Study of thermal properties of antioxidant lipoamide and its composites with colloid silica

摘要

Lipoamide (LM), amide of a-lipoic acid, is a very powerful antioxidant. However, information on its physicochemical properties, in particular on its thermal behavior, is very limited. In the present work, a DSC study of LM showed that heating above the melting point led to formation of a mixture of polymeric and crystalline forms of LM. In order to increase thermal stability of the drug, LM was encapsulated in colloid silica with various surface chemistry. It was found that encapsulation of LM in unmodified and organomodified silica materials slowed down the process of thermal degradation of the drug. The effect of silica matrix modification on the thermal degradation was revealed. It was shown that the interactions in the drug-silica composites play an important role in thermal stabilization of LM. The indicated thermal behavior of LM and a-lipoic acid in free form and in the synthesized composites was compared.