Isolation, identification and usefulness of antifungal compounds from Zuccagnia punctata for control of toxigenic ear rot pathogens

Abstract

Infusion, tincture and decoction of leaves of Zuccagnia punctata Cav. were assayed on growth of Fusarium verticillioides, F. graminearum sensu stricto, F. boothii, F. meridionale, F. subglutinans and F. thapsinum. The tincture showed the lowest IC50 on mycelial growth. A diethyl ether fraction of the tincture showed the highest antifungal activity in microdilution assays on F. verticillioides and F. graminearum. The antifungal constituents were separated by silica gel chromatography and identified as 2´,4´-dihydroxychalcone, 2´,4´-dihydroxy-3´-methoxychalcone and 7-hydroxy-3´,4´-dimethoxyflavone. These chalcones had the lowest MIC and MFC values on F. verticillioides and F. graminearum sensu stricto. 2´,4´-Dihydroxychalcone was mildly toxic and the remaining identified compounds were non-toxic in the brine shrimp assay. 2´,4´-Dihydroxychalcone in mixtures with commercial food preservatives showed additive effects on F. graminearum sensu stricto and synergistic ones on F. verticillioides. 2´,4´-Dihydroxy-3´-methoxychalcone showed synergistic effects in mixtures. Our results suggest that addition of chalcones to food preservatives allows reduction in the doses of the preservatives required for control of Fusarium species.