Abstract
In this report, protein hydrolysate (TGH) of blood cockle (Tegillarca granosa) was prepared using a two-enzyme system (Alcalase treatment for 1.5 h following Neutrase treatment for 1.5 h). Subsequently, six antioxidant peptides were isolated from TGH using ultrafiltration and chromatography methods, and their amino acid sequences were identified as EPLSD, WLDPDG, MDLFTE, WPPD, EPVV, and CYIE with molecular weights of 559.55, 701.69, 754.81, 513.50, 442.48, and 526.57 Da, respectively. In which, MDLFTE and WPPD exhibited strong scavenging activities on DPPH radical (EC50 values of 0.53 ± 0.02 and 0.36 ± 0.02 mg/mL, respectively), hydroxy radical (EC50 values of 0.47 ± 0.03 and 0.38 ± 0.04 mg/mL, respectively), superoxide anion radical (EC50 values of 0.75 ± 0.04 and 0.46 ± 0.05 mg/mL, respectively), and ABTS cation radical (EC50 values of 0.96 ± 0.08 and 0.54 ± 0.03 mg/mL, respectively). Moreover, MDLFTE and WPPD showed high inhibiting ability on lipid peroxidation. However, MDLFTE and WPPD were unstable and could not retain strong antioxidant activity at high temperatures (>80 °C for 0.5 h), basic pH conditions (pH > 9 for 2.5 h), or during simulated GI digestion. In addition, the effect of simulated gastrointestinal digestion on TGP4 was significantly weaker than that on MDLFTE. Therefore, MDLFTE and WPPD may be more suitable for serving as nutraceutical candidates in isolated forms than as food ingredient candidates in functional foods and products.
Highlights
Toxic reactive oxygen species (ROS) induced by oxidative stress destroy structures of some functional biomacromolecules including DNA, proteins, and membrane lipids, which further lead to some chronic diseases, such as liver damage, type 2 diabetes, asthma, neurodegenerative diseases, and arthritis [1,2,3]
Defatted muscle of blood cockle was hydrolyzed under a two-enzyme system (Alcalase treatment for 1.5 h following Neutrase treatment for 1.5 h), and the degree of hydrolysis (DH) and yield of the resulted hydrolysate were 19.32 ± 1.37% and 9.62 ± 0.86%, respectively
the resulting hydrolysate (TGH) was further fractionized with MW Cut Off (MWCO) membranes of 3, 5, and 10 kDa, and four fractions including TGH-I(10 kDa) were prepared
Summary
Toxic reactive oxygen species (ROS) induced by oxidative stress destroy structures of some functional biomacromolecules including DNA, proteins, and membrane lipids, which further lead to some chronic diseases, such as liver damage, type 2 diabetes, asthma, neurodegenerative diseases, and arthritis [1,2,3]. Oxidative deterioration produces some off-flavors and harmful lipid metabolites, which negatively influence the food quality and somatic functions [2,4]. Eliminating superfluous ROS is important for keeping cellular homeostasis. People often use synthetic antioxidants to prevent and intervene ROS damage, but the negative effects of synthetic antioxidants, including liver damage and carcinogenesis, limit their scope of usage and dosage [5,6]. Mar. Drugs 2019, 17, 251; doi:10.3390/md17050251 www.mdpi.com/journal/marinedrugs
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