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
1
H NMR,
13
C 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.