Revealing of free radical scavenging and angiotensin I-converting enzyme inhibitor potency of pigmented rice seed protein

Abstract

The potential source of bioactive protein from pigmented rice seed was investigated by buffered extracting from nine varieties (Merah-SP, Gogo Niti-2, Merah Wangi, Super Manggis, Lamongan-1, Mota, Ketan Hitam-2, Beureum Taleus, and Aek Sibundong) and non-pigmented rice (IR-64) as a control. The potent contributor to free radical scavenging of extracted proteins was evaluated by analyzing their free amino acid composition. The free radical scavenging and angiotensin-I converting enzyme (ACE-I) inhibitory activity of these proteins were analyzed in-vitro. The free radical scavenging activity was analyzed using various standard methods, including radical cation 2,2-azinobis-3-ethylbenzothiazoline-6-sulphonate acid (ABTS •+ ), hydroxyl radical (OH • ) and defense against radical-mediated DNA damages by hydroxyl. Total free amino acid content ranged between 77.7-181.2 g/100 g protein, and among them, Ketan Hitam-2 displayed the highest abundant antioxidant amino acid grouping (23.23%) and shown significantly higher ABTS •+ activity (IC 50 =8.64 µg/mL) and OH • activity (IC 50 =20.33 µg/mL). Moreover, Ketam Hitam-2 also exhibited notable ACE-I inhibitory activity (IC 50 =6.20 µg/mL) and protected hydroxyl-induced oxidative damage to DNA. The in-vitro systems for free radical scavenging and ACE-I inhibitory were used to acquire the data. The potency of Ketan Hitam-2 seed protein could be utilized as a natural nutraceuticals compound.