Study On The Synthesis And Stability Of Methylated EGCG

EGCG3"Me has been isolated from green tea for the first time in 1982, and then its potential anti-allergic activity is reported. In recent years, some other methylated EGCG have been discovered in tea or vivo metabolites. EGCG4"Me is separated from oolong tea in 1999. Methylated EGCG is superior to EGCG in anti-allergy, anti-cell toxin, inhibiting lipoxygenase, mycobacterium tuberculosis bacteria, iNOS, protecting the liver cells, etc. The separation methods of methylated EGCG include Sephadex LH-20 chromatography, HSCCC, Toyopearl HW-40S medium-pressure chromatography, and pHPLC. Because its content in tea is not high, it is necessary to make some research in synthesis of methylated EGCG. The synthetic methods of methylated EGCG include chemical synthesis and biosynthesis. The chemical syntheses manily include diazomethane synthesis, iodomethane synthesis, dimethyl sulfate synthesis, benzyl protective group synthesis, nitrobenzene sulfonyl protecting groups synthesis.In this paper, EGCG is used as raw material; dimethyl sulfate is used as methylation reagent. Methylation products were extracted by ethyl acetate, and then isolated by silica gel column, the gel column and reversed-phase silica gel column. Two kinds of methylated derivatives are obtained, and then determined by ESI-MS, MS/MS and 1H-NMR. Their structures are EGCG4"Me and EGCG4'Me. The synthesis of methylated EGCG is improved through single-factor experiment. The suitable conditions are: EGCG/dimethyl sulfate = 1:1, adequate NaHCO3, in acetone solution, 60℃water bath under reflux 5 hours. The change of EGCG4"Me and EGCG in artificial simulation gastric juice and artificial simulation intestinal juice is determined by HPLC. The results show that EGCG4"Me take off methyl and generating EGCG in artificial simulation gastric juice, the stability of EGCG4"Me is improved as methylation in the artificial intestinal fluid. Meanwhile, the DPPH? radical scavenging capacity of EGCG4"Me and EGCG is determined. In the range of 0.001~1mg/mL, the DPPH? radical scavenging capacity of EGCG4"Me is increased as the concentration's increase. And the DPPH? radical scavenging capacity of EGCG4"Me and EGCG is similar. High-purify EGCG4"Me is obtained from experiment, it can provide the basis for germplasm selection, its related biological functions and product development.