Antioxidant, antidiabetic, and antihypertensive activities of defatted pigmented rice bran protein hydrolysates

Food-derived protein hydrolysates or peptides with health benefits may help to treat chronic diseases like cancer, diabetes, and hypertension. These components can be converted into bioactive ingredients suitable for use in functional foods, pharmaceuticals, and nutraceuticals, thereby creating significant value opportunities in food production. Bran, the hard-outer layer of cereal grain, is a by-product of the milling process to produce refined grains. Pigmented rice bran provides 12–16% protein and is an excellent source to produce protein hydrolysates using commercial proteases. In this investigation, the major rice bran proteins, including prolamin, albumin, globulin, and glutelin, were extracted sequentially using the modified Osborne method after raw rice bran (BRRI-Dhan-84) had been defatted. Proteins extracted from rice bran were lyophilized into powder form, and rice bran protein molecular weights were assessed using SDS-PAGE. The rice bran proteins were hydrolyzed under optimal conditions for the three commercial proteases: trypsin, alcalase, and neutrase. Trypsin hydrolyzed glutelin had the highest DPPH (76.445 ± 0.435%) and ABTS+ (99.114 ± 0.491%) radical scavenging activities. Neutrase-digested globulin and albumin exerted the highest α-amylase (77.450 ± 0.550%) and α-glucosidase (65.344 ± 0.736%) inhibitory activities, respectively. Albumin digested by trypsin exhibited the highest ACE (96.227 ± 0.355%) inhibitory activities. Our study suggests that bioactive peptides in the protein hydrolysates, produced through enzymatic hydrolysis, may be responsible for these inhibitory activities. Antioxidant, antidiabetic, and antihypertensive properties of rice bran protein hydrolysates have explored a new window for using them as nutraceuticals, however, further in vivo investigation is needed before human consumption.