Effects Of Red Chicory (Cichorium Intybus L.) Dietary Fiber On Bioaccessibility And Intestinal Inflammation During Digestion And Absorption Of Red Chicory Polyphenols

Red Chicory is a perennial herb of the Asteraceae family,with bright red leaf balls.Chicory is rich in nutrients.Its polyphenol content is high,and it has many pharmacological effects,such as antioxidant,anti-inflammatory,anti-viral,antibacterial,anti-tumor,anti-ultraviolet,and plant growth and reproduction.Therefore,chicory polyphenols have broad application prospects in medicines and personal care products,making them a research hotspot in the field of phytochemicals.However,the biological activity of red chicory polyphenols is closely related to its bioavailability,and other nutrients in the diet often affect its bioavailability.For example,the dietary fiber in chicory cannot be directly absorbed and utilized by the human body,and needs to be metabolized and utilized by microorganisms in the gastrointestinal tract.However,it has been reported that dietary fiber can affect the body’s gastrointestinal tract function and biological accessibility of small molecular food functional factors such as polyphenols.Therefore,this project used red chicory as raw material,and obtained red chicory polyphenols from it.Then,by simulating in vitro gastrointestinal digestion and Caco-2 absorption model,the effects of red chicory dietary fiber on the bioaccessibility and bioabsorption of red chicory polyphenols during digestion and absorption were determined.Finally,the Caco-2/RAW264.7 cell model was used to further explore the effect of red chicory dietary fiber on the intestinal inflammation of red chicory polyphenols after digestion and absorption,in order to provide a better understanding of the utilization of chicory polyphenols.The research and development of related functional foods provides new ideas and theoretical basis.The main research contents and results of this paper are as follows:(1)The red chicory polyphenols were extracted,purified and identified.The extraction process of red chicory polyphenols was optimized based on response surface methodology,and the optimal extraction process conditions were obtained: ethanol concentration 87.45%,solid-liquid ratio 1:23.05(g/mL),extraction times 4 times,extraction time 1.82 h.The total flavonoid content of the alcohol extract was determined by sodium nitrate-aluminum nitrate-sodium hydroxide colorimetric method.Under this condition,the actual extraction rate of total flavonoids from chicory was4.61%.The macroporous resin was further used to purify the alcoholic extract of red chicory,and the adsorption and desorption effects of 8 macroporous resins on the alcoholic extract of red chicory were compared.The results showed that the macroporous resin NKA-9 was the best resin.The optimal purification conditions were:pH of the sample solution = 4.0,adsorption time = 2 h,ethanol concentration = 60%,and loading concentration = 0.75 mg/mL.At this time the adsorption of red chicory polyphenols by NKA-9 resin belongs to multi-layer adsorption.After that,qualitative and quantitative analysis of the purified chicory was carried out.UPLC-QTRAPMS/MS results showed that 5-caffeoylquinic acid was the highest content of phenolic acid(58.00 g/kg),quercetin-3-O-(6″-O-malonyl)-glucoside was the most abundant flavonoid(29.63 g/kg).(2)The gastrointestinal digestion process of purified red chicory was simulated in vitro,and it was found that anthocyanin-3-O-(6″-O-acetyl)-glucoside in red chicory was unstable during digestion,while quercetin-3-O-(6″-O-acetyl)-glucoside is more stable.After the introduction of red chicory dietary fiber,digestion simulation was carried out.The results showed that the total amount of flavonoids and phenolic acids was lower than that of the purified red chicory group,and the effects on each flavonoid and phenolic acid were different.For example,after adding soluble dietary fiber,the content of quercetin-7-O-(6″-O-acetyl)-glucoside in the supernatant of small intestinal digestive juice was decreased.After that,the changes in antioxidant capacity before and after digestion were determined in the purified red chicory group(cp),the purified red chicory + soluble dietary fiber group(cp+sdf),the purified red chicory + insoluble dietary fiber group(cp+idf),the red chicory powder group(c).It was found that: after gastrointestinal digestion,DPPH free radical inhibitory ability and FRAP free radical inhibitory ability were significantly reduced.In addition,the two free radical inhibitory abilities have a strong relationship with the phenolic compound 5-caffeoylquinic acid and the flavonoid quercetin-3-O-(6″-O-acetyl)-glucoside.(3)Based on the Caco-2/RAW264.7 cell model,the evaluation of purified red chicory(cp),purified red chicory + soluble dietary fiber of red chicory(cp+sdf),purified red chicory + insoluble dietary fiber of red chicory(cp+ idf),red chicory powder(c),red chicory soluble dietary fiber(sdf),red chicory insoluble dietary fiber group(idf)after gastrointestinal digestion on RAW264.7 macrophage inflammatory response and Caco-2 monolayer effects of tight junction proteins.The results showed that in the co-culture model,cp,cp+sdf,cp+idf,c,sdf and idf had no significant effect on the expression levels of TNF-α in LPS-induced RAW264.7 cells after gastrointestinal digestion.And there was no significant effect on the mRNA levels of TNF-α,IL-1β,IL-6 and IL-10 secreted by RAW264.7 cells.However,the cp+idf and cp+sdf groups were able to increase the mRNA expression level of the tight junction protein ZO-1 in Caco-2 cells.