Evaluation of a new copper(II)-curcumin complex as superoxide dismutase mimic and its free radical reactions
Evaluation of a new copper(II)-curcumin complex as superoxide dismutase mimic and its free radical reactions
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DOI：
10.1016/j.freeradbiomed.2005.05.005
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发表时间：
2005-09-15
影响因子：
7.4
通讯作者：
Priyadarsini, KI
中科院分区：
文献类型：
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作者：
Barik, A;Mishra, B;Priyadarsini, KI
合成了姜黄素的单核(1：1)铜配合物，并测定了其超氧化物歧化酶(SOD)活性。通过元素分析、红外光谱、核磁共振、紫外-可见光谱、红外光谱、质谱学和热重-差热分析等方法对该配合物进行了表征，结果表明，一个铜原子与一个乙酸基和一个水分子配位在姜黄素的酮烯醇基上。循环伏安研究表明，该络合物是一个可逆的Cu2+/Cu2+对，对NHE的电位为0.402 V。姜黄素铜(II)络合物溶于脂类和二甲基亚砜，不溶于水。停流光谱仪测定其清除二甲基亚砜中超氧阴离子自由基的速率常数为1.97×10~5M~(-1)·S(~(-1))。与超氧阴离子自由基反应后，络合物完全再生，显示出催化中和超氧阴离子自由基的活性。即使当超氧自由基的化学计量比是络合物的10倍时，也能观察到络合物的完全再生。超氧阴离子自由基的EPR监测进一步证实了这一点。用黄嘌呤/黄嘌呤氧化物法测定了该络合物的模拟超氧化物歧化酶活性，结果表明，5 mU g的络合物相当于1个单位的超氧化物歧化酶。该络合物可抑制辐射诱导的脂质过氧化，并显示清除自由基的能力。它与DPPH自由基的反应速率常数比姜黄素小10倍。在TX-100胶束溶液中，叠氮自由基对姜黄素络合物进行脉冲辐解诱导的单电子氧化产生强吸收(约500 nm)的苯氧基自由基，表明姜黄素的酚类部分在与铜的络合过程中保持不变。结果表明，新的铜(II)-姜黄素络合物具有超氧化物歧化酶活性、自由基中和能力和抗氧化能力。用密度泛函理论进行了量子化学计算，以支持实验观察。(C)2005 Elsevier Inc.保留所有权利。
A mononuclear (1:1) copper complex of curcumin, a phytochemical from turmeric, was synthesized and examined for its superoxide dismutase (SOD) activity. The complex was characterized by elemental analysis, IR, NMR, UV-VIS, FPR, mass spectroscopic methods and TG-DTA, from which it was found that a copper atom is coordinated through the keto-enol group of curcumin along with one acetate group and one water molecule. Cyclic voltammetric studies of the complex showed a reversible Cu2+/Cu+ couple with a potential of 0.402 V vs NHE. The Cu(II)-curcumin complex is soluble in lipids and DMSO, and insoluble in water. It scavenges superoxide radicals with a rate constant of 1.97 x 105 M-1 s(-1) in DMSO determined by stopped-flow spectrometer. Subsequent to the reaction with superoxide radicals, the complex was found to be regenerated completely, indicating catalytic activity in neutralizing superoxide radicals. Complete regeneration of the complex was observed, even when the stoichiometry of superoxide radicals was 10 times more than that of the complex. This was further confirmed by EPR monitoring of superoxide radicals. The SOD mimicking activity of the complex was determined by xanthine/xanthine oxidase assay, from which it has been found that 5 mu g of the complex is equivalent to I unit of SOD. The complex inhibits radiation-induced lipid peroxidation and shows radical-scavenging ability. It reacts with DPPH radicals with rate constant 10 times less than that of curcumin. Pulse radiolysis-induced one-electron oxidation of the complex by azide radicals in TX-100 micellar solutions produced strongly absorbing (similar to 500 nm) phenoxyl radicals, indicating that the phenolic moiety of curcumin remained intact on complexation with copper. The results confirm that the new Cu(II)-curcumin complex possesses SOD activity, free radical neutralizing ability, and antioxidant potential. Quantum chemical calculations with density functional theory have been performed to support the experimental observations. (c) 2005 Elsevier Inc. All rights reserved.