Photochemical outcome modification of diflunisal by a novel cationic amphiphilic cyclodextrin

Abstract

The effects of a novel cationic amphiphilic cyclodextrin (SC6CDNH2) on the photoprocesses of the phototoxic non-steroidal anti-inflammatory drug diflunisal (DF) have been investigated in aqueous medium. Association between DF and SC6CDNH2 was indicated by steady-state absorption, induced circular dichroism and fluorescence spectroscopy. Laser flash photolysis and steady-state photolysis experiments revealed a particular sensitivity of the DF photochemistry to the new microenvironment. Reduction of the triplet state generation efficiency, lengthening of its lifetime, changes in the photoionisation pathways, besides remarkable drug photostabilization and modification of the stable photoproducts distribution, were observed. A rationale for these modifications to the photochemistry of DF based on the multifaceted role of SC6CDNH2 in influencing the efficiency of the primary photochemical act and in interfering with secondary radical reactions is proposed. Relation of the overall results to the phototoxic effects displayed by the drug is also commented upon.