Environ Exp Biol (2016) 14: 163–172

In vitro antioxidant and α-amylase inhibitory properties of watermelon seed protein hydrolysates

Abstract

Proteins from watermelon (Citrullus lanatus L.) seed were isolated using acid-induced precipitation method and then hydrolysed using pepsin, trypsin and alcalase. The hydrolysates were investigated for in vitro antioxidant and α-amylase inhibitory properties. The yield of peptic hydrolysis (68.9 ± 1.0%) was significantly higher than of tryptic (41.4 ± 1.1%) and alcalase (38.5 ± 0.5%) hydrolysis. Peptic hydrolysate showed the highest radical-scavenging ability whereas tryptic hydrolysate gave the highest reducing ability. In a concentration-dependent manner, the hydrolysates demonstrated potent α-amylase inhibitory ability with alcalase and tryptic hydrolysates exhibiting 86.0 ± 3.9 and 83.0 ± 3.5% α-amylase inhibition respectively (IC⁵⁰ 0.149 to 0.234 mg mL^–1). Kinetic analysis revealed that the three enzyme hydrolysates inhibited α-amylase activity via a non-competitive inhibition mechanism. The results therefore indicate that these multidirectional bioactivities of watermelon seed protein hydrolysates may serve as useful tools in the formulation of antidiabetic agents.