Regulating the secondary metabolism in grape berry using exogenous 24-epibrassinolide for enhanced phenolics content and antioxidant capacity.

The objective of this study is to investigate the influence of application of exogenous 24-epibrassinolide (EBR) on the antioxidant capacity, anthocyanins and phenolics content of Vitis vinifera grape berry (cvs. Yan 73 and Cabernet Sauvignon). The grapevine clusters were sprayed with 0 (control), 0.10, 0.40, or 0.80 mg/l of 24-epibrassinolide during veraison, respectively. The EBR application increased the activities of phenylalanine ammonia-lyase (PAL) and UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT), the content of total phenolics, tannins, flavonoids and anthocyanins, individual anthocyanins and the antioxidant capacity of matured grape skins in both varieties. The application also increased the content of flavonoids and anthocyanins in Yan73 pulp. Compared to the other treatments, the treatment of EBR at 0.40 mg/l had significantly higher level than the control in all above assays. Our results indicated that the exogenous EBR treatment can significantly promote grape ripening and enhance anthocyanins and other phenolics contents and antioxidant capacity in the grape skin.