Phenol-based lipophilic fluorescent antioxidant indicators: a rational approach.
Phenol-based lipophilic fluorescent antioxidant indicators: a rational approach.
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基于苯酚的亲脂性荧光抗氧化指标：合理的方法。
DOI：
10.1021/jo900335z
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
G. Cosa
中科院分区：
文献类型：
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作者：
K. Krumova;P. Oleynik;P. Karam;G. Cosa
研究了新型抗氧化指示剂B-TOH（BODIPY-α-生育酚加合物）的反应性、电化学和电化学物理性质。我们还研究了新制备的BODIPY-3，5-二叔丁基-4-羟基苯甲酸加合物（B-BHB），并比较了两组探针的结果。我们的研究结果突出了B-TOH作为荧光抗氧化剂指示剂的潜力，并有助于说明在制备受体报告型荧光抗氧化剂指示剂时应考虑的因素。基于实验值的氧化还原电位的报告BODIPY和从氧化还原电位估计的苯酚受体片段，关到发射增强最近报道的B-TOH后，过氧自由基清除可以明确地分配到失活的分子内光诱导电子转移（PeT），其操作在还原形式的B-TOH。在B3 LYP/6- 31 G（d）水平上对HOMO能级相对于真空进行的理论计算进一步支持了B-TOH清除过氧自由基时PeT机制的失活。荧光寿命和荧光量子产率测量范围内的溶剂极性，从己烷到乙腈，为B-TOH，B-BHB，和他们的BODIPY前体PM 605或PMOH，是一致的分子内非辐射衰变途径在B-TOH操作。该途径在B-BHB中不起作用，其中基于电化学研究，认为PetT具有高度吸能性。随后对本文研究的两种荧光团-苯酚加合物的抗氧化性质的分析表明，B-TOH抗氧化活性与α-生育酚（最有效的天然存在的脂溶性抗氧化剂）的抗氧化活性相当，而B-BHB是较差的抗氧化剂。过氧自由基引发的苯乙烯自氧化和激光闪光光解研究的H-原子提取率枯氧基自由基的研究表明，B-TOH和2，2，5，7，8-五甲基-6-羟基苯并二氢吡喃（PMHC），α-生育酚类似物缺乏phytil尾巴的反应模式相似。对B-BHB的类似反应性研究强调了其较差的抗氧化活性。在一般情况下，这项工作提供了大量的信息，可用于设计关/上脂溶性荧光抗氧化剂指示剂的基础上苯酚部分。
The reactivity, electrochemistry, and photophysics of the novel antioxidant indicator B-TOH, a BODIPY-alpha-tocopherol adduct, were investigated. We also studied a newly prepared BODIPY-3,5-di-tert-butyl-4-hydroxybenzoic acid adduct (B-BHB) and compared the results for both sets of probes. Our results highlight the potential of B-TOH as a fluorescent antioxidant indicator and help illustrate the considerations to be taken into account in preparing a receptor-reporter-type fluorescent antioxidant indicator. Based on the experimental values of the redox potentials for the reporter BODIPY and from the redox potentials estimated for the phenol receptor segment, the off-to-on emission enhancement recently reported for B-TOH upon peroxyl radical scavenging can be unequivocally assigned to the deactivation of an intramolecular photoinduced electron transfer (PeT) which operates in the reduced form of B-TOH. Theoretical calculations performed at the B3LYP/6-31G(d) level on HOMO energy levels relative to vacuum further support the deactivation of a PeT mechanism upon peroxyl radical scavenging by B-TOH. Fluorescence lifetimes and fluorescence quantum yields measured in a range of solvent polarities, from hexane to acetonitrile, for B-TOH, B-BHB, and their BODIPY precursors PM605 or PMOH, are consistent with an intramolecular nonradiative decay pathway operative in B-TOH. This pathway is not operative in B-BHB where PeT is deemed highly endergonic based on electrochemical studies. A subsequent analysis on the antioxidant properties of both fluorophore-phenol adducts studied herein indicates that B-TOH antioxidant activity is on par with that of alpha-tocopherol, the most potent naturally occurring lipid soluble antioxidant, whereas B-BHB is a poor antioxidant. Oxygen uptake studies upon peroxyl radical initiated styrene autoxidation and laser flash photolysis studies on the rate of H-atom abstraction by cumyloxyl radicals reveal similar reactivity patterns for B-TOH and 2,2,5,7,8-pentamethyl-6-hydroxychroman (PMHC), an alpha-tocopherol analogue lacking the phytil tail. Analogous reactivity studies on B-BHB underscore its poor antioxidant activity. In general, this work provides substantial amount of information useful in designing off/on lipid soluble fluorescent antioxidant indicators based on phenol moieties.