Purple and red rice (<i>Oryza sativa</i> L.) bran polyphenols show antiobesity and antidiabetic activities

Abstract Background and Objectives Rice bran is a source of bioactive polyphenols. This study aimed to characterize the antidiabetic potential of different rice brans (one brown, two red, and two purple) by examining their ability to inhibit α‐amylase, α‐glucosidase, and pancreatic lipase, and to stimulate glucose uptake in adipocytes. Findings All pigmented bran extracts significantly inhibited α‐glucosidase. Both red rice brans inhibited α‐amylase close to 50% at the highest dose tested. All four pigmented rice brans inhibited lipase in vitro (IC 50 values 4.38–10.09 mg/mL). The pigmented rice brans studied contained higher levels of total polyphenolic content (TPC), total flavonoid content (TFC), and antioxidant capacity when compared to brown rice bran. Purple bran contained anthocyanins and red brans contained proanthocyanidins. The pigmented brans consisted of higher levels of total benzoic acids, while the brown rice bran had higher levels of total cinnamic acids. Tricin was identified in all pigmented brans. Conclusions Our study indicates that pigmented rice brans have the ability to manage obesity and diabetes due to their inhibitory effects on lipid and carbohydrate digestion. Several bioactive polyphenols were identified. Significance and Novelty The potential of pigmented rice bran to inhibit α‐amylase, α‐glucosidase, and lipase was confirmed.