trans-Urocanic Acid

• CAT Number: R065042
• CAS Number: 3465-72-3
• Molecular Formula: C6H6N2O2
• Molecular Weight: 138.126
• Purity: ≥95%
• Storage: -20°C
• IUPAC Name: (E)-3-(1H-imidazol-5-yl)prop-2-enoic acid
• InChI: InChI=1S/C6H6N2O2/c9-6(10)2-1-5-3-7-4-8-5/h1-4H,(H,7,8)(H,9,10)/b2-1+
• InChIKey: LOIYMIARKYCTBW-OWOJBTEDSA-N
• SMILES: C1=C(NC=N1)C=CC(=O)O

trans-Urocanic acid is a major epidermal chromophore for the immunosuppressive effects of UV radiation that is produced in mammalian stratum corneum by the action of histidine ammonialyase on L-histidine. It contributes to the acidification of the surface of the stratum corneum, and its function has been proposed as that of an endogenous sunscreen, endowing a low-level of protection (SPF ~ 1.5) against UV-induced DNA damage and excessive keratinocyte apoptosis. Upon UVB exposure, trans-urocanic acid is converted to the cis isomer, which is known to activate regulatory T cells.

Reference

1.Gibbs, N.K., and Norval, M. Urocanic acid in the skin: a mixed blessing? Journal of Investigative Dermatology 131(1), 14-17 (2011).