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At least 55 records · Page 3Linked to original sources
PubMed1996

Determination of isonicotinic acid in the presence of isoniazid and acetylisoniazid. Studies on isonicotinic acid formation from isoniazid in isolated rat hepatocytes.

In comparison with the hepatocytes obtained from intact rats and rats pretreated with phenobarbital or 3-methylchoranthrene, the amount of isonicotinic acid (INA) formed from isoniazid (INH) increased substantially after incubation at 37 degrees C using the pretreated hepatocytes. This suggests an oxidative pathway for INA formation from INH, apart from hydrolysis. In order to explore the exact mechanism of INA formation in the hepatocytes, an HPLC assay for INA in the presence of INH and acetylisoniazid was developed. In this assay, INA was extracted after the preparation of an ion pair with tetra-n-butylammonium hydroxide, and analysed using an ODS column and a mobile phase consisting of 0.067 M potassium dihydrogenphosphate solution-methanol (96:4, v/v). The method is simple, accurate and especially suitable for INA determination after incubation of INH in isolated rat hepatocytes.

Animals↗
PubMedDate not supplied

Drug metabolism in experimental tuberculosis: II. Modification of monooxygenase activities due to infection by the administration of isonicotinic acid hydrazide.

Isonicotinic acid hydrazide (INH) upon administration to tuberculous guinea pigs exhibited curative effect by bringing back the tissue weights to normal. The reduced hepatic content of cytochrome P450 and NADPH-cytochrome C reductase activity of tuberculous guinea-pigs was restored to normal by INH treatment. Also a similar effect of INH was observed in the case of aminopyrine-N-demethylase and benzphetamine-N-demethylase in the liver and lung of tuberculous guinea-pigs. But INH had little effect on the content of cytochrome b5 and NADH-cytochrome b5 reductase activity. The hepatic and pulmonary activities of glutathione-S-transferase exhibited a tendency to come back to normal while UDP-glucuronyl transferase was unaffected by INH administration to the infected animals. The results suggest that the treatment of tuberculous guinea-pigs with INH cause the normalisation of disturbed hepatic and pulmonary metabolism.

Animals↗
PubMed1976

Inhibition of transcription by isonicotinic acid hydrazide.

Isonicotinic acid hydrazide (INH) reacts with the CMP moiety of a polynucleotide at slightly acid and alkaline pH. The reaction product, when used as a template in the cell-free transcription step, greatly diminishes the incorporation of GMP. In this system we were not able to show that INH -- in contrast with hydrazin -- is potentially capable of producing point mutations, since noncomplementary incorporation could not be observed with a poly(C)/INH adduct as template. Hydrazine could not be detected when INH was incubated with liver-cell fractions.

Binding, Competitive↗
PubMedDate not supplied

Niacin. II: Identification of isonicotinic acid in niacin by liquid chromatography with diode array detection.

Isonicotinic acid impurity in bulk niacin was detected and identified by comparison with a reference material by liquid chromatography with a diode array detector. The niacin was dissolved in dilute hydrochloric acid and chromatographed on an amine column with a mobile phase of methanol and water acidified with formic acid. Isonicotinic acid has a relative retention time of 1.5 compared with niacin (nicotinic acid), and the wavelengths of maximum ultraviolet (UV) absorbance for isonicotinic acid and niacin are 270 and 260 nm, respectively. The amount of impurity found in the niacin sample was 0.3%. Twelve formulations, including sustained-release products, one bulk material, and the United States Pharmacopoeia (USP) reference standard were tested. The impurity was detected in only the bulk and USP reference material samples.

Chromatography, Liquid↗
PubMed2006

Identification of a cytochrome P450 cDNA (CYP98A5) from Phaseolus vulgaris, inducible by 3,5-dichlorosalicylic acid and 2,6-dichloro isonicotinic acid.

To investigate the involvement of cytochrome P450s in the metabolism of plants treated with xenobiotic agrochemicals, bean leaves were treated with 3,5-dichlorosalicylic acid (DC-SA), a priming agent of plant defense and 2,6-dichloroisonicotinic acid (DC-INA), a chemical inducer of systemic acquired resistance. Through the use of directed differential display reverse transcription polymerase chain reactions, a differentially expressed cDNA amplicon, found to be up-regulated by both DC-SA and DC-INA treatment, was identified as a cytochrome P450 cDNA, CYP98A5. The nucleotide sequence indicates extensive homology to 3'-hydroxylases of p-coumaroyl esters. Dot blot analysis of leaves treated with various SA and isonicotinic acid derivatives showed enhanced expression of CYP98A5 due to DC-SA and DC-INA. Northern blot analysis of a time-dependent induction study of CYP98A5 in treated bean leaves indicated that DC-SA induces CYP98A5 mRNA transcripts earlier than DC-INA. Both inducers resulted in high transcript levels 24-48 h after treatment. The up-regulation of CYP98A5 is supportive of the conditioning and sensitizing effects of DC-SA and DC-INA to elicit a more rapid and effective defense response.

Amino Acid Sequence↗