Investigation of Brazilian grape juice metabolomic profile changes caused by methyl jasmonate pre‐harvest treatment

Grape juice is a major source of potential health-promoting bioactive polyphenols, especially for children and those who do not consume wine. Since the subtropical climate may negatively affect the concentrations of grape polyphenols, especially anthocyanins, elicitors such as methyl jasmonate (MeJa) could be used to promote polyphenol biosynthesis. This work aimed at investigating the impact of MeJa treatment on grape juice produced via a traditional low-cost process from two Vitis labrusca cultivars and in two Brazilian regions. The untargeted LC–MS analytical protocol demonstrated that Isabel Precoce juices strongly benefited from MeJa treatment, especially regarding their anthocyanic profile, regardless of the cultivation region. Known MeJa markers in wine and V. vinifera grapes (flavanols, flavonols and stilbenes) in this experiment had mixed behaviours depending on the region/variety/cultivation. Moreover, it was found that all the detected hydroxycinnamates were influenced by the treatment, especially the concentration of their glucosides, which was increased. Glutathione, 2-S-glutathionyl caftaric acid and indole lactic acid glucoside were identified for the first time as MeJa treatment biomarkers in grape products, indicating a possible positive effect on juice antioxidant properties.