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PHOTOCHEMISTRY OF 5‐ S ‐CYSTEINYLDOPA
Author(s) -
Costantini Claudio,
d'Ischia Marco,
Palumbo Anna,
Prota Giuseppe
Publication year - 1994
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1994.tb03939.x
Subject(s) - chemistry , photochemistry , diastereomer , oxygen , glutathione , reactive oxygen species , photodissociation , superoxide dismutase , hydrogen peroxide , antioxidant , stereochemistry , organic chemistry , biochemistry , enzyme
‐The photochemical behavior of 5‐ S ‐cysteinyldopa (5‐ S ‐CD), a colorless product of melanocyte metabolism, was investigated in neutral phosphate buffer with biologically relevant UV radiation. Exposure of 5‐ S ‐CD to pyrex‐filtered UV light (wavelengths > 320 nm) was found to induce an oxygen‐dependent reaction, leading to, besides abundant polymeric materials, the benzothiazine derivatives I and II (two diastereoisomers). Superoxide dismutase exerted a small inhibitory effect on 5‐ S ‐CD consumption, whereas other active oxygen scavengers had no effect on the reaction course. Addition of glutathione as a hydrogen donor completely suppressed the reaction. With UVB light (wavelength range 280–320 nm) photolysis of 5‐ S ‐CD proceeded mainly with formation of 3 ,4‐dihydroxy‐phenylalanine, arising presumably by photohomolytic cleavage of the S‐CH 2 bond followed by desulfuration. These results are of interest in relation to the high susceptibility of fair‐complexioned individuals to actinic damage and skin cancer.