Studies On Antioxidative Activity Peptide And Agiotensin I-Converting Enzyme (ACE) Inhibitory Peptide Derived From The Hydrolyzation Of RD Protein With Protease And Extraction Of Rice Dregs (RD) Protein

The technologies optimum conditions of extracting protein from rice dregs(RD), rice protein modifying, extracting antioxidative activity peptide and angiotensin I-converting enzyme (ACE)inhibitory peptide to were studied. Enzymatic method, alkaline method, gelatin filtration, high performance liquid chromatography (HPLC) and mass spectrum (MS) were employed in the research.The optimum conditions of extracting protein from RD with enzymatic method were enzyme dosage [E]/[S]=1 %, ratio of raw material to water (R/W) 1:4, pH=8.0, temperature = 65℃, time = 7h. Under these conditions, extractive rate of rice protein was 62.6%, and the concentration of protein in the extract was 84.0%. The optimum conditions extracting protein from RD with alkaline method were alkali concentration 0.8%, R/W 1:6, temperature = 65℃, time = 6h. Under these conditions, extractive rate of rice protein was 76.2%, and the concentration of protein in the extract was 80.0%.There was evident improvement in the dissolvability, emulsifiability and foamability of protein extracted from RD after its modification with alcalase. In 4% hydrolysates neutral solution, the nitrogen solubility index (NSI), emulsifying ability, foam ability were 95%, 55%, 70% respectively.The hydrolysates which derived from the hydrolyzation of RD protein with alcalase possessed not only reducibility, but the power of scavenging DPPH radicle. The capability of scavenging DPPH radicle was compared among hydrolysates, tea polyphenol, butylated hydroxyl anisole (BHA) and vitamin C. The result showed that the hydrolysates had merely parallel power to scavenge DPPH radicle with BHA. When the reducibility as response value, response surface optimization experiments were performed. The results showed that the optimal conditions for extracting antioxidative activity peptides were as follows: pH=7.74, temperature=61.5℃, ratio of water to material 5.23.The hydrolysates by trypsin were found to have the highest inhibitory activity to ACE after the activity compare of hydrolysates by neutrase, acid protease, Flavourzyme, alcalase, pepsin, trypsin. Response surface optimization experiments were conducted to investigate the hydrolyzation with trypsin. The results showed that the optimal conditions were as follows: pH=8.02, temperature=37.0 °C, enzyme dosage [E]/[S]=1.5 %, ratio of water to material 4.13, time span 4h. Under the optimal conditions, the ACE inhibitory activity of hydrolysates was 84.95%.After the separation of hydrolysates with polyglucan gelatin Sephadex G-15, six peptides ingredients were gotten, which were F-I, F- II, F-III, F-IV, F-V, F-VI. Among them, F-V had the highest ACE inhibitory activity. Four ingredients in F-V were found after HPLC analysis, and F-V-IV account for 93.89%. The F-V-IV analyzed with MS after prepared with RP-HPLC and the result showed that the primary structure of F-V-IV was FNGFY (Phe-Asn-Gly-Phe-Tyr) .Animal experiments with RD hydrolysates in different dose (1 mg/kg, 10 mg/kg, 50 mg/kg) and Captopril (1 mg/kg) were conducted. The once-oral administration result showed that the blood pressure of spontaneous hypertension rats (SHR) drop for 10.96 mmHg, 16.77 mmHg, 26.39 mmHg, 16.61 mmHg in 1 mg/kg, 10 mg/kg, 50 mg/kg hydrolysates and 1 mg/kg Captopril respectively after 1h administration. The results of long term oral administration experiments showed that the blood pressure of SHR drop for 16.88 mmHg, 26.22 mmHg in 10 mg/kg and 20 mg/kg respectively after lmonthadministration. RD hydrolysates not only promote the growth of SHR, but also have no influence on heart rate.