Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Kanda-surugadai, Chiyoda-ku, Tokyo 101-0062, Japan.
In Vivo. 2011 Jan-Feb;25(1):49-53.
Melatonin shows antioxidant/prooxidant activity but its mechanism of action remains unknown.
The radical-scavenging activity of melatonin and various melatonin/co-antioxidant mixtures in a 1:1 molar ratio was evaluated in terms of the length of the induction period (IP) for polymerization of methyl methacrylate (MMA), initiated by thermal decomposition of 2,2'-azobisisobutyronitrile (AIBN) or by benzoyl peroxide (BPO) under nearly anaerobic conditions, which was monitored by differential scanning calorimetry (DSC).
The observed IP (A) for a pinoline, L-ascorbyl 2,6-dibutyrate (ASDB), vitamin E (alpha-, beta-, gamma- or delta-T) or 2-mercaptoethanol (2ME) mixture was compared with the calculated total sum of IP (melatonin+each co-antioxidant) (B). For both the AIBN and BPO systems, the A/B for the melatonin/ASDB, beta-T, gamma-T or delta-T mixture was 0.3-0.7, whereas that for the melatonin/2ME mixture was approximately 1. For the AIBN system, the A/B for the melatonin/alpha-T or pinoline mixture was 0.7-0.8. By contrast, for the BPO system, that for the melatonin/alpha-T or pinoline mixture was approximately 1.
The prooxidant effect of the melatonin/ascorbate or vitamin E mixtures induced by radical-oxidizing activity may help to explain the anticancer activity of melatonin in biological systems.
褪黑素具有抗氧化/促氧化活性，但作用机制尚不清楚。
采用差示扫描量热法（DSC），以甲基丙烯酸甲酯（MMA）聚合诱导期（IP）的长短来评价褪黑素和各种 1:1 摩尔比的褪黑素/共抗氧化剂混合物的自由基清除活性，该诱导期由 2,2'-偶氮二异丁腈（AIBN）或过氧化二苯甲酰（BPO）热分解引发，在近无氧条件下进行。
比较了 pinoline、L-抗坏血酸 2,6-二丁酸酯（ASDB）、维生素 E（α-、β-、γ-或 δ-T）或 2-巯基乙醇（2ME）混合物的观察到的 IP（A）与计算得出的总 IP（褪黑素+每种共抗氧化剂）（B）的总和。对于 AIBN 和 BPO 两种体系，褪黑素/ASDB、β-T、γ-T 或 δ-T 混合物的 A/B 为 0.3-0.7，而褪黑素/2ME 混合物的 A/B 约为 1。对于 AIBN 体系，褪黑素/α-T 或 pinoline 混合物的 A/B 为 0.7-0.8。相比之下，对于 BPO 体系，褪黑素/α-T 或 pinoline 混合物的 A/B 约为 1。
自由基氧化活性诱导的褪黑素/抗坏血酸盐或维生素 E 混合物的促氧化剂效应可能有助于解释褪黑素在生物系统中的抗癌活性。
