Production and evaluation of antifungal stilbenoids in Dracaena cochinchinensis elicited by fungal inoculation

Abstract

Plants infected by fungal elicitors produce phytoalexins. As one of the most valuable traditional medicines, dragon’s blood is harvested from the trunks of Dracaena cochinchinensis elicited by fungal species. However, the functional metabolites exhibiting antifungal activity in dragon's blood remain unclear. In the current study, three new stilbenoids (1―3), one new chalcone (4), and one new flavane (5), together with one known compound (6), were identified from dragon’s blood of D. cochinchinensis elicited by Fusarium graminearum. Among these compounds, compound 3, (7E)-2,4-dihydroxy-1-methylstilbene, exhibited a broad-spectrum inhibitory activity against four pathogenic fungal strains of maize, including Exserohilum turcicum, Bipolaris maydis, Curvularia lunata, and F. graminearum. Inspiringly, compound 3 showed a stronger inhibitory activity (half-maximal inhibitory concentration, IC50: 11.02 ± 1.12 μg/mL) against the elicited fungus F. graminearum than that of a commercial fungicide, nystatin (IC50: 16.23 ± 3.10 μg/mL). Additionally, a dramatically low electron density was observed in the cell walls of F. graminearum, suggesting that compound 3 might exert its function by directly targeting cell walls. Compound 3 also showed potent antioxidant activities, which was validated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical inhibition assays. Collectively, our findings highlight that stilbenoids in dragon’s blood of D. cochinchinensis have promising potential for the future development of natural fungicides for organic farming.