GC-ToF-MS based phytochemical analysis and anti-mycotoxigenic activity of South African medicinal plants, Mystroxylon aethiopicum (Thunb.) Loes. and Spirostachys africana Sond

• Published in: South African journal of botany 2023-02, Vol.153, p.11-20
• Main Authors: Molele, P.K., Makhafola, T.J., Mongalo, N.I.
• Format: Article
• Language: English
• Subjects: antioxidant; food safety; GC-ToF-MS; Medicinal plants; Mystroxylon aethiopicum (Thunb.) Loes. antifungal; Selectivity index; Spirostachys africana Sond
• ISSN: 0254-6299; 1727-9321
• DOI: 10.1016/j.sajb.2022.12.007

•Organic extract from leaves of Strychnos mitis exhibited a potent antimycotoxigenic activity.•Mystroxylon aethiopicum showed notable mycelial growth inhibition against Fusarium verticiloides.•Phytocompounds identified from both Mystroxylon aethiopicum and Spirostachs africana such as tetradecane, heptadecane (14.96%) and n-hexadecanoic acid may well explain biological activity observed. The use of pesticides and fungicides in the treatment and management of pathogenic mycotoxin producing fungal strains is detrimental to human health. Such fungal strains produce toxins which result low production of crops and many human and animal infections when ingested. In our quest in finding possible plant-based pesticides, the in vitro anti-mycotoxigenic activity of plants extracts and their mycelial growth inhibition against fungal pathogens have been assessed. Antifungal activity was carried out using microdilution assay while the cytotoxicity was explored against African green monkey (Vero). Organic extracts from Strychnos mitis S.Moore exhibited lowest minimum inhibitory concentration (MIC) value of 0.01 mg/ml against three Fusarium species and further MIC value of 0.08 mg/ml against three Aspergillus species at 24 hr incubation period. In the mycelial growth inhibition (MGI), Mystroxylon aethiopicum (Thunb.) Loes. showed the highest mycelial growth inhibition yielding 44.38% against Fusarium verticiloides in a three-day incubation period. Organic extract from S. africana exhibited the lowest lethal concentration (LC50) value of 0.10 mg/ml against both cell African green monkey (Vero) and bovine dermis cell lines. In the antioxidant assay, extracts from S. africana and M. aethiopicum exhibited a noteworthy antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH), yielding 50% inhibition (IC50) values of 0.51 and 0.74 mg/100 ml, respectively. In the Gas-chromatography time-of-flight mass spectrometry (GC-ToF-MS) analysis, M. aethiopicum extract exhibited the presence of tetradecane (15.7%) while Spirostachys africana Sond. yielded n-hexadecanoic acid (12.1%) and nonadecane,2-methyl (12.1%). These results suggest that phytocompounds from these medicinal plants are likely to inhibit growth of fungal strains, preventing oxidation of crops and should be further explored in vivo and used to develop a bio-fungicide with less side effects compared to synthetic fungicides. These plants could assist in increasing possible food yields, preventing decay, promote foo