Black Gram (Vigna mungo L.) Husk as a Source of Bioactive Compounds: An Evaluation of Starch Digestive Enzyme Inhibition Effects

This research recovered bioactive compounds from black gram husk (BGH, a by-product of sprout processing) using different ethanol concentrations and maceration times. Based on the results, the highest phenolic and saponin contents were recovered using an 80% ethanolic solution for 3 h, with the extract having both antioxidant and starch digestive enzyme inhibition effects. The major bioactive compounds present in the extract were gallic acid, gentisic acid, ferulic acid, and vitexin. The extract from BGH had an effective binding affinity to α-glucosidase, resulting in a potent ability of the extract to delay enzyme activity. Based on in vitro starch digestion using cooked rice as a model, adding the extract (10 mg/mL) increased the resistant starch content (from 53.9% to 55.9%) and lowered the estimated glucose index (from 83.1% to 81.0%) as compared to the control without the extract. Based on the overall results, the BGH extract could be promising as a functional ingredient with antioxidant activity and the ability to control postprandial blood glucose levels in the development of healthy food products.