eISSN: 1896-9151
ISSN: 1734-1922
Archives of Medical Science
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4/2007
vol. 3
 
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abstract:

Basic research
Antioxidative potential of black tea polyphenols in vitro and protective effects in vivo on mitochondrialredox status during experimental oral carcinogenesis

P. Vidjaya Letchoumy
,
K.V.P. Chandra Mohan
,
Yukihiko Hara
,
Siddavaram Nagini

Arch Med Sci 2007; 3, 4: 330-339
Online publish date: 2008/01/09
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Introduction: To evaluate the in vitro and in vivo antioxidant properties of the black tea polyphenols Polyphenon-B and BTF-35.
Material and methods: The in vitro antioxidant activity of black tea polyphenols was screened using a panel of assays including 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2’-azinobis-(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS), hydroxyl radical anion (OH), superoxide anion (O2•–), and nitric oxide (NO) radical scavenging assays as well as assay for reducing power. The in vivo antioxidant potential was evaluated in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model. Hamsters were divided into 6 groups. Animals in groups 1 to 3 were painted with 0.5% DMBA three times a week for 14 weeks. While hamsters in group 1 received no further treatment, animals in groups 2 and 3 received a diet containing 0.05% Polyphenon-B and BTF-35 respectively, from four weeks before DMBA painting until the end of the experiment. Animals in groups 4 and 5 were given Polyphenon-B and BTF-35 alone respectively, and group 6 animals served as controls. All the animals were sacrificed after 18 weeks.
Results: In in vitro studies, both Polyphenon-B and BTF-35 showed high radical scavenging activity and reductive potential. Dietary administration of Polyphenon-B and BTF-35 suppressed DMBA-induced HBP tumours by modulating mitochondrial lipid and protein oxidation and enhancing manganese superoxide dismutase (MnSOD), catalase (CAT), reduced glutathione (GSH) and GSH-dependent enzymes in the buccal pouch and liver. Conclusions: Our study suggests that the antioxidative properties of tea polyphenols may be responsible for chemoprevention of HBP carcinogenesis. Of the two tea polyphenols analysed, BTF-35 was more effective than Polyphenon-B both in vitro and in vivo.
keywords:

antioxidants, chemoprevention, mitochondria

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