28 , and compound 317 also was found in the whole plant of C. pallida 90 . 8-Methoxydihydrosanguinarine ( 319 ) and dihydrosanguinarine ( 320 ) were obtained from C. mucronifera 99 ( Figure 15 ). The pyrrolephenanthridines have a non-linear tetracyclic structure (6-6-6-5) containing three six-membered rings (“phenanthridine”) and one five-membered ring (“pyrrole”). The N -atom and two carbons are common to the phenanthrene and pyrrole, while the points of fusion result in either a pyrrolo[3,2,1-de]phenanthridine (e.g., 321 ) or a 5,10b-ethanophenanthridine (e.g., 326 , 328 ). Lycorine-type alkaloids, including lycorine ( 321 ), acetycaranine ( 322 ), caranine ( 323 ), galanthine ( 324 ), 9- O -demethylgalanthine ( 325 ), as well as α-crinane types, haemanthamine ( 326 ), haemanthidine ( 327 ), and β-crinane types, ambelline ( 328 ), 11- O -acetylambelline ( 329 ), 1- O -acetylbulbisine ( 330 ), undulatine ( 331 ), crinamidine ( 332 ), buphanamine ( 333 ) and srinine ( 334 ), were isolated from Zephyranthes robusta , Chlidanthus fragrans , Nerine bowdenii and Narcissus poeticus cv. Brackenhurst by Cahlíková and collegaues, these compounds show moderate antitumor activities 131 - 136 . In 2018, a novel lycorine-related iminium salt, 6,7,11b,11c-didehydrolycorinium salt ( 335 ), as well as the above compounds were isolated from bulbs of both Crinum firmifolium and C. hardyi 137 . Seco-isopowellaminone ( 336 ), 326 and incartine ( 337 ) also were isolated from Narcissus poeticus cv. Pink Parasol 138 ( Figure 16 ). The isoquinoline ring in manzamine alkaloids is both attached to a β-carboline (9 H -pyrido[3,4- b ]indole) heterocycle and fused with two polycyclic N -containing systems. Since manzamine A hydrochloride (keramamine A, 338 ) was initially isolated from an Okinawan sponge in 1986, almost 100 natural manzamines have been isolated from Indian and Pacific sponges 9 , 139 - 145 . In 2017, five new manzamine alkaloids, kepulauamine A ( 339 ), manzamine B N -oxide ( 340 ), 3,4-dihydromanzamine B N -oxide ( 341 ), 11-hydroxymanzamine J ( 342 ), and 31-hydroxymanzamine A ( 343 ), together with new hydrogen chloride salts of the known manzamine J N -oxide and 3,4-dihydromanzamine J N -oxide, as well as five known manzamine alkaloids, 32,33-dihydro-31-hydroxymanzamine A ( 344 ), 338 , 6-deoxymanzamine X ( 345 ), manzamine B ( 346 ), and neo -kauluamine ( 347 ), a manzamine dimer, were isolated from an Indonesian Acanthostrongylophora sp. sponge 146 ( Figure 17 ). Emetine ( 348 ) as well as its analogs are present in three plant families, Alangiaceae, Icacinaceae , and Rubiaceae . Structurally, 348 contains both pyridoisoquinoline and isoquinoline heterocycles linked through a methylene bridge. Another heterocycle found in compounds from this classification is a 2,3,4,9-tetrahydro-1 H -pyrido[3,4- b ]indole. Previous studies showed that 348 can be used as an emetic and expectorant, 147 and recently, its antiviral and anti-trypanosomes activities were proved 148 , 149 . In 2017, a new emetine isoquinoline alkaloid, 7′,10-dide- O -methylcephaeline ( 349 ), as well as the known 10- O -demethylprotoemetine ( 350 ) were identified and isolated from Ophiorrhiza nutans 95 . In 2018, two new alkaloids of this type, 8-hydroxytubulosine ( 351 ) and 9-demethyltubulosine ( 352 ), were isolated from Alangium longiflorum 97 ( Figure 18 ). Like aporphine alkaloids, morphine alkaloids have a 1-benzylisoquinoline skeleton with one additional ring closure. However, the added bond is between the 2′-carbon in the pendant phenyl ring and carbon 4a, rather than 1a, at the isoquinoline ring junction. Morphinan or 1,3,4,9,10,10a-hexahydro-2 H -10,4a-(azanoethano)phenanthrene is the prototype chemical skeleton of this alkaloid classification. However, compounds with several structural variations, including rearranged (e.g., spiro) or additional rings, are found as well. In 2014, two morphinandienones, (+)-sebiferine ( 353 ) and (−)-milonine ( 354 ), were isolated from Dehaasia longipedicellata 38 . Also, new bistetrahydroisoquinolines with morphinane-proaporphine and morphinane-benzyltetrahydroisoquinoline types, sinomacutines A–C ( 355-357 ), and cephalonine-2- O -β- d -glucopyranoside ( 358 ), together with sinomenine ( 359 ) and sinoacutine ( 360 ) were isolated from the rhizomes of Sinomenium acutum 40 . Subsequently, two new compounds, 8-demethoxycephatonine ( 361 ) and 7( R )-7,8-dihydrosinomenine ( 362 ), along with eight morphine alkaloids, 359 , 8-demethoxyrunanine ( 363 ), 14-episinomenine ( 364 ), sinomenine N -oxide ( 365 ), salutaridine ( 366 ), acutumine ( 367 ), acutumidine ( 368 ) and dauricumine ( 369 ) were isolated from a rhizome extract of Sinomenium acutum 81 . Then in 2018, the morphinadienone pallidine ( 370 ) was found for the first time in Unonopsis floribunda 36 and O -methylflavinantine ( 371 ) was isolated from Thalictrum cirrhosum 43 ( Figure 19 ). As indicated by the classification’s name, tetracyclic phthalideisoquinoline alkaloids contain both bicyclic isoquinoline and bicyclic phthalide (fused benzene and gamma-lactone ring) systems. From the basic structure of a 1-benzylisoquinoline, the ester functionality (O-C=O) forming the lactone is inserted between the benzyl linking carbon and an alpha-carbon on the pendant phenyl ring. Two phthalideisoquinoline alkaloids, (+)-bicuculline ( 372 ) and (+)-corlumine ( 373 ), were isolated from Fumaria officinalis and Viola tianschanica in 2016 and 2017, respectively 24 , 150 . Three undescribed isoquinolines, (9 S ,7′ S ) tomentelline A ( 374 ), (9 S ,7′ R ) tomentelline A ( 375 ), (9 R ,7′ S ) tomentelline B ( 376 ) together with adlumidine ( 377 ) and (+)-capnoidine ( 378 ) were isolated for the first time from Corydalis tomentella 28 . Five pairs of isoquinoline alkaloid enantiomers, mucroniferanines A–E ( 379-383 ), two inseparable epimeric pairs, mucroniferanines F ( 384 ) and G ( 385 ), and five known isoquinoline alkaloids, 377 , (±)-hypecorinine ( 386 ), (−)-7′- O -methylegenine ( 387 ), sibiricine ( 388 ) and (+)-humosine A ( 389 ) were obtained from C. mucronifera 99 . Capnoidine ( 390 ) was isolated from a third related species, C. dubia 151 ( Figure 20 ). Seldom found in nature, the benzopyrroloisoquinolines have a linear tetracyclic structure (6-6-6-5) containing two aromatic six-membered rings, one non-aromatic six-membered heterocyclic ring and one five-membered heterocyclic ring. Thus, the alkaloid N -atom and one adjacent carbon are shared by benzopyrrole and isoquinoline systems. In 2017, a dimeric benzopyrroloisoquinoline alkaloid, tengerensine ( 391 ) with a rare unsymmetrical cyclobutane adduct was isolated from Ficus fistulosa var. tengerensis 152 ( Figure 21 ). The simplest compounds are 1-phenylethylisoquinolines (-CH 2 CH 2 C 6 H 5 ) rather than 1-benzylisoquinolines (-CH 2 C 6 H 5 ). However, more complex rearranged compounds, including those with a tetracyclic 6-7-5-6 system, also belong to this classification. In 2016, the new compound fumarostrejdine ( 392 ) and its known oxo-derivative (±)- O -methylfumarofine ( 393 ) were isolated from Fumaria officinalis 24 ( Figure 22 ). In 2014, a new alkaloid, coptichine ( 394 ), from the Coptidis Rhizoma - Euodiae Fructus couple showed significant cytotoxicity against NCI-N87 cells 61 . Coptisonine ( 395 ) from Coptis chinensis showed significant stimulation of glucose uptake 89 . Sallisonine D ( 396 ) was isolated from the rhizomes of Sinomenium acutum 40 . A new compound, alternamine A ( 397 ) was isolated from the aerial parts of Alternanthera littoralis 153 . The phenethylisoquinoline alkaloid (±)-7-benzyloxy-1-(3-benzyloxy-4-methoxyphenethyl)-1,2,3,4-tetrahydro-6-methoxy-2-methylisoquinoline oxalate ( 398 ) was targeted as a novel ABCB1 inhibitor based on high-throughput screening of a chemical library 154 ( Figure 23 ). Tomentelline C ( 399 ), tomentelline D ( 400 ), and 6,7-methylenedioxy-2-(6-acetyl-2,3-methylenedioxybenzyl)-1(2 H )-isoquinolinone ( 401 ) were obtained for the first time from Corydalis tomentella . They exhibited hepatoprotective activities 28 . Oleracein E ( 402 ) was isolated from the medicinal plant Portulaca oleracea 31 . Two undescribed isoquinoline alkaloids, pipermullesines B ( 403 ) and C ( 404 ), were isolated from the aerial parts of Piper mullesua 155 . Zhang et al . 156 isolated a structurally unusual cyclopenta[ de ]isoquinoline alkaloid, delavatine A ( 405 ), from Incarvillea delavayi . It exhibited substantial cytotoxicity and anti-inflammatory activities 157 . A novel tropoloisoquinoline alkaloid, neotatarine ( 406 ), was isolated from a 95% ethanol extract of the rhizome parts of Acorus calamus L in 2017 158 ( Figure 23 ).

As an important class of alkaloids, isoquinoline alkaloids have various chemical structures and pharmacological activities. However, the potential of this promising and expanding platform of active natural compounds has only been partially developed by both the academic community and the pharmaceutical industry to date. Over the past century, the discovery of morphine opened a new area for the development of central analgesic agents, and the application of berberine in the clinic has inspired a new wave for the discovery of alternative, green antibacterial drugs. During the past five years, the identification of additional new compounds, significant biological activities or novel mechanism of actions will undoubtedly contribute to the continual development of future new drugs. Continued attention and long-lasting research on the isolation and identification of naturally occurring isoquinoline alkaloids will open the way to targeted pharmacological modelling and synthetic modifications, resulting in new and better drugs based on the original effects of these alkaloids.

Isoquinoline alkaloids, an important class of N -heterocyclic bioactive natural products, are common throughout the plant kingdom 1 . They are likely derived from tyrosine or phenylalanine building blocks and show a wide range of structural diversity 2 . Since the first bioactive isoquinoline alkaloid, morphine, was isolated from the opium plant in the early 19th century 3 , this compound class has attracted considerable scientific attention. Increasing numbers of isoquinoline alkaloids have been isolated and identified from natural sources, and various studies have reported their antitumor, antimalarial, antibacterial, antifungal, antiparasitic and insecticidal, antiviral, anti-inflammatory, antiplatelet and other activities 4 - 12 . As lead compounds in the drug discovery and development process, isoquinoline alkaloids have high probabilities of success, 13 as reflected by several revolutionary drugs, such as the analgesic morphine, the antibacterial berberine, the antitussive codeine 14 , the antirheumatic sinomenine 15 , and the acetylcholinesterase inhibitor galanthamine 16 ( Figure 1 ). Therefore, the search for novel isoquinolines as promising drug leads remains an active area of study in natural product chemistry. In view of the importance and significant biological activities of isoquinoline alkaloid natural products, several thousand publications (journal articles, books and patents) on isoquinoline alkaloids have been recorded over the past 200 years. The increasing numbers of publications reflect the research intensity and importance of this field, as well as the bright prospect for drug development from these compounds. Some excellent earlier reviews on the chemical structures and biological properties of isolated isoquinoline alkaloids have contributed significantly to the general scientific understanding of this kind of compounds 5 , 6 , 8 , 9 , 10 , 11 , 12 , 17 - 21 . However, during the past five years, significant studies and novel technologies, such as metabolomics, were widely reported and used to identify alkaloids from plants. Many new compounds were isolated, and novel pharmacological activities and comprehensive mechanism of actions were investigated by researchers worldwide. Hence, a more comprehensive and up-to-date review is merited. Therefore, this review combines newer literature reports as well as presents the developments in this field particularly from the perspective of biological activities. It covers not only the chemical structures of isolated isoquinoline alkaloids ( Table 1 ), but also their biological activities and mechanism of actions. We hope that this review will provide new indications or directions for the development of these compounds as new clinically useful therapeutic agents.

In the search to find potential antitumor agents from isoquinoline alkaloids, the most commonly studied bioactivity is the cytotoxicity of new isolated and known compounds from plants. In this review, we list in Table 2 the inhibitory rates and the IC 50 values of compounds against various cancer cell lines corresponding to different human tumors, such as HL-60 (acute promyelocytic leukemia), Jurkat (acute T cell leukemia), MOLT-4 (acute lymphoblastic leukemia), A549 (lung carcinoma), H1299 (non-small cell lung cancer), COLO-201 (colorectal adenocarcinoma), AGS (gastric adenocarcinoma), PANC-1 (pancreas epithelioid carcinoma), A2780 (ovarian carcinoma), HeLa (cervix adenocarcinoma), MCF-7 (breast adenocarcinoma) and SAOS-2 (osteosarcoma). From this table, we found that most compounds exhibited moderate cytotoxicity with IC 50 values ranging from 10 to 50 μM 22 , 25 , 26 , 33 , 38 , 40 , 45 , 46 , 61 , 85 , 97 , 105 - 109 , 111 , 113 , 125 , 136 , 146 , 152 , 156 , 159 . Three Amaryllidaceae alkaloids, lycorine ( 321 ), haemanthamine ( 326 ) and haemanthidine ( 327 ), showed the best cytotoxicity against 17 human cell types with individual IC 50 values in the range of 0.30-9.80 μM compared with other compounds listed in Table 2 . Higher antiproliferative effects also were reported. Unfortunately, the cytotoxic activities of positive agents were not investigated in this reference 136 . The alkaloids caused cells to accumulate preferentially at G1 and G2 stages of the cell cycle with increased p16 expression and Chk1 Ser345 phosphorylation. Concerning a pro-apoptotic effect in the Jurkat leukemia cell line, compound 327 was more active than 326 130 . These results also provided a new clue for developing these alkaloids as potential antitumor agents. 8-Hydroxytubulosine ( 351 ) from Alangium longiflorum also exhibited remarkable antiproliferative activity. It presented better activities against A549, MDA-MB-231, MCF-7 and KB cell lines than the positive drug doxorubicin and the known alkaloid 9-demethyltubulosine ( 352 ). The IC 50 values of 351 were 0.21, 0.06, 0.12 and 0.09 μM, respectively 97 . The aporphine alkaloid (−)-norboldine ( 86 ) exhibited potent cytotoxicity towards pancreatic cancer cell line BxPC-3 with an IC 50 value of 27.06 μM, but no toxicity towards the normal pancreatic cell line 60 . Two oxoaporphines, 145 and 146 , showed cytotoxicity against glioma stem cells (GSC-3 # ) with IC 50 values of 32.52 and 32.81 μM, respectively, while the IC 50 of the antitumor drug taxol was 15.92 μM 46 . However, the antitumor activity in vivo and the mechanism underlying the cytotoxicity of the compounds are still unclear and should be studied further. During the past five years, numerous studies have investigated and reported antitumor mechanism of known and new isolated isoquinoline alkaloids. In this section, we will briefly introduce the antitumor mechanisms of some prominent molecules. Berberine ( 161 ) shows antitumor effects against various tumor cells. Noteworthy, it presents the strongest cytotoxicity against AZ521 cell with the IC 50 value of 2.60 μM, while the IC 50 of the antitumor drug cisplatin was 9.50 μM. Berberine inhibited cancer cell proliferation via several mechanisms of action, such as the positive regulation of reactive oxygen species and the apoptotic pathway as well as suppressed cancer metastasis by stopping transferase activity 160 - 163 . The potential targets also include mitochondrial function, DNA topoisomerase and arylamin N -acetyltransferase activity, NF- κ B signal pathway, the EGF and the VEGF receptors, etc. In human hepatoma cells, the alkaloid’s antiproliferative effect on might be mediated via the CAR metabolic and the arachidonic acid pathways, cPLA 2 , COX-2 gene expression and mitochondria-mediated apoptosis also were suppressed in vitro and in vivo 164 - 166 , and the IC 50 values against human hepatoma Bel-7404, H22 and HepG2 HCC cells were 9.21, 43.20 and 82.80 μM, respectively. However, the cytotoxicity of berberine against the normal hepatic embryonic cells was weak, the IC 50 value was 122.4 μM for the HL-7702 at 72 h. The further report showed that it blocked the caspase 3-iPLA 2 -AA-COX-2-PGE 2 pathway of ovarian cancer cells and reversed the repopulation, which was triggered by the chemotherapy drug VP16 167 . In breast tumors, berberine significantly down-regulated the expression of NF- κ B and proliferating cell nuclear antigen (PCNA) In vivo 168 . However, the targets of berberine against the different breast cancer are different, it activated caspase-9/cytochrome c-mediated apoptosis to inhibit the growth of two triple negative breast cancer cell (TNBC) lines (IC 50 43.28 μM for BT549 and 47.51 μM for MDA-MB-231 cells) in vitro 169 and inhibited the proliferation and migration of breast cancer ZR-75-30 cells (IC 50 5.30 μM) by targeting Ephrin-B2 170 . Reports indicated that berberine mediates epigenetic reprogramming via HDAC inhibition and regulates Bcl-2/Bax family proteins in the human lung cancer A549 cell line 171 . Furthermore, it inhibited the growth of intestinal polyps in animals and patients with the familial adenomatous polyposis and cell growth in colon cancer by down-regulating β-catenin signaling via binding RXRα 172 . In human glioblastoma cells, berberine induced senescence by down-regulating the EGFR-MEK-ERK signaling pathway 173 , and modulated the expression of epigenetic regulators in acute myelocytic leukemia cell lines HL-60/ADR and KG1-α 174 . The PI3K-Akt and mitogen-activated protein kinase (MAPK) signaling pathways in the treatment of thyroid carcinoma also were affected 175 , 176 . As an berberine isoquinoline alkaloid, coptisine ( 165 ) also affected PI3K/Akt and mitochondrial-associated apoptotic pathways 177 , it exhibited remarkably cytotoxic activities against HCT-116 cells by activating the caspase protease family, inducing G1-phase cell cycle arrest and increasing apoptosis 178 . The protoberberine alkaloid palmatine ( 166 ) induced cell apoptosis in MCF-7 breast cancer cells, after the treatment (1 μM, 10.8 J/cm 2 ) the early apoptotic and late apoptotic rates increased significantly up to 21.16% and 9.86% in photodynamic therapy 179 . Meanwhile, protoberberine stylopine ( 195 ) both functioned as an AKR1C3 inhibitor and significantly inhibited the AKR1C3-mediated reduction of the anthracycline drug daunorubicin within cells, the IC 50 was 0.9 μM in DHO assay 180 . Liensinine ( 62 ) induced apoptosis and mitochondrial dysfunction, and significantly inhibited the proliferation and colony-forming ability of colorectal cancer cells accompanied by activation of the JNK signaling pathway in a dose-dependent manner 181 . However, the structurally related neferine ( 61 ) sensitized A549 cells to low doses of doxorubicin and inhibited human lung cancer cell growth through MAPK activation and cell cycle arrest 182 , 183 . Through the mitochondria apoptosis pathway, 3,8-diolisoquinoline ( 1 ) and 1-methoxy-4,5-diolisoquinoline ( 2 ) induced apoptosis in U87 cells with the IC 50 values of 3.46 and 2.14 μM, the Bcl-2/Bax protein ratio also was down-regulated 22 . 6,7-Dimethoxy-1,2,3,4-tetrahydro-isoquinoline-3-carboxylic acid ( 7 ) had a significant anti-proliferative effect on human hepatoma (Huh-7) cells in vitro (EC 50 13.97 μM) by inhibiting the action of caspase-8 184 , and blocked IL-6/JAK2/STAT3 oncogenic signaling in dimethylhydrazine-induced colorectal carcinoma 185 . Good in vivo anti-neoplastic properties were also found 184 . Certain naphthylisoquinoline alkaloids are noteworthy due to their anti-pancreatic cancer activity. In one study 109 , ancistroyafungines A–D ( 259–262 ), 6- O -methylhamatine ( 235 ), 4′- O -demethylancistrocladine ( 236 ), ancistroguineine A ( 263 ), ancistrobertsonine A ( 264 ), ancistrobrevine B ( 265 ), ancistrotectoriline A ( 214 ), 6,5′- O,O -didemethylancistroealaine A ( 266 ), 6- O -demethylancistroealaine A ( 267 ), 7- epi -ancistrobrevine D ( 268 ), and ancistrocladiniums A ( 243 ) and B ( 269 ) showed moderate to strong anti-austerity activities against PANC-1 pancreatic cancer cells in a concentration-dependent manner. Their preferential cytotoxicity (PC) 50 values ranged from 7.60 to 67.80 μM. Among of these compounds, compound 259 (PC 50 , 22.7 μM) was found to be almost three times less active than its 5′- O -demethyl analog compounds 260 and 262 (PC 50 , 7.60 μM and 9.70 μM, respectively), which has two methoxy functions at C-5′ and C-4′. Structure-activity relationship (SAR) analysis indicated that O -methylation in the naphthalene portion and the substitution pattern of the isoquinoline portion play a crucial role for the cytotoxic activities of the alkaloids, especially an OMe/OH pattern seems favorable for the activity. In a second study, 111 ancistrobonsolines A 1 ( 281 ) and A 2 ( 282 ) also displayed significant PC against PANC-1 cells under nutrient-deprived conditions. Above reports suggest that the naphthylisoquinoline alkaloids are promising lead structures for the advancement of antitumor agents. The benzophenanthridine alkaloids chelidonine ( 300 ) and homochelidonine ( 301 ) potently induced cell death in several blood cancer cell lines, such as MOLT-4, Jurkat, HL-60, Raji, PBMCs, MRC-5 and WI-38, their IC 50 values ranged from 1.80 to >10 μM. For MOLT-4 and Jurkat cells, treatment with chelidonine induced cell cycle arrest at the G2/M cell cycle (IC 50 4.60 and 2.20 μM, respectively); treated with homochelidonine underwent biphasic dose-dependent G1 and G2/M cell cycle arrest in MOLT-4 cells (IC 50 4.80 μM), and an increase in G2/M cell population in Jurkat cells (IC 50 5.60 μM). Both alkaloids inhibited tubulin polymerization in A549 cells 125 . In addition, lycorine ( 321 ) presented the good therapeutic effect in a patient-derived glioblastoma xenograft by directly interacting with and inhibiting the activation of EGFR cancer cells 186 . The potent cytotoxicity against other various cancer cells, including HL-60, Jurkat, MOLT-4, A549, also were found with IC 50 values from 0.80 to 1.40 μM. Noroxyhydrastinine ( 22 ) exhibited potent melanogenesis-inhibitory activities by inhibiting the expression of protein levels of tyrosinase, TRP-1, and TRP-2 partly in a-MSH-stimulated B16 melanoma cells, the melanin content was 76.10% at 10.00 μM 33 , 159 . Multidrug-resistant (MDR) cancers present a critical clinical problem. Bringmann et al . have investigated the effects of naphthylisoquinolines. Mbandakamines C, D and F ( 291, 2923, 297 ) showed strong cytotoxic effects against human leukemia (CCRF-CEM) and MDR tumor cells (CEM/ADR5000) with IC 50 values from 1.50 to 19.94 μM 113 . This result indicated that the axial chirality is necessary to the bioactivity. Ancistectorine D ( 212 ) and ancistrobenomine B ( 220 ) also demonstrated comparable cytotoxic effects against both cell lines (IC 50 4.5 and 3.5 μM for 212 ; 25.83 and 21.38 μM for 220 ; 0.017 and 30.07 μM for positive control doxorubicin) 105 , 106 . The overexpression of ATP-binding cassette (ABC) transporters is a common mechanism leading to MDR cancer cells. Tetrandrine ( 57 ) and tangchinoline ( 58 ) from Stephania tetrandra reversed multidrug resistance by increasing the intracellular concentration of anticancer drugs and inhibiting P-glycoprotein activity in the MDR human cancer cells Caco-2 and CEM/ADR5000, the IC 50 values were 19.38 and 24.98 μM respectively for compound 57 49 . Hernandezine ( 51 ) selectively inhibited the transport function of the ABC drug transporter ABCB1 and enhanced drug-induced apoptosis in cancer cells at nanomolar concentrations (IC 50 3.85-27.25 nM). It could be further developed as a novel reversal agent for combination therapy in patients with MDR cancer due to its nontoxicity 45 . Scoulerine ( 204 ) exhibited promising suppression of cancer cell growth and reduced the mitochondrial dehydrogenases activity of the evaluated leukemic cells with IC 50 values ranging from 2.70 to 6.50 μM. Further study showed that it also interfered with microtubule elements of the cytoskeleton, checkpoint kinase signaling and p53 proteins 96 . Diabetes mellitus (DM) is mainly characterized by abnormal hyperglycemia, polydipsia, polyuria, polyphagia, and emaciation 187 , 188 , and persistent hyperglycemia can lead to several chronic diabetic complications, including neuropathy, nephropathy, cardiopathy, and retinopathy 189 . Currently, the global prevalence of DM is 8.5% among adults and is rising most rapidly in middle- and low-income countries 190 . Natural products have been increasingly applied to treat DM 191 , 192 . Over the past five years, the beneficial effects of berberines and protoberberine alkaloids on DM, atherosclerosis and hyperlipidemia have been proved in different animal models 193 , 194 . Berberine ( 161 ) affects multiple pathways, including p38 MAPK-GLUT4, JNK, and PI3K-Akt, related to the metabolism of glucose and lipids 89 , 195 . For anti-diabetic activity, berberine regulated the glyco- and lipo-metabolism and stimulated of adenosine 5′-monophosphate-activated protein kinase (AMPK) 196 in Zucker diabetic fatty (ZDF) rats, and also inhibited miR-106b/SIRT1 pathway by reversing miR-106b over-expression and up-regulating sirtuin 1 (SIRT1) both in islets of diabetic mice and pancreatic NIT-1 cells induced by high glucose 88 , 197 . By activating the AMPK pathway, the pioglitazone-induced bone loss in diabetic rats also were protected 198 . The toxic towards to mice or rats in vivo test is weak. Meanwhile, it may improve insulin resistance by increasing the expression of adiponectin receptors and the ratio of high-molecular weight to total adiponectin in rats fed a high fat diet (HFD) 199 , and improved glucose uptake and insulin-stimulated glucose consumption in palmitate-induced insulin-resistant H9c2 cardiomyocytes 200 - 202 . DM is closely related to the development of cardiovascular diseases 203 . Vascular dysfunction is a distinctive phenotype in DM, and diabetic vascular complication is associated with impaired endothelial function, augmented vasoconstriction, and increased oxidative stress 204 . Berberine can exert a cardio-protective effect by attenuating myocardial apoptosis via Notch1/Hes1-PTEN/Akt signaling as well as inhibiting excessive autophagy in cardiomyocytes through the regulation of AMPK and mTOR signaling 205 , 206 . In addition, berberine relieved cerebral arterial contractility in a STZ-induced diabetic rat model by regulating intracellular Ca 2+ management in smooth muscle cells and, thus, has an extra-protective effect on diabetic vascular dysfunction 207 . Diabetic nephropathy (DN) is a major cause of morbidity and mortality in patients with diabetes and is highly prevalent in end-stage renal disease 208 . Many studies have reported that berberine exhibits renoprotective effects in DN rats via regulating the various pathways, such as the PGE 2 -EP1-Gαq-Ca 2+ signaling pathway 209 , TLR4/NF-κB 210 and S1P2/MAPK signaling pathway 211 . Tang et al . 212 suggested that berberine (50-100 mg/kg) improved histopathological changes in the diabetic kidney, while it significantly reversed the diabetic-induced increases in the levels of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) as well as the decreases in the levels of β-arrestins 1 and 2. In NIT-1 pancreatic β cells, it inhibited PA-induced lipid accumulation by decreasing lipogenesis and increasing lipid oxidation 213 . In an experimental diabetic kidney model and high glucose-cultured glomerular mesangial cells (GMCs), berberine suppressed the expression of FN, ICAM-1, and TGF-β1 possibly by negatively regulating NF- κ B and RhoA/ROCK 214 , 215 . Furthermore, it inhibited the Sphk1/S1P signaling pathway and MAPK activation, lowered AP-1 activity, and ultimately deceased fibronectin overproduction 216 - 218 . In 2016, Zhou et al . 219 reported that berberine can positively affect DN by improving micro pathology and increasing neuritin expression via the MAPK pathway. In diabetic rats, the alkaloid exhibited renoprotective effects by changing the levels and regulation of the AGEs-RAGE-PKC-b-TGF-b1 signaling pathway 220 . Obesity has become a worldwide public health problem. It is an established risk factor for metabolic diseases including type 2 diabetes 221 , 222 and closely related to the metabolism of triacylglycerol (TG) in adipocytes. Adipose triglyceride lipase (ATGL) and hormone-sensitive lipase are rate-limiting enzymes that control the hydrolysis of TG. Berberine affects the metabolism of TG 223 by increasing the expression of ATGL and therefore stimulating basal lipolysis in mature adipocytes through the coupled mechanisms linked to the AMPK pathway 224 . In addition, coptisine ( 165 ), a related alkaloid, inhibited obesity-related inflammation in Syrian golden hamsters through the LPS/TLR4-mediated signaling pathway 225 . The aporphine isoquinoline alkaloid stephalagine ( 94 ) could be used as a potential anti-obesity agent due to its significant pancreatic lipase inhibitory activity (IC 50 8.35 μg/ml). 70 In 2016, berberine ( 161 ), coptisine ( 165 ), palmatine ( 166 ), epiberberine ( 163 ), and jatrorrhizine ( 162 ) were evaluated for antihyperglycemic, antidyslipidemic and antidiabetic hyperlipidemic effects in HepG2 cells and diabetic KK-Ay mice 226 . All five alkaloids effectively modulated hyperglycemia and hyperlipidemia. Berberine and coptisine promoted glucose consumption in vitro as well as suppressed fasting blood glucose level and improved glucose tolerance in vivo . In the mice, the levels of serum total cholesterol and triglycerides were decreased by palmatine and jatrorrhizine. Moreover, diminished hepatomegaly was found in jatrorrhizine-treated mice 226 . SAR analysis showed that the methylene-dioxy groups at C2, C3, C9, and C10 positions are the key functional groups for the antihyperglycemic and antihyperlipidemic effects. Briefly, the oxidized form of methylene-dioxy group at the C-2 and C-3 positions and/or at C-9 and C-10 positions of compound 163 would inhibit the activities of rat lens aldose reductase and human recombinant aldose reductase activities, and the methylene-dioxy group is very important to the binding activity of coptisine to β-cell membranes. Berberine and coptisine had better antihyperglycemic effects than compounds 162, 163, 166 that may be associated with the methylene-dioxy group at the C-2 and C-3 positions, because the C-2 and C-3 positions of the latter three compounds were substituted by methoxy group or phenolic hydroxyl group. In a subsequent study, a combination of the five alkaloids showed synergistic cholesterol-lowering in HepG2 cells and hypercholesterolemic hamsters, which was greater than that of the single alkaloids 227 . Activation of AMPK activation and alteration of neutral lipid metabolism may explain the hypoglycemic effect of berberine in differentiated cardiomyocytes 228 . Berberine and its metabolites exert lipid-lowering effects in human hepatoma cells metabolites likely by low density lipoprotein receptor up-regulation 229 . A meta-analysis of randomized clinical trials indicated that berberine can improve lipid profiles in dyslipidemia with acceptable safety 230 . He et al . 231 suggested that the related alkaloid coptisine might be used as an anti-hypercholesterolemia agent as it inhibited cholesterol synthesis by suppressing 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) expression and increasing the use and excretion of cholesterol through up-regulation of low-density lipoprotein receptor (LDLR) and CYP7A1 expression. Atherosclerotic coronary artery disease is a leading cause of death and disability in diabetic patients, and diabetic patients with atherosclerosis usually show moderate hyperhomocysteinemia (HHCY). Berberine increased atherosclerotic plaque stability in Apoe −/− mice with HHCY by activating the peroxisome proliferator-activated receptor-γ (PPARG) and suppressing oxidative stress in endothelial cells 232 . It also protected rat retinal Müller cells from high-glucose-induced apoptosis by enhancing autophagy and activating the AMPK/mTOR signaling pathway 233 . Acting on the TGFβ1-PI3K/Akt pathway, berberine reduced injury to podocytes caused by exosomes derived from high glucose-induced mesangial cells 234 . Berberine showed good effects on bone parameters in the treatment of HFD-fed/streptozocin-induced diabetic rats and, thus, could have therapeutic potential in diabetic osteoporosis 235 . Isoquinoline alkaloids exhibit good antibacterial and antifungal activities. A high content of berberine ( 161 ) is found in the well-known Chinese drug ( Huangliansu ) taken to treat intestinal infections caused by Escherichia coli , Bacillus dysteriae , and other microorganisms. The authors have recently described the significant antifungal activity of sanguinarine ( 299 ) and its possible use as a bio-fungicide for crop protection 236 . From 2014 to 2018, many publications have reported the antibacterial and antifungal activities of isoquinoline alkaloids; findings are briefly discussed below or listed in Table 3 . 23 , 71 , 77 , 237 , 94 , 146 . Berberine ( 161 ) exhibited antibacterial activity against Candida albicans with an MIC value of 75.53 μM. It affected the synthesis of membrane ergosterol and induced increased membrane permeability causing loss of intracellular material to the outer space (DNA/protein leakage) as well as membrane depolarization and lipid peroxidation of membrane constituents 238 . Berberine also effectively protected mice infected with Salmonella typhimurium 239 . Further studies reported that this alkaloid could treat H. pylori -induced chronic gastritis by attenuating the BAFF-triggered Th17 response 87 . Berberine as well as palmatine ( 166 ), coptisine ( 165 ), epiberberine ( 163 ), and jatrorrhizine ( 162 ) acted as concentration-dependent inactivators of urease with IC 50 values from 3.0 to 5087 μM for HPU ( Helicobacter pylori urease) and 2.3 to >10,000 μM for JBU (jack bean urease). Epiberberine was the most potent inhibitor against both ureases with IC 50 values of 3.0 μM for HPU and 2.3 μM for JBU and was more effective than the standard urease inhibitor acetohydroxamic acid (83 μM for HPU and 22 μM for JBU). The further studies showed that two methoxyl groups in the A ring as the polar systems and the dimethylene group in the D ring as the hydrophobic ring system of epiberberine are the functional structural groups for the potent urease inhibition. This alkaloid could be used in the treatment of diseases associated with ureolytic bacteria and could be further developed into a promising therapeutic approach for the treatment of urease-related diseases 240 . Meanwhile, berberine ( 161 ) and palmatine ( 166 ) suppressed Clostridium perfringens growth with MIC values of 44.7 and 52.2 μM, respectively 77 . In 2017, some manzamine alkaloids from Acanthostrongylophora sp. sponge were found to show antibacterial activity 146 . neo -Kauluamine ( 347 ) showed the best activity (MIC ~0.001 μM) against Bacillus subtilis , Kocuria rhizophila and Salmonella enterica , and 11-hydroxymanzamine J ( 342 ) had the best activity (MIC 0.053 μM) of all isolated compounds against Staphylococcus aureus and Proteus hauseri . MIC values of the positive drug ampicillin were around 0.001 μM. 3,4-Dihydromanzamine B N -oxide ( 341 ) and 31-hydroxymanzamine A ( 343 ) demonstrated marked activities against some tested microorganisms. neo -Kauluamine and the hydrogen chloride salt of manzamine J N -oxide displayed mild inhibition against isocitrate lyase from Candida albicans , and the latter manzamine alkaloid was the only compound with activity against bacterial sortase A 146 . The simple isoquinoline alkaloid carnegine ( 3 ) showed antibacterial activity with MIC ranging from 564-2259 μM against various strains. The time-kill curves indicated potent and rapid bactericidal activity 23 . Michellamine B ( 276 ), a dimeric naphthylisoquinoline alkaloid, inhibited E. coli MraY (IC 50 456 μM) and B. subtilis MraY (IC 50 386 μM) and showed antimicrobial activity against B. subtilis 241 . Photodynamic therapy was discovered at the beginning of the last century and mostly used as a cancer therapy; however, it has emerged as a promising treatment alternative against infectious diseases. The oxoaporphine alkaloid isomoschatoline ( 129 ) had an absorption profile with bands at 600-700 nm, was positive for singlet oxygen production and exhibited photodynamic antimicrobial activity against both gram-positive and gram-negative bacteria and some Candida ssp. yeast strains at sub-inhibitory concentrations 237 . Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that is resistant to many antibiotics and can cause various problems ranging from skin infections to pneumonia to bloodstream infections 242 . Much effort has been put into the fight against this bacterium. Berberine ( 161 ) was active in vitro against clinical isolates of MRSA and lowered the MICs of ampicillin and oxacillin 243 . It also was synergistic with ceftazidime and cefepime against MRSA 41 . Bacteria do not develop resistance to berberine since its MIC within the same bacterial cultures ( E. coli, S. aureus, B. subtilis, Proteus vulgaris, S. typhimurium and Pseudomonas aeruginosa ) did not increase over 200 generations 244 . Dihydrocheleryhtrine ( 312 ) and N -methylcanadine ( 200 ) from Zanthoxylum tingoassuiba presented anti-MRSA activity against the four tested clinical isolates S. aureus strains 1-4 (MIC ranging from 76.9 to 307.8 μM) and were more active than chloramphenicol against strain 4 and ATCC25923 94 . N -Formyl-asimilobine-2- O -β-D-glucoside ( 95 ) was equipotent against S. aureus and MRSA strains; the inhibition zone against both strains was 8.0 mm in diameter. The inhibitory diameters with the positive control kanamycin sulfate were 40 and 34 mm, respectively 71 . Bavarsadi et al . 245 reported that the administration of incremental levels of sanguinarine ( 299 ) decreased microbial counts in the ileum and improved other intestinal health indices in laying hens. Antiviral activity is one of the important bioactivities for berberine ( 161 ). In vitro , it regulated signaling pathways related to inflammation, such as NF- κ B 246 and AMPK/mTOR 247 signaling pathways. In addition, berberine attenuated autophagy in adipocytes by targeting BECN1 248 and inhibited the replication of respiratory syncytial virus (RSV), herpes simplex virus (HSV), human papillomavirus (HPV), and human cytomegalovirus (HCMV) 249 - 251 . Berberine suppressed viral infection-induced up-regulation in the TLR7 signaling pathway, such as TLR7, MyD88, and NF- κ B (p65), at both the Mrna and protein levels, as well as significantly inhibited the viral-induced increases in Th1/Th2 and Th17/Treg ratios and inflammatory cytokine production 252 . In addition, berberine inhibited EV71 replication by down-regulating autophagy and the MEK/ERK signaling pathway, while the 50% toxicity concentration (TC 50 ) was 73.10 μmol/L in Vero cells and the TC 50 of the positive agent pirodavir was 27.49 μmol/L 253 . Corydine ( 90 ) and norisoboldine ( 91 ), aporphine alkaloids from Croton echinocarpus leaves, displayed significant in vitro anti-HIV potential. The latter compound more potently inhibited HIV-1 reverse transcriptase enzyme activity 69 . Several michellamine-type dimeric naphthylisoquinoline alkaloids inhibited replication of HIV reference strain IIIB/LAI in A3.01 T lymphoblast cell cultures: michellamine A 2 ( 270 ) (IC 50 , 29.6 μM), A 3 ( 271 ) (IC 50 , 15.2 μM), A 4 ( 272 ) (IC 50 , 35.9 μM), and B ( 276 ) (IC 50 , 20.4 μM). However, michellamines A ( 275 ) and B 3 ( 274 ) were not active 110 . Emetine ( 348 ) inhibits protein synthesis in mammalian, yeast and plant cells by inhibiting the aminoacyl-sRNA transfer reaction at the 40S ribosomal subunit 254 - 256 . It also inhibits DNA synthesis in mammalian cells 257 . Emetine inhibited replication of DNA viruses [buffalopoxvirus (BPXV) and bovine herpesvirus 1 (BHV-1)] as well as RNA viruses [peste des petits ruminants virus (PPRV) and Newcastle disease virus (NDV)]. After treatment, the syntheses of viral RNA (PPRV and NDV) and DNA (BPXV and BHV-1) as well as viral entry (NDV and BHV-1) were reduced and inhibited. Emetine significantly inhibited replication of NDV. Moreover, this alkaloid significantly inhibited BPXV-induced pock lesions on chorioallantoic membrane (CAM) along with associated mortality of embryonated chicken eggs. It significantly delayed NDV-induced mortality in chicken embryos associated with reduced viral titers. Hence, emetine could have significant therapeutic value against certain viruses by inhibiting viral RNA and DNA replication without producing an antiviral drug-resistant phenotype 148 . Japanese encephalitis virus (JEV) is a major cause of severe encephalopathy. Huang et al . 258 suggested that the protoberberine isoquinoline alkaloid (−)-tetrahydropalmatine ( 192 ) could be a strong drug candidate for the treatment of JEV infection, because it exhibited a neuroprotective effect in a JEV strain GP-78 infected mouse model. The major isoquinoline alkaloid berberine ( 161 ) exerts significant anti-inflammatory activity 259 , 260 and could be used to treat inflammation and other related diseases via different mechanisms of action, for example, ischemic stroke through downregulation of pro-inflammatory cytokines and upregulation of anti-inflammatory cytokines 261 or acute pancreatitis via JNK deactivation 262 . Meanwhile, berberine suppressed Th17 responses and improved chronic relapsing colitis induced with dextran sulfate sodium (DSS) in C57BL/6 mice 263 . The alkaloid also improved the survival of septic and LPS-intoxicated mice and decreased inflammation and tissue injuries in the lung, spleen and gut as well as improved disrupted energy utilization, oxidative status, amino acid metabolism and nucleic acid metabolism 264 , 265 . In macrophages, berberine has no cellular toxicity on RAW264.7 cells at the concentration up to 5 μM, however, it inhibited M1 polarization via the AKT1/SOCS1/NF- κ B signaling pathway 266 and exerted anti-inflammatory effects by inhibiting NF- κ B signaling via Sirt1-dependent mechanisms at the same concentration 267 . Furthermore, by inhibiting TH17 cell response, berberine could exert an anti-arthritic effect and improve various autoimmune diseases, such as rheumatoid arthritis 268 . It suppressed NLRP3 (nucleotide-binding oligomerization domain-like receptor [NLR] pyrin domain-containing-3) inflammasome activation in monosodium urate (MSU) crystal-stimulated RAW 264.7 macrophages and pro-inflammatory cytokines through the upregulation of Nrf2 (nuclear factor erythroid-2-related factor 2) transcription factor and alleviated MSU crystal-induced inflammation in rats 269 . One mechanism of action against rheumatoid arthritis was inhibition of IL-21/IL-21R-mediated inflammatory proliferation via attenuation of the PI3K/Akt signaling pathway and amelioration of IL-21 mediated osteoclastogenesis 270 . Norisoboldine ( 91 ) exerts anti-arthritic activity via anti-inflammatory and immune-regulatory effects. Mechanism of action studies showed that this alkaloid prevented both the infiltration of inflammatory cells and destruction of bone and cartilage in joints in adjuvant-induced arthritic rats, as a substrate of P-glycoprotein (P-gp) 271 - 273 . The anti-arthritic mechanism involved inhibition of inflammatory synovial hyperplasia by promoting the release of cytochrome C and regulating the expression of Bax and Bcl-2 proteins via a mitochondrial-dependent pathway 274 , as well as prevention of synovial angiogenesis by moderating the Notch1 pathway-related endothelial tip cell phenotype 275 , 276 . Tong et al . 277 suggested that norisoboldine induced the generation of intestinal Treg cells by the activation of AhR (aryl hydrocarbon receptor) as well as promoted Treg differentiation and then reduced the development of colitis by regulating AhR/glycolysis axis and subsequent NAD + /SIRT1/SUV39H1/H3K9me3 signaling pathway 278 . Furthermore, norisoboldine reduced IL-1β production in LPS-stimulated RAW264.7 cells and decreased the serum level of IL-1β in collagen-induced arthritis 273 , 279 . Finally, the compound inhibited activation of the NLRP3 inflammasome by regulating the AhR/Nrf2/ROS signaling pathway and thereby improved the TNBS (2,4,6-trinitrobenzene sulfonic acid)-induced colitis in mice 271 . Nuclear transcription factor- κ B (NF- κ B) plays an important role in inflammation, sepsis and immunity 280 . Hence, great attention has been focused on compounds that produce inhibitory effects on the NF- κ B pathway. Demethyleneberberine ( 164 ) reduced inflammatory responses by inhibiting the NF- κ B pathway and regulating the balance of Th cells 281 . Chelidonine ( 300 ) also significant inhibited NF- κ B activity and related pathways at the concentrations of 5-20 μM, such as the TLR4/NF- κ B signaling pathway, in HCT116 cells and RAW264.7 macrophages 282 , and it did not display cytotoxic effect with concentrations up to 20 μM. These results indicated that NF- κ B pathway is very important to the anti-inflammatory activity of isoquinoline alkaloids. In addition, this alkaloid inhibited mitogen-activated protein kinase pathway activation by blocking c-Jun N -terminal kinase and p38 phosphorylation 283 . Salutaridine ( 366 ), dauricumine ( 369 ), dauriporphine ( 128 ) and cheilanthifoline ( 197 ) significantly inhibited receptor activator of NF- κ B ligand-induced differentiation of mouse bone marrow-derived macrophages into multinucleated osteoclasts 73 . Zhang et al . 156 reported that delavatine A ( 406 ) significantly decreased LPS-induced activation of NF- κ B by suppressing the p65 subunits and the phosphorylation of I κ B α 157 . Palmatine ( 166 ) promoted the proliferation of goat endometrial epithelial cells at the concentrations of 10–100 μg/mL, and reduced LPS-induced inflammatory responses through inhibition of the TRIF-dependent NF- κ B pathway 284 . Boldine ( 85 ) and reticuline ( 23 ) from Litsea cubeba exerted anti-inflammatory activity and potential synergistic effects in vivo partly by inhibiting the expression of pro-inflammatory cytokines, such as TNF-α and IL-6, perhaps resulting from interaction with JAK2/STAT3 and NF- κ B pathways 67 . Tetrandrine ( 57 ) inhibited I κ Bα and NF-κB p65 phosphorylation in LPS-induced RAW 264.7 and chondrogenic ATDC5 cells 285 . Coptisine ( 165 ) inhibited IL-1β-induced inflammatory responses by suppressing the NF- κ B and MAPK pathways signaling pathway, as well as suppressing the expression of iNOS, COX-2, matrix metalloproteinase-3 (MMP-3) and MMP-13, and NF- κ B activation in IL-1β-induced human OA chondrocytes 286 , 287 . Other anti-inflammatory mechanisms of action of isoquinoline alkaloids were also investigated. Palmatine ( 166 ), which has been used to treat abdominal pain, enteritis, gastritis, chronic endometritis, and pelvic inflammation, exerted protective effects on acute and chronic inflammation in experimental animal models 288 - 290 . Zhou et al . 291 reported that this compound exerted chondroprotective effects in IL-1β-induced rabbit chondrocytes and an experimental OA model by inhibiting the Wnt/β-catenin and Hedgehog signaling pathways. As a potent IDO-1 inhibitor, palmatine improved dextran sulfate sodium-induced colitis by mitigating colonic injury, preventing gut microbiota dysbiosis, and regulating tryptophan catabolism 292 . Compared with mice administered TNBS, mice treated with capnoidine ( 378 ) showed significantly improved clinical symptoms as well as reduced colon pathology and histological inflammation in the colon. Moreover, inflammatory cytokines profiles within the colon were altered and levels of p-I κ B-α (Ser32) and p-NF- κ B p65 (Ser536) were reduced 151 . Alkaloids from Portulaca oleracea inhibited NO production in lipopolysaccharide-induced murine macrophage RAW 264.7 cells (EC 50 18.0–498 μM). Among them, oleracein E ( 403 ) and ( S )-(−)-salsolinol (15 ) were more potent (EC 50 35.4 and 58.7 μM, respectively) than the positive control 3,4-dihydroxybenzohydroxamic acid. Additionally, some alkaloids showed β2-adrenergic receptor (β2-AR) agonist activity in the CHO-K1/GA15 cell line, which stably expresses β2-AR as detected by a calcium assay. The EC 50 value of ( R )-(+)-1-benzyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline was 87.9 nM 31 . Corynoline ( 314 ) from Corydalis bungeana inhibited inflammatory mediators in LPS-stimulated RAW264.7 cells and attenuated LPS-induced acute lung injury in mice by activating Nrf2 129 , 293 , 294 . The unique alkaloid dactyllactone A ( 126 ) inhibited the expression of IL-1β and PGE2 in a dose-dependent manner in LPS-induced RAW264.7 cells 78 . Decarine ( 313 ) significantly inhibited IL-6 and IL-8 production in TNF-α + IL-1β-induced Caco-2 cells at a concentration of 20 μM 128 . 6a R -2′-Carboxylthaliadine ( 116 ), 3-methoxy-2′-methoxycarbonyl-oxohernandalincin ( 141 ), predicentrine ( 119 ), oxopurpureine ( 143 ) and laudanosine ( 43 ) from Thalictrum cirrhosum . significantly inhibited T lymphocytes with IC 50 values of 43.90, 40.80, 43.70, 39.70 and 42.30 μM, respectively 43 . Berberine hydrochloride ( 161 ) has beneficial effects against cellular oxidative stress 295 , 296 . It reduced H 2 O 2 -induced growth inhibition and DNA damage as well as apoptosis in C2C12 cells by suppressing the accumulation of intracellular reactive oxygen species via activation of the Nrf2/HO-1 pathway 297 . Additionally, the alkaloid improved the antioxidant status of intestinal tissue in mice 298 . The related alkaloid coptisine ( 165 ) exerted an antioxidant activity against AAPH-induced toxicity by activating Akt and JNK/Nrf2/NQO1 pathways 299 . The bisbenzylisoquinoline alkaloid (−)- O - O -dimethylgrisabine ( 36 ) exhibited potent antioxidant activity (44.3%) in the reducing power assay and IC 50 values of 18.38 and 64.30 μg/mL in DPPH and metal chelating assays, respectively. Thus, it is a good reductant with the ability to chelate metals and prevent pro-oxidant activity 38 . By preventing NF- κ B translocation, neferine ( 61 ) from the same compound classification protected muscle cells from oxidative stress. It also prevented apoptosis by decreasing the mitochondrial membrane potential and reactive oxygen species (ROS) production in cells subjected to hypoxia as well as inhibited the expression of the downstream regulator COX-2 59 , 300 . Two aporphine isoquinoline alkaloids, (−)-boldine ( 85 ) and (−)-norboldine ( 86 ), exhibited good to low potency in three antioxidant activity assays, DPPH (IC 50 136.96, 255.21 μM), reducing power (34.37, 52.10%), and metal chelating (IC 50 785.64, 501.55 μM) 59 . Two other aporphines, isocorydine ( 92 ) and norisocorydine ( 93 ), also showed antioxidant effects in these assays 59 . The protoberberine phellodendrine ( 198 ) showed good antioxidant effects in vivo . It improved the decreased survival rate and abnormally elevated heart rate of zebrafish embryos. In vitro, the compound decreased the increased ROS production, lipid-peroxidation and cell death rate caused by AAPH-induced oxidative stress, most likely by down-regulation of AKT phosphorylation and NF- κ B3 expression 93 . Oleracein E ( 403 ) has a rare tetrahydroisoquinoline/pyrrolidone tricyclic skeleton and a catechol moiety 301 . It improved cognitive function, reversed abnormal brain antioxidant biomarkers (GSH, T-AOC, MDA and SOD) to normal levels, and inhibited hippocampal neuronal apoptosis in d -galactose/NaNO 2 -induced senescent mice and in some apoptotic indices induced by AlCl 3 302 , 303 . Parasitic diseases present a threat worldwide, particularly among developing countries, and cause considerable morbidity and mortality globally. Examples include trypanosomiasis, leishmaniasis and schistosomiasis 304 - 310 . Compared with synthetic molecules, natural products are believed to have significant advantages as lead compounds against these diseases, and some isoquinoline alkaloids have demonstrated antiparasitic activity. The naphthylisoquinoline alkaloid ancistectorine D ( 212 ) showed the highest potency against the protozoan parasites Trypanosoma cruzi and Leishmania donovani with IC 50 values of 4.40 μM and 1.20 μM, respectively, while ancistrobonsolines A 1 and A 2 ( 281, 282 ) showed weak-to-moderate antiprotozoal activities 111 . The bisbenzylisoquinoline 6,5′,6′,7′,12-pentamethoxy-2,2′-dimethyloxyacathan ( 50 ) effectively killed both wild type L. donovani (EC 50 6.8 μM) and sodium antimony gluconate (SAG)-resistant promastigotes (EC 50 8.2 μM). Also, at a concentration of 50 μM, it almost completely inhibited the protozoan DNA topoisomerase IB activity 44 . Alternamine A ( 397 ) showed moderate antiprotozoal effects against T. cruzi trypomastigotes and L. amazonensis amastigotes with IC 50 values of 0.23 and 0.16 μM, respectively. The IC 50 values of the positive drugs (crystal violet against T. cruzi and amphotericin B against L. amazonensis ) were 0.18 and <0.01 μM 153 . Ealapasamines A–C ( 287–289 ) exhibited excellent in vitro antimalarial activity against chloroquine-sensitive (NF54) and chloroquine-resistant (K1) strains of the malaria parasite P. falciparum ; the IC 50 values were 418, 210 and 34 nM (NF54) and 452, 138 and 6.3 nM (K1). Thus, ealapasamine C was the most active naphthylisoquinoline against the resistant strain K1. Its cytotoxicity was comparatively low (6.0 μM), giving a high selectivity index of nearly 1000 106 . Dioncophyllines F, C 2 and D 2 ( 249–251 ) showed high and specific activity against P. falciparum 108 , while mbandakamines C ( 291 ) and D ( 292 ) exhibited promising activity against the same parasite 32 . Two morphinandienones, (+)-sebiferine ( 353 ) and (−)-milonine ( 354 ), from Dehaasia longipedicellata showed potent to moderate activity against a chloroquine-resistant strain of P. falciparum K1 with IC 50 values ranging from 0.03 to 30.40 μM. (−)-Milonine exhibited potent activity with an IC 50 value of 0.10 μM, comparable to that of the positive standard, chloroquine (0.09 μM). Meanwhile, they showed no toxicity towards the normal pancreatic cell line (hTERT-HPNE) 60 . Bisbenzylisoquinolines also exhibit significant antiparasitic activity. In 2014, Omole et al . 48 found that two new bisbenzylisoquinoline (−)-pseudocurine ( 55 ) and (−)-pseudoisocurine ( 56 ) exhibited strong to moderate anti-plasmodial activity against both strains of P. falciparum D6 (CQ-susceptible) (IC 50 0.49 μM, 1.26 μM), and W2 (CQ resistant) (IC 50 0.522 μM, 2.798 μM). (−)- O - O -Dimethylgrisabine ( 59 ), isolated from Dehaasia longipedicellata , exhibited significant activity against a chloroquine-resistant strain of P. falciparum K1 with an IC 50 value of less than 0.031 μM and no toxicity towards the normal pancreatic cell line (hTERT-HPNE) 38 . (+)-Laurotetanine ( 87 ) and (+)-norstephasubine ( 69 ) exhibited strong antiplasmodial activity against P. falciparum strain K1 with IC 50 values of 0.19 and 0.12 μM, respectively 68 . Two aporphines, (−)-boldine ( 85 ) and (−)-norboldine ( 86 ), showed moderate activity against a chloroquine-resistant strain of P. falciparum K1 with IC 50 values of 2.60 and 9.28 μM, respectively, while that of chloroquine was 0.09 μM. Isocorydine ( 92 ), norisocorydine ( 93 ) and boldine ( 85 ) bound free heme and neutralized the electrons produced during the P. falciparum -mediated hemoglobin destruction and prevented oxidative damage in the host 60 . Stephanine ( 149 ), a dehydroaporphine, displayed antiplasmodial activity against P. falciparum strains 3D7 and W2 with IC 50 values of 0.69 μM and 1.32 μM, but its cytotoxicity against 184B5 cells led to low selectivity indexes (9.10 and 4.70). The positive drug chloroquine had IC 50 values of 2628.3 and 134.2 against the two respective parasite strains. Berberine chloride ( 161 ), coptisine chloride ( 165 ), palmatine chloride ( 166 ) and dehydrocorydaline nitrate showed strong anti-malarial effects (IC 50 90%) 311 . Berberine also displayed in vivo anticoccidial activity 312 . Among four isoquinoline alkaloids, sanguinarine ( 299 ) presented the strongest insecticidal activity against 3rd instar Lymantria dispar with a LD 50 value of 4.96 μg/larva. The rank order of insecticidal capacity was sanguinarine > chelidonine ( 300 ) > berberine hydrochloride ( 161 ) > coptisine ( 165 ), and the methylenedioxyphenyl(l,3-benzodioxole) group might play a key role in the larvicidal activity on L. dispar . Except for coptisine, the alkaloids also significantly reduced the food intake of the larvae and suppressed activity of digestive enzymes. Hence, the alkaloids induced antifeeding and larval lethality on L. dispar larvae 124 . Heitziquinone ( 308 ) from Zanthoxylum heitzii presented the weak or inactive toxicity against brine shrimp ( Artemia salina ) 127 . Cis - and trans -protopinium ( 187, 188 ) from Fumaria parviflora showed nematicidal activity against the southern root-knot nematode Meloidogyne incognita . In an in vitro study, the application of cis- and trans -protopinium at a concentration of 561.18 μM to nematode eggs and second stage juveniles for 120 h of incubation led to 100% values for the area under cumulative percent hatch inhibition and mortality. In the greenhouse and field settings during spring and autumn, application of the alkaloids at a concentration of 841.77 μM significantly reduced the nematode galling index, the number of females per gram of root, and the reproduction factor, as well as increased plant height, fresh and dry shoot weights, and root length 91 . Alzheimer’s disease (AD), a common neurodegenerative disease, is characterized by low levels of the neurotransmitter acetylcholine in the brain region involved with cognition. Berberine was highly tolerated when taken orally and freely blood-brain-barrier permeable 313 . Hence, it shows significant promise and activity for treating numerous neurodegenerative conditions, including Alzheimer’s, Huntington’s, and Parkinson’s diseases 314 , 315 . Berberine ( 161 ) provided neuroprotection via inhibition of the mTOR signaling pathways and activation of cell survival and antioxidative signaling pathways, such as up-regulated PI3K/AKT/Bcl-2 and Nrf2/HO-1 antioxidative signaling pathways 246 , 316 . Berberine reduced the accumulation of amyloid β (Aβ) and decreased the expression of β-site APP cleaving enzyme-1 by activating AMPK in N2a mouse neuroblastoma cells stably expressing human Swedish mutant APP695 (N2a/APP695sw), N2a cells 316 , and also inhibited Aβ-protein-induced apoptosis in primary cultured hippocampal neurons via the mitochondria-related caspase pathway 317 . Subsequently, Huang et al . 318 suggested that berberine improves cognitive impairment by promoting autophagic clearance and inhibits production of Aβ in an APP/tau/PS1 mouse model of Alzheimer’s disease. Furthermore, berberine presented a neuroprotective effect against environmental heavy metal-induced neurotoxicity and Alzheimer’s-like disease in rats via its anti-inflammatory/antioxidant mechanisms 319 . Postoperative cognitive dysfunction (POCD) is a significant cause of morbidity after surgery, especially in elderly patients. In an in vivo study, berberine alleviated POCD by suppressing neuroinflammation in aged mice and, in an in vitro study, it suppressed LPS stimulated production of TNF-α and IL-1β in BV2 cells 320 . Meanwhile, the alkaloid markedly improved aging-related reductions in cognitive ability and muscular function and activation of the AMPK/SIRT1/PGC-1α pathway in skeletal muscle 321 . Also, berberine is a potential alternative therapy for TDP-43-related neuropathology in frontotemporal dementia and amyotrophic lateral sclerosis 322 . Depression is the most common mental disorder in humans. Berberine up-regulated BDNF expression in the hippocampus to lessen corticosterone-induced depressive-like behavior in mice 323 and enhanced dopamine expression to alleviate symptoms of anxiety in rats with post-traumatic stress disorder 324 . It also exerted antidepressant-like effects in ovariectomized mice and decreased immobility time in a dose-dependent manner. Berberine’s activation of the 5-HT 2 receptor via the BDNF-CREB and eEF 2 pathways activation may be partially related to these antidepressant-like effects. Furthermore, after berberine treatment, greater reduction was seen in c-Fos induced by ovariectomy 325 . Epileptogenesis transforms a normal brain to an epileptic condition, eventually leading to seizures. Status epilepticus is a life-threatening neurologic condition with seizures of longer duration. Studies showed that berberine relieved status epilepticus and spontaneous recurrent seizures in an intrahippocampal kainite model of epilepsy and exerted neuroprotective effect via suppression of oxidative stress, neuroinflammation, and possibly apoptosis. Berberine also reduced cognitive deficits and hyperphosphorylation of tau by inhibiting the activation of the NF- κ B signaling pathway 326 . Cholinesterase (acetylcholinesterase, AChE; butyrylcholinesterase, BChE) inhibitors enhance cholinergic function by prolonging the availability of ACh released into the neuronal synaptic cleft. While several isoquinoline alkaloids, (+)-nornantenine ( 88 ), (+)-laurotetanine (79), (+)- N -methyllaurotetanine ( 89 ), (+)-oridine ( 153 ), (+)- N -methylisococlaurine ( 24 ) and (+)-reticuline ( 23 ), were inactive or exhibited poor inhibitory effects against AChE (IC 50 > 200 μM), they exhibited a wide range of BChE inhibitory activity (IC 50 3.95–288.34 μM) 37 . The protoberberine alkaloids (−)-stylopine ( 195 ) and (−)-sinactine ( 196 ) displayed weak inhibitory activity against AChE; however, sinactine potently inhibited the activity of prolyl oligopepetidase (POP), a neuronal enzyme involved in cognitive disorders, with IC 50 of 53 μM 24 . Protopine ( 210 ) and cryptopine ( 211 ) showed weak inhibitory activities against AChE (IC 50 230 and 209 μM) and BuChE (IC 50 477 and 271 μM) 24 . Among phthalideisoquinoline alkaloids, (−)-mucroniferanine D ( 382 ), mucroniferanine F ( 384 ) and mucroniferanine G ( 385 ), exhibited AChE inhibitory activities with IC 50 values of 28.3, 12.2 and 11.3 μM, respectively 99 , while (+)-bicuculline ( 372 ) was only weakly active against AChE, BuChE, and POP with higher IC 50 values of 626 μM, 329 μM and 190 μM, respectively 24 , 150 . The pyrrolophenanthridine alkaloids seco-isopowellaminone ( 336 ), haemanthamine ( 326 ) and incartine ( 337 ) also exhibited weak anti-human AChE activity 138 . (+)-Parfumidine ( 79 ), a spirobenzylisoquinoline alkaloid, exhibited POP inhibitory activity with an IC 50 value of 99 μM, compared with 3.27 μM for the positive drug (Z)-pro-prolinal 24 . The known benzophenanthridine alkaloid chelerythrine potently and selectively inhibited an isoform of recombinant human monoamine oxidase A (MAO-A) with an IC 50 value of 0.55 μM. It acted as a reversible competitive inhibitor (IC 50 0.22 μM) and was more potent than the antidepressant drug toloxatone (IC 50 1.10 μM), which also is a selective, reversible MOA inhibitor. Chelerythrine can be deemed a potential lead compound for the design of novel reversible MAO-A inhibitors 327 . Berberine ( 161 ) caused signification reduction in hepatic steatosis 328 , 329 . Although its bioavailability was less than 1% in some studies 330 , 331 , the alkaloid was typically concentrated in the liver after oral administration 332 . Berberine exerts anti-hyperglycemic and anti-dyslipidemic effects and can also ameliorate nonalcoholic fatty liver disease (NAFLD) via regulation of the hepatic SIRT1-UCP2 pathway 332 - 334 . By regulating cholesterol metabolism and inhibiting COX2-prostaglandin synthesis, the compound improved blockade of autophagic flux in the liver 335 . Moreover, berberine lessened the deposition of triglycerides in the liver following intraperitoneal injection or oral gavage 336 . It also protected against methotrexate-induced liver injury and attenuated oxidative stress and apoptosis, possibly through up-regulating the Nrf2/HO-1 pathway and PPARγ 337 . Moreover, berberine reduced staphylococcal enterotoxin B-mediated acute liver injury via regulation of HDAC expression 338 . Wang et al . 339 investigated the effects of tetrahydroberberine ( 179 ) and tetrahydropalmatine ( 192 ) on the expression of mouse liver cytochrome P450s and their liver toxicity in mice. Tetrahydroberberine induced mRNA expression of Cyp1a2 , Cyp3a, and Cyp2e1 , while tetrahydropalmatine inhibited Cyp1a2 . While oral tetrahydroberberine increased mouse serum aspartate transaminase, total bilirubin, and liver malondialdehyde levels, as well as induced liver edema, tetrahydropalmatine did not cause such effects. In 2018, study results showed that tiliamosine ( 54 ) could be used to treat non-alcoholic steatohepatitis 53 . Norsanguinarine ( 316 ), (−)-6-acetonyldihydrisanguinarine ( 317 ) and cavidilinine ( 318 ) from Corydalis tomentella exhibited moderate hepatoprotective activities at a concentration of 10 μM 28 . At a concentration of 10 μM, three stereoisomeric isoquinoline alkaloids (9 S ,7′ S ) tomentelline A ( 374 ), (9 S ,7′ R ) tomentelline A ( 375 ), (9 R ,7′ S ) tomentelline B ( 376 ), together with hendersine B methyl ester ( 46 ), bicucullinine ( 47 ), hendersine B ( 48 ), and (+)-capnoidine ( 378 ) presented moderate hepatoprotective activities with relative survival rates of 33.28–52.57% 28 . The aporphine alkaloid norpurpureine ( 101 ) exhibited activity (IC 50 80 μM) against platelet aggregation stimulated by adenosine 5′-diphosphate (ADP), collagen and thrombin. It gradually inhibited granule secretion and adhesion of activated platelets to immobilized fibrinogen. At the intra-platelet level, norpurpureine prevented agonist-stimulated calcium mobilization and cAMP reduction. Its molecular target could be an effector common effector to Ca 2+ and cAMP signaling, such as the PLC-PKC-Ca 2+ pathway and phosphodiesterases 74 . In addition, the isoquinoline alkalkaloid berberine ( 161 ) has been associated with myocardial protective effects 340 - 342 . By differentially modulating the activities of p-STAT1, p-STAT3 and p-STAT4 and, thus, suppressing Th17 and Th1 cell differentiation, the compound protected against myosin-induced myocardial injury in rats 340 . Subsequent reports showed that berberine protected the heart from ischemia/reperfusion injury induced by NaH 2 PO 4 partly though reducing myocardial autophagy and apoptosis via the AMPK/mTOR and AK2/STAT3 signaling pathways in vivo and in vitro 343 , 344 as well as reducing the striatum apoptosis via activation of the BDNF-TrkB-PI3K/Akt signaling pathway in the middle cerebral artery occlusion-induced cerebral ischemia/reperfusion model 345 . The related compound coptisine ( 165 ) also attenuated pro-inflammatory cytokines, including IL-1β, IL-6, and tumor necrosis factor-α, in heart tissue after myocardial ischemia/reperfusion injury 346 . Neferine ( 61 ), a bisbenzylisoquinoline-type alkaloid, prevented hyperglycemia-induced endothelial cell apoptosis through suppression of ROS/Akt/NF- κ B 347 . Also, it blocked Na v 1.5 channels in myocardia under the open and inactivating states and, thus, was an open channel blocker of Na v 1.5 channels 348 , 349 . Finally, ambinine ( 315 ), a benzophenanthridine alkaloid, had protective effects on H9C2 myocardial cells. It demonstrated anticoagulation and thrombolytic effects in vitro by significantly degrading blood clots and delaying plasma recalcification time in a dose-dependent manner (1.21-4.84 mM) 228 . Gastric ulcers are one of the most common gastrointestinal disorders. The anti-ulcer/gastroprotective effect of berberine ( 161 ) might involve positive regulation of antioxidant and anti-inflammatory status mediated, at least partially, through the Nrf2 signaling pathway and p38 MAPK translocation 350 . Palmatine ( 166 ) hydrochloride tablets have been used clinically to cure intestinal and gynecological inflammation, bacillary dysentery, respiratory and urinary tract infections, surgical infections and eye conjunctivitis. Wang et al . 351 also reported that this alkaloid may protect the gastric mucosa by increasing PGE 2 and decreasing PAF as well as against gastric ulcers, perhaps associated with anti-inflammatory status. After orally administrating palmatine for seven consecutive days, ulcer areas were significantly decreased with inhibitory rates of 51% to 62%. Cavidine ( 194 ), a protoberberine isoquinoline alkaloid and potent inhibitor of COX-2, exerted a gastroprotective effect against gastric ulceration, which might be associated with the stimulation of PGE2, reduction of oxidative stress, suppression of NF- κ B expression and subsequently reduced COX-2 and pro-inflammatory cytokines 352 , 92 . Pretreatment with this compound had a protective effect on acetic acid-induced ulcerative colitis in mice 264 . Berberine ( 161 ) is a good candidate to protect against the deleterious effect of chronic lead intoxication on the kidney 353 . Molecular, biochemical, and histopathological analysis indicated that this alkaloid exerted renoprotective effects in an animal model of lead-induced nephrotoxicity by inhibiting lipid peroxidation and enhancing antioxidant defense system mechanisms. Berberine also protected against renal ischemia/reperfusion injury by regulating the Sirt1/p53 pathway 354 . Magnoflorine ( 100 ), an aporphine isoquinoline alkaloid, efficiently enhanced myoblast differentiation by activating the p38 MAP kinase and Akt pathways and increased the numbers of multinucleated and cylinder-shaped myotubes. It might be a promising lead compound for the development of a drug to combat muscle atrophy 73 . Berberine ( 161 ) exhibited a protective effect against light-induced photoreceptor degeneration associated with diminished oxidative stress in the mouse retina. Thus, it could provide protection against retinal diseases 250 . Neuropathic pain is a major public health problem. Berberine ( 161 ) administration (i.p.) increased both mechanical and thermal pain thresholds in a dose-dependent manner. Moreover, berberine administration reversed the mRNA and protein expression of TRPV1 in dorsal root ganglion neurons after peripheral nerve injury and significantly inhibited capsaicin-induced pain behaviors. This action on neuropathic pain may be associated with the down-regulation of the heat and capsaicin receptor, TRPV1, in the dorsal root ganglia of rat neurons. Accordingly, berberine could be used to treat neuropathic pain originated in the peripheral nervous system 355 . Osteoarthritis, a common degenerative joint disease, is a major cause of joint dysfunction in the elderly 356 . Berberine ( 161 ) prevented articular degeneration cartilage by activating the Akt/p70S6K/S6 signaling pathway in interleukin-1β-induced rat chondrocytes as well as a rat model 357 . It also prevented NO-induced rat chondrocyte apoptosis and cartilage degeneration via AMPK and p38 MAPK signaling 358 . Moreover, the compound promoted sodium nitroprusside-stimulated chondrocyte proliferation by promotion of G1/S phase transition and synthesis of proliferating cell nuclear antigen in cartilage and bone marrow-derived mesenchymal stem cells as well as osteogenic differentiation through activation of the Wnt/β-catenin signaling pathway 359 , 360 . In addition, berberine may be used to treat adenomyosis by inhibiting growth and inflammatory invasive phenotypes of ectopic stromal cells 361 and acute respiratory distress syndrome (ARDS) by alleviating endothelial glycocalyx degradation and promoting glycocalyx restoration in LPS-induced ARDS 362 .