Preparation and identification of antioxidant peptides from Spirulina platensis

Abstract

Spirulina is a very economical microalgae, its protein content is high and the content and proportion of essential amino acids required by the human body are up to the proportion specified by FAO or even above. In addition, spirulina also has a variety of biological activities such as antioxidant, blood pressure lowering, blood sugar lowering, and immune regulation. In this study, spirulina was used as raw material, and the phycobiliprotein protein was extracted by repeated freeze-thaw method and water immersion extraction method, and the extraction rate of the two methods was compared. Antioxidant peptides were prepared by alkaline protease, pepsin, trypsin, papain and enzymatic hydrolysis, which acted on 1h, 2h, 3h, 4h, and 5h, respectively, and the antioxidant capacity of the isolated antioxidant peptides was determined, and the ABTS+ radical scavenging rate was determined by ultrafiltration as three components less than 3 kDa, greater than 3 kDa, less than 10 kDa, and greater than 10 kDa. The results showed that the extraction rate of phycobiliprotein by water immersion extraction method was about 43.13%, while the extraction rate of phycobiliprotein by repeated freeze-thaw method was about 65.46%. The extraction rate of repeated freeze-thaw method is better than that of water immersion extraction method. Compared with the hydrolysis effect of the four enzymes at the optimal enzymatic hydrolysis time, papain had the best effect on preparing antioxidant peptides, and the DPPH and ABTS+ radical scavenging rates of papain's enzymatic hydrolysate were 61.21±6.58% and 58.12±8.83%, respectively. The ABTS+ radical scavenging rates of alkaline protease digest (CPCAH) and papain digest (CPCPH) less than 3 kDa were relatively higher, 81.29±0.8%, 81.07±1.05%, respectively. It can be seen that the relative molecular weight of antioxidant active peptides in spirulina is mostly concentrated in the range of less than 3 kDa. The obtained CPCAH-F3 and CPCPH-F3 were then identified by mass spectrometry to obtain the relative molecular weight, amino acid sequence and hydrophobicity analysis of multiple peptides, and the peptides with strong antioxidant capacity were usually rich in hydrophobic amino acids. This experiment further verified the antioxidant capacity of spirulina, and laid an experimental foundation for the development and research of spirulina as a functional food. The object of the work is spirulina antioxidant peptides. The subject of the work is antioxidant activity of peptides from spirulina. The aim of the work is to isolate and study properties of spirulina antioxidant peptides. The tasks of the work are to extract phycobiliprotein with different methods, provide the study of antioxidant activity with DPPH and ABTS+ radical scavenging rates, identify molecular weight, amino acid sequence and hydrophobicity of spirulina antioxidant peptides.