Study On The Effects Of Loquat Leaves Polyphenols In Improving Insulin Resistance

Loquat is a family of Rosaceae.The leaves of loquat are rich in a variety of active substances,with antioxidant,anti-tumor,blood lipid and chemical defense and other biological activity.Loquat leaf polyphenols is one of the most active substances in recent years and it got increasing attention from researchers.In this work,the separation of polyphenol components from loquat leaves and the improvement of insulin resistance were studied.Furthermore,the effects of solvent type,concentration,ratio of material to liquid,extraction temperature and extraction time on the extraction of polyphenols from loquat are studied.Orthogonal design is used to optimize the extraction conditions of polyphenols in loquat leaves.Under the optimized extraction conditions(70%ethanol,solid-liquid ratio 1/15,40℃,extraction 2 h),the extraction was 2 times and the content of polyphenol was 9.9 mg/g loquat.The extraction conditions are as follows:the loading concentration was 1.5 mg/mL,the loading volume was 6 BV,the loading flow rate was 1.5 BV/h.The elution solution was extracted by macroporous adsorption resin column chromatography.70%ethanol,flow rate 1.5 BV/h,elution volume of 2 BV to obtain loquat leaf polyphenol purified components.Additionally,the antioxidant capacity of β-carotene linoleic acid oxidation system was evaluated by antioxidant ability of loquat polyphenols,IC50 was 0.91 mg/mL.The antioxidant capacity of polyphenols in loquat leaves was evaluated by AAPH-induced oxidative stress model.The concentration of AAPH was 5 mmol/L,the concentration of polyphenols was 10,20 and 30 μg/mL.Among them,30 μg/mL had obvious effect,ROS relative fluorescence value was 0.89.The results showed that the antioxidant ability of loquat leaf polyphenols was good,and the optimal concentration of insulin was 10-6 mol/L.The insulin resistance model of HAEC was significantly improved in the range of 30 μg/mL.The insulin resistance model was established by insulin in HAEC cells.The total RNA and total protein were extracted and analyzed by quantitative PCR and Western Blot.The results of quantitative PCR showed that the expression levels of IRS-1,PI3K and PDE3B were up-regulated in the polyphenol group compared with the model group.The results of Western Blot showed that the expression of IRS-1,PI3K and GLUT4 were up-regulated.OGTT experiments showed that the high dose of polyphenoland the low dose group(400 mg/kg,200 mg/kg)were all within 2 h of the insulin resistance model.In the low dose group,the blood glucose level of the model mice was restored within 20 min,and the fat index of the model mice was decreased.Compared with the model group,the levels of ALT and AST in the polyphenol serum were decreased,the level of HDL was increased,the LDL level was decreased.The level of GSH in liver tissue was increased,and the level of MDA in liver tissue was decreased.HE staining showed that fat cells of adipocytes were smaller and the degree of liver and kidney injury was improved.