The antifungal activity of twenty-four southern African Combretum species (Combretaceae)

Abstract

The antifungal activities of acetone, hexane, dichloromethane and methanol leaf extracts of 24 South African Combretum species were determined against five fungal animal pathogens (Candida albicans, Cryptococcus neoformans, Aspergillus fumigatus, Microsporum canis and Sporothrix schenckii) representing yeasts, moulds and dimorphic fungi. MIC's determined after 48 h were usually two times higher than values determined after 24 h. Most of the antifungal extracts had MIC values of c. 0.08 mg/ml, some with MIC values as low as 0.02 mg/ml. These are substantially better values that reported in the literature to date. M. canis was the most susceptible microorganism followed by S. schenckii. A. fumigatus was the most resistant of the pathogens tested. Methanol extracted the highest quantity from leaves, but the acetone extracts had the highest antifungal activity in practically all cases. The methanolic extracts of C. moggii and C. petrophilum were however most active against all the pathogens. All extracts of C. nelsonii were also very effective against all the pathogens. Based on these results and work done earlier, C. nelsonii was selected for fractionation and bioassay-guided isolation of the antifungal compounds followed by C. albopuntactum, and C. imberbe.