The Interaction Between Grape Seed Procyanidins And Meat Proteins And Its Effects On Digestion,Absorption And Antioxidant Activity

Procyanidins are a group of phenolic polymers synthesized by the condensation of flavane-3-alcohol or flavane-3,4-diol,which have a variety of biological activities such as antioxidant,immune regulation,anti-tumor and cardiovascular function improvement.Procyanidins are widely found in fruits and vegetables,and these physiological active substances can be consumed in daily diet.Meat protein is an essential nutrient element in the diet.It has been reported that when dietary proteins and polyphenols are ingested together,they interact with each other and thus affect the functional characteristics.However,most of the existing literatures focus on the interaction between a single polyphenol substance and a single protein,and there is very little research on the interaction and mechanism between polyphenol complex and meat protein.Based on this,the interactions between grape seeds procyanidins(GSP)and pork protein(PP),chicken protein(CP),fish protein(FP),and the effects of GSP and protein binding on their digestion,absorption and antioxidant activities were studied in this paper.The interaction mechanism between polyphenols and meat protein was also revealed,which may provide theoretical guidance and reference for rational diet.The main research contents and results are as follows:1.Interaction and mechanism between GSP and meat proteinThe interaction and mechanism of GSP with three kinds of meat proteins were studied by spectroscopy and circular dichromatography combined with mathematical analysis,and the free radical scavenging activity analysis in vitro was used to evaluate the antioxidant activity of the complex.The results showed that GSP can bind to three kinds of meat proteins and make their fluorescenc have obvious quenching effect.The quenching effect increases with the increase of GSP concentration,and the quenching process belongs to static quenching.At 297 K,298 K and 310 K,the binding constants(K_A)of GSP and PP were 215.61,112.51 and 45.87 M^-1,respectively.The K_A of GSP and CP were 463.34,469.06 and 478.74 M^-1,respectively.The K_A of GSP and FP are62.12×10³?9.69×10³?1.02×10³ M^-1,respectively.The combination of GSP with PP and FP was exothermic reaction,and the main forces were van der Waals force and hydrogen bond.The combination of GSP and CP was an endothermic reaction,and the main force was hydrophobic interaction.GSP reduced the?-helix by 7.8%and increased the?-sheet by 1.87%of PP;GSP reduced the?-helix by 4.66%and?-sheet by 1.29%of CP;while GSP had no effect on the secondary structure of FP.Compared with GSP,the ability of the complex of GSP combined with three proteins to clear DPPH·and ABTS⁺·was enhanced.2.Effect of GSP combined with three proteins on its digestion performanceIn vitro simulated digestion combined with chromatographic analysis was used to study the effects of GSP combined with three meat proteins on their gastrointestinal digestion and antioxidant activity.Firstly,four major polyphenols in GSP were analyzed and identified:catechin(C),epicatechin(EC),proanthocyanin B2(B2)and epicatechin gallate(ECG).Before the simulated digestion,the contents of C,B2,EC and ECG decreased significantly(p<0.05)after PP,CP and FP were added to the GSP solution,respectively falling to about 75%,30%,50%and 20%.After oral digestion,the contents of C,B2 and ECG in GSP decreased slightly,while the contents of EC were basically unchanged.The contents of four polyphenols in GSP-PP,GSP-CP and GSP-FP groups were basically unchanged.After stomach digestion,the contents of C and EC in GSP increased,the contents of ECG decreased,and the contents of B2remained unchanged;the contents of C,B2,EC,and ECG in the GSP-protein complex group all increased.After intestinal digestion,the contents of C,B2,EC and ECG in GSP decreased.The contents of C and ECG in the GSP-protein complex group were higher than that in GSP,and the content of B2 and EC was lower than that in GSP.3.Effect of GSP combined with three proteins on its absorption characteristicsThe absorption characteristics of the intestinal digestive fluids of GSP,GSP-PP,GSP-CP,and GSP-FP were studied by Caco-2 as the cell model.The P_app of GSP,GSP-PP,GSP-CP and GSP-FP varied at different absorption time.When the absorption time was 120 min,the P_app of C and B2 in GSP intestinal digestive fluid was the largest,the P_app of EC in GSP-PP intestinal digestive fluid was the largest,and the P_app of ECG in GSP-CP intestinal digestive fluid was the largest.The P_app values of four phenols in different intestinal digestive fluid samples were in the range of 1?15×10^-6cm/s,and the absorption effects were good.The three proteins had a certain inhibitory effect on the absorption of C,B2 and EC.CP promoted the absorption of ECG,FP and PP had a certain inhibitory effect on the absorption of ECG,but the inhibitory effect was not significant.