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Solvent effects on the galvinoxyl radical-scavenging dynamics of catechins
https://repo.qst.go.jp/records/64495
https://repo.qst.go.jp/records/6449583557c11-55c9-4145-b437-8463114ec2e2
| Item type | 会議発表用資料 / Presentation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2012-02-13 | |||||
| タイトル | ||||||
| タイトル | Solvent effects on the galvinoxyl radical-scavenging dynamics of catechins | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_c94f | |||||
| 資源タイプ | conference object | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
Kawashima, Tomonori
× Kawashima, Tomonori× Nakanishi, Ikuo× Imai, Kohei× Ohkubo, Kei× Fukuhara, Kiyoshi× Fukuzumi, Shunichi× Matsumoto, Kenichiro× 川島 知憲× 中西 郁夫× 今井 耕平× 松本 謙一郎 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | It is known that there are three mechanisms for the radical-scavenging reactions of phenolic compounds, such as tocopherol and (+)-catechin, i.e., one-step hydrogen-atom transfer (HAT) from the phenolic OH group to radicals, electron transfer from phenolic compounds to radicals followed by proton transfer (ET-PT), and sequential proton-loss electron transfer (SPLET). The scavenging reaction of galvinoxyl radical, used as a reactive oxygen-centered radical model, by catechin was reported to proceed via ET-PT. Although, three mechanisms of radical scavenging are known to be controlled by solvents, there are few reports on the solvent effect on the radical-scavenging mechanisms of catechins. We report herein the kinetics and mechanism of the radical-scavenging reaction by (+)-catechin and (–)-epicatechin in various solvents. The UV-vis absorption change was monitored after mixing of deaerated acetonitrile (MeCN) solutions of galvinoxyl radical (GO•), as a stable model of reactive oxygen species, and (+)-catechin using the stopped-flow technique. The radical-scavenging rate constants (k) of (+)-catechin and (-)-epicatechin were determined to be 6.1 x 10 and 1.1 x 102 M-1 s-1, respectively. No effect of acetic acid (CH3COOH) on the GO-scavenging reaction by catechins indicates that these scavenging reactions proceed via ET-PT. In methanol (MeOH), the pseudo-first order rate constant (kobs) for (+)-catechin increased with increasing concentration of (+)-catechin and reached a constant value. In the case of (-)-epicatechin, the kobs value was increased linearly with an increase in concentration of (-)-epicatechin. When CH3COOH was added to the reaction solutions in order to inhibit the deprotonation of catechins in MeOH, the k values of catechins were significantly decreased. The effect of CH3COOH on the k values was also observed in ethanol (EtOH). These results suggest that the GO•-scavenging reaction by catechins may proceed via the SPLET mechanism in protic media, such as MeOH and EtOH. |
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| 会議概要（会議名, 開催地, 会期, 主催者等） | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 第19回日本学術振興会先端研究拠点事業セミナー：Winter School in Fukuoka 2012 | |||||
| 発表年月日 | ||||||
| 日付 | 2012-02-04 | |||||
| 日付タイプ | Issued | |||||
