While ozone depletion and sun exposure make us prone to UV overexposure, the benefits of sunlight, such as vitamin D production and mood boosting, are overwhelmed by its deleterious effects on skin. Solar erythema, photo-dermatosis, photo-aging and skin cancers are well-documented examples of such effects. Thus in despite the use of sunscreens, photo-protection remains currently a major issue and complementary strategies need to be implemented.
L-2-Thiohistidine is a natural sulfur-containing analog of L-histidine. It has been found as a post-translational modification of copper proteins, such as molluskan hemocyanin and fungal tyrosinase, in the vicinity of the copper ion that is coordinated at the active site of these proteins.
Stable towards oxygen, L-2-thiohistidine is an efficient antioxidant through its ability to prevent singlet oxygen (1O2) formation. This supports the protective effect of L-2-thiohistidine that has been reported in studying the photochemical inactivation of various enzymes. L-2-thiohistidine can also trap ONOO- and OH° and it has been shown to chelate divalent cations of metals such as copper
