urocanic acid

Urocanic acid (4-Imidazoleacrylic acid), synthesized in the epidermis, functions as a primary absorber of ultraviolet (UV) radiation in mammalian skin.

trans-Urocanic Acid ((E)-Urocanic acid), a compound predominantly distributed in the hippocampus and prefrontal cortex, is an isomer of cis-UCA, an epidermal UV-protectant, which enhances the stability of tenofovir eplerenomide in long-acting HIV applications. trans-Urocanic acid potently modulates immune trans-urocanic acid effectively modulates immune function, inhibits human natural killer cell activity in vitro, and can be used in Alzheimer's disease research.

Histidine (abbreviated as His or H) is an alpha-amino acid. The L-isomer is one of the 22 proteinogenic amino acids, i.e., the building blocks of proteins. It is classified as a charged, polar because of the hydrophilic nature of the imidazole side chain.