Oxidative breakdown and conversion of urocanic acid isomers by hydroxyl radical generating systems.
cis-Urocanic acid (cis-UCA), formed from trans-urocanic acid (trans-UCA) by photoisomerization, has been shown to mimic suppressive effects of UV on the immune system. It is our hypothesis that UCA oxidation products in the skin play a role in the process of immunosuppression. Recently, both UCA isomers were found to be good hydroxyl radical scavengers and in this context we investigated the formation of products resulting from the interaction of hydroxyl radicals with UCA. Hydroxyl radicals were generated by (1) UV/H(2)O(2) (photooxidation), (2) ferrous ions/H(2)O(2) (Fenton oxidation) and (3) cupric ions/ascorbic acid. Oxidation products were identified by spectrometric methods and assessed by reversed-phase HPLC analysis. The photooxidation of UCA was induced by UV-B and UV-C, but not by UV-A radiation. Photooxidation and Fenton oxidation of trans-UCA, as well as of cis-UCA yielded comparable chromatographic patterns of UCA oxidation products. Several of the formed products were identified. The formation of three identified imidazoles was shown in UV-B exposed corneal layer samples, derived from human skin.
Kammeyer
A
A
Department of Dermatology, Academic Medical Center, University of Amsterdam, The Netherlands. a.kammeyer@amc.uva.nl
Eggelte
T A
TA
Overmars
H
H
Bootsma
A
A
Bos
J D
JD
Teunissen
M B
MB
D002021:Buffers; D002851:Chromatography, High Pressure Liquid; D004492:Edetic Acid; D016166:Free Radical Scavengers / Q000737:chemistry*; D006801:Humans; D006861:Hydrogen Peroxide; D017665:Hydroxyl Radical / Q000138:chemical synthesis*; D007093:Imidazoles / Q000032:analysis; D007501:Iron; D010084:Oxidation-Reduction; D010777:Photochemistry; D012867:Skin / Q000737:chemistry / Q000528:radiation effects; D013237:Stereoisomerism; D014466:Ultraviolet Rays; D014560:Urocanic Acid / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects
D002021:Buffers; C045076:Fenton's reagent; D016166:Free Radical Scavengers; D007093:Imidazoles; D017665:Hydroxyl Radical; D004492:Edetic Acid; D006861:Hydrogen Peroxide; D007501:Iron; D014560:Urocanic Acid; C005954:imidazoleacetic acid