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 concentrationdependent 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 (IC 50 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.

Cucurbitaceae Seed Protein Hydrolysates as a Potential Source of Bioactive Peptides with Functional Properties

“…On the other hand, high-yield protein isolates can be extracted from Cucurbitaceae seeds in alkaline conditions when not aiming only for cucurbitin but for all protein fractions in one [ 18 , 19 , 23 – 25 ]. First, the defatted seed meal is treated using NaOH solution (pH 8–10).…”

“…Following the extraction process, cucurbitin [ 10 , 22 ], the protein isolate [ 23 – 27 ], or the defatted seed meal itself [ 17 ] can be hydrolyzed in order to obtain Cucurbitaceae seed protein hydrolysates. Generally, enzymatic hydrolysis is preferred for any type of protein since it can guarantee less drastic hydrolytic conditions and more specific cleavage sites in comparison to chemical hydrolysis [ 28 , 29 ].…”

“…The specificity of the enzymes used in Cucurbitaceae seed protein hydrolysis is thought to result in different DH and molecular weight distributions of the hydrolysates [ 17 , 22 , 23 ]. Venuste et al [ 17 ] analyzed the influence of four different enzymes (Alcalase, Flavourzyme, Protamex, and Neutrase) on the hydrolysis process of pumpkin (Cucurbita moschata) seed protein meal.…”

“…The authors suggest that, due to the specificity of the two enzymes, the same protein was hydrolyzed at different peptide bonds, resulting in a different composition of the hydrolysates. Similarly, Arise et al [ 23 ] studied the influence of enzyme type (Pepsin, Trypsin, and Alcalase) on the hydrolysis process of watermelon ( Citrullus lanatus L.) seed proteins. In this study, Trypsin produced a higher DH (26.26 ± 0.27%) than Pepsin and Alcalase (19.38 ± 0.86 and 13.16 ± 1.82%, resp.).…”

Kinetic characteristics of partially purified invertase from <em>Citrullus lanatus</em> Rind

“…It comprises of about 6% sugar, 91% water and the residual portion consisting of vitamins and minerals. Water melon has been reported in several studies to have therapeutic properties, including antihypertensive, anti-diabetic, antioxidant, anti-inflammatory and antimicrobial effects (Arise et al, 2016a;Arise et al, 2016b;Erhirhie and Ekene, 2013). The rind of watermelon rind is usually discarded as waste, although it is edible (Al-Sayed and Ahmed, 2013).…”