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关键词 茶多酚 提取法 沉淀法
The research on the extracting method of tea polyphenols from tea
Li Ang，Luo Yifan，Chen Jianjing
Class1，Grade2000，Department of Clinical Medicine，Zhongshan Medical College Zhongshan Univ ersity，Guangzhou510080.
【Abstract】 Objective To study the extracting method of tea polyphenols from green tea.Methods The orˉganic resolvents and metal salts were used.The affecting factors and improving conditions of the two methods were disˉcussed.Results The results of two methods supply an experimental basis for the promotion ofextraction of tea polyphenols.Conclusion The tea polyphenols extraction with metal salts as precipitator is quite promising.
Key words tea polyphenols extracting method precipitating method Tea is rich in a kind of polyhydroxyl mass，i.e.tea polyphenols（TP），which is mainly composed of catechins（weighed as much as79%of TP）.
It can greatly efficaˉciously resist to cancer，caducity，radiationand free radiˉcals damage，and to lower down blood sugar and blood lipid.To extract TP better，in this experiment，organic resolvents and metal salts were used respectively，and by virtue of comparison between these two methods，a better way could be found.
1 Experiment and materials
1.1 Materials and Appliance Green tea（provided by the tea graduate school of Guangdong agricultural acadeˉmy of sciences），constant temperature heat booster，conˉstant temperature drier，instruments for filtration and exˉtraction.
1.2 Reagents FeC 4 H 4 O 6 solution，the buffer phosˉphate solution（pH7.5），alcohol chloroform（AR），CH 3 COOC 2 H 5 （AR），NaHCO 3 ，ZnCl 2 （AR），Al 2（SO 4 ） 3 ·18H 2 O（AR），HCl.
1.3 Organic resolvents extracting methods to extract The National Major Foundation of China“973”（No:G1998051201），The Scientific Technology Foundation of Guangdong Province（No:2KB01202S）Luo Yifan，E-mail:xuxuan@scnu.edu.cn tea polyphenols This method was based on the theory that TP was well soluble in water，alcohol，CH 3 COOC 2 H 5 ，etc.Therefore，we could use water or alˉcohol to extract TP from tea，and CH 3 COOC 2H 5 could be used for further extraction form aquatic layer.Reclaiming CH 2 COOC 2 H 5 and solid TP could be produced.The conˉcrete course was as following figure1.
1.4 Metal salts precipitating method to extract TP This method was based on the theory that TP was well soluble in water and could react with a certain kindsof metal salts to produce deposits at the specific pH values so that TP could be separated from other components.Used hydrochloric acid to dissolve deposits then extractˉed TP with help of CH 3 COOC 2 H 5 to get solid TP.The concrete course was as following figure2.
1.5 The estimation of content of TP Accurately weighed0.1g of TP powder we had just produced，then added water to dissolve it completely and added again to100ml.Accurately imbibed1.00ml of the above soluˉtion，replaced it to a25ml volumetric flask and added water for4ml，the FeC 4 H 4 O 6 solution for5ml，the added the very buffer solution to the scale.Using purified water to make a blank comparison.At the condition that the colorimetric utensil had a breadth of1cm，and the waveˉlength was540nm，then used photometer to calculate its absorbence to estimate the content of TP.Fig.1the flow chart for organic resolvents extracting methods to extract tea polyphenolsFig.
2 the flow chart for metal salts precipitating method to extract TP2 Discussion
2.1 The organic resolvents extracting methods （1）The experiment showed that the extractive productive rate was increased with the elevation of the extractive temperature.The aquatic circumfluence with a temperaˉture between90℃to95℃was used，the quantity of tea:alcohol=1:7.5，with a time of1.5h，which would increase the extractive productive rate of both TP and caffeine.（2）Alcohol was superior to water in extracting TP if alcohol was used to soak out TP.（3）The comparaˉtive experiments showed that CH 3 COOC 2 H 5 was the ideal organic resolvent to extract TP.CH 3 COOC 2 H 5 had a strong effect on extracting TP selectively，and the initial eradication of impurity was satisfying.It was proper to select CH 3 COOC 2 H 5 as the extractive resolvent.
2.2 The metal salts precipitating method Tea polyphenols can react with manykinds of metallic ions.And the combination is precipitated，which makes good separation between tea polyphenols and other ingrediˉents.At the same condition，the extraltive efficiency of tea polyphenols is:Al 3+ >Zn 2+ >Fe 3+ >Mg 2+ >Ba 2+ >Ca 2+ .The quantity of the metal salts was proper.TP are relatively stable when the pH value is between2to7.In this experiment，Zn 2+ （pH≈5.6）are selected to reassure that the final production we got remains non-oxidized.We have tried several reagents to adjust pH value of thesolution，the result is as follows:NaHCO 3 >Na 2 CO 3 >NH 3 ·H 2 O>NaOH.NaHCO 3can react with both acid and alkali，the pH value of its aquatic solution is nearly8.6.So it’s unlikely to make the local of the solution oxidized due to alkalinity.
2.3 The result analysis From table1，the results show that TP produced by metal salts precipitating method had a better color and luster as well as less imˉpurity than those of organic resolvents extracting method.Meanwhile the extractive productive rate of the former was higher than that of the latter.Notwithstanding the purity is converse，but we think that tea polyphenols extraction with metal salts as precipitator is quite promising.The method is still further improved.Tab.1 The results from two methods to extract TP method Crude productioncolor weight（g） crude productiverate（%） Pure rate（%） final productive rate （%）Organic resolventsextracting method Yellow andgreen powder 5.9953 2.99 81.3 2.43 Metal saltsprecipitating method Brown powder 8.1875 8.19 75.2 6.16（PS:crude productive rate=crude production weight/tea weight;final productive rate=crude production weight ˇ pure rate/tea weight）
参考文献
1 董文宾.食品科技，2002，9:45-47.
2 赵元鸿.云南大学学报（自然科学版），1999，21（4）:317-318.