A Planar Catechin Analogue as a Promising Antioxidant with Reduced Prooxidant Activity
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- 作者：Kiyoshi Fukuhara ; Ikuo Nakanishi ; Tomokazu Shimada ; Kei Ohkubo ; Kentaro Miyazaki ; Wataru Hakamata ; Shiro Urano ; Toshihiko Ozawa ; Haruhiro Okuda ; Naoki Miyata ; Nobuo Ikota ; and Shunichi Fukuzumi
- 刊名：Chemical Research in Toxicology
- 出版年：2003
- 出版时间：January 2003
- 年：2003
- 卷：16
- 期：1
- 页码：81 - 86
- 全文大小：132K
- 年卷期：v.16,no.1(January 2003)
- ISSN：1520-5010
文摘
A planar catechin analogue (1H2), in which catechol and chroman moieties in (+)-catechinare constrained to be coplanar, is an efficient radical scavenger compared to the native catechin,and are nearly as effective as quercetin, a strong radical scavenger. The dianion (12-) of 1H2produced by the reaction of 1H2 with 2 equiv of tetramethylammonium methoxide reducedmolecular oxygen (O2) to generate superoxide anion (O2
-). The resulting radical anion (1-)from 1H2 underwent intramolecular proton transfer to give an o-semiquinone radical anionform of 1-, which shows a characteristic ESR spectrum with g value of 2.0048. Although thesame mechanism has also been shown for (+)-catechin, the rate constant of electron transfer(ket) from 12- to O2 is about a half of that reported for (+)-catechin, indicating that the electrontransfer from 12- to O2 is slower than that from (+)-catechin dianion to O2. Together withefficient protection against DNA strand breakage induced by the Fenton reaction, the smallket value for 1H2 implies that, in physiologically relevant systems, there is less of a possibilityof generating oxygen radicals responsible for prooxidant activity with 1H2 than that with (+)-catechin. The strong radical scavenging ability and less-efficient generation of O2- suggestthat the planar catechin analogue may be useful for the prevention and/or treatment of free-radical-associated diseases.
-). The resulting radical anion (1-)from 1H2 underwent intramolecular proton transfer to give an o-semiquinone radical anionform of 1-, which shows a characteristic ESR spectrum with g value of 2.0048. Although thesame mechanism has also been shown for (+)-catechin, the rate constant of electron transfer(ket) from 12- to O2 is about a half of that reported for (+)-catechin, indicating that the electrontransfer from 12- to O2 is slower than that from (+)-catechin dianion to O2. Together withefficient protection against DNA strand breakage induced by the Fenton reaction, the smallket value for 1H2 implies that, in physiologically relevant systems, there is less of a possibilityof generating oxygen radicals responsible for prooxidant activity with 1H2 than that with (+)-catechin. The strong radical scavenging ability and less-efficient generation of O2- suggestthat the planar catechin analogue may be useful for the prevention and/or treatment of free-radical-associated diseases.