Antifungal activity of eucalyptus-derived phenolics against postharvest pathogens of kiwifruits
Oh S.O., Kim J.A., Jeon H.S., Park J.C., Koh Y.J., Hur H. and Hur J.S.
The Plant Pathology Journal, 24(3) p. 322-327, 2008.
2008
บทคัดย่อ
Antifungal activities of natural substrances from Eucalyptus darlympleana, E. globules, E. gunnii and E. unigera were evaluated against postharvest pathogens of kiwifruits, Botrytis cinerea, Botryosphaeria dothidea, and Diaporthe actinidiae, to screen effective natural substances as an alternative to chemical fungicides. Methanol extract of the Eucalyptus trees showed strong antagonistic activity against the pathogenic fungi. Among them, E. unigera and E. darlympleana effectively inhibited mycelial growth of the pathogens. For chemical identification of the antifungal substances, the methanol extract of E. darlympleana leaves was successively partitioned with CH₂Cl₂, EtOAc, n-BuOH and H₂O. Among the fractions, CH₂Cl₂, and n-BuOH showed strong inhibitory activity of mycelial growth of the fungi. Five compounds were isolated from EtOAc and n-BuOH fractions subjected to SiO₂column chromatography. Two phenolic compounds (gallic acid and 3,4-dihydroxy-benzoic acid) and three flavonoid compounds (quercetin, quercetin-3-O-α-L-rhamnoside, quercetin-3-O-β-D-glucoside) were identified by ¹H-NMR and ∨13C-NMR spectroscopy. Among them, only gallic acid was found to be effective in mycelial growth and spore germination of B. cinerea at relatively high concentrations. The results suggest that gallic acid can be a safer and more acceptable alternative to current synthetic fungicides controlling soft rot decay of kiwifruit during postharvest storage.