Abstract

In vitro antifungal activity of acetone, methanol, hexane and dichloromethane leaf extracts of six plant species (Bucida buceras, Breonadia salicina, Harpephyllum caffrum, Olinia ventosa, Vangueria infausta and Xylotheca kraussiana) was determined using a serial dilution assay against Aspergillus fumigatus. These plant species were selected from 600 evaluated, inter alia, against two animal fungal pathogens. All plant extracts were screened for antifungal activity against A. fumigatus. Of the six plant species, B. salicina had the best antifungal activity against the test microorganism with a minimum inhibitory concentration (MIC) value of 0.08 mg/ml. Some of the extracts had moderate to low activity against the tested microorganism. Antioxidant activity of the aforementioned plant extracts were investigated using a qualitative assay (2, 2-diphenyl-1-picrylhydrazyl (DPPH)). The plant extracts of five of the plant species did not have strong antioxidant activity. The methanol extract of X. kraussiana was the most active radical scavenger in the DPPH assay amongst the six medicinal plants screened. No quantitative assay was conducted since the plant extracts did not possess strong antioxidant activity. A bioautography assay was used to determine the number of active compounds in the plant extracts. No antifungal compounds were observed in some of the plant extracts with good antifungal activity shown in the microdilution assay, so synergistic effects of more than one active compound are possible. B. salicina was the most promising plant species with at least three distinct antifungal compounds. Plant extracts with low MIC values could be a good source of bioactive components with antimicrobial potency.

Key words: Antioxidant activity, antifungal activity, 2, 2-diphenyl-1-picrylhydrazyl (DPPH), minimum inhibitory concentration, bioautography assay, Breonadia salicina.