ISOLATION OF AN ANTIFUNGAL TRITERPENES FROM COMBRETUM NELSONII (COMBRETACEAE) LEAVES

Abstract

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 MIC’s of the mixture to the different pathogens varied from 0.2 – 1.6 µg/ml; Candida albicans (0.9 µg/ml), Cryptococcus neoformans (0.4 µg/ml), Aspergillus fumigatus (1.6 µg/ml), Microsporum canis (0.2 µg/ml) and Sporothrix schenckii (0.2 µg/ml). Microsporum canis and S. schenckii were the most susceptible followed by C. neoformans. Aspergillus fumigatus was the most resistant. The Rf value of the mixture of asiatic acid and arjunolic acid was 0.27 in CEF, 0.09 (BEA) and 0.55 (EMW) which was active against all pathogens. In vitro cytotoxicity of the mixture gave an LC50 of 10.58 µg/ml towards Vero monkey kidney cells. These results partly validate the ethnobotanical use of many Combretum species for conditions that may be of bacterial aetiology. Acknowledgements: The National Research Foundation (NRF) and National Department of Agriculture (South Africa) provided funding. Dr L. McGaw (UP) for helping with toxicity studies.