Involvement of epicatechin in the regulation of lipoxygenase activity during activation of quiescent Colletotrichum gloeosporioides infections of ripening avocado fruits

Abstract Avocado lipoxygenase activity increased from 20 to 40 μmole O 2 h −1 g −1 fresh weight of peel in unripe fruits during the first hour after harvest, and in ripening fruits 4 to 5 days after harvest. Concomitantly, the concentration of the antifungal compound cis, cis -1-acetoxy-2-hydroxy-4-oxo-heneicosa-12, 15-diene decreased from approx. 1700 to 200 μg g −1 fresh weight of peel. The concentration of epicatechin in the peel was inversely correlated with lipoxygenase activity in each case, and decreased significantly when lipoxygenase increased. The amount of lipoxygenase in the crude extract of the fruit peel during ripening, which was determined by the ELISA technique, ranged between 10 and 30 μg g − fresh weight of peel during ripening, and was not correlated with the changes in the enzyme activity. The results suggest that the differences in lipoxygenase activity are not correlated with changes in the amount of this enzyme, but rather result from changes in the concentrations of its inhibitor, epicatechin.