The Stability Of Gallocatechin Gallate Under The Solution Condition

Tea polyphenolic compounds are the main physiological active ingredients of tea,while catechins are the principal part of the composition.Catechins consist of eight compounds including EC((-)-epicatechin),ECG((-)-epicatechin gallate),EGC((-)-gallocatechin),EGCG((-)-epigallocatechin gallate),GCG((-)-gallocatechin gallate),GC((-)-gallocatechin),CG((-)-catechin gallate),and C(+(-)catechin),showing various bioactivities such as anticancer,antibacterial,anti-inflammatory,free radicals scavenging,hypertension preventing and inhibiting,and anticardiovascular.At present,EGCG,the most abundant catechin compound in tea,has obtained the most in-depth research due to its powerful biological activity.Meanwhile,it has been found that the compound is instable and vulnerable to environmental factors such as temperature,acidity,metal ions,and oxygen,etc.Some research has shown that GCG,the stereoisomer of EGCG possesses better bioactivity than EGCG in some aspects,such as inhibiting lipid oxidation and peroxidation,preventing high blood pressure,suppressing growth of bacteria,etc.Up to now,almost no study concerning the stability of GCG has been carried out,so we initialized this investigation to compensate for the inadequacy on GCG research.The experimental results showed that the stability of GCG was easily influenced by diversified environmental factors.We adopted pure water,tap water and 11 kinds of salts to explore the stability of GCG under different factors and the results showed that the influence of different metal ions on GCG stability was dependent on the type of metal ion and its concentration.We found that metal ions like Cu2+,Fe3+,and Fe2+ exhibited relatively strong effect on GCG,and the higher the concentration of metal ions,the greater the influence on GCG stability.When modulating the pH of the solution,we found GCG stability was relatively higher in weak acidic condition.When adjusting temperature,we found that GCG was basically stable at temperatures lower than 40?,but at higher than 40? its decomposition rate accelerated as the temperature went up.In various buffer solutions(50 mM,pH 7.4)GCG was unstable and the fastest GCG degradation was observed in PBS.According to the GCG stability in different conditions,we utilized HPLC and LC-MS technology to test its degradation products and the results showed that in boiling water GCG mainly gave ester hydrolysis and isomerization reactions,producing GA(gallic acid),GC/EGC,and EGCG;In tap water and buffer system,GCG degradation products were GA,theasinensin A/D,GC,P2,and GCG quinine etc.Based on the above data,we set up several methods to stabilize GCG.For example GCG can be stabilized by addition of EDTA(ethylene diamine tetraacetic acid)to a final concentration of higher than 0.5 mM in tap water,or by addition of VC(vitamin C)to a final concentration of 1 mM in Tris-HCl buffer.