Study On Purification Of Tea Polyphenol And Eparation Of Ester Catechin Monomer

Tea polyphenol is the general term for more than30kinds of multi-hydroxylphenolic compounds which are extracted from tea and account for about10%³5%ofthe dry weight of tea, including catechin, flavonoid and their glycoside, anthocyanin,leucoanthocyanidin, phenolic acid and depside etc. The catechin is the maincomponent of tea polyphenol and accounts for about70%⁸0%of its amount. Manystudies have indicated that the ester catechin plays a major role in antioxidant,anti-tumor, anti-cardiovascular and anti-cerebrovascular diseases, cancer preventionand radiation protection, so the ester catechins EGCG and ECG which play a leadingrole are given more attention and their separation is necessary to further research andapplication. It is difficult to separate catechin monomer effectively for the similarityof structure and property, there is a practical significant to explore a simple,economical and practical method to separate ester catechin monomer. In this paper,the material was Longnan summer and fall tea, the purification of tea polyphenol andthe separation of the ester catechins EGCG and ECG were studied, the methods andresults were as follows:1. The single factor and orthogonal experiments were used to optimize theprocess of depriving caffeine from tea polyphenol by emathlite adsorption, theresulted indicated that the optimum conditions of emathlite adsorption were wereemathlite dosage30g/L, adsorption time40min, adsorption times3and stirring rate120r/min. The effects of these factors on the caffeine content was in order ofadsorption times> emathlite dosage> stirring rate> adsorption time, and adsorptiontimes has significant effects on the caffeine content （P<0.05）. In addition, afteradsorption of caffeine in tea polyphenol by emathlite, the caffeine content decreasedfrom3.68%±0.25%to0.06%±0.01%and caffeine removal rate was98.25%, thecontent of catechin active substance was improved, the significant isomerictransformation between EGCG and GCG didn’t occur.2. The conditions of ethanol precipitation for the purification of tea polyphenolwere optimized by single factor and orthogonal test, the results indicated that theoptimum conditions of ethanol precipitation were volume ratio of extract to ethanol1:4, ethanol concentration100%, precipitation time6h and precipitation times2. The effects of these factors on the tea polyphenol content and mass was in order of ethanolconcentration> precipitation times> the ratio of volume> precipitation time, andethanol concentration has significant effects on the tea polyphenol content and mass（P<0.05）. In the optimal process, the tea polyphenol content was54.99%, the yield oftea polyphenol was68.46%.3. The enrichment process of ester catechin via ethyl acetate extraction andpolyamide column chromatography was studied. The results indicated that theoptimum conditions of ethyl acetate extraction were volume ratio of extract to ethylacetate1:4, extraction time30min, and extraction times2and pH of extract5.0, theeffects of these four factors on the tea polyphenol content was in order of extractiontimes> pH of extract> the ratio of volume> extraction time, and none of them had asignificant effects on the tea polyphenol content （P>0.05）. The effects of these fourfactors on the tea polyphenol mass was in order of extraction times> the ratio ofvolume> pH of extract> extraction time, and extraction times had a significanteffects on the tea polyphenol mass （P<0.05）. In the optimal process, the teapolyphenol content was89.23%, the yield of tea polyphenol was15.56%. The optimalconditions of polyamide column chromatography was that water,10%,20%,60%ethanol gradient elution was the best elution method, the flow rate was4mL·min^-1,polyamide granularity was90meshes and the sample weight was0.6g. The yield ofthe ester catechin was46.7%, the content of EGCG was65.8%while ECG was27.7%.4. The separation process of ester catechin monomer EGCG and ECG bymesolow liquid chromatography was studied. The results indicated that the optimumconditions of mesolow liquid chromatography were that eluent was ethanol, the flowrate was6mL·min^-1, gradient elution was0²CV: water;2⁴.5CV:10%ethanol;4.5⁷CV:35%ethanol;7⁸.5CV:10%ethanol;8.5¹1.5CV:80%ethanol, thesample weight was0.6g. The ester catechin monomer was determined by highperformance liquid chromatography and infrared spectrometry, which showed that thepurity of EGCG and ECG were95.6%and92.8%, the extraction rate were90.8%and89.6%, respectively.