PLANT ANTIFUNGAL EXTRACTS ACTIVE AGAINST PLANT PATHOGENIC FUNGI

Abstract

The antifungal activity of six plant leaf extracts (Bucida buceras, Breonadia salicina, Harpephyllum caffrum, Olinia ventosa, Vangueria infausta and Xylotheca kraussiana) prepared using four extractants (acetone, methanol, hexane and dichloromethane) was investigated. For selection of the plants, preliminary studies showed that out of 350 plant species screened for antimicrobial activity, these plants exhibited the best activities against two animal fungal pathogens, Cryptococcus neoformans and Candida albicans. A serial microdilution method was used to determine minimum inhibitory concentrations (MICs) of the extracts against seven plant pathogenic fungi (Aspergillus niger, A. parasiticus, Colletotrichum gloeosporioides, Penicillium janthinellum, P. expansum, Trichoderma harzianum and Fusarium oxysporum). All plant extracts were active against the tested microorganisms. B. buceras extracts had the best antifungal activity against four of the fungi, with MIC values as low as 0.02 mg/ml and 0.08 mg/ml against Penicillium expansum, P. janthinellum, Trichoderma harzianum and Fusarium oxysporum, P. janthinellum, T. harzianum and F. oxysporum were the most sensitive fungal species, with the same average MIC values of 0.28 mg/ml, and the remaining four fungi were more resistant to the extracts tested, with MIC values above 1 mg/ml. The number of active compounds in the plant extracts was determined using bioautography with the above-mentioned fungal pathogens. Breonadia salicina and O. ventosa were the most promising plant species, showing at least three antifungal compounds while the other plants showed none in this technique. Bioactivity-guided fractionation of B. salicina leaf extract led to the isolation of three active compounds, the structures of which are being elucidated