The effects of corni fructus extract and its fractions against α-glucosidase inhibitory activities in vitro and sucrose tolerance in normal rats.

Corni fructus (Cornus officinalis Sieb. et Zucc.) is a traditional medicine exerting multifaceted protective effects against diabetes and its complications. In this study, to further identify the physiological effects of corni fructus against diabetes and its complications, we investigated α-glucosidase inhibitory activities in vitro and employed the sucrose tolerance test as an indicator of the control of the postprandial blood glucose level. In vitro assays showed that corni fructus extract has a higher inhibitory activity than its major components. Then, corni fructus extract was fractionated again to screen the fractions showing a strong inhibitory activity against α-glucosidase. Of the tested fractions, five showed a rate of α-glucosidase inhibition of over 80%. Next, the four abundant fractions were evaluated their IC(50) values, as well as the inhibition mode in vitro and plasma glucose level after sucrose loading in normal Wistar rats. As a result, the IC(50) values of these fractions were between 1.1-2.1 μg/ml. Among the four fractions, three showed mixed inhibition, while one (Fr. 4-9) showed the competition-independent inhibition of α-glucosidase. In addition, Fr. 4S-1 significantly inhibited the rise in the plasma glucose levels at a dose of 20 mg/kg body weight after sucrose loading. These results indicate that Fr. 4S-1 from corni fructus has a potential to control postprandial hyperglycemia by α-glucosidase inhibition.