Rice bran protein hydrolysate (<50 kDa RBPH) from Thai jasmine variety demonstrating a high Angiotensin I converting enzyme (ACE) inhibitory activity was purified and characterised. ACE inhibitory peptides were obtained from a two-step purification process: gel filtration and preparative reverse-phase high-performance chromatography (RP-HPLC) and then identified by mass spectrometer hybrid quadrupole-time-of-flight. A novel peptide GSGYF in the RBPH was firstly identified and found to have a partial sequence homology of Oryza sativa Japonica Group. This sequence was further synthesised to exhibit as good an inhibition potency with IC 50 value of 2.11 µg mL À1 as Captopril (1.15 µg mL À1 ). The cytotoxicity test revealed that this RBPH is non-toxic against Vero cells. In addition, the <50 kDa RBPH was resistant to in vitro digestion by pepsin and trypsin. These findings suggest that the RBPH containing ACE inhibitory peptides is likely to be safer and healthier than synthetic drugs and can be an effective food supplement for lowering blood pressure.

This research aimed to elucidate significant factors affecting antioxidant capacity of protein hydrolysates from tilapia processing byproducts. Effects of protein type, substrate concentration (0.4-1.2%) and time of hydrolysis (0-60 min) on antioxidant abilities were investigated. Antioxidant activity of the alkaline-aided protein hydrolysate (APH) hydrolyzed by Protease G6 at 1.2% and 60 min hydrolysis was comparable to the control (minced tilapia muscle hydrolysates) and was more effective than the myofibrillar protein and sarcoplasmic protein hydrolysates. Principal component analysis showed that the APH exert their antioxidant capacity by peroxyl radical quenching ability. These findings provide evidence that the APH from fish byproducts can be alternatively used as a natural antioxidant.