Riboflavin degradation in the presence of quercetin in methanol under continuous UV-B irradiation: the ESI–MS–UHPLC analysis

The presented work deals with continuous UV-B irradiation of riboflavin in MeOH solution, leading to its degradation under anaerobic as well as aerobic conditions (faster in the former case), which is related to riboflavin photosensitizing properties (type I photosensitizer in the first case, and type II in the other one). Addition of quercetin, a well-known antioxidant in the system causes a decrease of the (riboflavin) degradation in both cases. In anaerobic conditions it might be a consequence of quercetin antioxidant scavenging activity, while under aerobic conditions it could be related to singlet oxygen formation. The degradation dynamics—in both systems, in the presence and in the absence of quercetin—is well synchronized with dynamics formation of the two major products, lumiflavin and lumichrome. Graphical abstract