Journal Article

Green tea catechins partially protect DNA from <sup>·</sup>OH radical-induced strand breaks and base damage through fast chemical repair of DNA radicals

Robert F. Anderson, Louisa J. Fisher, Yukihiko Hara, Tracy Harris, Wai B. Mak, Laurence D. Melton and John E. Packer

in Carcinogenesis

Volume 22, issue 8, pages 1189-1193
Published in print August 2001 | ISSN: 0143-3334
Published online August 2001 | e-ISSN: 1460-2180 | DOI: https://dx.doi.org/10.1093/carcin/22.8.1189
Green tea catechins partially protect DNA from ·OH radical-induced strand breaks and base damage through fast chemical repair of DNA radicals

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The catechins, (–)-epicatechin (EC), (–)-epigallocatechin (EGC), (–)-epicatechin gallate (ECG) and (–)-epigallocatechin gallate (EGCG) are believed to be active constituents of green tea accounting for the reported chemoprevention of certain cancers. The molecular mechanisms by which the measured low concentrations (ca. micromolar) of catechins in humans can reduce the incidence of carcinogenesis is not clear. Using an in vitro plasmid DNA system and radiolytically generating reactive oxygen species (ROS) under constant scavenging conditions, we have shown that all four catechins, when present at low concentrations, ameliorate free radical damage sustained by DNA. A reduction in both prompt DNA single-strand breaks and residual damage to the DNA bases, detected by subsequent incubation with the DNA glycosylases formamidopyrimidine (FPG), endonuclease III (EndoIII) and 5′ AP endonuclease exonuclease III (ExoIII), was observed. EGCG was found to be the most active of the catechins, with effects seen at micromolar concentrations. Combined fast-reaction chemistry studies support a mechanism of electron transfer (or H-atom transfer) from catechins to ROS-induced radical sites on the DNA. These results support an antioxidant role for catechins in their direct interaction with DNA radicals.

Keywords: D0, the radiation dose required on average to produce one DNA single-strand break; E(1), one-electron reduction potiential at pH 7 versus normal hydrogen electrode; EC, (−)-epicatechin; ECG, (−)-epicatechin gallate; EDTA, ethylenediaminetetraacetic acid; EGC, (−)-epigallocatechin; EGCG, (−)-epigallocatechin gallate; EndoIII, endonuclease III; Exoll, exonuclease III; FPG, formidopyrimidine-DNA glycosylase; G(ess), yield of endonuclease-indiced DNA single-stand breaks per absorbed dose (Gy); G(ssb), radiation chemical yield of single-strand breaks per absorbed dose (Gy); G(ssb′), reduction in G(ess) due to the presence of catechins; Gy, absorbed radiation dose (J/kg); ROS, reactive oxygen specie; TAE, Tris/acetic acid/EDTA buffer; Tris, tris(hydroxy-methyl)aminomethane

Journal Article.  5084 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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