Caffeine, in green tea

GOTO T, YOSHIDA Y, Kiso M and NAGASHIMA H (1996) Simultaneous analysis of individual catechins and caffeine in green tea , J Chromatogr A, 749, 295-9. 

K Ohta, A Yoshida, K Harada. HPLC analysis of free amino acids and caffeine in green tea cultivated by hydroponics. Nippon Nogei Kagaku Kaishi 69 1331-1339, 1995. 

The NCI testing effort used tea extracts, tea polyphenol-enriched fractions, isolated catechin fractions, and a theaflavin-rich fraction. The black and green tea extracts were tested in both caffeinated and decaffeinated forms. The percentage of polyphenols in both green and black teas were approximately the same. However, levels of EGCG and caffeine in green tea are four- to five-fold that of black tea. Theaflavins are unique to black tea due to the oxidation process. 

An e-tongue with multivariate calibration techniques (PCA-ANN) was found able to quantify catechins and caffeine in green tea in contrast to reverse phase HPLC... 

WANG H, HELLiwELL K and YOU X (2000a) Isocratic elution system for the determination of catechins, caffeine and gallic acid in green tea using HPLC ,Pood Chem, 68 (1), 115-21. 

Green tea has been used for generations in China as medicine to treat headaches, body aches, and poor digestion and to improve well-being and life expectancy. Ingredients in green tea include antioxidants, bioflavonoids, and caffeine. Green tea is probably safe in low doses, as it is consumed daily in many Asian cultures without reported side effects. 

White tea also contains the highest amounts of flavones, 14.2- to 21.4-fold higher than other teas. Flavones have the strongest antioxidative activities. Another benefit of drinking white tea over other teas is its lower level of caffeine. There is only 15 mg of caffeine per serving for white tea, considerably less than the 40 mg in black tea and 20 mg in green tea. ... 

A study by Dulloo et al. showed that caffeine and catechins produced a thermogenic effect via sympathetic activation of NE, and that the effect of green tea extracts on the metabolic rate in humans is greater than that explained by caffeine content per se. In table 13.2, diurnal, nocturnal, and total 24 h energy expenditure values are presented for placebo, caffeine, and green tea extract. Diurnal energy expenditure... 

Tea leaves contain more caffeine than the coffee bean, but because a relatively smaller quantity of leaves is used in preparing tea, this beverage contains slightly less caffeine than does coffee. In green tea there is a considerable quantity of a volatile oil that also passes into the infusion, and the flavor of black tea also arises from volatile substances (theon). Both black and green tea contain about 7% tannic acid, but this is extracted only slowly. The bitter taste in tea that has been prepared too long is due to the tannic acid. 

Q. Chen, J. Zhao, Z. Guo, X. Wang, Determination of caffeine content and main catechinscon-tents in green tea (Camellia sinensis L.), using taste sensor technique and multivariatecalibra-tion. J. Food Compos. Anal. 23, 353-358 (2010)... 

Although green tea usually contains less caffeine than black tea, it is by no means caffeine-free. A cup of black tea may contain as much as an espresso (about 100 mg). A cup of green tea typically contains about one third of this amount. High tatmin content in green tea slows down the take-up of caffeine and moderates the stimulating effect. Recent research shows that the presence of an amino acid named L-theanine is also significant (Fig. 3.25). 

Figure 7.55 Some of the phenolic compounds, including proanthocyanidins and hydrolysable tannins, present in green tea (Camellia sinensis) infusions. The predominant purine alkaloid is caffeine with trace levels of theobromine.

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