Biological activity of two related triterpenes isolated from Combretum nelsonii (Combretaceae) leaves.

Antifungal bioassay-guided fractionation of Combretum nelsonii leaf extracts afforded two closely related triterpenes, asiatic acid and arjunolic acid. Antifungal activities of the mixture of asiatic acid and arjunolic acid were determined against five fungal animal pathogens. The minimum inhibitory concentrations of the mixture to the different pathogens varied from 0.2 to 1.6 microg mL(-1); Candida albicans (0.9 microg mL(-1)), Cryptococcus neoformans (0.4 microg mL(-1)), Aspergillus fumigatus (1.6 microg mL(-1)), Microsporum canis (0.2 microg mL(-1)) and Sporothrix schenckii (0.2 microg mL(-1)). Microsporum canis and S. schenckii were the most susceptible followed by C. neoformans. Aspergillus fumigatus was the most resistant. The R(f) value of the mixture of asiatic acid and arjunolic acid was 0.27 in CEF (chloroform : ethylacetate : formic acid), 0.09 (BEA; benzene : ethanol : ammonium hydroxide) and 0.55 (EMW; ethylacetate : methanol : water) which was active against all pathogens. In vitro cytotoxicity of mixture gave an LC(50) of 10.58 microg mL(-1) towards Vero monkey kidney cells.