Separation And Purification Of Flavonoid Glycosides From Myrica Rubra Sieb.et Zucc. Fruit And Their α-Glucosidase Inhibitory Activities

In the present study, the a-glucosidase and a-amylse inhibitory acitivities in Chinese bayberry (Myrica rubra Sieb. et Zucc.) pulp of 19 cultivars were analyzed. Separation and purification of main flavonoid glycosides compounds from ’Biqi’ pulp was established. a-Glucosidase inhibitory activity and antioxidant activity of different fractions of flavonoid glycosides extacts of ’Biqi’ pulp were also evaluated. The main results are as follows:1. There were significant differences in α-glucosidase and a-amylse inhibitory activities among different cultivars.’Muye’ pulp extract showed markedly a-glucosidase inhibitory activity with the inhibitory rate of 83.95% at the concentration of 5 mg/mL whereas that of ’Dingao’ was just 40.57%. The IC50 values of a-glucosidase varied from 2.12-2.90 mg/mL among the 12 bayberry cultivars, such as ’Biqi’,’Muye’,’Wandao’ etc, while the IC50 values varied from 3.12-7.86 mg/mL among the other 7 cultivars. Furthermore, the majority cultivars showed strong a-amylse inhibitory activities with the inhibitory rate between 54.64 to 71.27% at the concentration of 10 mg/mL except ’Langdangzi’,’Zaotanmei’ and ’Dingao’ with the inhibitory rate of 17.41-23.23%.2. Efficient simultaneous purification of four flavonoid glycosides, i.e. cyanidin-3-O-glucoside (C3G), myricetin-3-O-rhamnoside (myricitrin), quercetin-3-O-galactoside (hyperoside), quercetin-3-O-rhamnoside (quercitrin), from ’Biqi’ pulp was established by the combination of C18 Sep-Pak(?) Cartridges (SPE) column chromatography and semi-preparative HPLC (Semi-prep HPLC). After the first cleaning-up with SPE column, the purity of C3G increased from 0.47% in the crude extract to 54.12% in the SPE column sample, and myricitrin, hyperoside, querccitrin increased from 0.02% in the crude to 2.42%, from 0.06% to 7.75%, and from 0.03% to 3.84%, respectively. Further Semi-prep HPLC purification resulted in final purity of 99.17% for C3G, and the purities of myricitrin, hyperoside, querccitrin were all more than 90%.3. a-Glucosidase inhibitory activities and antioxidant activities of the purified flavonoid glycosides and different fractions from bayberry pulp extracts were evaluated. It showed that the 50% fraction had the highest a-glucosidase inhibitory activity (ICso=0.18 mg/mL), which was better than that of acarbose (ICso=0.37 mg/mL). All of the four purified compounds showed markedly a-glucosidase inhibitory activity with the inhibitory rate of 65.41% for C3G,83.60% for myricitrin, 78.59 for hyperoside and 73.20% for quercitrin at the concentration of 5 mg/mL. In addition, the antioxidant activity of the crude was correlated with the content of the four flavonoid glycosides.