Aims: The purpose of this research was to identify antifungal compounds from leaves of Schinus and Schinopsis species useful for the control of toxigenic Fusarium species responsible of ear rot diseases. Methods and Results: Leaves of Schinopsis (S. lorentzii and S. haenkeana) and Schinus (S. areira, S. gracilipes and S. fasciculatus) were sequentially extracted with dichloromethane, ethyl acetate and methanol. The antifungal activity of the fraction soluble in methanol of these extracts (fCH 2 Cl 2 , fAcEt and fMeOH, respectively) was determined by the broth microdilution method and the discdiffusion method. The minimum inhibitory dose (MID), the diameter of growth inhibition (DGI) and the minimum concentration for 50% inhibition of fungal growth (MIC 50 ) were calculated. The fCH 2 Cl 2 and fAcEt of the Schinopsis species had the lowest MID and MIC 50 values and the highest DGI. The antifungal compounds were identified as lupeol and a mix of phenolic lipids. The last one had the highest antifungal activity with MIC 50 31-28 lg g À1 and 165-150 lg g À1 on Fusarium graminearum and Fusarium verticillioides, respectively. The identified metabolites completely inhibited fumonisin and deoxynivalenol production at lower concentrations than ferulic acid, a natural antimycotoxigenic compound. Conclusions: It was proven that lupeol and phenolic lipids were inhibitors of both fungal growth and mycotoxin production of toxigenic Fusarium species. This fact is specially interesting in the control of the toxigenic Fusarium species because several commercial antifungals showed to stimulate mycotoxin biosynthesis at sublethal concentrations. Significance and Impact of the Study: Control of toxigenic Fusarium species requires compounds able to inhibit both fungal growth and mycotoxin production. Our results suggest that the use of lupeol as food preservative and the phenolic lipids as fungal growth inhibitors of F. verticillioides and F. graminearum did not imply an increase in mycotoxin accumulation.
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 MIC value of 500 μg/mL which was twofold higher than that required for prothioconazole (MIC = 250 μg/mL). Sublethal concentrations of PALK modify the morphogenesis in germinating macroconidia, and decreased fungal production of HO 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.
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