Urocanic acid isomers are good hydroxyl radical scavengers: a comparative study with structural analogues and with uric acid

UV-exposure of the epidermis leads to the isomerisation of trans-UCA into c is-UCA as well as to the generation of hydroxyl radicals. This study shows by means of the deoxyribose degradation test that UCA isomers are more powe rful hydroxyl radical scavengers than the other 4-(5-)substituted imidazole derivatives, such as histidine, though less powerful than uric acid. UCA, present in relatively high concentrations in the epidermis, may well be a m ajor natural hydroxyl radical scavenger. (C) 1999 Elsevier Science B.V. All rights reserved.