Abstract
This study was conducted to search for novel natural bioactive compounds (peptides and phenolic compounds) with hypoglycemic, antioxidant, and anti-diabetic potential from barley protein fractions and isolates. Protein isolate and globulin, prolamin, glutein-1, and glutein-2 fractions of barley flour were extracted from barley flour. Free and bound phenolic compounds were extracted from protein isolate and protein fractions. Protein isolate and protein fractions from barley were subjected to pancreatic hydrolysis to obtain peptides. Peptide and both free and bound phenolic compounds were subjected to determine antioxidant and their potential to inhibit the key enzymes relevant to diabetes and hypertension using in vitro models. The extracted phenolic from prolamin fraction and protein isolate revealed the highest content of total phenolics (2.0-2.4 mg/g), antioxidant activity (65-73%), angiotensin converting enzyme-inhibitory activity (73-87%), and α-amylase inhibitory activity (57-77%) as compared to that of other protein fractions. Hydrolysates of prolamin fraction exhibited the highest antioxidant activity (77.7%) and angiotensin converting enzyme-inhibitory activity (61.3%) as compared to all other protein fractions and protein isolate. Poor correlations were obtained between total phenolic content, antioxididant activity, ACE-inhibitory activity, and α-amylase inhibitory activity of phenolic compounds from protein fractions and isolate. On the other hand, positive correlations were obtained between antioxididant activities, angiotensin converting enzyme-inhibitory activity, and the degree of hydrolysis of peptides from hydrolyzed protein fractions and protein isolate. Our findings indicated that prolamin fraction and protein isolate were recommended to be used as hypoglycemic, antioxidant, and anti-diabetic ingredients as potential candidates in functional, nutraceutical, and pharmaceutical industries.