title: Different oxidative pathways of isonicotinic acid hydrazide and its meta-isomer, nicotinic acid hydrazide.
abstract: 1. Superoxide was generated during the auto-oxidation of the antituberculous drug, isonicotinic acid hydrazide (INH), but not with its meta-isomer, nicotinic acid hydrazide (NH). During Fe(3+)-stimulated oxidation of INH and NH, aromatic hydroxylation occurred which was inhibited by the chelating agent, phytic acid. 2. A mixture of myeloperoxidase (MPO) and a hydrazide induced formation of compound III (oxyperoxidase) and aromatic hydroxylation which was stimulated by phytic acid. INH was considerably more potent than NH. 3. Co-oxidation of a hydrazide and thyroxine (T4) in the MPO system resulted in the formation of a pink-coloured product (maximum absorbance at 504 nm) which was more stable with NH than with INH. 4. The hydrazides and Cl- acted synergistically on MPO haem modification when co-oxidised in the MPO-H2O2 system. INH was more destructive than NH. 5. The different oxidative pathways of the hydrazides are consistent with the fact that an acyl intermediate of INH, unlike that of NH, is resonance stabilized.
authors.affiliation: Department of Pharmacology, Medical School, University of Stellenbosch, Tygerberg, South Africa.
authors.forename: B J
authors.initials: BJ
authors.lastname: van der Walt
authors.forename: J M
authors.initials: JM
authors.lastname: van Zyl
authors.forename: A
authors.initials: A
authors.lastname: Kriegler
mesh_terms: D002273:Carcinogens / Q000378:metabolism*; D002384:Catalysis; D005290:Ferric Compounds / Q000737:chemistry; D006834:Hydrazines / Q000378:metabolism*; D006900:Hydroxylation; D007538:Isoniazid / Q000378:metabolism*; D009539:Nicotinic Acids / Q000378:metabolism*; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000378:metabolism; D010833:Phytic Acid / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013481:Superoxides / Q000378:metabolism; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D013974:Thyroxine / Q000737:chemistry / Q000378:metabolism
chemical_list: D002273:Carcinogens; D005290:Ferric Compounds; D006834:Hydrazines; D009539:Nicotinic Acids; D017392:Thiobarbituric Acid Reactive Substances; D013481:Superoxides; D010833:Phytic Acid; C028571:nicotinic acid hydrazide; D009195:Peroxidase; D013974:Thyroxine; D007538:Isoniazid