Cytotoxicity, antifungal and antioxidant properties of Lonchocarpus capassa leaf extracts

Background: Lonchocarpus capassa is a medicinal plant used to treat diseases such as fungal infections, diarrhoea, oral candidiasis, and stomach complaints in South Africa. Aim: The study aimed to investigate the cytotoxicity and antifungal compounds isolated from L. capassa leaf extracts. Setting: The study was conducted in Muduluni village, Makhado Local Municipality, Limpopo province. Methods: Leaf extracts were screened for antifungal activity against fungal pathogens: Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus. Bioassay-guided fractionation using column chromatography of the acetone extract led to the isolation of six antifungal compounds. Nuclear Magnetic Resonance spectroscopy and Mass Spectrometry were used for the identification of compounds. The antioxidant activity of the plant extracts was investigated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays. Cytotoxicity of isolated compounds was determined using the 3-(4,5-dimethylthiazol)-2,5-diphenyl tetrazolium bromide (MTT) assay against Vero monkey kidney cells. Results: The plant extract had an excellent minimum inhibitory concentrations (MIC) value of 40 μg/mL against the microorganisms. Compound 1 was identified as Lupeol, Compound 3 as Friedelin, and Compound 4 as 6-(γ,γ-Dimethylallyl)-3’,4’-dimethoxy-6”,6”-dimethylpyrano-[2”,3”:7,8]-flavanone (Compound 4). Compounds 2 and 5 were not identified because of the presence of mixtures of long-chain fatty acids. Friedelin was the most active radical scavenger in the DPPH assay. The compounds were not toxic with an LC50 value of ˃ 0.2 mg/mL. Conclusion: Screening of medicinal plants could provide lead to the discovery of novel antifungal agents. Contribution: The results support the traditional use of L. capassa to combat fungal infections in humans.