Study On Extraction,Structure Identification And Improvement Effect Of British Red Kidney Bean Polysaccharides On T2DM Mice

British red kidney bean is a common leguminous herbaceous crop with purplish red appearance.It is one of the main cultivated varieties of kidney bean in Heilongjiang Province.It is popular among consumers because of its bright color,full grains and high nutritional value.It contains protein,anthocyanins,polysaccharides,saponins and other biological active components,which can improve the non-specific immunity of human body and enhance the resistance to disease.Polysaccharide has been widely concerned in the field of prevention and treatment of diabetes mellitus due to its natural,multiple active functions,small toxic and little side effect.Polysaccharides are an active ingredient in British red kidney bean.Few studies have shown that British red kidney bean polysaccharides have certain in vitro antioxidant activity.Diabetes is one of the most common chronic non-communicable diseases in the world.It is characterized by hyperglycemia,insulin resistance and other diseases,accompanied by complications such as liver inflammation,which seriously endangers life.It has been suggested that non-starch polysaccharides can be degraded into short-chain fatty acids by intestinal flora as substrates,which can improve the intestinal environment and change the structure of intestinal flora,thus improve the symptoms of type 2 diabetes mellitus（T2DM）.However,there was no report on the improvement of T2DM symptoms by British red kidney bean polysaccharides.In this paper,British red kidney bean polysaccharides were prepared from British red kidney bean as raw material.The physical and chemical properties of British red kidney bean polysaccharides,its improvement effect on obesity and T2DM caused by obesity were investigated through physical and chemical properties determination,in vitro test and in vivo test.It provides reference for intensive processing of British red kidney bean and theoretical basis for research on improving the functional factors of T2DM and developing new anti-T2DM functional food.The main results are as follows:（1）British red kidney bean was used as raw material by hot water extraction.Single factor test and response surface test were used to optimize the extraction process with the yield of polysaccharides as index,extraction temperature,extraction time and solid-liquid ratio.The physical and chemical properties,functional properties and antioxidant activity in vitro were studied.The results showed that the optimum extraction rate was 4.86%under the conditions of92℃extraction temperature,1.5 h extraction time and 1:45（g/m L）solid-liquid ratio.The chemical composition showed that the polysaccharides were mainly composed of neutral sugar（33.02±0.21%）,uronic acid（24.79±0.35%）)and protein（3.84±0.32%）.Physicochemical results showed that the British red kidney bean polysaccharides were loose and irregular heterosaccharide,which were composed of Man,Glc N,Rha,Glc,Gal,Xyl,Ara and Fuc,and had good thermal stability.The results of functional analysis showed that the polysaccharide had good hydration properties and oil holding capacity,which were（4.64±0.37 g/g）,（85.19±0.26%）and（3.24±0.21g/g）,respectively.In vitro antioxidant results showed that British red kidney bean polysaccharides had good scavenging ability of DPPH free radical and·OH free radical,69.85%and 53.61%when the polysaccharide concentration was 5 mg/m L,respectively,and the scavenging rate of free radical were proportional to the concentration of polysaccharides solution.（2）The levels of FBG,INS and Hb A_1c were decreased and glucose tolerance was increased in T2DM mice treated with British red kidney bean polysaccharides;mesentery fat accumulation decreased,TC,TG and LDL-c level decreased,HDL-c level increased;the levels of GSH-Px,GSH and CAT increased,while the levels of GPT,MDA,NO and TNF-αdecreased.（3）The intake of British red kidney bean polysaccharides can increase the production of colonic content SCFAs in T2DM mice.The three main colonic content SCFAs were acetic acid,propionic acid and butyric acid.Microflora analysis showed that the intestinal flora of mice mainly included Bacteroidetes,Firmicutes,Actinomycetes,Verrucomicrophyla,Proteobacteria,etc,and Firmicutes and Bacteroidetes were the dominant bacteria.British red kidney bean polysaccharides can improve the intestinal microenvironment by decreasing the Firmicutes/Bacteroidetes ratio and increasing the abundance of Akkermansia,Faecalibacterium and Gordonibacter to improve the intestinal microenvironment.Correlation analysis showed that intestinal flora was positively correlated with GSH,GSH-Px and CAT contents,and negatively correlated with FBG,INS and IL-1β.The results showed that under the optimal conditions of extraction temperature 92℃,extraction time 1.5 h,solid-liquid ratio 1:45（g/m L）,the extraction rate was 4.86%,and the polysaccharides had good antioxidant activity in vitro.Intake of British red kidney bean polysaccharides can enhance insulin sensitivity and improve T2DM characteristics;improve blood lipid index and obesity,relieve liver inflammation caused by T2DM,protect liver with lipid metabolism disorder,and improve abnormal metabolism of blood lipid;SCFAs produced by glycolysis of British red kidney bean Polysaccharides can improve the intestinal microenvironment and improve the intestinal health of mice,increase the abundance of beneficial bacteria and regulate the composition of intestinal flora,so as to maintain intestinal health.These results suggest that polysaccharides from British red kidney bean may improve the intestinal microenvironment and improve the intestinal health status of mice by increasing the SCFAs produced by fermentation,thus improving insulin resistance and regulating the characteristics of T2DM.These results can provide a theoretical basis for the application of red kidney bean polysaccharides in functional food.