In vitro α-amylase inhibitory and antioxidant properties of soluble proteins and their peptic hydrolysates from raw and cooked commercially available oatmeal

Arvin Paul P. Tuaño, University of the Philippines Los Banos
Lance Aaron G. Tan, De La Salle Medical and Health Sciences Institute
Mia Bianca S. Hernandez, De La Salle Medical and Health Sciences Institute
Ramon E. Lu, De La Salle Medical and Health Sciences Institute


Background and objectives: Ready-to-eat cereal-based foods like quick-cooking oatmeal are commonly available in the market often highlighting the levels of nutrients and the effects of dietary fiber. Information about the proteins in these foods is limited to content only. This study measured two health-related bioactivities of the salt-soluble proteins in commercially available oatmeal using in vitro assays. Soluble proteins and their peptic hydrolysates extracted from raw and cooked commercially available oatmeal were analyzed for their in vitro α-amylase inhibitory activity and antioxidant properties in an attempt to determine the health-promoting potential of the protein portion of oatmeal. Total soluble proteins were extracted from the raw and cooked oatmeal samples using saline solution, precipitated, and dialyzed, and their gel electrophoretic profiles were also studied. Findings: Two major protein bands were found in both extracts with estimated molecular weight range of 22–24 and 54–56 kDa, respectively. Soluble proteins generally had low inhibitory activity toward α-amylase (~5%) but increased when these were hydrolyzed with pepsin. The crude proteins from cooked oatmeal showed the highest α-amylase inhibitory activity. Metal-reducing ability was higher for the unhydrolyzed proteins from raw (48%) and cooked (32%) oatmeal than for their peptic hydrolysates (5% and 9%, respectively), while radical-scavenging activity was higher for the peptic hydrolysates (65%–90%) than for the unhydrolyzed proteins (3%–12%). Conclusions: The soluble proteins of commonly consumed quick-cooking oatmeal offer health benefits such as glucose-lowering potential via α-amylase inhibition and antioxidant properties via metal-reducing capacity. Their peptic hydrolysates may slightly reduce starch digestibility but showed promising radical-scavenging potential. Significance and novelty: Current findings may be useful to cereals manufacturing industry and to consumers who consider other health-related benefits of whole grain food products aside from nutrient content and beneficial effects of dietary fiber.