4-Cl-edaravone and (<i>E</i>)-2-chloro-3-[(<i>E</i>)-phenyldiazenyl]-2-butenoic acid are the specific reaction products of edaravone with hypochlorite

Abstract

3 Methyl 1 phenyl 2 pyrazolin 5 one (edaravone) is a synthetic one electron antioxidant used as a drug for treatment against acute phase cerebral infarction in Japan. This drug also reacts with two electron oxidants like peroxynitrite to give predominantly 4 nitrosoedaravone but no one electron oxidation products. It is believed that this plays a significant role in amelioration of amyotrophic lateral sclerosis. The drug was approved for treat ment of amyotrophic lateral sclerosis in Japan and USA in 2015 and 2017, respectively. In this study, we examined the reaction of edaravone with another two electron oxidant, hypochlorite anion (ClO-). Edaravone reacted with ClOin 50% methanolic phosphate buffer (pH 7.4) solution containing typical two electron reductants, such as glutathione, cysteine, methionine, and uric acid, as internal references. The concentration of edaravone decreased at a similar rate as each co existing reference, indicating that it showed com parable reactivity toward ClOas those references. Furthermore, 4 Cl edaravone and (E) 2 chloro 3 [(E) phenyldiazenyl] 2 butenoic acid (CPB) were identified as primary and end products, respec tively, and no one electron oxidation products were detected. These results suggest that edaravone treatment can bring greater benefit against ClOrelated injury such as inflammation, and 4 Cl edaravone and CPB can be good biomarkers for ClOinduced oxidative stress.

Edaravone, a scavenger for multiple reactive oxygen species, reacts with singlet oxygen to yield 2-oxo-3-(phenylhydrazono)-butanoic acid

“…Therefore, MPO-induced edaravone oxidation was studied. As expected, OPB was significantly formed in addition to 4-Cl-edaravone and CPB, which are specific oxidation products of ClO − , (9) accompanied with edaravone decomposition (Fig. 7A).…”

“…In order to estimate edaravone reactivity to 1 O 2 , the ratio of the rate constants of edaravone and the internal reference was evaluated as described previously. (6,9) Briefly, the edaravone and co-existing internal reference competitively decreased where both rate constants were defined as k E and k R respectively (equations 3, 4). The ratio of the rate constants (k E /k R ) is given by equation 5 as a solution of simultaneous differential equations.…”

“…Edaravone reacts with many kinds of ROS. We previously examined the antioxidant activity of edaravone against free radicals derived from thermal decomposition of azo-initiators,‍ ( 8 ) peroxynitrite (ONOO‍ − ),‍ ( 6 ) and ClO‍ − .‍ ( 9 ) Edaravone strongly inhibits peroxyl radical-mediated oxidation of soy-phosphatidylcholine liposomal membranes induced by the lipid-soluble initiator 2,2'-azobis(2,4-dimethylvaleronitrile) or water-soluble 2,2'-azobis(2-amidinopropane) dihydrochloride.‍ ( 8 ) We also showed that edaravone can react with ONOO‍ − 30-fold faster than does UA, which is an essential scavenger of ONOO‍ − in vivo .‍ ( 6 ) Recently, we reported that edaravone has comparable reactivity to ClO‍ − with thiol and sulfide residues, which are endogenous scavengers for ClO‍ − .‍ ( 9 ) Furthermore, we identified their reaction products ( Fig. 1 ); free radicals-, ONOO‍ − -, and ClO‍ − -induced edaravone oxidation yield 4-oxoedaravone and its hydrolysate 2-oxo-3-(phenylhydrazono)-butanoic acid (OPB),‍ ( 8 ) predominantly 4-NO-edaravone and slightly 4-NO 2 -edaravone,‍ ( 6 ) and 4-Cl-edaravone and ( E )-2-chloro-3-[( E )-phenyldiazenyl]-2-butenoic acid (CPB),‍ ( 9 ) respectively.…”

“…We previously examined the antioxidant activity of edaravone against free radicals derived from thermal decomposition of azo-initiators, (8) peroxynitrite (ONOO − ), (6) and ClO − . (9) Edaravone strongly inhibits peroxyl radical-mediated oxidation of soy-phosphatidylcholine liposomal membranes induced by the lipid-soluble initiator 2,2'azobis(2,4-dimethylvaleronitrile) or water-soluble 2,2'-azobis(2amidinopropane) dihydrochloride. (8) We also showed that edaravone can react with ONOO − 30-fold faster than does UA, which is an essential scavenger of ONOO − in vivo.…”

“…(6) Recently, we reported that edaravone has comparable reactivity to ClO − with thiol and sulfide residues, which are endogenous scavengers for ClO − . (9) Furthermore, we identified their reaction products (Fig. 1); free radicals-, ONOO − -, and ClO − -induced edaravone oxidation yield 4-oxoedaravone and its hydrolysate 2-oxo-3-(phenylhydrazono)-butanoic acid (OPB), (8) predominantly 4-NOedaravone and slightly 4-NO 2 -edaravone, (6) and 4-Cl-edaravone and (E)-2-chloro-3-[(E)-phenyldiazenyl]-2-butenoic acid (CPB), (9) respectively.…”