Digestive enzyme inhibition activity of the phenolic substances in selected fruits, vegetables and tea as compared to black legumes

The inhibition of starch and fat digestion by phenolic substances is relevant to the management of type-II diabetes. Total phenolics, total flavonoids and condensed tannin content in crude, semi-purified extracts (purified by XAD-7 column) from eight types of foods (black tea, green tea, blueberry, blackberry, red cabbage, broccoli, black turtle bean and black soybean) and five fractions from legumes (fractionationed by Sephadex LH-20 column) were compared for their antioxidant capacities and digestive enzymes (α-amylase, α-glucosidase and lipase) inhibition capacity. Results showed that semi-purified extract from black turtle bean compared favorably with tea and berries in digestive enzyme inhibition. Semi-purified extracts from legumes, tea and berries showed more potency (lower IC50 values) against α-amylase, α-glucosidase than commercial inhibitors. Several fractions from legumes exhibited more potency against these digestive enzymes than commercial inhibitors. Myricetin showed the highest potency against α-amylase, α-glucosidase and lipase (IC50: 0.38 mg/mL, 0.87 μg/mL and 15 μg/mL, respectively).