Study on Interactions Between Dietary Anthocyanins and Common Endogenous Proteins

Author:Zhang Jiao Jiao

Supervisor:zheng xiao dong xiao jian bo


Degree Year:2019





Anthocyanins are widely found in roots,stems,leaves,flowers and fruits of plants which have been used as natural food pigments for a long time.Because they have health benefits,such as anti-oxidation,anti-cancer,prevention of cardiovascular diseases and so on,there are highly development value and application prospects.Anthocyanins have been widely concerned by domestic and abroad research scholars.As a kind of small molecules,anthocyanins are firstly transported to specific targets by binding to transporters in the blood,and then effectively chimeric with sites of different cell/subcellular structures,thus exerting different biological functions.Therefore,study on the interactions between anthocyanins and proteins is of great significance to further clarify the biological functions of anthocyanins.Anthocyanins are instable because of flavylium ion(FI)being part of their structures.In this dissertation,the stability of edible anthocyanins and interactions between them and common proteins(API)were studied in order to help understand the whole process of anthocyanin bioavailability,absorption and metabolism in human body,and understand how anthocyanin drives biological functions.It is expected to provide data basis and theoretical support for improving the absorption and bioavailability of anthocyanins and enhancing the biological activity of anthocyanins.The main results are as follows:1.The stability of anthocyanins in cell culture condition was studied by liquid chromatography and cell culture.It was found that the structures of anthocyanins(glycosyl group,hydroxyl group and methoxy group)were closely related to their stability.Additionally,the type of solvent and other compounds in solution also affected the stability of anthocyanins.The experimental results demonstrate that:(1)anthocyanins are very instable in cell culture condition,and the biological function of anthocyanins may originate from the function of their degraded compounds rather than anthocyanins themselves;(2)glycosylation has a strong influence on the degradation rate of anthocyanins,which is manifested by the fact that the stability of glycosylated form is much higher than that of not glycosylated form;(3)in the same glycosylation conditions,the degradation anthocyanins with more hydroxyl groups are more likely to occur,and anthocyanins with high degree of methoxylation are more stable;(4)except pH influence,proteins or/and other compounds in the culture medium also play important role in the degradation of anthocyanins,especially to not glycosylated form.2.The interactions between anthocyanins and human serum albumin were studied through pharmacokinetic methods.Human serum albumin,a common transporter in blood,was used to transport,absorb and ultimately work on specific targets through the transformation between AP and AF.It was found that:(1)the binding force of not glycosylated form was greater than that of glycosylated form;(2)in the same glycosylation conditions,there are no strong regularity on hydroxylation effect and methoxylation effect of binding force as the same glycosylated degree;(3)the distribution coefficient(XLogP3)was negatively correlated with the binding force;(4)the topological polar area(TPSA)was positively correlated with the binding force.3.Anthocyanins have been reported to inhibit key enzymes of glycometabolism.In order to explore anthocyanin’s inhibited mechanisms,this dissertation has operated the method of enzymatic kinetics to calculate and compare the IC50 and Km under different enzyme inhibition models to explore how anthocyanins inhibit the activity of α-glucosidase.The results have exhibited that:(1)with the same FC structure,the inhibitory ability of not glycosylated form is stronger than that of glycosylated form;(2)the inhibitory ability of anthocyanins with high degree of hydroxylation and methoxylation is stronger;(3)hydroxylation and methoxylation affected the inhibition of anthocyanins to α-glucosidase through different mechanisms: hydroxylation through increasing the degraded rate of anthocyanins to increase the inhibitory ability of the enzyme;while methoxylation through increasing the binding force between anthocyanin and the α-glycosidase to improve the inhibitory ability;(4)chalcone,a probable degraded product in anthocyanin aqueous solution,with anthocyanin,to inhibits the α-glycosidase together;(5)anthocyanin solution has both competitive and non-competitive inhibitory effects on the α-glycosidase,which may be related to its instability in solutions.4.To further clarify how anthocyanins inhibit α-glucosidase and anthocyanin-glucosidase(AP),synchronous fluorescence and fluorescence were applied to study the binding mode between anthocyanins and glycosidase,and the in silico molecular docking was used to analyze the binding force between them.The results showed that:(1)the number of binding sites between anthocyanins and glycosidases was one(n?1)except pt,which was close to two;(2)the binding forces between not glycosylated form and glucosidase was stronger than that of glycosylated form,except the binding force of between Dp-glc and glucosidase was stronger than that of Dp;(3)there was no strong correlation between binding sites and binding force,so as to molecular energy of anthocyanins and binding force;(4)In the process of anthocyanin-glycosidase binding,the polarity around tyrosine residue(Tyr)changed,but the polarity around tryptophan residue(Trp)did not change a lot;(5)the fluorescence quenching phenomenon was mainly caused by tryptophan residue;(6)the fluorescence quenching effect of not glycosylated form to glycosidase was more obvious than that of glycosylated form,except the quenching effect of Mv-glc to glycosidase was more obvious than that of Mv,the interaction between flavylium cation(Mv)and glycosidase is different from that of other FCs;(7)the binding of anthocyanin-glycosidase complexes exist electrostatic adsorption,hydrogen bonding,and different forms of pi system(pi-pi Stack,pi-Anion,pi-pi T shaped,pi-Allyl).In conclusion,by studying the stability of anthocyanins and their interaction with common proteins(API),it can help to understand the whole process of anthocyanins bioavailability,absorption and metabolism in human body and how anthocyanins operate biological functions.It is expected to provide basic data and theoretical support to improve the absorption and bioavailability of anthocyanins and to enhance the physiological activity of anthocyanins.