Preparation And Biological Activity Of Low Molecular Weight Peptide From Rhopilema Esculentum Kishinouye

Jellyfish（Rhopilema esculentum Kishinouye）is rich in nutritional value,with high-quality protein and iodine,iron,zinc,calcium and other minerals.Jellyfish can relieve and improve the symptoms of bronchitis,bronchitis,gastric ulcer and asthma,and it is supposed to be a high-quality raw material for the preparation of antioxidant peptides by enzymolysis.Peptides with smaller molecular weight showed stronger antioxidant activity.At present,there has not been reported on the preparation and activity of small molecular peptides from jellyfish.In this study,the preparation process of low molecular weight peptide from Rhopilema esculentum Kishinouye（RKLP）was optimized,and the physicochemical properties,biological activities and functional properties of RKLP were studied.A RKLP water chestnut powder compound tablet was prepared.It may provide some references value for high value utilization of jellyfish.The main results were as follows:（1）Determination of preparation technologies of RKLP.The antioxidant peptides of jellyfish were prepared by two-enzyme stepwise enzymatic hydrolysis.Response surface test was used to optimize the enzymatic hydrolysis conditions,and RKLP was obtained by ultrafiltration.The preparation technologies were:Salted jellyfish was cleaned repeatedly,soaked in deionized water for 48h（change the water every 8h）,broken and drained with a wall breaker.The alkaline protease 3%was adding in jellyfish homogenate,p H 7.5,the enzymolysis conducting 50°C for 2h,and the enzymolysis was inactivated at 90°C for 10mins.Then add the neutral protease 1%in jellyfish homogenate,p H 7,50°C for 2h,and then inactivate the enzyme at 90°C for 10mins.The jellyfish hydrolysate was cooled and centrifuged at 9000rpm for 30min.After centrifugation,supernatant was taken through 3.5k Da ultrafiltration membrane and freeze-dried to obtain RKLP.（2）Identification of physical and chemical properties of RKLP.Amino acid composition was analyzed by automatic amino acid analyzer.The results showed that RKLP had abundant amino acid composition,and the proportion of hydrophobic amino acid was up to 31.3%.Fourier infrared analysis showed that RKLP had amide and imidazole functional groups,peptide bond,ether and hydroxyl group,α-helix structure,β-folding and random curling secondary structure.Uv spectrum analysis concluded that RKLP had a peptide structure.A total of 12 peptides were identified and analyzed by mass spectrometry.The molecular structure and configuration of RKLP were predicted by pepdraw and PEP-FOLD3.RKLP had a wide variety of primary and secondary structures.It was speculated that RKLP had good antioxidant activity.Scanning electron microscopy（SEM）showed uneven surface of the sample.（3）Studies on biological activity and functional properties of RKLP.DPPH,O₂^-,ABTS⁺and OH^-free radical scavenging were used to determine the antioxidant activity of RKLP in vitro antioxidant model.The results showed that RKLP had the scavenging effect on DPPH,O₂^-,ABTS⁺and OH^-free radicals.The effect of RKLP on the proliferation of macrophages in RAW264.7 mice was determined by proliferation rate method,which showed that RKLP could promote the proliferation of macrophages in mice.The ACE inhibitory activity of RKLP was determined by high performance liquid chromatography,which showed that RKLP had inhibitory effect on ACE.The coagulation activity and sugar binding properties of RKLP were determined by multiple dilution method.The results showed that RKLP had agglutination effect on erythrocytes with agglutination titer of 2⁴,and had inhibitory effect on glycoproteins,but had no inhibitory effect on monosaccharides.The antibacterial activity of RKLP was determined by filter paper method.The results showed that RKLP had an inhibitory effect on Enterobacter aerogenes and Escherichia coli.The effect of RKLP on Saccharomyces cerevisiae was determined by ultraviolet spectrophotometry,which showed that RKLP had inhibitory effect on the growth of saccharomyces cerevisiae cells.Emulsifying performance analysis showed that RKLP had good emulsifying activity and stability.（4）Preparation of RKLP water chestnut powder composite tablets.Taking DPPH·clearance rate as the index,the ratio of RKLP:1:2 was determined.Single factor and orthogonal test determined the optimal proportion of supplemental materials:magnesium stearate 2%,microcrystalline cellulose 30%,sodium carboxymethyl cellulose 3%,erythritol 60%.The surfaces of RKLP water chestnut powder composite tablets were smooth,non-crack,light yellow and white,which can meet the quality standard of tablets and pass the stability test..