Photodegradation of Dacarbazine Catalyzed by Vitamin B.sub.2 and Flavin Adenine Dinucleotide Under Visible-Light Irradiation

Purpose 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 B.sub.2 and flavin adenine dinucleotide (FAD) under light-emitting diode (LED) or fluorescent light irradiation. Methods Dacarbazine was irradiated with LED (405 nm) or fluorescent light in the presence of various equivalents of vitamin B.sub.2 or FAD. The photodegradation of the drug in D.sub.2O was monitored by .sup.1H nuclear magnetic resonance spectroscopy. Results Dacarbazine dissolved in D.sub.2O decomposed in the presence of vitamin B.sub.2 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 B.sub.2, and 1H-imidazole-5-carboxamide 6, a new product formed in the presence of vitamin B.sub.2. Irradiation with LED light was more effective than irradiation with fluorescent light in degrading dacarbazine. Conclusion Vitamin B.sub.2 and FAD induced dacarbazine photodegradation. Thus, the interfusion of vitamin B.sub.2 or FAD under excessive light exposure should be avoided during the intravenous administration of dacarbazine. Graphical