High-performance liquid chromatographic determination of rufloxacin and its main active metabolite in biological fluids.

A high-performance liquid chromatographic method is described for the determination of a fluoroquinolone, rufloxacin, and its N-desmethyl metabolite in plasma, urine and bile. Samples are chromatographed on a poly(styrene-divinylbenzene) column, the eluate being monitored with a fluorescence detector. The method was validated and a detection limit of 10 ng/ml for both rufloxacin and its metabolite in all the biological matrices considered was found. The method was successfully applied in pharmacokinetic studies.     

Antioxidant activity of indapamide and its metabolite

An antioxidant activity of indapamide (IDP) and its metabolite (OH-IDP) is demonstrated in this study. Both IDP and OH-IDP were found to scavenge 1,1-diphenyl-2-picryl-hydrazyl free radical. The scavenging effect of OH-IDP was stronger than that of IDP. Lipid peroxidation of rat liver microsomes initiated by reduced nicotinamide adenine dinucleotide phosphate (NADPH) and adenosine diphosphate (ADP)-Fe3+ was inhibited by IDP and OH-IDP with IC50 values of about 6 and 2 microM, respectively. The lipid peroxidation in human erythrocyte membrane, induced by 2,2'-azobis-(2-amidinopropane dihydrochloride) treatment, was also inhibited by 10 microM IDP. The antioxidant capacity of OH-IDP was at almost the same level as that of alpha-tocopherol, tested for comparison. The present data show that IDP and OH-IDP at micromolar concentrations are able to trap the free radicals involved in the lipid peroxidation.     

Determination of pyridate and its main metabolite CL-9673 in plant materials

Summary The application of a simple reversed-phase, HPLC-UV method for the determination of the contact herbicide pyridate and its main metabolite 3-phenyl-4-hydroxy-6-chloropyridazine-known as CL-9673-in green cereals, grains and straw is described. The method is based on a simple extraction, separation of pyridate from its metabolite, hydrolysis of pyridate to CL-9673, high-performance liquid chromatographic separation of CL-9673 in both fractions using only one reversed phase column and UV-detection.The method is sensitive down to 3 ngg^–1 CL-9673 in green plants and grain and 5ngg^–1 in straw.In the range 0.05–1.0mgkg^–1 recoveries are between 73.7% and 109% from green plants, between 77.7% and 102% from grains and between 77.3% and 87.5% from straw.     

Biotransformation of physalin H and leishmanicidal activity of its transformed products

The transformation of physalin H (1) with Rhizopus stolonifer and Cunninghamella elegans has afforded two new physalins, 6,7-dehydrophysalin H (2) and 6-deoxyphysalin H (3), along with a known isophysalin B (4). Their structures were elucidated by spectroscopic analysis. All of these compounds have shown potent leishmanicidal activity with IC50 values in the range of 6.03-13.80 microM.     

Determination of denzimol, a new anticonvulsant agent, and its main metabolite in biological material by gas chromatography and high-performance liquid chromatography

Two methods, using gas chromatography (GC) and high-performance liquid chromatography (HPLC), were developed in order to investigate the pharmacokinetics of denzimol hydrochloride, N-[beta-[4-(beta-phenylethyl)phenyl]-beta-hydroxyethyl] imidazole hydrochloride, which is a new anticonvulsant drug, and of its main metabolite, N-[beta-[4-(beta-phenyl-beta(alpha)-hydroxyethyl)phenyl] -beta-hydroxyethyl]-imidazole (referred to as M2), in humans. Both methods involve the use of a homologue of denzimol as an internal standard. The GC method is more sensitive (sensitivity limit 2.5 ng/ml for denzimol and 15 ng/ml for M2) and was utilized for the determination of denzimol and M2 in plasma. The GC method is specific, precise (relative standard deviations are 3.26, 2.12 and 1.72% at 10, 100 and 1000 ng/ml for denzimol and 6.45, 4.17 and 3.38% at 50, 500 and 1000 ng/ml for M2) and accurate (mean recovery +/- S.D. is 102.58 +/- 4.10% for denzimol and 99.72 +/- 7.75% for M2). The HPLC method is very simple and quick to perform. This method has a sensitivity limit of 0.5 micrograms/ml for denzimol and 1 microgram/ml for M2, and allows the determination of both compounds in urine with high selectivity, reproducibility (relative standard deviations are 2.05, 3.50 and 1.02% for denzimol and 2.78, 2.80 and 1.73% for M2, at concentrations of 15, 35 and 70 micrograms/ml) and accuracy (mean recovery +/- S.D. is 103.57 +/- 2.97% for denzimol and 95.91 +/- 1.59% for M2). The common anticonvulsants, when present in plasma, do not interfere with the monitoring of denzimol levels.     

Nonaqueous capillary electrophoresis method for the analysis of gleevec and its main metabolite in human urine

The viability of nonaqueous capillary electrophoresis (NACE) was investigated for determination of gleevec and its main metabolite in human urine using a fused-silica capillary. Baseline separation of the studied solutes was obtained using a nonaqueous solution composed of 12 mM ammonium acetate and 87.6 mM acetic acid in methanol-acetonitrile (ACN) (80:20, v:v) providing analysis time shorter than 3 min. Different aspects including stability of the solutions, linearity, accuracy and precision were studied in order to validate the method in the urine matrix. Detection limits of 24 microg L(-1) for gleevec and its metabolite were obtained. A robustness test of the method was carried out using the Plackett-Burman fractional factorial model with a matrix of 15 experiments. The developed method is simple, rapid and sensitive and has been used to determine gleveec and its metabolite at clinically relevant levels in human urine. Before NACE determination, a solid-phase extraction (SPE) procedure with a C18 cartridge was necessary. Real determination of these analytes in two patient urines were done.     

反相离子对高效液相色谱法测定动物血浆中的恩诺沙星及其代谢物

建立了用反相离子对ＨＰＬＣ测定动物血浆中恩诺沙星（ＥＲＦＸ）及其代谢产物环丙沙星（ＣＰＦＸ）浓度的方法。血浆中药物用二氯甲烷萃取,选用ＯＤＳ柱,甲醇－四丁基氢氧化铵溶液为流动相,吡哌酸（ＰＰＡ）作内标,检测波长２７２ｎｍ。方法简便、快速、灵敏、准确,适用于ＥＲＦＸ及其代谢物ＣＰＦＸ血药浓度的测定和药代动力学研究。并首次测定了黄牛血浆中的ＥＲＦＸ和ＣＰＦＸ。     

Determination of carbaryl and its metabolite 1-naphthol in commercial formulations and biological fluids

A simple and sensitive method for the determination of carbaryl in whole blood and commercial formulations, based on normal, and synchronous first- and second-derivative fluorescence spectra, is presented. Solvent effects on the spectral characteristics of carbaryl solutions and the influences of instrumental parameters are described in detail. Two methods have been developed, with neutral (for carbaryl) and basic (for 1-naphthol) media. Detection limits of 0.9 and 0.7 ng/ml were achieved for carbaryl and 1-naphthol, respectively, with the first-derivative approach.     

Determination of etretinate and its main metabolite in human plasma using normal-phase high-performance liquid chromatography

A high-performance liquid chromatographic procedure has been developed for the determination of astemizole and its primary metabolite in plasma and animal tissues. Both compounds and the internal standard were extracted from alkalinized plasma with heptane--isoamyl alcohol and analyzed using a reversed-phase column and UV monitoring at 254 nm. The detection limits for both compounds were 1 ng/ml of plasma and 5 ng/g of tissue and extraction recoveries were sufficiently high (71-84%). The method was applied to plasma and tissue samples from dogs after repeated oral administration, and to plasma samples from a volunteer taking a 300-mg oral dose of the drug. The results were compared with those obtained by a formerly developed radioimmunoassay.     

HPLC-DAD determination of plasma levels of the antipsychotic risperidone and its main metabolite for toxicological purposes

A new, rapid analytical method, based on liquid chromatography with diode array detection, has been developed and applied to the determination of risperidone and its main active metabolite 9-hydroxyrisperidone in human plasma. The chromatographic separation was obtained on a C8 (150 x 4.6 mm, 5 microm) column, using a mobile phase composed of acetonitrile (27%) and a pH 3.0 phosphate buffer (73%). A sample clean-up procedure was carried out by using C8 cartridges and eluting the analytes with methanol. The extraction yield was highly satisfactory for both analytes, with average absolute recovery values of about 95%. The experimental conditions permitted the quantitative determination of risperidone and 9-hydroxyrisperidone with high precision (RSD < 3.6%) and satisfactory sensitivity (LOQ = 4 ng mL(-1)). The method was applied to plasma samples from a patient who had tried to poison himself with 150 mg of risperidone, and was undergoing polypharmacy.     

Mixed-mode solid-phase extraction for sample cleanup in hair analysis for methadone and its main metabolite

A simple and rapid method for the determination of methadone and its main metabolite EDDP in hair has been developed and validated. The analytes were completely extracted from the matrix after a short alkaline incubation, and the extracts were further cleaned up by solid‐phase extraction using mixed‐mode cartridges. Linearity was obtained from 0.1 (lower limit of quantitation, LLOQ) to 30 ng/mg for both compounds, with correlation coefficients higher than 0.99. Intra‐ and interday precision and accuracy were in conformity with internationally accepted guidelines for bioanalytical method validation, and the cleanup procedure presented mean extraction efficiencies higher than 90% for both analytes. This high efficiency greatly contributed to the low limits of quantitation achieved, and therefore this method can be successfully applied in the determination of methadone and EDDP in hair samples in clinical and forensic scenarios where these compounds are involved. Copyright © 2010 John Wiley & Sons, Ltd.     

Gas chromatographic-mass spectrometric assessment of the pharmacokinetics of amineptine and its main metabolite in volunteers with liver impairment

A pharmacokinetic study of amineptine (Survector) and its C5 metabolite, resulting from a beta-oxidation of the heptanoic acid side-chain, was undertaken with ten human volunteers, who received a single 100-mg tablet of amineptine orally. They were affected with liver impairment in order to determine if this situation would alter greatly the pharmacokinetic parameters. The internal standard was the octanoic acid homologue. Analyses were carried out by gas chromatography (GC) and GC-mass spectrometry using TMS ester derivatives. Plasma samples were extracted using a C18 reversed-phase cartridge at pH 4.0. Mass fragmentographic measurements on the plasma samples were performed on the m/z ions (M + H)+ and (base peak)+ using ammonia chemical ionization. The global evaluation of precision was good and the coherence between the two modes of measurements, (base peak)+ and (M + H)+ ions, gave a regression factor r close to unity. For amineptine the total body clearance and mean residence time were accurate and precise with eight volunteers, but only four volunteers showed such coherent data for the slope of the elimination curve, beta, and half-life. However, the beta value, half-life and mean residence time of the C5 metabolite were accurate and precise with seven, eight and ten volunteers, respectively. It is concluded that the drug was still detoxified at normal levels.     

High-performance liquid chromatography of pefloxacin and its main active metabolites in biological fluids

We describe a high-performance liquid chromatographic (HPLC) method for the analysis of pefloxacin, a new antibacterial agent, in plasma and urine following administration of a therapeutic dose in humans. HPLC assay of pefloxacin and its two main active metabolites in urine is also described. The applicability of the methods to pharmacokinetic studies of pefloxacin in humans is demonstrated.     

Determination of amineptine and its main metabolite in plasma by high-performance liquid chromatography after solid-phase extraction

Amineptine and its main metabolite were determined simultaneously in plasma by high-performance liquid chromatography using quinupramine as internal standard. The method comprised adsorption on Extrelut column from alkaline plasma, elution with diethyl ether-methylene chloride, evaporation in the presence of 0.01 M hydrochloric acid and injection of the acid solution onto a mu Bondapak C18 column, using acetonitrile-0.025 M potassium dihydrogenphosphate as mobile phase and ultraviolet detection at 210 nm. Average steady-state concentrations of the two compounds were determined in four patients under treatment regimen (two 100-mg doses of amineptine per day, at 8.00 and 12.00 h). The concentrations determined 20 h after the last dose were undetectable in all cases, whereas the concentrations determined 1 h after the second dose were found to be 780 +/- 96 ng ml-1 for amineptine and 690 +/- 137 ng ml-1 for its metabolite. The technique can also be applied to whole blood with, if necessary, identification on the basis of the ultraviolet spectrum obtained by photodiode-array detection.     

Enantioselective assay of chloroquine and its main metabolite deethyl chloroquine in human plasma by capillary electrophoresis

A sensitive assay for the determination of chloroquine (Clq) and its pharmacologically active metabolite deethyl chloroquine in plasma by capillary electrophoresis (CE) is developed. Plasma levels of drug and metabolite are measured using HeCd laser-induced fluorescence (LIF) detection over a range of three orders of magnitude from 2 to 1000 ng/mL after liquid-liquid extraction. A limit of detection of 0.5 ng/mL is achieved. Validation of the method yields intra- and interday precision data within the limits of 10% (20% at limit of quantitation) and intra- and interday accuracy data greater than 6% throughout the whole working range. The method is applied for the drug monitoring of patients treated with Clq. Based upon this assay, two enantioselective CE-LIF methods for Clq and its main metabolite are developed. Mixtures of substituted gamma-cyclodextrins are used as chiral selectors. A baseline separation of the enantiomers of both analytes in one run is achieved in less than 11 min (method A) and less than 9 min (method B), respectively. Hydroxychloroquine is used as the internal standard for both methods.     

Synthesis and biological activity of kalkitoxin and its analogues

Total syntheses of kalkitoxin, isolated from the Caribbean Lyngbya majuscula, and its analogues, 3-epi-, 7-epi-, 8-epi-, 10-epi-, 10-nor-, and 16-nor-kalkitoxin, were achieved via oxazolidinone-based diastereoselective 1,4-addition reaction of a methyl group and efficient TiCl(4)-mediated thiazoline ring formation as the key steps. The biological activities of synthetic kalkitoxin and its analogues were evaluated with brine shrimp.     

Liquid chromatographic method for the simultaneous determination of sulphasalazine and its main metabolites in biological fluids

Summary An HPLC procedure was developed for the simultaneous determination of salicylazosulphapyridine, and its main metabolites 5-aminosalicylic acid and sulphapyridine, in human serum and synovial fluid. The analytical procedure consisted of a single ion-pair extraction step for an Extrelut column with methylene chloride. The investigated compounds and the added sulphadimidine internal standard were eluated from a Hypersil-MOS reversed-phase column by stepwise gradient; mobile phase was methanol-0.01 M potassium dihydrogenphosphate (3:7, 0.0–2.0 min and 8:2, 2.1–6.5 min).     

Transformations of alkaloids of the quinazolin-4-one group in the animal organism

Summary It has been found by chromato-mass spectrometry that the main product of the transformation of deoxy-vasicinone excreted with rat urine in the unbound form is vasicinone. Vasicinone used as a drug is excreted predominantly in the unchanged form.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 250–254, March–April, 1977.