Antifungal activity of 40 plant essential oil components against Diaporthe fusicola from postharvest kiwifruits and their possible action mode

The antifungal activity of essential oils is closely related to their components and contents. The study aimed to explore the structural activity of essential oil (EO) components against Diaporthe fusicola and modes of action. The results showed most of the tested compounds showed inhibitory effects on the growth of D. fusicola and carvacrol was the strongest one with half maximal effective concentration (EC50) of 11.21 mu L/L. The chemical structures of the tested compounds had great influences on their antifungal activity, in which the presence of CHO group, C--C group or Ar-OH group in any EO components significantly increase the antifungal potency, but the increment of carbon chain length of saturated fatty aldehyde decreased antifungal activity. In order to analyze the antifungal action mode of EO components, the correlations between EC50 and oxidation-reduction potential (ORP), cell-membrane permeability and respiration inhibition of the tested compounds were further evaluated. The results showed antifungal activities of these EO components seemed to be accomplished by increase of cell membrane permeability and inhibition of the respiration of D. fusicola. The levels of increased membrane permeability, inhibited respiration and ORP of chemicals were all significantly correlated with EC50. This results indicated the action mode of these EO components against D. fusicola may be associated with the increment of cell membrane permeability and respiration inhibition via disrupting redox homeostasis in fungal cells, and oxidation-reduction property could be used as a secondary indicator for screening the antifungal agent from EO components.