Anthelmintic, antifungal, genotoxicity and cytotoxic activities of acetone leaf extracts, fractions and isolated compounds from Ptaeroxylon obliquum

Ptaeroxylon obliquum (Rutaceae) is traditionally used in South Africa to treat many ailments in humans and animals, including parasitic infections. In this study the antiparasitic, antifungal, genotoxic and cytotoxic activities of acetone leaf extracts of P. obliquum, fractions and isolated compounds were determined. The in vitro anthelmintic activity was investigated against Haemonchus contortus ova and larvae using egg hatching and larval development assays. The antifungal activity was determined by serial microplate dilution method against Aspergillus fumigatus, Cryptococcus neoformans and Candida albicans. The mutagenic activity was determined using the Ames test with Salmonella typhimurium (TA98, TA100 and TA102) strains. Cellular toxicity was determined against Vero African green monkey kidney and human liver (C3A) cell lines.

Three compounds were isolated from the chloroform fraction using silica gel open column chromatography and were characterized as obliquumol, eranthin and a mixture of lupeol and β-amyrin. The anthelmintic activity of the extract and obliquumol against H. contortus ova and larvae indicated that the compound was more effective than the crude extract with an EC50 as low as 95 µg/ml against the larvae. Obliquumol and eranthin had excellent antifungal activity against the fungi with minimal inhibitory concentrations (MIC) values ranging from 2 – 16 µg/ml. All the tested samples were non-genotoxic against the tested Salmonella strains. The acetone crude extract was toxic with an IC50 value as low as 14.2 µg/ml against the Vero cells. However, the isolated compounds were not toxic against either Vero or C3A cells and had good selectivity index values against the opportunistic fungal pathogens. The results of the anthelmintic activity indicated potential in the management of H. contortus which may explain the ethnoveterinary use of this plant species. Further exploration of the activity of the purified compounds, particularly their promising antifungal activity, is under way.