Antifungal activity of stigmasterol, sitosterol and ergosterol from Bulbine natalensis Baker (Asphodelaceae)

Abstract

Bulbine natalensis Baker. (Asphodelaceae) is indigenous to only southern Africa and is widely used as a skin remedy. B. natalensis contain secondary metabolites that have antibacterial properties. Phytosterols are a group of steroid alcohols and phytochemicals that occur naturally in plants. Aspergillus, Penicillium and Fusarium species are considered to be the most toxigenic fungi. They produce a large consortium of mycotoxins that include aflatoxins B1, B2, G1, G2, fumonisin B1 and ochratoxins. They are found in foodstuffs and are not destroyed by normal industrial processing or cooking since they are heat-stable. The purpose of the project was to extract and quantify phytosterols, such as ergosterol, stigmasterol and sitosterol from B. natalensis using phytochemical methods such as thin layer chromatography and high performance liquid chromatography. The extract was tested against Aspergillus flavus, Penicillium digitatum and Fusarium verticilloides for antifungal activities. 1 ml of saponified extract contained 0.07 µg of sitosterol, 0.16 µg of stigmasterol and 0.37 µg of ergosterol. Saponifiable, unsaponifiable and crude extracts showed minimal activity against F. verticilloides, whereas potent activity was exhibited against A. flavus. Key words: Bulbine natalensis, phytosterols, secondary metabolites, antifungal activity, mycotoxins.