仿刺参精低分子质量多肽的制备及抗氧化作用

本实验以仿刺参精为原料，制备出多肽并考察其体外和体内抗氧化活性。以清除羟自由基（?OH）能力为指标，考察木瓜蛋白酶、复合蛋白酶和风味蛋白酶的5 种酶解方式产生的酶解产物的活性，优化实验用酶。经超滤分级后，测定各级组分的分子质量分布、可溶性蛋白质含量、多肽含量和清除?OH能力。选择清除?OH能力较好的低分子质量多肽组分，测定氨基酸组成，设定低、中、高剂量组（100、200、600 mg/kg（以体质量计，下同））、模型对照组、和空白对照组进行42 d小鼠灌胃实验。实验完成后，检测小鼠血液中超氧化物歧化酶（superoxide dismutase，SOD）活力、谷胱甘肽过氧化物酶（glutathione peroxidase，GSH-Px）活力、谷胱甘肽（glutathione，GSH）含量、丙二醛（malondialdehyde，MDA）含量和蛋白质羰基含量。结果表明，由木瓜蛋白酶水解，经超滤制备的＜1 000 u仿刺参精多肽具有较好的体外清除?OH能力，其半数抑制浓度为6.02 mg/mL，含量占比为58%，氨基酸组成中谷氨酸等酸性氨基酸和酪氨酸等疏水性氨基酸含量丰富。小鼠抗氧化模型实验表明，实验组生长正常，高剂量多肽组小鼠体内SOD活力显著提高（P＜0.05），GSH的含量提高极显著（P＜0.01）、GSH-Px活力也呈剂量依赖性升高，但未达到差异显著（P＞0.05）。MDA和蛋白质羰基含量得到有效降低，后者达到差异显著（P＜0.05）。研究结果显示：＜1 000 u仿刺参精多肽具有提高小鼠抗氧化能力的效果，可以作为相关功能产品开发的原材料。

Preparation and Antioxidant Activity of Low Molecular Weight Peptide from Apostichopus japonicus Sperm

The chemical components and in vivo antioxidant activity of peptides prepared from Apostichopus japonicus sperm were detected. The best enzyme to prepare antioxidant peptides from Apostichopus japonicus sperm was selected by comparing the hydroxyl radical scavenging activities of five protein hydrolysates obtained with papain, protamex and flavourzyme. After ultrafiltration of the hydrolysates, the weight distribution, soluble protein and polypeptide contents and hydroxyl radical scavenging capacity of the fractions were determined. The low molecular weight component of the peptide with higher hydroxyl radical scavenging capacity was analyzed for its amino acid composition, and then it was orally administered to mice at low, middle and high dosages (100, 200, 600 mg/kg), respectively. The administration period for the three dosage groups as well as the model control and blank control groups lasted for 42 days. At the end of administration, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities, GSH, malondialdehyde (MDA) and protein carbonyl contents were measured in the serum of mice. Results showed that the peptide prepared by papain hydrolysis and ultrafiltration with molecular weight cut-off of < 1 000 u had better hydroxyl radical scavenging capacity in vitro with half maximal inhibitory concentration of 6.02 mg/mL, accounting for 58% of the total peptides. The acidic amino acid glutamic acid and the hydrophobic amino acid tyrosine dominated its amino acid composition. The results of antioxidant tests with a mouse model showed that all experimental mice could normally growth, and serum SOD activity and GSH content in the mice from the high-dosage group were improved significantly (P < 0.05) and highly significantly (P < 0.01), respectively. The activity of GSH-Px also exhibited a dosage-dependent improvement, but did not show a significant difference (P > 0.05). The contents of MDA and protein carbonyl were both reduced and the latter was significant (P < 0.05). All these results demonstrated that the peptide with a molecular weight less than 1 000 u could enhance antioxidant function in mice, and therefore it has potential as an ingredient of functional foods.