Abstract:To study the effects of flavonoids on the activity of α-glucosidase and their inhibitory kinetic characteristics in different polar extraction phases of the alcohol extract of Opisthopappus taihangensis (Ling) Shih, the ethyl acetate phase, n-butanol phase, residual water phase and petroleum ether phase of flavonoids from Opisthopappus taihangensis were extracted. A screening model of α-glucosidase activity inhibition was established by in vitro (PNPG) method. Lineweaver-Burk curves were drawn to analyze the type of inhibition of α-glucosidase by flavonoids from Opisthopappus taihangensis. Flavonoids from Opisthopappus taihangensis in different polar extraction phases showed different degrees of inhibition on α-glucosidase, and a significant dose-effect relationship was found between the inhibitory activity and the concentration of flavonoids. Among them, the flavonoid content and α-glucosidase inhibitory activity in the ethyl acetate phase and n-butanol phase were significantly higher than those in the other extraction phases and higher than that of the acarbose, while the inhibitory activity of glucosidase is lower than that of acarbose. The inhibitory activity was: ethyl acetate (IC50=1.01 mg/mL) ＜n-butanol (IC50=1.25 mg/mL) ＜acarbose (IC50=1.47 mg/mL) ＜residual water (IC50=1.77 mg/mL) ＜petroleum ether (IC50=2.12 mg/mL). Enzyme inhibition kinetics studies found that α-glucosidase of flavonoids from Opisthopappus taihangensis in ethyl acetate phase and n-butanol phase is competitive and non-competitive mixed type; flavonoids from Opisthopappus taihangensis in residual water phase and petroleum ether phase α-glucosidase is a mixed type of competition and anti-competition. The flavonoids of different polar extraction phases of Opisthopappus taihangensis have α-glucosidase inhibitory activity, and have good potential in developing health foods or medicines that assist in lowering blood sugar. Ethyl acetate phase and n-butanol phase flavonoids can be developed as novel α-glucosidase inhibitors.
