In vitro anthelminthic activity and secondary metabolites analysis of leaves of Aloe vera (L.) Burm. f. (Xanthorrhoeaceae) against bovine parasite Onchocerca ochengi and drug resistant strains of the free-living nematode Caenorhabditis elegans

Abstract Background Human onchocerciasis caused by the filarial worm, Onchocerca volvulus is a parasitic that forms nodules under the skin. In the developing countries, it has been estimated that more than 80% of the population rely on traditional medicines for their primary healthcare needs. The aim of this work was to assess the nematicidal activities of Aloe vera on Onchocerca ochengi and Caenorahbditis elegans and to determine the phytochemical compounds. Methods Nodules were collected from the umbilical region of infected cattle, dissected and male worms were cultured in RPMI-1640. Worms were incubated for 48 h and 72 h with different concentrations of A. vera extracts in RPMI-1640 and M9-buffer. Polyphenol, tannin and flavonoid contents of extract were determined by using gallic acid and rutin as standards. The antioxidant activity was evaluated by DPPH radical scavenging method. Results The anthelmintic effect of A. vera extract against O. ochengi was concentration dependent with LC50 of 20.71 µg/mL and 11.75 µg/mL after 48 and 72h respectively. A. vera extract exerted concentration dependent lethal effects (LC50 = 2747 and LC50 = 1937 µg/mL) against C. elegans (WT). MeOH-CH2Cl2 of A. vera extract exhibited high DPPH activity with an IC50 value of 15 µg/mL and 9 µg/mL for ascorbic acid. The highest activity in adult worms was observed with the MeOH (100: 0) and AcOEtMeOH fractions with LC50 values of 12.82 and 15.50 µg/mL respectively. EcOEtMeOH (8:2 v/v) was more effective (LC50 = 250 µg/mL) on WT C. elegans. A. vera contains polyphenols (1015.05 and AcOEtMeOH = 893.60), flavonoids (25.35 and MeOH = 225.76) and tannins (401.37 and Hex = 788.89). Conclusions A. vera showed in vitro nematicidal activity against O. ochengi and C. elegans. Aloe vera could be used as alternative anthelmintic for onchocerciasis treatment.