Effect of germination period on the antioxidant activities and angiotensin-I converting enzyme inhibitory of Indonesian black rice

Abstract

Indonesian black rice (Oryza sativa L., Ketan Hitam-2) is pigmented rice with high potency as a nutraceutical compound, especially with its high protein content. The effect of the germination period on antioxidant activities and angiotensin I-converting enzyme (ACE-I) inhibitory of Indonesian black rice seed protein was studied to determine its potential use as a nutraceutical ingredient. In this study, the bioactive peptide was produced by protein modification through the germination process for 0, 2, 4, and 6 days. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and amino acid composition were conducted to determine the changes in protein during the germination period. Two antioxidant methods (ABTS•+ and OH•) were performed to determine the antioxidant activity and the defence against radical-mediated DNA damage by hydroxyl. Meanwhile, the antihypertensive potency was analysed by ACE-I inhibitor activity. The results showed that the antioxidant-protected hydroxyl radical-induced oxidative DNA damage and ACE-I inhibitor activities were increased during the germination period. The IC50 value of ABTS•+ and hydroxyl radical scavenging on the sixth-day germination were 28.18 μg/mL, and 24.84 μg/mL, respectively, lower than the control (before germinated). Moreover, the IC50 value of ACE-I Inhibitory activities during the six-day germination was (9.07 μg/mL). The above results indicated that the germination period could increase the activity of bioactive peptides in Indonesian black rice. It might be used in future nutraceuticals and human health applications.