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Titolo:
Scavenging of hydrogen peroxide and inhibition of ultraviolet light-induced oxidative DNA damage by aqueous extracts from green and black teas
Autore:
Wei, HC; Zhang, XS; Zhao, JF; Wang, ZY; Bickers, D; Lebwohl, M;
Indirizzi:
Mt Sinai NYU Med Ctr, Dept Dermatol, New York, NY 10029 USA Mt Sinai NYU Med Ctr New York NY USA 10029 rmatol, New York, NY 10029 USA Mt Sinai NYU Med Ctr, Dept Community Med, New York, NY 10029 USA Mt Sinai NYU Med Ctr New York NY USA 10029 ty Med, New York, NY 10029 USA Columbia Univ, Dept Dermatol, New York, NY 10027 USA Columbia Univ New York NY USA 10027 Dept Dermatol, New York, NY 10027 USA
Titolo Testata:
FREE RADICAL BIOLOGY AND MEDICINE
fascicolo: 11-12, volume: 26, anno: 1999,
pagine: 1427 - 1435
SICI:
0891-5849(199906)26:11-12<1427:SOHPAI>2.0.ZU;2-G
Fonte:
ISI
Lingua:
ENG
Soggetto:
INDUCED COLON CARCINOGENESIS; INDUCED SKIN CARCINOGENESIS; A/J MICE; POLYPHENOL FRACTION; TUMOR INITIATION; DRINKING-WATER; HAIRLESS MICE; INDUCED LUNG; SKH-1 MICE; TUMORIGENESIS;
Keywords:
green tea; black tea; skin carcinogenesis; melanoma; skin cancer; scavenging of H2O2; antioxidant; EGCG; free radicals;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
38
Recensione:
Indirizzi per estratti:
Indirizzo: Wei, HC Mt Sinai NYU Med Ctr, Dept Dermatol, Box 1047, New York, NY 10029 USA Mt Sinai NYU Med Ctr Box 1047 New York NY USA 10029 , NY 10029 USA
Citazione:
H.C. Wei et al., "Scavenging of hydrogen peroxide and inhibition of ultraviolet light-induced oxidative DNA damage by aqueous extracts from green and black teas", FREE RAD B, 26(11-12), 1999, pp. 1427-1435

Abstract

Aqueous extracts of green and black teas have been shown to inhibit a variety of experimentally induced animal tumors, particularly ultraviolet (UV) B light-induced skin carcinogenesis. In the present study, we compared the effects of different extractable fractions of green and black teas on scavenging hydrogen peroxide (H2O2), and UV irradiation-induced formation of 8-hydroxy 2'-deoxyguanosine (8-OHdG) in vitro. Green and black teas have been extracted by serial chloroform, ethyl acetate and n-butanol, and divided into four subfractions designated as GT1-4 for green tea and BT1-4 for black tea, respectively. The total extracts from green and black teas exhibited apotent scavenging capacity of exogenous H2O2 in a dose-dependent manner. It appeared that the total extracts from black tea scavenged H2O2 more potently than those from green tea. When tested individually, the potency of scavenging H2O2 by green tea subfractions was: GT2 > GT3 > GT1 > GT4, whereas the order of efficacy for black tea was: BT2 > BT3 > BT4 > BT1. Tn addition, we demonstrated that total fractions of green and black teas substantially inhibited the induction of 8-OHdG in calf thymus by all three portions ofUV spectrum (UVA, B and C). Consistent with the capacity of scavenging H2O2, the subfractions from black tea showed a greater inhibition of UV-induced 8-OHdG than those from green tea. At low concentrations, the order of potency of quenching of 8-OHdG by green tea subfractions was: GT2 > GT3 > GT4 > GT1 and The efficacy of all subfractions became similar at high concentrations. All subfractions of the black tea except BT1 strongly inhibited W-induced 8-OHdG and the order of potency was: BT2 > BT3 > BT3 > BT1. Addition of (-)-epigallocatechin gallate (EGCG), an ingredient of green tea extract,to low concentration of green and black tea extracts substantially enhanced the scavenging of H2O2 and quenching of 8-OHdG, suggesting the important role of EGCG in the antioxidant activities of tea extracts. The potent scavenging of oxygen species and blocking of UV-induced oxidative DNA damage may, at least in part, explain the mechanism(s) by which green/black teas inhibit photocarcinogenesis.

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Documento generato il 01/12/20 alle ore 08:00:11