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A Review on the Beneficial Effects of Tea Polyphenols on Human Health |
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J. Gupta,
Y.H. Siddique,
T. Beg,
G. Ara and M. Afzal |
Abstract:
The aim of this review is to focus some light on the
beneficial effects of the tea polyphenols on human health, based on various
laboratory, epidemiological and clinical studies carried out on tea and
tea polyphenols in the last few years. Tea is second only to water as
the most consumed beverage in the world. Tea has been consumed worldwide
since ancient times to maintain and improve health. The health benefits
associated with tea consumption have resulted in the wide inclusion of
green tea extracts in botanical dietary supplements, which are widely
consumed as adjuvants for complementary and alternative medicines. Depending
upon the level of fermentation, tea can be categorized into three types:
green (unfermented), oolong (partially fermented) and black (highly to
fully fermented). Black tea represents approximately 78% of total consumed
tea in the world, whereas green tea accounts for approximately 20% of
tea consumed. Tea is particularly rich in polyphenols, including catechins,
theaflavins and thearubigins, which are thought to contribute to the health
benefits of tea. Tea polyphenols comprise about one-third of the weight
of the dried leaf and they exhibit biochemical and pharmacological activities
including antioxidant activities, inhibition of cell proliferation, induction
of apoptosis, cell cycle arrest and modulation of carcinogen metabolism.
Several studies demonstrate that most tea polyphenols exert their effects
by scavenging Reactive Oxygen Species (ROS) since excessive production
of ROS has been implicated in the development of a variety of ailments
including cancer of the prostate gland (CaP). Tea catechins include (-)-epicatechin
(EC),(-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG) and (-)-epigallocatechin
gallate (EGCG). These catechins have been shown to be epimerized to (-)-catechin
(C), (-)-gallocatechin (GC), (-)-catechin gallate (CG) and (-)-gallocatechin
gallate (GCG), respectively, during heat treatment. Tea polyphenols act
as antioxidants in vitro by scavenging reactive oxygen and nitrogen
species and chelating redox-active transition metal ions. Among the health-promoting
effects of tea and tea polyphenols, the cancer-chemopreventive effects
in various animal model systems have been intensively investigated; meanwhile,
the hypolipidemic and antiobesity effects in animals and humans have also
become a hot issue for molecular nutrition and food research. In vitro
and animal studies provide strong evidence that tea polyphenols may possess
the bioactivity to affect the pathogenesis of several chronic diseases,
especially cardiovascular disease and cancer. Research conducted in recent
years reveals that both black and green tea have very similar beneficial
attributes in lowering the risk of many human diseases, including several
types of cancer and heart diseases.
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How to cite this article:
J. Gupta, Y.H. Siddique, T. Beg, G. Ara and M. Afzal, 2008. A Review on the Beneficial Effects of Tea Polyphenols on Human Health. International Journal of Pharmacology, 4: 314-338.
DOI: 10.3923/ijp.2008.314.338
URL: https://scialert.net/abstract/?doi=ijp.2008.314.338
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| COMMENTS |
29 May, 2017
dr karami:
please give me cite this article for endnote |
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