Antioxidant and Blood Sugar-Stabilizing Activities of Extracts from Three Coloured Rice Varieties in Streptozotocin-Induced Diabetic Mice

Abstract

Purple brown rice (Oryza sativa L. indica), red rice (Oryza sativa L. Orysa), and black glutinous rice (Oryza sativa l. Glutinosa Tanaka) are three popular types of staple food, which are beneficial to human health. The present study was conducted to evaluate the antioxidant and hypoglycemic effects of three ethanol extracts from Vietnamese rice in streptozotocin-induced diabetic mice. Ethanol extracts were prepared from three varieties of rice, which included black glutinous rice (EOGT96), red rice (EOLO96), and purple-brown rice (EOLI96). Swiss albino male mice were divided into six groups: I (negative control), II (positive control), III (drug control group), IV (EOLT96), V (EOLI96), and VI (EOLO96). The antioxidant activity of the various extracts was evaluated using the DPPH (2,2-diphenyl-1-picrylhydrazyl) and nitric oxide methods. The total phenolic content and the α-amylase inhibitory activity were also determined. The DPPH results revealed that the EOLI96 produced the highest antioxidant activity (IC50 = 19.38 ± 0.64 μg/mL), and the EOGT96 was only 3.7 times less potent at scavenging free radicals than the quercetin standard. In comparison to the other two extracts from rice varieties, the extract from EOGT96 also had the highest total polyphenol content. Blood sugar levels were much lower in the group of mice given the EOGT96 than in the control group, and they were similarly comparable to those of the animals administered glibenclamide. The findings of this study revealed that ethanol extract from black glutinous rice can reduce diabetes by lowering high blood sugar levels when used at the appropriate dosage.