Preparation And Activity Evaluation Of Rice Angiotensin Converting Enzyme Inhibitory Peptides

Hypertension is one of the high risk factors for coronary heart disease,stroke,chronic kidney disease,retinopathy,atherosclerosis and other diseases.Currently,angiotensin-converting enzyme inhibitors,known as ACE inhibitors,are the main drugs used in the treatment of hypertension.However,these synthetic drugs have significant side effects.Therefore,the preparation of natural bioactive peptides with ACE inhibitory effect from food protein provides a new possibility for the prevention and adjuvant treatment of hypertension.In this study,rice ACE inhibitory peptides were prepared from rice protein by enzymatic hydrolysis,and the structure of the preliminarily separated and purified small molecule peptides with ACE inhibitory activity was identified.The activity of rice ACE inhibitory peptides was verified at the cell level.In order to improve its bioavailability and stability,rice ACE inhibitory peptide microcapsules were prepared by sodium alginate embedding technology.The details are as follows:(1)A reaction system of ACE inhibitory peptide prepared from rice protein was established.Based on the single factor experiment,the p H,temperature,substrate concentration and enzyme dosage were optimized by response surface methodology.The optimal parameters were obtained as follows:p H was 7.7,temperature was 49.0?,substrate concentration was 0.13 g/m L,trypsin dosage was 3680 U/g and reaction time was 3 h.Under the optimal conditions,the ACE inhibitory rate of rice polypeptide was75.17%,which was in good agreement with the predicted value of the model,and the soluble nitrogen recovery rate of rice protein was 82.63%.(2)DA201-C macroporous resin desalination and Sephadex G-25 Gel chromatography were used to preliminarily separate and purify rice ACE inhibitory peptides.Macroporous resin showed good desalting effect on rice ACE inhibitory peptides,and the molecular weight distribution of rice ACE inhibitory peptides after desalting was mainly below 1,000 Da(97.99%).The rice ACE inhibitory peptides were enriched by Sephadex G-25 Gel chromatography,and three components were obtained.The maximum ACE inhibitory rate of component I was 87.07%,and its IC₅₀ value was1.04 mg/m L.The amino acid sequence of component I was identified by MALDI TOF/TOF MS MS analysis as Val-Pro-Phe-Arg-Pro(VPFRP).(3)Based on human umbilical vein endothelial cells(HUVECs)model,the effect of rice ACE inhibitory peptide on vascular endothelial cells was studied,and the mechanism of rice ACE inhibitory peptide on blood pressure was explored.The results showed that rice ACE inhibitory peptide could inhibit the secretion of ET-1.The down-regulation of ACE and ET-1 mRNA expression and up-regulation of ACE2 mRNA expression were detected by fluorescence quantitative PCR.The results showed that rice ACE inhibitory peptide had the effect of lowering blood pressure at the cellular level.(4)Rice ACE inhibitory peptide microcapsules were successfully embedded with sodium alginate.The encapsulation efficiency,peptide carrying capacity and particle size were 55.86%,0.14 g/g and 0.24 mm,respectively.The results of SEM,FTIR,DSC and XRD showed that there might be hydrogen bond and electrostatic force between rice ACE inhibitory peptide and sodium alginate.After 6 h digestion in vitro,the cumulative release rate of microcapsules was 72.92%.Therefore,alginate encapsulation had a certain sustained release effect on the release of rice ACE inhibitory peptides and improved the bioavailability of rice ACE inhibitory peptide in gastrointestinal tract.Kopcha model showed that the release pattern of rice ACE inhibitory peptide microcapsules followed the dual control of diffusion and erosion.After 8 weeks of storage,the EE of rice ACE inhibitory peptide microcapsules was52.42%,and the ACE inhibitory activity of microcapsules was 71.47%.The results indicated that rice ACE inhibitory peptide microcapsules had good stability and could effectively protect the biological activity of ACE inhibitory peptide during storage.