Preparation of alcalase hydrolysed rice bran protein concentrate and its inhibitory effect on soybean lipoxygenase activity

Summary Rice bran protein concentrate ( RBPC ) was prepared from defatted rice bran and hydrolysed by alcalase at different hydrolysis times. As the hydrolysis times increased, the degree of hydrolysis ( DH s) increased. RBPC hydrolysate obtained at 50 min ( RBPCH ‐50) had the highest inhibitory efficiency on soybean lipoxygenase ( LOX ) activity (66%). The inhibition kinetics of the reaction analysed by Lineweaver–Burk plots indicates that RBPCH ‐50 is a competitive inhibitor. RBPCH ‐50 inhibited soybean LOX with an IC 50 of 11.73 μg μL −1 RBPCH ‐50, and the obtained K I was 4.59 μg μL −1 RBPCH ‐50. LOX inhibitory activity of RBPCH ‐50 was significantly higher than that of 50 and 100 ppm butylated hydroxyanisole ( BHA ) and 50, 100, and 200 ppm butylated hydroxytoluene ( BHT ) ( P  ≤   0.05); however, LOX inhibitory activity of RBPCH ‐50 was similar to that of 200 ppm BHA ( P  >   0.05). Therefore, RBPCH might potentially be used as a natural LOX inhibitor.