Antiglycemic Activity of Vietnamese Scutellaria barbata Extract in Streptozotocin-Induced Diabetic Mice

Scutellariabarbata D. Don (S. barbata), a medicinal herb commonly used in traditional Chinese and Korean medicine, consists of bioactive neoclerodanes and flavonoids. However, its anti-hyperglycemic activity has not been reported. In this work, we used bioassay-guided fractionation to find effective anti-hyperglycemic fractions of S. barbata. The chemical components of these fractions were also determined structurally; they are scutellarin (1), luteolin (2), naringenin (3), tricin (4), baicalein (5), baicalin (6), apigenin (7), and wogonin (8). The most potent fraction SB6 consisting of flavonoids 5, 6, 7, and 8 showed 89% inhibition of α-glucosidase in the in vitro experiment. In further in vivo experiments on streptozotocin (STZ)-induced diabetic mice, SB6 exhibited significant anti-hyperglycemic activity comparable to metformin after 28 days of treatment. This fraction, however, did not show efficiency in reducing the weight gain of the treated mice.