Inhibition of wheat bran and it's active compoments on α-glucosidase in vitro

BACKGROUND: Wheat bran is a traditional Chinese medicine; however, it is mostly used as feedstuff in China. Wheat bran is widely accepted as an important ingredient in many low-glycemic index foods in modern western societies; however, its glycemic control mechanism is unknown. OBJECTIVE: To determine potent α-glucosidase inhibitory compounds from wheat bran and to identify the inhibition on α-glucosidase. MATERIALS AND METHODS: Ethanolic extract of wheat bran was prepared to evaluate the inhibitory activity on α-glucosidase, then fractionation of the extract was guided by in vitro enzyme-inhibition assay, and the potent α-glucosidase inhibitory compounds were identified by high performance liquid chromatography and atmospheric pressure chemical ionization-mass spectrometry; finally the enzyme inhibition process was studied using the Michaelis-Menton and the Lineweaver-Burk equations. RESULTS: Both baker's yeast and rat intestinal enzymes were mostly inhibited (87.9% and 66.8% inhibition, respectively) at concentration 0.6 mg/mL of the ethanolic extract of wheat bran. The petroleum ether fraction in the ethanolic extract of wheat bran showed significant activity against rat intestinal α-glucosidase, and revealed a dose-dependent effect. The inhibition was 76.57% at 0.3 mg/mL and 100% at 0.6 mg/mL. The active fraction 13 of petroleum ether fraction was identified as alkylresorcinols (ARs). ARs showed strong inhibition towards α-glucosidase and its IC(50) value was found to be 37.58 μg/mL. The enzyme kinetic studies showed that, in the presence of ARs, the Michaelis-Menton constant (K(m)) remains constant whereas the maximal velocity (V(max)) decreases, revealing a non-competitive type of inhibition. CONCLUSION: The therapeutic potentiality of ARs in the management of the postprandial hyperglycemia will proliferate the utilization of wheat bran in controlling type 2 diabetes.