Nitric oxide (NO)-releasing pathway of FK409 in the presence of sulfhydryl-bearing compounds.
OBJECTIVE
We have recently reported that degradation of FK409 with generation of NO is spontaneous and is accelerated in the presence of sulfhydryl-bearing compounds, such as L-cysteine (Cys) and glutathione (GSH). The purpose of the present study is to investigate the NO-releasing pathway of FK409 in the presence of sulfhydryl-bearing compounds.


METHODS
The degradation process of FK409 in the presence of Cys or GSH was investigated by means of 1H-nuclear magnetic resonance (NMR) spectroscopy and high-performance liquid chromatography (HPLC).


RESULTS
The degradation of FK409 in the presence of Cys was dependent on concentration of Cys, and showed pH-dependency, accelerating with an increase in pH. The 1H-NMR spectra of FK409 with Cys suggested that time-dependent elimination of the hydrogen atom at the alpha-position of the nitro moiety (5-position) was accelerated by Cys in weakly alkaline solution. Cys and GSH were transformed readily, concomitant with FK409 degradation, to give their oxidized forms and probably S-nitrosothiols.


CONCLUSIONS
The effect of sulfhydryl-bearing compounds on FK409 degradation is due to the acceleration of deprotonation of the hydrogen atom at the 5-position by thiolate anion as well as hydroxyl ion. Sulfhydryl-bearing compounds reacted with the released NO resulting in formation of disulfides via intermediate S-nitrosothiols.
Fukuyama
S
S
Analytical Research Laboratories, Fujisawa Pharmaceutical Co., Ltd., Osaka, Japan.
Azuma
T
T
Hirasawa
Y
Y
Morokoshi
N
N
Akama
T
T
Koda
S
S
Kita
Y
Y
D002851:Chromatography, High Pressure Liquid; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D009569:Nitric Oxide / Q000378:metabolism*; D009574:Nitro Compounds / Q000494:pharmacology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology
D009574:Nitro Compounds; D010975:Platelet Aggregation Inhibitors; D013438:Sulfhydryl Compounds; D014665:Vasodilator Agents; D009569:Nitric Oxide; C061872:FK 409