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首页> 外文期刊>International Journal of Electrochemical Science >Electrochemical Behavior of the Super Antioxidant, a-Lipoic Acid
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Electrochemical Behavior of the Super Antioxidant, a-Lipoic Acid

机译：超级抗氧化剂α-硫辛酸的电化学行为

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We have investigated the complex cyclic voltammetric behaviour of the sodium salt of -lipoic acid inthe absence and presence of the background electrolytes, sodium chloride and phosphate buffer.Absorption data indicated deviations from Beer law above 10 mM suggesting strong solute-soluteinteractions at higher concentrations. By scanning in a wide range of potentials, +2.0 to -2.0V, andusing 1 mM -lipoic acid (sodium salt), it was possible to identify the irreversible formation ofthiolsulfonate, reversible formation lipoic acid S-oxide, reversible formation of dihydrolipoic acid, andreversible formation of dimers of lipoic acid. The oxidation of dihydrolipoic acid and the dimers oflipoic acid were influenced by the concentration of lipoic acid as well as the scan rate. Evidence ispresented for the formation of S-oxides of lipoic acid dimers or higher polymers that are different fromlipoic acid S-oxide. In the active region, the cathodic current produced depended on the concentrationof -lipoic acid. The reduction of -lipoic acid to dihydrolipoic acid was unaffected by the startinganodic potential. The oxidation of dihydrolipoic acid was complicated by the formation of polymers oflipoic acid. With increasing concentrations of lipoic acid, the rate of increase in cathodic current due toreduction of lipoic acid was much higher than that of the reduction of lipoic acid S-oxide. Cathodiccurrent oscillations were observed in the presence of counter ions and 10 mM -lipoic acid. Higher pHproduced less reduction currents of -lipoic acid. Both the phosphate buffer and sodium chlorideproduced anodic shifts in the reduction peak of -lipoic acid. Phosphate buffer gave a higher anodicshift in the reduction peak than sodium chloride. The cathodic peak current was higher with increasingconcentrations of sodium chloride. It was possible to restrict the interference from different species onsome redox processes, such as the redox process of lipoic acid S-oxide formation and reversibleoxidation of dihydrolipoic acid, by restricting the range of the scanning potential and the concentrationof lipoic acid. These cyclic voltammetry data suggested the need to investigate the electrochemicalbehaviour of molecules without any background electrolytes, whenever possible, to gain informationon interactions near the double layer. This is contrary to the accepted practice in electrochemistry.Finally caution is suggested in deciding the oral dosage of lipoic acid supplements because of itstendency to polymerize under reducing biological conditions.
机译：我们研究了在不存在背景电解质，氯化钠和磷酸盐缓冲液的情况下，硫辛酸钠盐的复杂循环伏安行为。吸收数据表明，比尔定律偏离10 mM以上，表明在较高浓度下强溶质-溶质相互作用。通过在+2.0至-2.0V的宽电位范围内进行扫描，并使用1 mM-硫辛酸（钠盐），可以鉴定出不可逆的硫代磺酸盐形成，可逆的硫辛酸形成S-氧化物，可逆的二氢硫辛酸形成，可逆地形成硫辛酸的二聚体。二氢硫辛酸的氧化和硫辛酸的二聚体受硫辛酸浓度和扫描速度的影响。提供了与硫辛酸S-氧化物不同的硫辛酸二聚体或高级聚合物的S-氧化物的形成的证据。在活性区中，产生的阴极电流取决于硫辛酸的浓度。硫辛酸还原为二氢硫辛酸不受起始阳极电位的影响。二氢硫辛酸的氧化由于硫辛酸聚合物的形成而变得复杂。随着硫辛酸浓度的增加，由于硫辛酸的还原引起的阴极电流的增加速率远高于硫辛酸S-氧化物的减少。在存在抗衡离子和10 mM硫辛酸的情况下观察到阴极电流振荡。 pH值越高，产生的硫辛酸还原电流越小。磷酸盐缓冲液和氯化钠在-硫辛酸的还原峰中均产生阳极移位。磷酸盐缓冲液在还原峰中的阳极移位高于氯化钠。随着氯化钠浓度的增加，阴极峰值电流更高。通过限制扫描电势的范围和硫辛酸的浓度，可以限制不同物种对某些氧化还原过程的干扰，例如硫辛酸S-氧化物形成的氧化还原过程和二氢硫辛酸的可逆氧化。这些循环伏安法数据表明，有必要在可能的情况下研究不含任何背景电解质的分子的电化学行为，以获取有关双层附近相互作用的信息。这与电化学中公认的做法相反。建议在确定硫辛酸补充剂的口服剂量时要特别谨慎，因为它倾向于在降低的生物条件下聚合。

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