Photodegradation of Dacarbazine Catalyzed by Vitamin B₂ and Flavin Adenine Dinucleotide Under Visible-Light Irradiation

Drug photodegradation is a matter of great concern because it can result in potency loss and adverse side effects. This study examines the light-induced degradation of dacarbazine catalyzed by vitamin B₂ and flavin adenine dinucleotide (FAD) under light-emitting diode (LED) or fluorescent light irradiation.

Dacarbazine was irradiated with LED (405 nm) or fluorescent light in the presence of various equivalents of vitamin B₂ or FAD. The photodegradation of the drug in D₂O was monitored by ¹H nuclear magnetic resonance spectroscopy.

Dacarbazine dissolved in D₂O decomposed in the presence of vitamin B₂ or FAD under irradiation with LED or fluorescent light. The decomposition products were 2-azahypoxanthine 2, which has previously been observed after light irradiation in the absence of vitamin B₂, and 1H-imidazole-5-carboxamide 6, a new product formed in the presence of vitamin B₂. Irradiation with LED light was more effective than irradiation with fluorescent light in degrading dacarbazine.

Vitamin B₂ and FAD induced dacarbazine photodegradation. Thus, the interfusion of vitamin B₂ or FAD under excessive light exposure should be avoided during the intravenous administration of dacarbazine.