B6 vitamers as generators and scavengers of reactive oxygen species

B6 vitamers are important natural compounds for human life, principally for amino acid metabolism, and have been reported as potent scavenger molecules of both endogenous and exogenous reactive oxygen species (ROS). However, under UV-light excitation from UVC (200–280 nm) to UVA (315–400 nm), B6 vitamers act as endogenous photosensitizers that promote both cellular photodamage and enzyme inactivation. This occurs through classical photochemical mechanisms mediated by ROS, toxic photoproducts, and the formation of adducts with active protein sites. This minireview aimed to present and discuss the dual roles of B6 vitamers as generators and scavengers of singlet oxygen (an important reactive species in photodynamic processes) and various other ROS. We also examine the basic photophysical, photochemical, and protolytic equilibria principles of B6 vitamers and their role as photodamaging and photoprotecting compounds in UV-light mediated photobiological processes.