Coumarin derivative, 5′-hydroxy-auraptene, extracted from Lotus lalambensis, displays antifungal and anti-aflatoxigenic activities against Aspergillus flavus

Abstract

Pathogenic fungi are the primary infectious cause of plant diseases during pre- and post-harvest. Nuts, although recognized as a food with health benefits, are frequently contaminated by aflatoxins. In this study, we investigated the antifungal and anti-aflatoxigenic effects of our previously isolated phytochemical coumarin derivative, named (5′-hydroxy-aurapten) (5′-HA) from Lotus lalambensis Schweinf on Aspergillus flavus isolated from nuts. 5′-HA showed higher antifungal potential against A. flavus, by inhibiting its growth (MIC and MFC were 62.5 and 125 µg/l, respectively). 5′-HA also inhibited conidial germination of A. flavus by 60% at concentration 40 µg/ml. 5′-HA (40 µg/ml) displayed anti-aflatoxigenic activity against the production of aflatoxins, AFB1 and AFB2 by 50% and 23.3% respectively in association with the down-regulation of gene expression of early (aflA, alfB and alfC), middle (aflL, aflM and aflN) and late (aflP, aflQ and aflW) stages of aflatoxin biosynthesis pathway. 5′-HA (40 µg/ ml) resulted in the leakage of sugars from the mycelia by 235.8 μg/mL. Additionally, the extracellular conductivity in cells exposed to 5′-HA at 20, 40, and 80 µg/ml increased to values of 26.0 4, 43.2, and 55.1 μs/cm, respectively. Interestingly, 5′-HA significantly stimulated the activities of antioxidant enzymes, CAT (Catalase) and SOD (Superoxide dismutase) by 56.25% and 66.66% respectively. The anti-aflatoxigenic mechanism of 5′-HA was found to be mediated via modulating the oxidative stress process by upregulating the mRNA expression of the stress response transcription factors, atfA and atfB, by 2 and 2.5 folds respectively. In conclusion, our data identified 5′-HA as a novel natural antifungal compound against A. flavus that can be potentially applied to protect foodstuffs against aflatoxigenic fungi in agroindustry.