Distribution of Catechins, Theaflavins, Caffeine, and Theobromine in 77 Teas Consumed in the United States

JFS C: Food ChemisTry and Toxicology

Distribution of Catechins, Theaflavins, Caffeine, and Theobromine in 77 Teas Consumed in the United States

Mendel Friedman, Soo-Yeun Kim, Sin-Jung Lee, Gyeong-Phil Han, Jae-Sook Han, Kap-Rang Lee, and Nobuyuke Kozukue

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Introduction[pic 2]

lants, including tea leaves from Camelia sinensis (Beecher 2003), produce secondary metabolites, organic compounds that

are involved in the defense of the plants against invading patho- gens, including insects, bacteria, fungi, and viruses. In the case of tea leaves, these metabolites include polyphenolic catechins and theaflavins and the alkaloids caffeine and theobromine. Commer- cial teas can be classified into several major categories: unfermented green, semi-fermented oolong, and fully fermented black. Inactiva- tion of phenol oxidases in green tea prevents oxidations of the cat- echins, whereas phenolase-catalyzed oxidation of catechins in green tea results in the formation of dimeric theaflavins and polymeric thearubigins, which impart the black color to black tea (Schwimmer 1981; Bonoli and others 2003; Sang and others 2004; Shahidi and Naczk 2004). White tea is produced only in a province of China from tip buds of a special tea plant. Herbal teas are derived from plants other than Camelia sinensis.

Depending on the stereochemical configuration of the of the 3',

4'-dihydroxyphenyl and hydroxyl groups at the 2- and 3-positions of the C-ring, tea catechins can exist as 2 geometrical isomers: trans- catechins and cis-epicatechins (Figure 1). Each of the isomers, in turn, exists as 2 optical isomers: (+)-catechin and (–)-catechin and (+)-epicatechin and (–)-epicatechin, respectively. (–)-Catechin can

be modified by esterification with gallic acid to form (–)-catechin- 3-gallate, epicatechin-3-gallate, (–)-epigallocatechin-3-gallate, and (–)-gallocatechin-3-gallate, respectively. Oxidative coupling of dif- ferent catechins forms the 4 theaflavins.

Antioxidative tea components are reported to have beneficial protective effects against cancers (Michels and others 2005), cho- lesterol (Maron and others 2003; Vinson and others 2004), cerebral damage (Suzuki and others 2004), diabetes (Vinson and Zhang 2005), smoking (Schwarz and others 2005), and pathogenic bacteria (Yoda and others 2004; Friedman and others 2005). Green and black teas also contain the central nervous system stimulant caf- feine and the diuretics/vasodilators theobromine (Fisone and oth- ers 2004) and theophylline (Fernandez and others 2002). Black teas also contain the polymeric thearubigin pigments of undefined structure (Menet and others 2004). A need exists to relate the com- position of commercial teas to beneficial effects.

A wide variety of extraction conditions and analysis methods have been used resulting in a wide variety in measured concentrations of tea compounds. Previous studies include the following observations: Lee and Ong (2000) measured 4 catechins and theaflavins (ex- tracted with boiling water and incubated at 90 °C for 30 min) in 8 teas sold in Singapore using high-performance liquid chromatog- raphy (HPLC) and electrophoresis. The mobile phase used consist-

          ed of acetonitrile/trifluoroacetic acid. Although the analysis by

MS 20050331 Submitted 6/1/05, Revised 7/13/05, Accepted 8/16/05. Author Friedman is with Western Regional Research Center, Agricultural Research Service, U.S. Dept. of Agriculture, Albany, CA 94710. Authors Kim, S.-J. Lee, and K.-R. Lee are with College of Human Ecology, Yeungnam Univ., Gyongsan, Korea. Authors Phil, Han, and Kozukue are with Dept. of Food Service Industry, Uiduck Univ., Gyongbuk, Korea. Direct inquiries to author Friedman (E-mail: mfried@pw.usda.gov).

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electrophoresis was faster, it was only 1/5 as sensitive as HPLC. Lin and others (Lin and others 2003) used an isocratic HPLC pro-

cedure with a mobile phase consisting of ethanol/H2O/formic acid to determine caffeine and 5 catechins in 31 Taiwanese tea leaves and tea flowers. Some of the flowers extracted with 75% ethanol at 60 °C for 30 min contained greater amounts of total catechins than

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[pic 6][pic 7]did extracts obtained with boiling water for 30 min and others con- tained lower amounts.

Khokhar and Magnusdottir (Khokhar and Magnusdottir 2002) used HPLC with acetonitrile as the eluent to determine the content of 5 catechins and caffeine in 4 black, 3 green, and 6 fruit teas (ex- tracted in boiling water for 5 min) consumed in the U.K. The amount of catechins and caffeine extracted in water increased in the range 60 °C to 100°C and was greatest at 100 °C for 5 min. The total catechin content ranged from 5.6 to 47.5 mg/g in black teas and from 51.5 to

84.3 mg/g in green teas. The estimated dietary intake of total tea catechins was 92.7 mg/d from black teas and 405.5 mg/d from green teas. The range for caffeine was from 92 to 146 mg/d.

Fernandez and others (Fernandez and others 2002) used HPLC with water/acetonitrile/formic acid as the mobile phase to measure catechin and xanthine profiles of 13 green and 42 black and red teas (extracted with 60:40 acetonitrile/water at room temperature for 1 h) originating from China, Japan, Kenya, India, and Sri Lanka. Their results suggest that catechin, gallic acid, and the methyl-xan- thine content may be used to differentiate the geographic origin of specific teas.

Cabrera and others (Cabrera and others 2003), using an HPLC method with a photodiode array detector, measured 4 catechins and caffeine levels in 15 black, green, and oolong teas sold in Spain (extracted with 80% methanol for 3 h and then twice more with 80% methanol containing 0.15% HCl for 3 h). They observed a wide vari- ation in the content of catechins among these teas. Red teas had the lowest levels.

Analysis by HPLC-MS of catechins, theaflavins, and purine alka- loids in Indonesian green and black tea infusions extracted with boiling water for 3 min (Del Rio and others 2004) gave the following results for green tea (in mg/L): total catechins, 4572; theobromine, 57; caffeine, 866; total theaflavins, 0. The values for black tea were 26, 224, 25, and 541, respectively.

In related studies, Sakakibara and others (2003) extracted polyphenols from vegetables, fruits, and teas with 90% methanol/ 0.5% acetic acid; Zhu and others (2004) analyzed tea compounds by GS-MS after steeping the tea leaves in water at 80 °C for 30 min; and Bonoli and others (2003) extracted teas with boiling water for 5 min. Other studies describe the analysis of tea polyphenols by HPLC with different detectors (Beecher and others 1999; Lee and others 2000) by micellar electrokinetic chromatography (Bonoli and oth- ers 2003), as well as by mass spectrometry (Menet and others 2004) and by HPLC/electrospray-mass spectrometry (Zhu and others 2004). Using UV spectroscopy, we previously showed that (–)-cat- echin and (–)-epigallocatechin resisted degradation at high pH (Friedman and Jürgens 2000). Catechins added to dough also resist- ed heat-degradation during the bread baking (Wang and Zhou