The Antihypertensive And Antioxidative Activity Of Casein Hydrolysates Modified By Plastein Reaction

Casein was hydrolysated by neutrase. The exogenous amino acids（phenylalanine leucine or proline）were introduced into hydrolysated casein（HC） by Plastein reaction in alcohol or the water phase. The products are termed as HCPHE-E, HCLEU-E, HCPRO-E, HCPHE, HCLEU and HCPRO. The ACE inhibition activity of the casein hydrolysates modificated by Plastein increased significantly in vitro. The casein hydrolysates and casein hydrolysates modificated by Plastein showed good stability under different temperature（20-120oC） or p H（2-10） and good digestion stability in vitro.The protective capacity of casein hydrolysates modified by Plastein reaction in HUVEC injured by H₂O₂: The leakage of lactate dehydrogenase（LDH） and malondialdehyde（MDA） content of the cells were significantly decreased after given casein hydrolysates modified by Plastein reaction. At the same time, superoxide dismutase（SOD） activity, the activity of glutathione reductase（GSH-Rd） and catalase（CAT） were significantly increased, while the change of glutathione（GSH） in the cells was not obvious. It showed that the casein hydrolysates modified by Plastein reaction has a good protective effect on HUVEC damaged by H₂O₂ and dose-dependent relationship.The effect of casein hydrolysate and casein hydrolysates modificated by Plastein on blood pressure in SHR rats: There were significant difference between casein hydrolysates and casein hydrolysates introduced Pro and Phe by Plastein reaction groups. After 2h administration, the decreasing ability of blood pressure was improved greatly after plastein reaction. After oral administration of 2 h, there was significant difference between the groups given HCPHE（HCPHE-E） and HCPRO HCPRO-E and that given HC（P<0.05）, The SBP and DBP decreased 23.36 ± 5.57 mmHg and 17.58 ± 3.18 mmHg.The effect of casein hydrolysates modificated by Plastein on RAS system and antioxidant defense system in SHR rats. The SHR rats were given casein hydrolysate and casein hydrolysates modificated by Plastein after 14 days: 1) The Effect on RAS system: The serum expression level of ACE, Ang II and aldosterone were lower than that in negative group, and the highest proportion of reduction were 39.56%, 39.60% and 47.07% respectively. The level of serum ACE of groups given HCPHE, HCPHE-E, HCPRO or HCPRO-E were reduced by 28.64% 36.20%, 29.23% and 41.59% respectively comparing with that given casein hydrolysates. There was a significant decrease of expression level in ALD between the groups given the casein hydrolysates modificated by Plastein and HC. While the ACE inhibition ability had no correlation between in vivo with that in vitro. 2) The Effect on antioxidant defense system: The activity of SOD in HC and casein hydrolysates modificated by Plastein groups were 85.54±4.25 U/m L and 88.89±5.32 U/m L, comparing with the saline group（80.03±5.21 U/m L）（P<0.05） significantly. What’s more,the CAT activity of groups given casein hydrolysate and casein hydrolysates modificated by Plastein was also enhanced. The highest T-AOC ability of groups which given HCPHE or HCPRO was 10.23±2.10 unit/m L serum, and 10.15±1.65 unit/mL serum respectively. The groups given HCPHE or HCPRO were 23.84% or 22.88% higher than the capacity of the group given casein hydrolysates.In summary, the casein hydrolysates modified with neutrase by Plastein has good stability and antioxidant activity in vitro. The antihypertensive activity of the casein hydrolysates introduced Phe and Pro modified by Plastein reaction is stronger than HC, and has a good antioxidant activity in vivo. The present study also showed that the effect of casein hydrolysate modificated by Plastein decreasing blood pressure in vivo was achieved through the synergistic effect of the RAS system and the antioxidant defense system.