Kiyoshi Tatsumi

Reduction of nitrofuran derivatives by xanthine oxidase and microsomes: Isolation and identification of reduction products☆

Abstract An investigation was carried out to identify the reduction products of nitrofurazone and AF-2 (2-furyl)-3-(5-nitro-2-furyl)acrylamide by milk xanthine oxidase, rat liver xanthine oxidase, and rat liver microsomes. Data obtained from mass spectrometry and other methods indicated that the ethyl acetate-extractable major product of each nitrofuran derivative should be the corresponding amine derivative or the equivalent compound. This conclusion was further confirmed by an examination of stoichiometry. The reduced nitrofurazone was finally identified as 5-amino-2-furfural semicarbazone by comparative studies with the authentic specimen. The reduced AF-2 was tentatively identified as 2-(2-furyl)-3-(5-oxo-2-pyrrolin-2-yl)acrylamide. A reduction pathway for this conversion is postulated.

Metabolism of furazolidone by milk xanthine oxidase and rat liver 9000g supernatant: Formation of a unique nitrofuran metabolite and an aminofuran derivative

Abstract In vitro metabolism of furazolidone ( N -(5-nitro-2-furfuryliden)-3-amino-2-oxazolidone) was investigated by using milk xanthine oxidase and rat liver 9000 g supernatant. As a result, a new type of reduction product was isolated as one of the main metabolites from the incubation mixture and it was tentatively identified as 2,3-dihydro-3-cyanomethyl-2-hydroxyl-5-nitro-1a, 2-di(2-oxo-oxazolidin-3-yl)iminomethyl-furo[2,3- b ]furan. In addition, the present study demonstrated the formation of N -(5-amino-2-furfurylidene)-3-amino-2-oxazolidone as a minor metabolite of nitrofuran in a milk xanthine oxidase system. The aminofuran derivative was easily degraded by milk xanthine oxidase under aerobic, but not anaerobic, conditions. The degradation appears to be due to superoxide anion radicals, hydroxyl radicals, and/or singlet oxygen, which are produced in this enzyme system.

Enzymic cis-trans isomerization of nitrofuran derivatives. Isomerizing activity of xanthine oxidase, lipoyl dehydrogenase, DT-diaphorase and liver microsomes

Xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2) supplemented with an electron donor could catalyze the cis-trans isomerization of 3-(5-nitro-2-furyl)-2-(2-furyl)acrylamide, 3-(5-nitro-2-furyl)-2-phenylacrylamide and 3-(5-nitro-2-furyl)-2-(2-furyl)acrylonitrile. The direction of isomerization (cis leads to trans, cis in equilibrium trans or trans leads to cis) is dependent on the chemical structure of these nitrofuran derivatives. Lipoyl dehydrogenase (NADH:lipoamide oxidereductase, EC 1.6.4.3), DT-diaphorase (NAD(P)H:(quinone-acceptor) oxidoreductase, EC 1.6.99.2) and liver microsomes could also catalyze the conversion of cis-3-(5-nitro-2-furyl)-2-(2-furyl)acrylamide to its trans isomer in the presence of an appropriate electron donor. Such isomerizing activity of these enzymes is much higher than their nitro-reducing activity. In addition, the cis-trans isomerization of some nitrofuran derivatives was demonstrated with the liver slices and the small intestines of rats. A new cis-trans isomerization mechanism which is based on transfer of a single electron by an enzyme system to a nitrofuran derivative to give the radical-anion was proposed. This postulated mechanism was supported by the preliminary experiments using pulse radiolysis technique.

Isolation and identification of urinary metabolites of AF-2 (3-(5-nitro-2-furyl)-2-(2-furyl)acrylamide) in rabbits.

Abstract After oral administration of AF-2 (3-(5-nitro-2-furyl)-2-(2-furyl)acrylamide) to rabbits, the two unique metabolites, M-I and M-II, were isolated from the urine. M-I, yellow needles of mp 117°, was identified as a new type metabolite of nitrofuran derivative, 2-(β-carboxypropionyl)-3-(5-methylthio-2-furyl) acrylamide by its mass, ir and nmr spectrometries. M-II, yellow solid, appears to be cis-trans isomer of M-I considering from its uv and mass spectral data, and the behavior on tlc.

Cis-trans isomerization of nitrofuran derivatives by xanthine oxidase

Enzymatic cis-trans isomerization of nitrofuran derivatives was 3-(5-Nitro-2-furyl)-2-(2-furyl)-demonstrated with milk xanthine oxidase. acrylamide (AF-2) and 3-(5-nitro-2-furyl)-2-(5-bromo-2-furyl)acrylamide (NFBFA) were mainly converted from the cis to the trans form by this enzyme supplemented with an electron donor. This enzymatic reaction was further characterized with respect to its cofactor requirements. Finally, a new cis-trans isomerization mechanism, which is based on transfer of a single electron by a nitroreductase such as xanthine oxidase to a nitrofuran derivative to give the anion free radical, was proposed.

Metabolism of drugs—LVI: The metabolic fate of phenacetylurea

Abstract The identification of 4-hydroxyphenacetylurea and 3-methoxy-4-hydroxy-phenacetylurea in the urine of rabbits fed phenacetylurea is reported together with that of unchanged phenacetylurea. In addition to these metabolites, hydrolyzed metabolites, phenaceturic acid, and phenylacetic acid were also demonstrated to be excreted into the urine. However, unlike some drugs that possess an amide group in the molecule, the excretion of phenacetylurea N -glucuronide could not be recognized. It is considered from the above results that the metabolic fate of phenacetylurea consists of two different pathways: one is hydrolysis of the ureide group, and the other is successive hydroxylation and methylation of the benzene nucleus. The methyl acetyl derivative of phenacetylurea N -glucuronide was synthesized by acylation of methyl 1-deoxy-1-thioureido-2,3,4-tri-o-acetyl-β- d -glucopyranosiduronate with phenylacetylchloride, and subsequent desulfurization with silver nitrate. 4-Hydroxyphenacetylurea and 3-methoxy-4-hydroxyphenacetylurea were synthesized by condensation of the corresponding acid esters with urea.

The mutagenic activity of ethyl N-hydroxycarbamate and its related compounds in Salmonella typhimurium

Alkyl N-hydroxycarbamates exhibited weak but significant mutagenic activity for Salmonella typhimurium TA100. The mutagenic potencies of these N-hydroxycarbamates were ranked thus: ethyl N-hydroxycarbamate greater than propyl N-hydroxycarbamate greater than methyl N-hydroxycarbamate. Acylation of ethyl N-hydroxycarbamate markedly enhanced its mutagenic activity for TA100. The highest mutagenic activity was observed with ethyl N-benzoyloxycarbamate among these acyl derivatives. Almost all the compounds were mutagenic to all the strains TA1535, TA100, TA98, especially to TA100.

The metabolism of phenyl o-(2-N-morpholinoethoxy)-phenyl ether hydrochloride in the rabbit and rat.

1. Urinary and faecal excretion of radioactivity in 120 h after oral administration of [U-14-C]phenyl o-(2-N-morpholinoethoxy)phenyl ether hydrochloride (200 mg/kg) were 92 and 3% dose in the rabbit, and 60 and 35% in the rat. 2. Urinary metabolites were produced by aromatic hydroxylation and aryl alkyl ether bond cleavage. Some evidence for formation of dioxomorpholino, oxohydroxymorpholino, and ethanolamino derivatives of the drug was obtained. 3. The aromatic hydroxylation product, p-hydroxyphenyl o-(2-N-morpholinoethoxy)phenyl ether hydrochloride had vasopressor activity comparable with the parent compound, but with shorter duration of action.

Studies on enzymatic reduction of aliphatic nitro compounds: Reductive dimerization of β-nitrostyrene and 1-nitro-4-phenylbutadiene

Abstract Enzymatic reduction of aliphatic nitro compounds, β-nitrostyrene (I), 1-nitro-4-phenylbutadiene (II), 1-nitro-4-phenyl-1-butene (III), 1-nitro-2-phenylethane (IV), and nitrophenylethane (V) was investigated in a xanthine oxidase-hypoxanthine system. I and II were easily reduced by the enzyme system under anaerobic conditions, but III, IV, and V resisted to the enzymatic reduction. The reduction products of I and II were isolated from the reaction mixtures and were identified as dimolecular compounds, 1,4-dinitro-2, 3-diphenylbutane and 1,4-dinitro-2,3-distyrylbutane, respectively, by mass, nuclear magnetic resonance, and infrared spectrometries, and by elementary analyses.

On the Metabolism and Mutagenic Activity of Nitrofuran Derivatives as Veterinary Medicines.

Furazolidone (FZD) and sodium nifurstyrenate (NSA-Na), antibacterial nitrofurans, have been used as veterinary medicines for the prevention and treatment of bacterial infections in swine or fish. Information about the metabolism of FZD or NSA-Na is very important for the safety evaluation of these compounds. The present review describes isolation and identification of metabolites of the nitrofurans in mammalian species (rats, rabbits and swine) or fish (gold fish, eel and sea bream), nitrofuran-metabolizing activities of liver preparations and results of mutation test for the nitrofurans and their metabolites.