Postharvest treatment with (-) and (+)-methyl jasmonate stimulates anthocyanin accumulation in grapes

The effect of the postharvest application of (-) and (+)-methyl jasmonate (MJ) enantiomers on grapes antioxidant capacity, total phenolic compounds and anthocyanin concentration was examined on days 5 and 7 after treatment. The study also includes grapes treated with MJ racemic mixture and grapes without treatment (control) for comparison. Exogenous application of MJ induced an enhancement in the antioxidant activity and total phenolic compounds when compared to control grapes; this increase was higher when the enantiomers, rather than the mixture, were used (up to 42% for the antioxidant activity and for total phenolic compounds). Similarly, a significant increase was also registered in the total anthocyanin concentration when the enantiomers were applied. This increase ranged from 14 % to 42 % after 5 days of storage and from 22 % to 64 % when grapes were stored for 7 days. It was also observed an enhancement on individual anthocyanin concentration when the enantiomers were used. Nevertheless, no effects were observed on the anthocyanin relative distribution as a consequence of (-/+)-MJ, (-)-MJ and (+)-MJ treatment. Postharvest treatment of grapes with MJ enantiomers is proposed as means to increase antioxidant activity and anthocyanin concentration in grapes. (C) 2014 Elsevier Ltd. All rights reserved.