Selective Extraction and Antioxidant Properties of Thiol-Containing Peptides in Soy Glycinine Hydrolysates.

Xiuzhen Ding,Caimeng Zhang,Xiangzhen Kong,Yeming Chen,Yufei Hua,Xiangyang Li

doi:10.3390/molecules23081909

Abstract

A highly selective procedure to extract thiol-containing peptides (TCPs) from complicated soy glycinin hydrolysates (SGHs) was described. This procedure included the reduction of disulfide bonds by 1,4-dithiothreitol (DTT) and enrichment of TCPs through Thiopropyl-Sephrose 6B covalent chromatography. TCPs were confirmed using a strategy based on mass shift after differential alkylation of sulfhydryl groups with iodoacetamide and N-ethylmaleimide by matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF-MS). The antioxidant activities of TCPs were evaluated using chemical assays. DTT reduction increased the concentration of sulfhydryl groups from 1.8 μmol/g to 113.8 μmol/g. The efficiency of the extraction was improved by optimizing the loading of sample, extraction and desorption time and the content of desorption reagent. Both of the adsorption and desorption process were found to fit a pseudo-second order model. MALDI-TOF-MS showed that 36 of the 45 extracted peptides were TCPs. The EC50 of TCPs for DPPH, hydroxyl radical, and superoxide anion radical was 0.1, 1.49 and 0.084 mg/mL, respectively. The reducing power of TCPs (0.2 mg/mL) was of 0.375. These results suggest that the combination of DTT reduction and Thiopropyl-Sepharose 6B covalent chromatograph was a successful pathway to extract TCPs from SGHs and the TCPs could be used as potential antioxidants.

Highlights

Thiol-containing compounds exert unique properties that could improve food safety, nutrition, and health
The main advantage of this reductant is the high degree of degree of specificity to disulfides but main disadvantage is that the SH groups could compete directly specificity to disulfides but main disadvantage is that the SH groups could compete directly with the with the sulfhydryl groups in soy glycinin hydrolysates (SGHs) in the latter procedure
These results indicated that DTT in thiol-containing peptides (TCPs) was almost removed by reversed phase chromatography

Summary

Introduction

Thiol-containing compounds exert unique properties that could improve food safety, nutrition, and health. Researchers showed that thiols could suppress the mutagenic activity of aflatoxin B1 [1]. Thiol groups exhibited great activity to react with the dehydroalanine and inhibit the formation of lysinoalanines during the alkali treatment of food proteins [3]. Thiol-containing compounds were able to improve the bioavailability of legume proteins by the way of formation of mixed disulfide bonds [4]. Some of thiol-containing compounds are used therapeutically to treat diseases, including acrylonitrile intoxication [5], alcoholand acetaminophen-induced liver and stomach injuries [6,7], liver necrosis induced by the tricyclic

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