A rapid, sensitive high performance liquid chromatographic method for the determination of meropenem in pharmaceutical dosage form, human serum and urine.

A new, simple, precise and rapid high performance liquid chromatographic method was developed for the determination of meropenem in human serum, urine and pharmaceutical dosage forms. Chromatography was carried out on an LC(18) column using a mixture of 15 mM KH(2)PO(4):acetonitrile:methanol (84:12:4; v/v/v), adjusted to pH 2.8 with H(3)PO(4). The proposed method was conducted using a reversed-phase technique, UV monitoring at 307.6 nm and cefepime as an internal standard. The retention times were 5.98 and 7.47 min for cefepime and meropenem, respectively. The detector response was linear over the concentration range of 50-10,000 ng/mL. The detection limit of the procedure was found to be 22 ng/mL. The detection limit for meropenem in human plasma was 108.4 ng/mL and the corresponding value in human urine was 179.3 ng/mL. No interference from endogenous substances in human serum, urine and pharmaceutical preparation was observed. The proposed method is sufficiently sensitive for determination of the concentrations of meropenem and may have clinical application for its monitoring in patients receiving the drug.

Some 3-thioxo/alkylthio-1,2,4-triazoles with a substituted thiourea moiety as possible antimycobacterials.

A series of novel N-alkyl/aryl-N'-[4-(4-alkyl/aryl-2,4-dihydro-3H-1,2,4-triazole-3-thione-5-yl)phenyl]thioureas 1-19 and three S-alkylated representatives of the former, N-alkyl/aryl-N'-[4-(3-aralkylthio-4-alkyl/aryl-4H-1,2,4-triazole-5-yl)phenyl]thioureas 20-22, were synthesized and tested for antimycobacterial activity against Mycobacterium tuberculosis H37Rv as well as Mycobacterium fortuitum ATCC 6841 which is a rapid growing opportunistic pathogen. Compounds 4 and 9-11 were found to possess the same MIC value with that of Tobramycin against M. fortuitum ATCC 6841 whereas 1-3 and 21 had positive response against M. tuberculosis H37Rv at varying degrees. Compound 21 was identified as the most potent derivative of the 1-22 series by an MIC value of 6.25 microg/mL and selectivity index of 1.6.

Metabolic and chemical studies on N-(4-chlorobenzyl)-N'-benzoylhydrazine.

The in vitro hepatic microsomal metabolism of N-(4-chlorobenzyl)-N'-benzoylhydrazine (CBBAH), a model compound representing N-alkyl substituted hydrazides, was studied using hepatic washed rat microsomal preparations fortified with NADPH to identify the possible N-oxidative, N-dealkylated and hydrolytic metabolites. CBBAH and its potential metabolites were prepared, characterized using spectroscopic techniques and then separated using a reversed phase HPLC system with UV detection at 254 nm. CBBAH was chemically converted to the corresponding hydrazone by m-chloroperbenzoic acid (m-CPBA) oxidation. CBBAH was incubated with rat microsomal preparations in the presence of NADPH, extracted into dichloromethane and evaporated finally under nitrogen. The TLC and HPLC results from the metabolic experiments showed that CBBAH produced the corresponding hydrolytic and N-dealkylated metabolites together with the corresponding hydrazone.

In vitro hepatic microsomal metabolism of N-benzyl-N-methylaniline.

In the present study, the in vitro microsomal metabolism of a tertiary aniline, N-benzyl-N-methylaniline (NBNMA) was studied to determine whether this compound produces an amide derivative (benzoyl) together with N-dealkylation and C- and N-oxidation products as metabolites. The preparations of the corresponding potential metabolites were undertaken and were separated using TLC and HPLC. Incubations were performed using rat microsomal preparations fortified with NADPH. The substrate and its potential metabolites were extracted into dichloromethane in the presence of NaCl and examined by TLC and HPLC-UV. The results indicated that NBNMA did not produce the corresponding amide (benzoyl derivative) or N-oxide metabolite but was dealkylated to the corresponding secondary amine. Two p-hydroxylated phenolic metabolites were also observed. These findings support the concept that nitrones are essential intermediate metabolites for the formation of amides from secondary aromatic amines (chemical rearrangement to amide via an oxaziridine intermediate). The carbinolamine produced from NBNMA does not seem stable enough to allow further oxidation to the amide and therefore this intermediate is broken down to the dealkylation products. N-Dealkylations and p-hydroxylations are major metabolic reactions following in vitro hepatic microsomal metabolism of the benzylic tertiary aniline, NBNMA.

Microsomal metabolism of N-benzyl-N-ethylaniline and N-benzyl-N-ethyl-p-toluidine.

The in vitro hepatic microsomal metabolism of two tertiary anilines, N-benzyl-N-ethylaniline (NBNEA) and N-benzyl-N-ethyl-p-toluidine (NBNEPT), was examined in order to determine whether these compounds produce amide derivatives (benzoyl or acetyl) in addition to N-dealkylation and N-oxidation products as metabolites. The preparation of these tertiary anilines and their corresponding potential metabolites was undertaken. The amines and metabolites were separated using TLC and HPLC. Incubations were performed using hamster microsomal preparations fortified with NADPH. The substrates and their potential metabolites were extracted into dichloromethane and examined by TLC and HPLC. The metabolic process of particular interest was the formation of amides from NBNEA and NBNEPT. The results from these experiments indicated that neither tertiary aniline (NBNEA and NBNEPT) produced amide (acetyl or benzoyl) or N-oxide metabolites. These substrates were dealkylated to the corresponding secondary amines via debenzylation and de-ethylation. Uncharacterised metabolites observed with substrates are proposed to be phenolic (for NBNEA) and hydroxymethyl (for NBNEPT). These findings support the concept that: nitrones are essential intermediates for the formation of amides from secondary aromatic amines (chemical rearrangement to amide via an oxaziridine intermediate); carbinolamines produced by NBNEA and NBNEPT are not stable enough to allow further oxidation to amides and therefore these intermediates are broken down to dealkylated products. The results are discussed in relation to the mechanism of metabolic amide formation from amines.

In vitro microsomal metabolism of nuclear chloro substituted secondary amines and imines.

The metabolism of N-(4-chlorobenzyl)-4-chloroaniline (CBCA), N-(4-chlorobenzyl)-4-chlorobenzylamine (CBCBA), and N-(4-chlorobenzylidene)-4-chlorobenzylamine (CBDCBA) were studied in vitro using rat liver microsomal preparations. The secondary amines produced the corresponding N-oxidation products (hydroxylamines and nitrones) and dealkylation products (4-chlorobenzaldehyde and primary amines). Both secondary amines failed to produce the corresponding amides, whilst the parent imine was detected as a metabonate. CBDCBA, the intermediate imine of CBCBA metabolism, was also incubated under similar conditions. However, no oxaziridine was detected.

In vitro microsomal metabolic studies on secondary aromatic amides.

Previous studies showed that amides are metabolites arising from certain secondary aromatic amines. However, some analogue amines did not lead to the formation of the corresponding amides when metabolised under identical conditions. We, therefore, wished to establish the factors preventing detection of amides. In the present study, we thought that amide detection as metabolites from secondary anilines may depend on the hydrolytic rate of the corresponding amide. We studied the in vitro hepatic microsomal metabolism of four aromatic amides i.e. N-(4-nitrobenzoyl)aniline (N4NBZA), N-benzoyl-4-nitroaniline (NBZ4NA), N-benzoylaniline (NBZA) and N-benzoyl-2,4,6-trimethylaniline (NBZTMA) which were (or not) detected following microsomal metabolism of secondary anilines in previous studies. Following the preparation, characterisation and separation of substrates and potential metabolites, incubations were carried out using rabbit microsomal preparations fortified with NADPH. The substrates and potential metabolites were extracted into dichloromethane and analysed by TLC, HPLC and UV. The results indicated that both steric and electronic factors may influence hydrolysis of amides. Three amides i.e. N4NBZA, NBZ4NA and NBZA yielded hydrolytic metabolites, whereas, NBZTMA did not. Para hydroxylated metabolites were also detected from N4NBZA and NBZA. These observations support the concept that one reason for not detecting amides as metabolites from secondary anilines in previous studies could be due to their rapid hydrolysis to the corresponding primary amines.

Synthesis and characterization of certain thiourea derivatives starting from 1,2,4-triazoline-3-thiones as potential antibacterial and antifungal agents.

Several N-substituted-N'-[4-(4-alkyl/aryl-2,4-dihydro-3H-1,2,4-triazole-3-thione -5-yl ) phenyl[thioureas were synthesized in order to examine their antibacterial and antifungal activities. The structures and purity of the synthesized compounds were confirmed by UV, IR and mass spectral data and elemental analysis. However, they were found not to possess significant antibacterial or antifungal activity.