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Review
. 2011 Aug;64(2):105-12.
doi: 10.1016/j.phrs.2011.05.007. Epub 2011 May 20.

Pharmacokinetic and chemoprevention studies on tea in humans

H-H Sherry Chow  1 , Iman A Hakim
Affiliations
Review

Pharmacokinetic and chemoprevention studies on tea in humans

H-H Sherry Chow et al. Pharmacol Res. 2011 Aug.

Abstract

Green tea and its major polyphenols constituents, tea catechins, have been shown to have many health benefits including cancer prevention. Tea catechins and tea catechin metabolites/catabolites are bioavailable in the systemic circulation after oral intake of green tea or green tea catechins. The metabolites/catabolites identified in humans include glucuronide/sulfate conjugates, methylated tea catechin conjugates, and microflora-mediated ring fission products and phenolic acid catabolites. Plasma levels of unchanged tea catechins in humans are mostly in the sub-μM or nM concentration range, which is much lower than the effective concentrations determined in most in vitro studies. However, some of the catechin metabolites/catabolites are present in the systemic circulation at levels much higher than those of the parent catechins. The contribution of catechin derived metabolites/catabolites to the biological effects associated with green tea is yet to be defined. A limited number of chemoprevention trials of green tea or green tea catechins have been conducted to date and have observed potential preventive activity for oral, prostate, and colorectal cancer. Emerging data from multiple ongoing intervention trials will further contribute to defining the cancer preventive activity of green tea or green tea catechins.

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Figures

Figure 1
Figure 1
Chemical structures of major green tea catechins.
Figure 2
Figure 2
Peak plasma tea catechin concentrations following a single dose administration of 800 mg EGCG (A) or Polyphenon E containing 800 mg EGCG, 148 mg EGC, 128 mg EC, and other green tea polyphenols (B) [8]. Black bars are data obtained from plasma samples without subjecting to glucuronidase/sulfatase treatment, representing unchanged catechins. Grey bars are data obtained from plasma samples treated with glucuronidase/sulfatase, representing total catechins (sum of unchanged catechins and catechin glucuronides/sulfates).
Figure 3
Figure 3
Metabolism and disposition of tea catechins in humans.
See this image and copyright information in PMC

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