Antifungal metabolites from Schinopsis balansae Engl (Anacardiaceae): isolation, identification and evidences of their mode of action on Fusarium graminearum Schwabe.

An antifungal activity-directed fractionation of leaf constituents from Schinopsis balansae on Fusarium graminearum yielded a fraction mainly made of a mixture of four 3-n-heptadec(en)ylcatechols (PALK). The PALK fraction showed on macroconidia germination a MIC100 value of 500 μg/mL which was twofold higher than that required for prothioconazole (MIC100 = 250 μg/mL). Sublethal concentrations of PALK modify the morphogenesis in germinating macroconidia, and decreased fungal production of H2O2 and deoxynivalenol biosynthesis at early fungal growth. Mixes of PALK and prothioconazole showed a synergic interaction. Our findings suggest that PALK constituents might restrict the adherence of F. graminearum to the surface of its hosts and its virulence on susceptible cereals. They deserve further research as additives of azole fungicides against F. graminearum.