Abstract
Proteins were extracted from perilla (Perilla frutescens L. Britton) seed by-products and hydrolyzed with an alkaline protease. Antioxidant peptides were purified from the hydrolysate by size-exclusion chromatography and RP-HPLC. Two peptides with strong antioxidant activity were identified as Tyr-Leu (YL) and Phe-Tyr (FY) with the molecular mass of 294.33 Da and 328.33 Da, respectively. Synthesized YL and FY efficiently quenched free radicals (DPPH, ABTS and hydroxyl radicals) and showed high oxygen radical absorbance capacity. The two peptides also inhibited lipid peroxidation in the rat liver. Furthermore, YL and FY could protect HepG-2 cells against hydrogen peroxide-induced oxidative damage without cytotoxicity. Based on the structure-activity analysis, the Tyr residue was crucial for the antioxidant activity of YL and FY. The results indicate that the protein hydrolysate from perilla seed by-products possessed potent biological activity and can be utilized to develop health-related nutraceutical ingredients.
Highlights
During cell metabolism, reactive oxygen species (ROS) are produced
Perilla seed protein hydrolysate was separated into three fractions (a, b, c) with a Sephadex G25 column (Fig 1A)
Fraction c with the longest retention time and lowest molecular weight showed the highest DPPH radical-scavenging activity (87.7%) at a concentration of 0.5 mg/ mL. This was in accordance with previous reports that peptides with smaller molecular weight from protein enzymatic hydrolysates had better antioxidant activity[6, 14]
Summary
When metabolism is disordered or attacked by exogenous free radicals, the balance between endogenous antioxidants and free radicals could be broken. Synthetic chemical antioxidants such as butyl hydroxy anisole (BHA), butylated hydroxytoluene (BHT), and tert-Butylhydroquinone (TBHQ) have strong antioxidant activity and are commonly used in the food industry[2]. These antioxidants possess potential risks, their usage should be strictly limited[3]. Antioxidant peptides can offer potential health benefits with low molecular weight, high activity, easy absorption, little or no negative side effects, and fast clearance from
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