Evaluation of alpha-glucosidase inhibition activity and glycosides in the Syringa pubescens Turcz from different geographical origin

Inhibition of α-glucosidase is an attractive strategy for the control of hyperglycaemia. Naturally occurring bioactive compounds are potential sources of α-glucosidase inhibitors. The Syringa pubescens Turcz (SP) is commonly used as Chinese folk medicine for treatment of hepatitis and cirrhosis. However, the anti-hyperglycemic activity of SP was lack of study and the report on compounds of α-glucosidase inhibitory activity of SP was also insufficient. In this study, the α-glucosidase inhibitory activity of SP extract was firstly assessed in vitro. The quantification analysis of bioactive glycosides in SP collected at different geographical origins and its correlation with α-glucosidase inhibitory activities were investigated. As the results, six glycosides including salidroside, echinacoisde, forsythoside B, verbascoside, isoacteoside and oleuropein were simultaneously determined using HPLC-DAD method. Moreover, SP collected from different geographical origins exhibited different concentrations of bioactive glycosides and had potential α-glucosidase inhibitory activity. The results of correlation analysis indicated that the amounts of glycosides were positively correlated with the α-glucosidase inhibitory activities of SP. Then, the evaluation of α-glucosidase inhibitory activity of six glycosides was performed. And docking study was conducted to predict the possible binding sites of forsythoside B. Forsythoside B might be the most possible α-glucosidase inhibitor in SP.