Antimicrobial Activity and Phytochemical Characterization of Baccharis concava Pers., a Native Plant of the Central Chilean Coast

Few Sclerophyllous plants from the central coast of Chile have been systematically studied. This work describes the phytochemical composition and antimicrobial properties of Baccharis concava Pers. (sin. B. macraei), a shrub found in the first line and nearby the pacific coast between latitudes 29-38⁰S. B. concava has been traditionally used by indigenous inhabitants of today central Chile for their anthelmintic properties, wound healing properties and as a diuretic. Hydro-alcoholic extracts of B. concava were prepared from leaves and small branches. The qualitative phytochemical characterization indicated presence of alkaloids, steroids, terpenoids, flavonoids, phenolic and tannins compounds. The antimicrobial activity of this extract was assessed in a panel of microorganisms including Gram-positive, Gram-negative bacteria and pathogenic yeasts. The extract displayed important antimicrobial effects against Gram positive, Candida albicans, and Cryptococcus neoformans, but not against Gram negative, for which an intact Lipopolysaccharide (LPS) is apparently the determinant of resistant to B. concava extracts. The hydroalcoholic extract was then fractionated through a sephadex LH-20/methanol-ethyl acetate column. Followed, the fractions were pooled according to a similar composition that was visualized by TLC/UV analysis. Fractions obtained by this criterion were assessed for their antimicrobial activity against Staphylococcus aureus. The fraction presenting the most antimicrobial activity was HPLC-ESI-MS/MS analyzed obtaining a composition rich in structures derived from caffeoylquinic acid, dicaffeoylquinic acid and quercetin, among others. In conclusion, the extracts of B. concava show a strong antimicrobial activity probably due to their composition rich in metabolites derived from caffeoylquinic acid and quercetin, that in turn could be responsible for helping with wound healing, as reported from its ancient cultural use. In addition, the development of antimicrobial therapies based in the molecules found in B. concava could help to combat infection caused by pathogenic yeasts and Gram-positive bacteria, without affecting the Gram-negative microbiota.