Photodegradation and In Silico Molecular Docking Study of a Diuretic Drug: Clopamide

Clopamide (CPD, 1) is a piperidine and sulfamoylbenzamide-based diuretic drug and a potential photosensitizing sulfonamide; its phototransformation was investigated using N,N-dimethylaniline (DMA) as an electron donor and 1,4-dicyanonaphthalene (DCN) as an electron acceptor in an immersion-well-type photochemical reactor fitted with a medium-pressure mercury vapor lamp (450 W). Photodegradation of the drug Clopamide resulted in two significant products via photoinduced electron transfer. Structures of these products were deduced from their ¹H NMR, ¹³C NMR, mass, and IR spectra. The photoproducts are 2- choloro-5-((2,6-dimethylpiperidin-1-yl)carbamoyl)benzenesulfonic acid (2) and 4-hydroxy-N-(2,6-dimethyl-1-piperidyl)-3-sulfamoyl benzamide (3). In addition to this, the comparative antioxidant potentials of the parent drug and its photoproducts were investigated using in silico molecular docking against tyrosinase in order to better understand the in vivo relevance of pharmacological action of the drug as a result of light-drug interactions. UV light has been observed to modify substituents on the benzene ring, hence loss of biological activity at the time of storage and in vivo cannot be ruled out. This suggests that Clopamide users should avoid light (natural or artificial) exposure to prevent from drug-induced photosensitivity.