Preparation And α-Glucosidase Inhibitory Activity Of Dihydromyricetin Derivatives

Diabetes mellitus,as one of the recognized diseases that harm health,not only causes serious complications,but also brings serious economic burden to the society.Current studies have confirmed that the control ofα-glucosidase activity is an effective means of diabetes prevention and treatment.At present,the syntheticα-glucosidase inhibitors for clinical use,such as acarbose,voglibose and miglitol,have serious side effects,so it is imperative to screen or design safe and effective novelα-glucosidase inhibitors.Dihydromyricetin is the main active ingredient in the leaves of Ampelopsis grossedentata.The related studies have also confirmed that it has certainα-glucosidase inhibitory activity,and it is a good lead compound for the design of novelα-glucosidase inhibitors.In this study,based on the systematic study of the molecular mechanism of dihydromyricetin inhibitingα-glucosidase,dihydromyricetin polymer and dihydromyricetin-beet pectin polymer were prepared,and their structures were characterized.Theα-glucosidase inhibitory activities were also evaluated.The results of this study can expand the application of plant-derived flavonoids in food field,and promote the green and efficient preparation of novelα-glucosidase inhibitors.The main research contents and relevant conclusions are as follows:1.Theα-glucosidase inhibitory activities of 15 common food-derived flavonoids were systematically compared.It was found that the performance of flavonoid aglycone was higher than that of corresponding flavonoid glycoside,and the inhibitory activity of flavonoid aglycone was positively correlated with the number of phenolic hydroxyl groups on the B-ring.Although the structures of myricetin and dihydromyricetin were similar,the inhibitory activity of myricetin was significantly superior to that of dihydromyricetin.Fluorescence analysis showed that the binding ability of myricetin toα-glucosidase was also higher than that of dihydromyricetin.In order to elucidate the underlying molecular mechanism,molecular simulation methods such as molecular docking and independent gradient model were introduced to investigate the binding behavior of myricetin and dihydromyricetin withα-glucosidase.It was found that they had different molecular orientations at the active center ofα-glucosidase,and they combined withα-glucosidase through hydrogen bond and van der Waals force,and the effect of myricetin on the enzyme was stronger,which confirmed the results of thermodynamic experiment.2.Dihydromyricetin has a variety of biological activities,but its low water-solubility and poor enzyme inhibition effect lead to its limited application in functional foods.The application of laccase for oxidative polymerization of dihydromyricetin is expected to solve this bottleneck,but relevant research has not been conducted.In this study,the effects of laccase catalysis conditions on the color,α-glucosidase inhibitiory and antioxidant activity of dihydromyricetin derivatives were systematically investigated,and the structure of the product was characterized by spectroscopic method.The results suggested that laccase could be used for the oxidation polymerization of dihydromyricetin.The concentration of laccase,p H,reaction time and temperature had regular effects on the color of the derivatives.After oxidative polymerization,theα-glucosidase inhibitory activity of dihydromyricetin was significantly increased,but theα-glucosidase activity of dihydromyricetin was decreased.The spectral analysis indicated that laccase catalyzed the oxidation of phenolic hydroxyl groups of dihydromyricetin to realize the polymerization of dihydromyricetin by ether bonding.3.By alkali induction method,sugar beet pectin could form the covalent polymer with dihydromyricetin.The molecular weight,total phenol content and antioxidant activity of the polymer were positively correlated with the addition amount of dihydromyricetin in the preparation process.The polymer could inhibitα-glucosidase in a mixed uncompetition and anti-competition mode,and its inhibitory activity depended on the total phenol content,and the highest activity(IC₅₀,8.92±0.28μg/m L)was much higher than that of dihydromyricetin(IC₅₀,20.26±0.64μg/m L),which could be attributed to its strong binding ability to enzyme proteins.The stability andβ-carotene protective effect ofβ-carotene nano-emulsion stabilized with sugar beet pectin-dihydromyricetin covalent polymer were positively correlated with its total phenol content,which were higher than those ofβ-carotene nano-emulsion stabilized by sugar beet pectin.