Effect Of Cross-linking Of Rice Protein With Ferulic Acid On Digestion And Absorption Of Ferulic Acid

Rice protein is a high quality vegetable protein with characteristics of high nutrition and hypoallergenic.Rice protein accounts for about 8%of the rice content,while the rice protein resources in China are relatively abundant because of the large sown area and the large yield of rice in our country.Ferulic acid is a kind of phenolic acid which is commonly found in plants,having strong physiological activities such as antioxidant,antibacterial,cholesterol-lowering and anti-cancer and is widely found in Chinese herbal medicines and food materials such as Angelica,Chuanxiong,Ferula,coffee,wheat bran and rice bran.Ferulic acid,like most of phenolic compounds,is easily oxidized and degraded in vitro.Our previous studies have shown that the cross-linking of rice protein could improve the oxidation stability of ferulic acid in vitro,but it is not known yet whether it will affect the release of ferulic acid in gastrointestinal digestion in vitro and its absorption in vivo.Therefore,we used ferulic acid as the main research object in this paper,and it was catalyzed by laccase to crosslink with rice protein.Then investigated their digestion by in vitro simulated gastrointestinal digestion and absorption by Caco-2 cell model.The main results are as follows:1.The FA relative content of RF decreased to 63.23%?82.63%,while it further decreased to 4.49%?40.63%after the catalysis of LAC.After oral digestion,the relative content of FA decreased.The FA relative content of RF increased or remained unchanged,while it increased to 4.99%?51.99%for RFL.The FA relative contents of RF and RFL both increased after gastric digestion and it was the acidic environment of simulated gastric juice and the hydrolysis of pepsin that released FA from RF and RFL complexes.After intestinal digestion,the FA relative content were relatively stable for FA,RF,and RFL.2.With the increase of FA concentration,DPPH radical scavenging capacity and ABTS+ radical scavenging capacity of FA,RF and RFL all increased gradually.Furthermore,RF>FA>RFL>RP.It also showed that RP could relatively reduce DPPH radical scavenging ability of FA,then improve its stability.After in vitro simulated digestion,there was no significant difference in DPPH radical scavenging capacity among RP,FA,and CK(p<0.05),while DPPH radical scavenging capacities of RF and RFL were both significantly higher than that of CK(p<0.05).During in vitro simulated digestion,ABTS+radical scavenging capacities of CK,RP,FA,RF,and RFL all increased gradually.After intestinal digestion,ABTS+ radical scavenging capacities of RP,FA,RF and RFL were all significantly greater than that of CK(p<0.05),and RF>FA>RFL>RP.3.After 21 days of Caco-2 cell culture,the cells were tightly arranged and seamless.The apparent permeability coefficient(Papp)of the transcellular transport marker propranolol was(2.77±0.31)×10-5 cm/s,which is close to the reference value of 2.75×10-5 cm/s.After 18 days of cell culture,the TEER value maintained about 370 ?/cm.With the increase of culture days,the difference of alkaline phosphatease(AKP)activity between apical lateral(AP)and basal lateral(BL)of Caco-2 increased linearly.Compared with 17 days after cell culture,the AKP activities of AP and BL after 21 days of cell culture both increased significantly(n=4,p<0.05).Therefore,the Caco-2 cell model established in our laboratory was successful,and could be used as an intestinal absorption model to study the intestinal absorption and transport of ferulic acid.HPLC result showed that FA was stable under the condition of 37? and 5%CO2(relative humidity 95%).Caco-2 cells viability was more than 90%after 2 h of culture with FA with concentrations ranging from 0 to 2000 ?g/mL.4.The FA cumulative transport amount(Qr)of FA,F-D,RF-D and RFL-D all increased linearly with the increase of cell absorption and transport time.And it showed that F-D = RF-D>FA>RFL-D,which indicated that the gastrointestinal digestion and RP were both beneficial to the absorption and transport of FA.The greater the FA concentration,the greater the FA cumulative transport amount of FA,F-D and RF-D.The FA Papp values of FA,F-D,RF-D and RFL-D with low FA concentrations were significantly higher than those with high FA concentrations(p<0.05).At 120 min,the FA Papp values were significantly lower than those of F-D and RF-D,while they were significantly higher than that of RFL-D(p<0.05).Meanwhile,there was no significant difference between F-D and RF-D(p<0.05).It showed that FA and RF were more easily absorbed and transported by Caco-2 cell monolayer after digestion.