Premium
Transformation of barbituric acid into alloxan by hydroxyl radicals: interaction with melatonin and with other hydroxyl radical scavengers
Author(s) -
Brömme H. J.,
Mörke W.,
Peschke E.
Publication year - 2002
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1034/j.1600-079x.2002.02936.x
Subject(s) - chemistry , radical , hydroxyl radical , barbituric acid , electron paramagnetic resonance , autoxidation , hydroxylation , spin trapping , photochemistry , medicinal chemistry , radical ion , hydrogen peroxide , organic chemistry , ion , enzyme , physics , nuclear magnetic resonance
Barbituric acid (2,4,6‐pyrimidinetrione) can be transformed by a non‐enzymatic hydroxylation into alloxan (2,4,5,6‐pyrimidinetetrone). This transformation can be used as a reaction indicating the formation of hydroxyl radicals (·OH). This conversion was detected using HPLC. Formation of ·OH was demonstrated by electron spin resonance (ESR) spectroscopy combined with spin‐trapping techniques. It was shown that ·OH generated via the F enton reaction abstracts first a hydrogen atom from barbituric acid (BA) and forms intermediately a paramagnetic derivative of BA. After a second attack by another ·OH, the BA radical is transformed into dialuric acid (DA), which autoxidizes via the alloxan radical (·ALX) to ALX. Superoxide radicals (·O 2 − ) are formed during autoxidation of DA and ·ALX. They are able to regenerate ferrous ions. As a result, traces of iron salts are capable of catalyzing the conversion of large amounts of BA into ALX. Several scavengers of ·OH were tested with regard to their efficiency in preventing the transformation of BA into ALX. Of all the scavengers analyzed, melatonin was shown to be one of the most potent compounds.