WEKO3
アイテム
金属イオン存在下におけるメラトニンのラジカル消去反応
https://repo.qst.go.jp/records/70445
https://repo.qst.go.jp/records/70445c77870b9-f690-4791-822d-286358544bfb
| Item type | 会議発表用資料 / Presentation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2011-06-01 | |||||
| タイトル | ||||||
| タイトル | 金属イオン存在下におけるメラトニンのラジカル消去反応 | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| 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 |
中西, 郁夫
× 中西, 郁夫× カビル, ゾーダー× 川島, 知憲× 上林, 將人× 松本, 謙一郎× 大久保, 敬× 福住, 俊一× 安西, 和紀× 小澤, 俊彦× 中西 郁夫× カビル ゾーダー× 川島 知憲× 上林 將人× 松本 謙一郎 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Melatonin (N-acetyl-5-methoxytryptamine), a pineal hormone, is known to show efficient antioxidative and radioprotective activities. Recently, we have reported that galvinoxyl raidcal (GO) used as a model of reactive oxygen radical was scavenged by melatonin in methanol (MeOH). However, the detailed molecular mechanism for the radical-scavenging reaction of melatonin has yet to be fully clarified. In this study, we explored the effect of a metal ion on the radical-scavenging rates of melatonin in order to clarify the involvement of the electron-transfer process, which is known to be accelerated in the presence of redox inactive metal ions. Upon addition of GO to a MeOH solution of melatonin at 298 K, the absorption band at 428 nm due to Go gradually decreased. The decay of the absorbance at 428 nm obeyed pseudo-first-order kinetics, when the concentration of melatonin ([melatonin]) was maintained at more than 10-fold excess of the GO concentration. The observed pseudo-first-order rate constant (kobs) increases linearly with increasing the melatonin concentration. From the slope of the linear plot of kobs vs [melatonin] is determined the second-order rate constant (k) for the GO-scavenging reaction of melatonin to be 6.4 x 10(-2) M(-1) s(-1) in MeOH at 298 K. When Mg(ClO4)2 (0.1 M) was added to the melatonin-GO system in MeOH, the k value was significantly increased (k = 1.4 x 10(-1) M(-1) s(-1)). Such an acceleration in the presence of the metal ion suggests that the GO-scavenging reaction of melatonin proceeds via a proton-coupled electron transfer rather than via a one-step hydrogen atom transfer. Similar results were obtained when GO was replaced by 2,2-diphyenyl-1-picrylhydrazyl radical (DPPH). No radical-scavenging was observed when melatonin was replaced by N-methylmelatonin, suggesting that the deprotonation of the N-H hydrogen may be responsible for the radical-scavenging activity of melatonin. The kinetic data together with the one-electron oxidation potential determined by the second-harmonic alternating current voltammetry (SHACV) as well as calculated thermodynamic parameters by the density functional theory (DFT) obtained in this study provide a detailed mechanistic insight into the antioxidative and radioprotective activities of melatonin. |
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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21回金属の関与する生体関連反応シンポジウム | |||||
| 発表年月日 | ||||||
| 日付 | 2011-05-31 | |||||
| 日付タイプ | Issued | |||||
