Antioxidant potential of gamma ray irradiated winged bean (Psophocarpus tetragonolobus) seed protein hydrolysate

Abstract

Background: Winged bean or Psophocarpus tetragonolobus (WB) seeds have high protein content and could be applied as a source of antioxidant proteins and peptides. The utilization of gamma rays in plant protein extraction provides consumers with a safe and harmless technology.

Objective: To determine the efficiency of gamma rays in the protein extraction process of WB seeds and investigate the antioxidant activity, cytotoxicity, cytoprotective effect of the gamma ray irradiated WB (WB-G) seed protein hydrolysate.

Methods:WB seeds were irradiated with gamma ray (WB-G) and total protein were extracted by acid-base extraction method. The total protein was further hydrolyzed with alcalase enzyme to obtain the protein hydrolysate. The antioxidant activity was evaluated by DPPH and ABTS assay. The cytotoxicity and cytoprotective effect were determined by MTT assay. The cellular reactive oxygen species was further analyzed by H2-DCFDA assay.

Results: The protein extracted from WB-G seeds showed higher protein yield and antioxidant activity than that of non-irradiated seeds. After hydrolysis with alcalase enzyme at 55°C for 6 hours, WB-G protein hydrolysate with degree of hydrolysis of 90.00±0.91% exhibited strong antioxidant activity with IC50 value of 10.30±0.02 µg/ml and 3.10±0.06 µg/ml as measured by DPPH and ABTS assay, respectively. Moreover, it showed no toxicity toward L929 mouse fibroblast cells and IPEC-J2 cell lines and can reduce the damage caused by H2O2. As determined in cellular reactive oxygen species by H2-DCFDA assay, the WB-G protein hydrolysate can reduce the level of ROS and subsequently the damage of cell by H2O2. 

Conclusions: This study demonstrated that gamma ray irradiation on the WB seeds can increase the protein yield and its protein hydrolysate exhibited promising antioxidant activity and cytoprotective effect on cells against H2O2 damage. It might be developed as an alternative food or feed supplement.

Keywords:Psophocarpus tetragonolobus; Gamma rays; Protein hydrolysate; Antioxidant activity; Cytoprotective effect