Nitrosation of melatonin by nitric oxide and peroxynitrite.
J Pineal Res
; 29(3): 184-92, 2000 Oct.
Article
in En
| MEDLINE
| ID: mdl-11034116
ABSTRACT
Peroxynitrite (ONOO-) is an endogenous molecule, formed by rapid coupling between *NO and O2*-. ONOO- is known to be a strong oxidant of thiols and metalloorganic compounds and also a nitrating agent of aromatic compounds such as tyrosine. However, its chemistry is not yet well elucidated under physiological conditions. Melatonin, which is an indole-amine produced by the pineal gland and other organs, has antioxidant properties. We show that melatonin reacts with ONOO- in phosphate-buffered solutions. We provide evidence of nitrosation and oxidation at the pyrrole nitrogen leading to 1-nitrosomelatonin and 1-hydroxymelatonin, these being the major reactions in aqueous phosphate-buffered solutions besides other aromatic hydroxylations and nitration. 4-Nitromelatonin is formed, but in small amounts. The kinetics of all transformations were strictly dependent on ONOO- decay, whereas yields varied with pH and the presence of CO2. The N-oxidation became competitive with nitrosation at pH 7.4, in medium containing a sufficient amount of CO2. A proposed mechanism involves the transient formation of melatonyl radical and ONOO* radical derived from ONOO- decay.
Search on Google
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Melatonin
/
Nitrates
/
Nitric Oxide
/
Antioxidants
Language:
En
Journal:
J Pineal Res
Journal subject:
ENDOCRINOLOGIA
Year:
2000
Document type:
Article
Affiliation country:
France