Isolation and identification of antioxidant compounds in Vaccinium bracteatum Thunb. by UHPLC-Q-TOF LC/MS and their kidney damage protection

Vaccinium bracteatum Thunb. is commonly used to stain and cook the rice, which then becomes black, named Wu Fan in Chinese. However, there are limited modern data on its pharmacological effects and active components relating to its traditional use. In the present study, the 50% EtOH eluates (C-b) of V. bracteatum exhibited a strong antioxidant effect assessed by two antioxidant assays (DPPH, ORAC) in vitro and a protective effect on KBrO3-induced kidney damage. Seven compounds in the C-b were identified as isoorientin (1), orientin (2), vitexin (3), isovitexin (4), isoquercitrin (5), quercetin-3-O-α-L-rhamnoside (6), and chrysoeriol-7-O-β-D-glucopyranoside (7). These seven compounds accounted for 0.31 mg/mg of C-b by HPLC analysis, and C-b mainly contained flavonoid compounds by UHPLC-Q-TOF-MS analysis. Flavonoids, especially isoorientin and orientin, were found to be responsible for the antioxidant effect. The results demonstrate that flavonoids may contribute to the health benefits of V. bracteatum in Chinese traditional food.