Effects of flavonoids-rich Chinese bayberry (Myrica rubra Sieb. et Zucc.) pulp extracts on glucose consumption in human HepG2 cells

Flavonoids composition of Chinese bayberry (Myrica rubra Sieb. et Zucc.) pulp extracts was characterized by LC-ESI-Q-TOF-MS and quantification of flavonoids in nine bayberry cultivars was carried out by HPLC. As a result, five flavonoids, i.e. cyanidin-3-O-glucoside (C-3-Glu), myricetin-3-O-rhamnoside (M-3-Rha), quercetin-3-O-galactoside (Q-3-Gal), quercetin-3-O-glucoside (Q-3-Glu), and quercetin-3-O-rhamnoside (Q-3-Rha) were identified and quantified. The glucose consumption activities of nine bayberry cultivars varied significantly among cultivars and they were well correlated with their total phenolics, total flavonoids contents, and DPPH scavenging activities. In addition, C-3-Glu and three quercetin-3-O-glycosides (Q-3-Glys, i.e. Q-3-Gal, Q-3-Glu, and Q-3-Rha), but not M-3-Rha, showed significant enhancement of glucose consumption in HepG2 cells. There were significant correlations between the glucose consumption activity with the contents of C-3-Glu and the sum of three Q-3-Glys, respectively. These results showed that bayberry cultivars with high content of C-3-Glu and Q-3-Glys may have great potential as hypoglycemic foods.