Preparation and identification of antioxidant peptides from protein hydrolysate of marine alga Gracilariopsis lemaneiformis
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In this experiment, Gracilariopsis lemaneiformis proteins were hydrolyzed by different proteases (trypsin, pepsin, papain, α-chymotrypsin, alcalase) to prepare antioxidant peptides. Comparing with other hydrolysates, α-chymotrypsin hydrolysates displayed the highest antioxidant activity. The hydrolysis conditions of α-chymotrypsin were further optimized using response surface methodology (RSM), and the optimal conditions were as follows: substrate concentration 10 mg/mL, reaction time 2.0 h, enzyme/substrate ratio (E/S) 1.9%, temperature 46.4 °C, and pH 9.2. After fractionation and separation by ultrafiltration, gel exclusion chromatography, and reversed-phase high-performance liquid chromatography, an antioxidant peptide was purified and identified as Glu-Leu-Trp-Lys-Thr-Phe by UPLC-MS/MS. The results also confirmed that Glu-Leu-Trp-Lys-Thr-Phe could significantly scavenge DPPH free radicals with an EC50 value of 1.514 mg mL−1. It seems that the smaller molecular size and hydrophobic and/or aromatic amino acids in its sequence contributed to its antioxidant activity. Thus, G. lemaneiformis protein hydrolysate may be a good source of natural antioxidants.
KeywordsGracilariopsis lemaneiformis Rhodophyta, Antioxidant peptides DPPH Optimization
This work was funded by the Sciences and Technology program in Ningbo (2017D10019), the Science and Technology Enrichment program in Ningbo (2016C10034), and the National Natural Science Foundation of China (31672674) and was also sponsored by the K. C. Wong Magna Fund from Ningbo University.
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