| Hypertension is a global disease which seriously threats to human health, and related to about 45% incidence of cardiovascular disease and death. Angiotensin I-convertingen enzyme (ACE, EC3.4.15.1) plays a key role in the blood pressure regulation system, inhibiting ACE activity can effectively regulate blood pressure, due to long-term use of synthetic ACE inhibitors drugs are often along with various side effects such as coughing, skin rashes and angioedema, there is an urgent need of ACE inhibitors for natural sources and without the side effects. Currently, various ACE inhibitory peptides with different structure have been isolated from plant and animal protein hydrolysates or natural organisms by many scholars, fermented food is also considered as an important potential source of ACE inhibitory peptides. Sour meat is a lactic acid bacteria fermented meat product and popular in ethnic minority areas of Chongqing, Sichuan, Guizhou, Guangxi and Hunan, has a rich diet culture connotation and wide range of edible. In this paper, the lab-made fermented sour meat was selected as raw material, modern separation and purification technology were used to isolate ACE inhibitory peptides from it, and the physical and chemical characteristics of ACE inhibitory peptides and the effect of ACE inhibitory peptides on thoracic aortic vascular endothelial cells function factor were studied, aims to provides functionality chemistry-related research data for developing and guiding reasonable diet of Sour meat. The main research results are as follows:1. Protein in sour meat occurred degradation during the process of fermentation, the content of protein nitrogen decreased with the extension of fermentation time, non-protein nitrogen and amino acid nitrogen increased with the extension of fermentation time, peptide nitrogen showed a downward trend after the first increase, reached at the maximum(226.5mg/100g) in about 20 days fermentation, indicated that there were peptides produced in sour meat in the fermentation process.2. Crude peptides were extracted from sour meat with different fermentation time and ACE inhibitory activity in vitro was measured. The results showed that compared to the fermentation 0 days (fresh pork),40 days and 60 days, crude peptides derived from sour meat fermentation 20 days exhibited the highest ACE inhibitory activity, ACE inhibition rate reached at 74.35%(concentration of 10mg/mL), the IC50 value was 2.75mg/mL; Ultrafiltration, D101 macroporous resin and Sephadex G-50 gel were further used for the purification of crude peptides derived from sour meat fermentation 20 days, F3 component obtained with the highest ACE inhibitory activity, ACE inhibitory rate was 59.18%(at a concentration of 1mg/mL), IC50 value decreased to 0.895mg/mL, the peptide content was 86.54%. F3 component was analyzed by reversed-phase high performance liquid chromatography(RP-HPLC), the result showed the F3 component was mainly composed of nine peaks; Amino acid composition analysis showed that F3 component contains 17 kinds of amino acids, including seven kinds of essential amino acids which human body can not synthesize, hydrophobic amino acids, aromatic amino acids and branched-chain amino acids in peptides accounted for 39.35%,10.69% and 13.65%, respectively, comply with the general structure characteristics of ACE inhibitory peptides.3. The physical and chemical properties of sour meat ACE inhibitory peptides were studied. The results showed that ACE inhibitory peptides had a strong hygroscopicity; In the setting pH range (3-10), emulsifying ability of ACE inhibitory peptides under alkaline conditions was stronger than the acidic conditions, and sour meat ACE inhibitory peptides in the pH of 9 had the strongest emulsion stability; Sour meat ACE inhibitory peptides had a strong pH and thermal stability, the change of ACE inhibitory activity at temperature of 4、25、 37 and 60℃ was lesser (p> 0.05), but ACE inhibitory activity at temperature of 100℃ decreased obviously, and reached a significant level (p<0.01); In addition, after treating by pepsin and trypsin, the ACE inhibitory activity remained stable, and showed a strong resistance to digestive enzymes.4. Rat thoracic aorta endothelial cells were selected as a model to study the effects of sour meat ACE inhibitory peptide on vascular endothelial cells function factors. The results showed that in a certain range of concentrations, the sour meat ACE inhibitory peptides had no significant toxic effects on vascular endothelial cells, and could promote the release of NO in vascular endothelial cells, reduce the secretion of ET-1, but did not show significant antioxidant capacity in vitro and ROS scavenging ability in cells. |
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