Extracts of the leaves and twigs of the threatened tree Curtisia dentata (Cornaceae) are more active against Candida albicans and other microorganisms than the stem bark extract

Abstract

Curtisia dentata is a popular medicinal plant in South Africa that has become vulnerable and scarce owing to over-exploitation by collection of bark. The aim of this study was to compare the antifungal activities of extracts of the leaves, twigs and bark of C. dentata to identify possible substitution of leaf material for bark for medicinal purposes. The methods used were thin layer chromatography (TLC) to compare the chemical composition, bioautography to ascertain the number of active compounds and microdilution assay to determine the minimal inhibitory concentrations of the extracts. TLC revealed differences in chemical compositions of the extracts of the leaves, twigs and bark of C. dentata. These differences were largely centred on the quantities of the various components in the extracts. The acetone extracts of the leaves had four bands active against Candida albicans and two in extracts of the stem bark on bioautograms. The Rf values of these bands indicated that they are also present in the leaves. The leaves were more active with an MIC of 0.11 mg/ml while the stem bark had an MIC of 0.61 mg/ml against C. albicans. The total activity values confirmed that the leaves (1072 ml/g) were five-fold more active than the bark (190 ml/g).