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.

Four pentacyclic triterpenoids with antifungal and antibacterial activity from Curtisia dentata (Burm.f) C.A. Sm. leaves.

ETHNOPHARMACOLOGICAL RELEVANCE: Curtisia dentata is used in southern Africa to treat various diseases of bacterial and fungal origin in humans and animals to such a degree that the species is vulnerable and declining [Dold, A.R., Cocks, M.L., 2001. Traditional veterinary medicine in the Alice district of the Eastern Cape Province, South Africa. South African Journal of Science 97, 375-379]. Preliminary studies indicated good activity against Candida albicans. AIM OF THE STUDY: The phytochemistry and antimicrobial activity of this plant species has not been extensively investigated, and a closer examination of the compounds responsible for antimicrobial activity was warranted. MATERIALS AND METHODS: Broth microdilution assay and bioautography were used to evaluate antibacterial and antifungal activity in Curtisia dentata leaf extracts and fractions. Bioassay-directed fractionation using column chromatography yielded four compounds characterised by spectroscopic methods. RESULTS: Lupeol (1), betulinic acid (2), ursolic acid (3) and 2alpha-hydroxyursolic acid (4) were isolated from Curtisia dentata leaves. Betulinic acid, ursolic acid and 2alpha-hydroxyursolic acid appreciably inhibited fungal growth with MIC values ranging from 8 to 63mug/mL. CONCLUSIONS: The isolation of four antibacterial and antifungal triterpenoids is reported for the first time from Curtisia dentata. This study provides information on the antimicrobial compounds of this species, as well as a preliminary rationale for the use in traditional South African medicine.