Relationship between flavonoid structure and reactive oxygen species generation upon ultraviolet and X-ray irradiation

[Display omitted] •Structure relationships of flavonoids and generation of three main ROSs under ultraviolet and X-ray radiation were confirmed.•The difference of ionization capacity between UV and X-ray could lead to different ROSs production of samples.•2,3-double bond was essential for flavonoids to produce superoxide anion radical (O2•−).•Two derivatives of quercetin could generate hydroxyl radical (•OH) under X-ray, which maybe resulted from their difference of •OH scavenging capacity. In this research, we aimed to reveal structures related to reactive oxygen species (ROS) generation of flavonoids upon ultraviolet (UV) or X-ray irradiation. ROS production of selected flavonoids was studied by using ROS fluorescence probes. We discuss the relationship between the structures of the flavonoids and the generation of three ROSs, superoxide anion radical (O2•−), hydroxyl radical (•OH), and singlet oxygen (1O2). Results showed that 2,3-double bond was an key structure for natural flavonoids to generate O2•−. We also discuss the effects of the ROS scavenging capacities on ROS generation through oxygen radical absorbance capacity (ORAC) tests. Derivatives of quercetin could produce •OH due to differences of ROS scavenging ability. Our results indicated that flavonoids and their derivatives, which were used as antioxidant reagents, can serve as ROS generators upon ultraviolet (UV) or X-ray irradiation.