Ammar H O
Pharmazie. 1976 Jun;31(6):373-4.
DL-alpha-Lipoic acid at low concentrations increases the stability of thiamine hydrochloride solutions, however, at higher concentrations the degradation rate of the vitamin is enhanced. The optimum concentration of lipoic acid at which its stabilizing efficiency is maximum is shifted on the addition of 20 ppm of copper, from 0.5 to 1.0 mmole/1, indicating that this optimum concentration is dependent on heavy metal ions concentration in the solution. In the presence of copper, the degradation rate of the vitamin in solutions containing lipoic acid at concentrations higher than its optimum concentration is lower than that in corresponding solutions in the absence of added copper. On the other hand, below the optimum concentration, the degradation rate of thiamine hydrochloride solutions in the absence of copper is lower than that of the corresponding solutions to which 20 ppm copper have been added. This indicates that the presence of either free copper ions or an excess of lipoic acid is deleterious to the stability of the vitamin.
低浓度的DL-α-硫辛酸可提高盐酸硫胺素溶液的稳定性，然而，在较高浓度下，该维生素的降解速率会加快。添加20 ppm铜后，硫辛酸稳定效率最高时的最佳浓度从0.5毫摩尔/升变为1.0毫摩尔/升，这表明该最佳浓度取决于溶液中的重金属离子浓度。在有铜存在的情况下，硫辛酸浓度高于其最佳浓度的溶液中维生素的降解速率低于未添加铜的相应溶液中的降解速率。另一方面，在最佳浓度以下，未添加铜时盐酸硫胺素溶液的降解速率低于添加了20 ppm铜的相应溶液的降解速率。这表明游离铜离子或过量硫辛酸的存在对维生素的稳定性有害。
