Nutritional Properity Of The Complex Of Tea Polyphenols And OSA Starch

Along with the change of social structure,eating habits,food composition,the accelerating of life rhythm,and the rapid development of aging population,chronic disease has become the major public health problem over the world.Tea polyphenols(TPLs),as an antioxidant factor,can reduce oxidative stress caused by hyperglycemia and hyperlipidemia,inhibit protein glycosylation and relieve so caused oxidative damage.They could also change the digestibility of starched through acting on the activity of enzymes.Thus,TPLs are often used in the diet intervention for chronic diseases such as obesity,diabetes.However,the bioavailability of TPLs is rather low due to the potential catechin sensitivity to digestive conditions,poor intestinal transport,and rapid metabolism and clearance.Starch derivative produced by appropriate modification of native starch,is preferential to be used as a controlled release carrier material.Moreover,starch itself is a physiologically active component.Thus,modified slow digestible starch was used as the carrier of TPLs.In this study,TPLs/OSA starch complex,a novel functional carbohydrate was established.The interaction between starch and OSA starch could maintain the sustained release of glucose from starch and improve digestive stability and bioavailability of TPLs carried.The effect of the complex on the aging progress induced by Dgalactose of mice with different diets was investigated.The main research contents and results are as follows:1.Octenyl succinic anhydride modified waxy maize starch,normal corn starch and high amylose starch(OSA modified starch)were prepared under the 3% addition of octenyl succinic anhydride.The DS of modified starch was positively related to the content of amylose in raw starches.OSA modification decreased the digestibility of raw starches.The content of rapidly digestible starch(RDS)in high amylose starch was decreased from 42.41% to 32.31%,while the content of resistant starch(RS)was increased from 50.42% to 71.47%.As for waxy corn starch and normal corn starch,along with the reduction of RDS content(from 85.6% ?80.7% to 57.9% ? 56.5%),the content of slow digestible starch(SDS)were significantly increased from 11.42%,10.60% to 29.63%,24.50%,respectively,which indicates improved slow digestive property of modified waxy corn starch and normal corn starch.After heat-moisture treatment in the conditions of 120?-15% water content-4 h,the SDS content of OSA modified waxy corn starch was further increased(from 29.6% to 38.3%),so OSA modified waxy corn starch with heat-moisture treatment(OSA starch,for short)was chosen as the carrier for following research.2.The influence of TPLs on the digestibility of starches depends on the dose added to the system.Under lower addition(1% starch weight base),TPLs increased the digestibility of OSA starch while higher addition(5-15% starch weight base)reduced it.TPLs noncompetitively inhibit the activity of pancreatic a-amylase but activate amyloglucosidase in a dose-dependent manner.However,when the two enzymes were employed together under the Englyst test condition at pH 5.2,a heterogeneous inhibition pattern was observed with a peak inhibition of 30% when the TPL content was 2.5 mg/mL,and a negative inhibition pattern when TPL content was greater than 4 mg/mL.The inhibition of TPLs on mixes enzymes was the main reason for the slow digestible property of modified starch especially after 5% addition of TPLs.A mouse model experimental results showed an extended and moderate postprandial glycemic response with a delayed and significantly decreased blood glucose peak,from 5mmol/L to 3 mmol/L.So 5% additioin of TPLs was used to establish the complex of TPLs and OSA starch(OSAT).Further studies revealed an increased hydrodynamic radius of OSA-starch molecules indicating an interaction between OSA-starch and TPLs.Additionally,decreased gelatinization temperature and enthalpy and reduced viscosity and emulsifiability of OSA-starch support their possible complexation to form a spherical OSAstarch-TPLs(OSAT)complex,in which the hydrophobic interaction between the OSA group of OSA-starch and aromatic hydrocarbons of TPLs is the major force for their complexation.3.Bioavailability and bioaccessibility were assessed in an in vitro digestion/Caco-2 cell model and KM mice respectively.In vitro digestive recovery of catechins in OSAT was modestly enhanced,especially EGCG and EGC.Differ from the continuously decrease in the process of digestion,the content of catechins in OSAT remain relatively stable.This might be due to the slow digestibility of OSAT which release catechins with the digestion of starch.Absorption of epigallocatechin(EGC)and epigallocatechin gal ate(EGCG)was significantly enhanced in OSAT relative to TPLs control in the plasma of mice.These data suggest that complexation with OSA starch may improve catechin bioavailability by enhancing bioaccessibility and intestinal uptake from OSAT.4.The moderate and extended postprandial glycemic response is likely caused by decreased activity of mucosal ?-glucosidase,which is noncompetitively inhibited by tea catechins released from the complex during digestion.Meanwhile,a significant decrease of malondialdehyde(MDA)and increased DPPH free radical scavenging activity and total antioxidant capacity in small intestine tissue demonstrated the antioxidative functional property of the OSAT complex.Thus,the complex of OSAT,acting as a functional carbohydrate material,not only leads to a flattened and prolonged glycemic response but also reduces the oxidative stress,which might be beneficial to health.5.Obesity combined with aging mouse model was induced by subcutaneous injection of Dglactose while giving 60% high fat diets to C57BL/6J mice.High fat diet accelerates the accumulation of advanced glycation end products in aging mice,and D-galactose enhanced the extent of dyslipidemia commonly occurred in obesity mice.OSAT intervention could ameliorate the lipid disturbance through increase the activity of LPL,HL,and the expression of PPAR-?,reduce the activity of FAS and the expression of SREBP-1c.The activity of SOD,GSH-Px,T-AOC were significantly increased and the content of MDA and AGEs in the liver were increased so that OSAT could ameliorate the hepatic injury of aging mice.Meanwhile,the content of AGEs,sRAGE,MDA,lipofuscin and TNF-? in the brain of aging mice were significantly decreased by OSAT which indicates that OSAT have anti aging effect by attenuating oxidative stress,enhancing immune function and inhibiting glycation in the brain.The mRNA expression of p16,p21 in the liver and brain of aging mice were down-regulated a indicated that OSAT might be beneficial to the prevention of aging.Overall,we found a novel functional carbohydrate with bioactivity.It works as a delivery system which could not only enhance the digestive stability and bioavailability of catechins,but also maintain a sustained release of glucose in the process of digestion.The complex also showed a potential anti-aging effect on D-galactose induced aging mice.Although OSA starch was not a commonly used food component,the complexation between TPLs and OSA starch laied a foundation for the exploitation of improving the nutritional value of functional carbonhydration and construction of biological active ingredient delievery system.