Sariahmetoglu M, Wheatley R A, Cakýcý Y, Kanzýk Y, Townshend A
Department of Pharmacology, Faculty of Pharmacy, University of Gazi, 06330 Ankara, Turkey.
Pharmacol Res. 2003 Oct;48(4):361-7. doi: 10.1016/s1043-6618(03)00177-4.
The antioxidant effect of melatonin was evaluated by using a flow injection analysis chemiluminescence (FIA-CL) method to measure alone its direct antioxidant behaviour in aqueous solutions. Inhibition by melatonin, DL-tryptophan or serotonin (5-hydroxytryptamine, 5-HT) of the steady CL emissions of various oxidants with luminol was measured. LogIC(50) values of melatonin were calculated: -2.6+/-0.1M for superoxide (O(2) radical(-)), -3.0+/-0.02 M, for hydrogen peroxide (H(2)O(2)), -4.7+/-0.04 M, for hypochlorous anion ((-)OCl), -2.8+/-0.1M, for hydoxyl (radical OH) and -2.0+/-0.03 M, for peroxynitrite (ONOO(-)). Thus melatonin exerted a limited direct antioxidant activity towards reactive oxygen species (ROS) in aqueous solutions, broadly comparable to that of tryptophan, but less than that of serotonin and of major antioxidants such as ascorbic acid. This suggests that where the benefits of melatonin are correctly attributed to antioxidant behaviour, this is mediated largely through antioxidant enzymes. The pharmacological implications are discussed.
通过流动注射分析化学发光（FIA-CL）方法评估褪黑素的抗氧化作用，以单独测量其在水溶液中的直接抗氧化行为。测量了褪黑素、DL-色氨酸或血清素（5-羟色胺，5-HT）对鲁米诺与各种氧化剂的稳定化学发光发射的抑制作用。计算了褪黑素的LogIC(50)值：超氧阴离子（O(2)自由基(-)）为-2.6±0.1M，过氧化氢（H(2)O(2)）为-3.0±0.02M，次氯酸根阴离子（(-)OCl）为-4.7±0.04M，羟基（自由基OH）为-2.8±0.1M，过氧亚硝酸盐（ONOO(-)）为-2.0±0.03M。因此，褪黑素在水溶液中对活性氧（ROS）的直接抗氧化活性有限，大致与色氨酸相当，但低于血清素和主要抗氧化剂如抗坏血酸。这表明，在褪黑素的益处正确归因于抗氧化行为的情况下，这主要是通过抗氧化酶介导的。讨论了其药理学意义。
