The effects of caffeic acid and epicatechin treatment on gray mold resistance and antioxidant metabolism in apples

Gray mold, caused by Botrytis cinerea , is a major disease affecting postharvest apples, where it significantly reduces their commercial value. In this study, we conducted in vitro tests at a laboratory scale that showed that two monomeric phenols, caffeic acid and epicatechin, can directly inhibit the growth of B. cinerea in a dose-dependent manner. In in vivo experiments, caffeic acid or epicatechin treatment significantly reduced the incidence of ‘Fuji’ “Fuji” apple gray mold and inhibited lesion development. Relative to the control group, caffeic acid-treated apples inoculated with B. cinerea showed greater accumulation of disease-related proteins, lower H 2 O 2 synthesis, less residual malondialdehyde (MDA), and reduced damage to cell membrane lipids. However, caffeic acid had no significant effect on the accumulation of superoxide anions (O 2 .− ), ascorbic acid (AsA), or glutathione (GSH). In contrast, epicatechin treatment not only induced the accumulation of reactive oxygen species and disease-related proteins in apples, but also activated AsA and GSH biosynthesis. Caffeic acid and epicatechin treatments both inhibited the invasion and expansion of pathogens but did so by regulating different disease-related proteins. Caffeic acid mainly promoted the accumulation of chitinase (CHI), while epicatechin mainly induced the synthesis of β-1,3-glucanase (GLU).