Determination of Tea Components with Antioxidant Activity
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- 作者：Carmen Cabrera ; Rafael Gimé ; nez ; and M. Carmen Ló ; pez
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2003
- 出版时间：July 16, 2003
- 年：2003
- 卷：51
- 期：15
- 页码：4427 - 4435
- 全文大小：109K
- 年卷期：v.51,no.15(July 16, 2003)
- ISSN：1520-5118
文摘
Levels of essential elements with antioxidant activity, as well as catechins, gallic acid, and caffeinelevels, in a total of 45 samples of different teas commercialized in Spain have been evaluated.Chromium, manganese, selenium, and zinc were determined in the samples mineralized with HNO3and V2O5, using ETAAS as the analytical technique. The reliability of the procedure was checked byanalysis of a certified reference material. Large variations in the trace element composition of teaswere observed. The levels ranged from 50.6 to 371.4 ng/g for Cr, from 76.1 to 987.6 
g/g for Mn,from 48.5 to 114.6 ng/g for Se, and from 56.3 to 78.6 ng/g for Zn. The four major catechins [(-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epicatechin (EC)], gallic acid (GA), and caffeine were simultaneously determined by a simple andfast HPLC method using a photodiode array detector. In all analyzed samples, EGCG ranged from1.4 to 103.5 mg/g, EGC from 3.9 to 45.3 mg/g, ECG from 0.2 to 45.6 mg/g, and EC ranged from 0.6to 21.2 mg/g. These results indicated that green tea has a higher content of catechins than bothoolong and fermented teas (red and black teas); the fermentation process during tea manufacturingreduces the levels of catechins significantly. Gallic acid content ranged from 0.039 to 6.7 mg/g; thefermentation process also elevated remarkably gallic acid levels in black teas (mean level of 3.9 ±1.5 mg/g). The amount of caffeine in the analyzed samples ranged from 7.5 to 86.6 mg/g, and thelower values were detected in green and oolong teas. This study will be useful for the appraisal oftrace elements and antioxidant components in various teas, and it will also be of interest for peoplewho like drinking this beverage.Keywords: Tea; trace elements; catechins; gallic acid; antioxidants; caffeine
g/g for Mn,from 48.5 to 114.6 ng/g for Se, and from 56.3 to 78.6 ng/g for Zn. The four major catechins [(-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epicatechin (EC)], gallic acid (GA), and caffeine were simultaneously determined by a simple andfast HPLC method using a photodiode array detector. In all analyzed samples, EGCG ranged from1.4 to 103.5 mg/g, EGC from 3.9 to 45.3 mg/g, ECG from 0.2 to 45.6 mg/g, and EC ranged from 0.6to 21.2 mg/g. These results indicated that green tea has a higher content of catechins than bothoolong and fermented teas (red and black teas); the fermentation process during tea manufacturingreduces the levels of catechins significantly. Gallic acid content ranged from 0.039 to 6.7 mg/g; thefermentation process also elevated remarkably gallic acid levels in black teas (mean level of 3.9 ±1.5 mg/g). The amount of caffeine in the analyzed samples ranged from 7.5 to 86.6 mg/g, and thelower values were detected in green and oolong teas. This study will be useful for the appraisal oftrace elements and antioxidant components in various teas, and it will also be of interest for peoplewho like drinking this beverage.Keywords: Tea; trace elements; catechins; gallic acid; antioxidants; caffeine