Isolation and Partial Purification of Winged Bean (Psophocarpus tetragonolobus (L.) Dc) Proteins with Bioactive Peptides Exhibiting Antioxidative and Antihypertensive Properties

Abstract

INTRODUCTION

According to the World Health Organization (2013), cardiovascular diseases account for almost one-third of the causes of death every year. From this fraction, hypertension covers about half of the primary reasons that trigger cardiovascular diseases. Moreover, many diseases can also be acquired by an individual having too much free radicals present in their body that have the capacity to attack healthy cells which may lead to cancer and brain malfunction. With this alarming impact on the health status of people, the research community conducts studies to find solutions to these health threats.

METHODS

Fifty grams of mature winged bean seeds were ground and defatted by adding n-hexane (1:10 w/v). The proteins of the 3 samples with 5 grams of the defatted meal, were extracted by adding 25 ml of extraction buffer. The resulting crude proteins were partially purified using ammonium sulfate precipitation at 35% and 80% saturation. The 3 precipitates (35P-80P) obtained were dissolved in an extraction buffer and was dialyzed three times for four hours in distilled water. The crude and the partially purified proteins (35P-80P) were characterized using Bradford assay and SDS-PAGE. The partially purified samples were then hydrolyzed using pepsin, trypsin and chymotrypsin, and the combination of the three enzymes in different digestion times (2, 12 and 24 hours). Verification was made using SDS-PAGE and the Densitometric Analysis. Antioxidative and antihypertensive properties were determined using the DPPH and ACE assay and the results of the samples were compared with positive controls.

RESULTS

The results showed that the 2-hr combined enzymes digest of both assays had the highest percentage of scavenging activity and percentage of Ace inhibition with 89.26 % and 78.76% respectively. The percentage of inhibition of the sample in the DPPH assay is higher by almost 1% compared to the positive control (potencee) with 88.52%. While on the ACE assay the positive control (captopril) has a higher percentage of ACE inhibitory activity with 88.16% compared to the 2-hr combined enzymes digest with 78.76%.

DISCUSSIONS

These results revealed that bioactive peptides extracted from mature winged bean seeds are potential antihypertensive and antioxidative sources.