Major Metabolites (major + metabolite)

Distribution by Scientific Domains
Distribution within Chemistry

Selected Abstracts

A Photophysical and Photochemical Study of 6-Methoxy-2-naphthylacetic Acid, the Major Metabolite of the Phototoxic Nonsteroidal Antiinflammatory Drug Nabumetone

F. Boscį
ABSTRACT Nabumetone is a phototoxic nonsteroidal antiinflammatory drug used for the treatment of osteoarthritis. However, nabumetone is considered a prodrug with its metabolite 6-methoxy-2-naphthylacetic acid the active form. Photophysical and photochemical studies on this metabolite have been undertaken. It undergoes photodecarboxylation in aerated aqueous and organic solvents. In addition to the accepted photodegradation pathway for related molecules, a new mechanism that implies generation of the naphthalene radical cation from the excited singlet and addition of O2 prior to the decarboxylation process has been demonstrated. Evidence for the involvement of the excited singlet state in this mechanism have been obtained by steady-state and time-resolved fluorescence experiments. The fluorescence quenching by O2 and the shorter singlet lifetime in aerated solvents support this assignment. Laser flash photolysis also supports this mechanism by showing the noninvolvement of the triplet in the formation of the naphthalene radical cation. Finally, the well-known electron acceptor CCl4 acts as an efficient singlet quencher, enhancing the route leading to the radical cation, preventing intersystem crossing to the triplet and thus resulting in a dramatic increase in the yield of 6-methoxy-2-naphthaldehyde, the major oxidative decarboxylation product; this constitutes unambiguous proof in favor of the new mechanistic proposals. [source]

(2-Ethyl-5-oxo-hexyl) Methylthiomethyl Phthalate as By-Product of the Swern Oxidation: Improved Synthesis of Ring-Deuterated Major Metabolites of Bis(2-ethylhexyl) Phthalate.

CHEMINFORM, Issue 52 2003
Hans-Detlev Gilsing
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Antiandrogenic effects of dibutyl phthalate and its metabolite, monobutyl phthalate, in rats

Makoto Ema
ABSTRACT, Developmental toxicity following administration of dibutyl phthalate (DBF) and its major metabolite, monobutyl phthalate (MBuP), by gavage was determined in Wistar rats. DBF on days 0,8 of pregnancy induced an increase in the incidence of preimplantation loss at 1250 mg/kg and higher and postimplantation loss at 750 mg/kg and higher. MBuP on days 0,8 of pregnancy produced an increase in the incidence of pre-and postimplantation loss at 1000 mg/kg. DBF on days 7,15 of pregnancy caused an increase in the incidence of fetuses with malformations at 750 mg/kg. MBuP on days 7,15 of pregnancy produced an increased incidence of fetuses with malformations at 500 mg/kg and higher. DBF on days 15,17 of pregnancy resulted in a decrease in the anogenital distance (AGD) of male fetuses and increase in the incidence of fetuses with undescended testes at 500 mg/kg and higher. MBuP on days 15,17 of pregnancy caused a decreased male AGD and increased incidence of fetuses with undescended testes at 250 mg/kg and higher. No effect of DBF and MBuP on the AGD was found in female offspring. The spectrum of fetal malformations, dependence of gestational days of treatment on the manifestation of teratogenicity, and alterations in development of the male reproductive system observed after administration of DBF were in good agreement with those observed after administration of MBuP. These findings suggest that MBuP may be responsible for the induction of developmental toxic effects of DBP. The doses that produced a decrease in the AGD and undescended testes in male offspring were lower than those producing maternal toxicity, fetal malformations after administration during major organogenesis, and embryonic loss. The male reproductive system may be more susceptible than other organ systems to DBP and MBuP toxicity after maternal exposure. [source]

On-line sample stacking and short-end injection CE for the determination of fluoxetine and norfluoxetine in plasma: Method development and validation using experimental designs

Chia-Chia Lu
Abstract A short-end injection CE method combining field-amplified sample stacking (FASS) is presented for the analysis of fluoxetine (FL) and norfluoxetine in plasma. In this study, FASS enhanced the sensitivity about 1100-fold, while short-end injection reduced the analysis time to less than 4,min. Parameters involved in the separations were investigated using a central composite design (CCD) and response surface methodology to optimize the separation conditions in a total of only 32 runs. Samples injected into the capillary for 99.9,s at a voltage of ,5,kV were stacked in a water plug (0.5,psi, 9,s). Baseline resolution of FL and its major metabolite was achieved using a BGE formulation consisting of phosphate,triethanolamine at low pH, and a separation voltage of ,10,kV. Five percent methanol was added as organic modifier to enhance selectivity and resolution. The linear range was between 10 and 500,ng/mL (r >0.9946), covering the expected plasma therapeutic ranges. The LOD in plasma were 4,ng/mL (S/N,=,3), a value comparable to that obtained using LC-MS, showing the success of the on-line stacking technique. Our method was also successfully validated in quantification and pharmacokinetic studies with three volunteer plasma samples and could be applied to pharmacogenetic studies. [source]

Rapid and sensitive determination of phosphorus-containing amino acid herbicides in soil samples by capillary zone electrophoresis with diode laser-induced fluorescence detection

Eva Orejuela
Abstract A straightforward and sensitive method has been developed for the analysis of phosphorus-containing amino acid herbicides (glufosinate and aminomethylphosphonic acid, the major metabolite of glyphosate) in soil samples. For this purpose, the analytical features of two indocyanine fluorescent dyes, sulfoindocyanine succinimidyl ester (Cy5) and 1-ethyl-1-[5-(N -succinimidyl-oxycarbonyl)pentyl]-3,3,3,3-tetramethyl-indodicarbocyanine chloride, as labeling reagents for the determination of these herbicides by CZE with diode LIF detection were investigated. Practical aspects related to the labeling chemistry and CZE separation showed that the two probes behave similarly, Cy5 being the best choice for the determination of these herbicides on account of its higher sensitivity. The optimum procedure includes a derivatization step of the pesticides at 25°C for 30,min and direct injection to CZE analysis, which is conducted within about 14,min using ACN in the running buffer. The lowest detectable analyte concentration ranged from 0.025 to 0.18,µg/L with a precision of 3.6,5.4%. These results indicate that indocyanine fluorescence dyes are useful as rapid and sensitive labels for the determination of these herbicides when compared with typical fluorescein dyes such as FITC and 5-(4,6-dichloro- s -triazin-2-ylamino) fluorescein, because they provide faster labeling reactions even at room temperature and the excess of reagent practically does not interfere the determination. Finally, the Cy5 method was successfully applied to soil samples without a preliminary clean-up procedure, and the herbicides were measured without any interference from coexisting substances. The recoveries of these compounds in these samples at fortification levels of 100,500,ng/g were 90,93%. [source]

Neuronal nitric oxide synthase (nNOS) mRNA is down-regulated, and constitutive NOS enzymatic activity decreased, in thoracic dorsal root ganglia and spinal cord of the rat by a substance P N-terminal metabolite

Katalin J. Kovacs
Abstract Nitric oxide (NO) in the spinal cord plays a role in sensory and autonomic activity. Pain induced by acetic acid in the abdominal stretch (writhing) assay and hyperalgesia associated with chronic pain are highly sensitive to NO synthase (NOS) inhibitors. Because substance P (SP) is released and up-regulated in some models of chronic pain, we hypothesized that an accumulation of SP metabolites may influence NOS expression and activity. To test this hypothesis, we examined the effect of intrathecally (i.t.) injected substance P (1-7) [SP(1-7)], the major metabolite of SP in the rat, on neuronal NOS (nNOS) mRNA in the thoracic and lumbar spinal cord, dorsal root ganglia (DRG) and on the corresponding constitutive NOS (cNOS) enzyme activity. Detected using quantitative RT-PCR, nNOS mRNA content in the thoracic spinal cord was decreased 6 h after injection of 5 µmol of SP(1-7) and returned to control 2 days later. In thoracic DRG, nNOS mRNA was reduced 48 h after SP(1-7). The cNOS enzymatic activity in thoracic spinal tissue was gradually decreased to a minimum at 72 h. Down-regulation of NOS by SP(1-7) in the thoracic area appears to be highly associated with capsaicin-sensitive primary afferent neurons. No similar changes in either parameter were measured in the lumbar area after SP(1-7). These data suggest that N-terminal SP fragments, which are known to cause long-term antinociception in the writhing assay, may do so by their ability to down-regulate NO synthesis along nociceptive pathways. [source]

Nonsteroidal antiinflammatory drug use and risk of bladder cancer in the health professionals follow-up study

Jeanine M. Genkinger
Abstract Nonsteroidal antiinflammatory drugs (NSAIDs) use, particularly aspirin, may lower the risk of several cancers, including bladder. NSAIDs may reduce development of bladder tumors by decreasing inflammation, inhibiting cycloxygenase-2, inhibiting proliferation and inducing apoptosis of cancer cells. However, acetaminophen, a major metabolite of phenacetin, may be positively associated with bladder cancer risk. Results from case-control studies on NSAIDs and acetaminophen use and bladder cancer risk are inconsistent. We investigated the association between NSAID and acetaminophen use and bladder cancer risk in a large cohort of US males. Among 49,448 men in the Health Professionals Follow-Up Study, 607 bladder cancer cases were confirmed during 18 years of follow-up. Relative risks (RR) and 95% confidence intervals (CI) were calculated by Cox proportional hazards models. Multivariate RR were adjusted for age, current smoking status, pack years, geographic region and fluid intake. No significant associations were observed for regular aspirin (,2 tablets per week), (RR = 0.99, 95% CI 0.83,1.18), ibuprofen (RR = 1.11, 95% CI 0.81,1.54), acetaminophen (RR = 0.96, 95% CI 0.67,1.39) or total NSAID use (not including acetaminophen; RR = 1.01, 95% CI 0.85,1.20) and bladder cancer risk compared with nonuse. Consistent use (over 6 years) of aspirin, ibuprofen, acetaminophen and total NSAIDs, compared to nonuse, was not associated with bladder cancer risk. No association was observed between aspirin frequency and dose and bladder cancer risk. We observed no effect-modification by smoking, age or fluid intake. Our results suggest that regular NSAID or acetaminophen use has no substantial impact on bladder cancer risk among men. © 2007 Wiley-Liss, Inc. [source]

Induction of olfactory mucosal and liver metabolism of lidocaine by 2,3,7,8-tetrachlorodibenzo- p -dioxin

Mary Beth Genter
Abstract Formulation of drugs for administration via the nasal cavity is becoming increasingly common. It is of potential clinical relevance to determine whether intranasal drug administration itself, or exposure to other xenobiotics, can modulate the levels and/or activity of nasal mucosal metabolic enzymes, thereby affecting the metabolism and disposition of the drug. In these studies, we examined changes in several of the major metabolic enzymes in nasal epithelial tissues upon exposure to the environmental contaminant 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD), as well as the impact of these changes on the metabolism of a model intranasally administered drug, lidocaine. Results of these studies show that TCDD can induce multiple metabolic enzymes in the olfactory mucosa and that the pattern of induction in the olfactory mucosa does not necessarily parallel that which occurs in the liver. Further, increases in enzyme levels noted by Western blot analysis were associated with increased activities of several nasal mucosal enzymes as well as with enhanced conversion of lidocaine to its major metabolite, monoethyl glycine xylidide (MEGX). These results demonstrate that environmental exposures can influence the levels and activity of nasal mucosal enzymes and impact the pharmacology of drugs administered via the nasal route. © 2002 Wiley Periodicals, Inc. J Biochem Mol Toxicol 16:128,134, 2002. DOI 10.1002/jbt.10032 [source]

Alterations in Brain Glucose Utilization Accompanying Elevations in Blood Ethanol and Acetate Concentrations in the Rat

ALCOHOLISM, Issue 2 2010
Robert J. Pawlosky
Background:, Previous studies in humans have shown that alcohol consumption decreased the rate of brain glucose utilization. We investigated whether the major metabolite of ethanol, acetate, could account for this observation by providing an alternate to glucose as an energy substrate for brain and the metabolic consequences of that shift. Methods:, Rats were infused with solutions of sodium acetate, ethanol, or saline containing 13C-2-glucose as a tracer elevating the blood ethanol (BEC) and blood acetate (BAcC) concentrations. After an hour, blood was sampled and the brains of animals were removed by freeze blowing. Tissue samples were analyzed for the intermediates of glucose metabolism, Krebs' cycle, acyl-coenzyme A (CoA) compounds, and amino acids. Results:, Mean peak BEC and BAcC were approximately 25 and 0.8 mM, respectively, in ethanol-infused animals. Peak blood BAcC increased to 12 mM in acetate-infused animals. Both ethanol and acetate infused animals had a lower uptake of 13C-glucose into the brain compared to controls and the concentration of brain 13C-glucose-6-phosphate varied inversely with the BAcC. There were higher concentrations of brain malonyl-CoA and somewhat lower levels of free Mg2+ in ethanol-treated animals compared to saline controls. In acetate-infused animals the concentrations of brain lactate, ,-ketoglutarate, and fumarate were higher. Moreover, the free cytosolic [NAD+]/[NADH] was lower, the free mitochondrial [NAD+]/[NADH] and [CoQ]/[CoQH2] were oxidized and the ,G, of ATP lowered by acetate infusion from ,61.4 kJ to ,59.9 kJ/mol. Conclusions:, Animals with elevated levels of blood ethanol or acetate had decreased 13C-glucose uptake into the brain. In acetate-infused animals elevated BAcC were associated with a decrease in 13C-glucose phosphorylation. The co-ordinate decrease in free cytosolic NAD, oxidation of mitochondrial NAD and Q couples and the decrease in ,G, of ATP was similar to administration of uncoupling agents indicating that the metabolism of acetate in brain caused the mitochondrial voltage dependent pore to form. [source]

Cotinine as a biomarker of tobacco exposure: Development of a HPLC method and comparison of matrices

Guilherme Oliveira Petersen
Abstract Tobacco dependence reaches one-third of the world population, and is the second leading cause of death around the world. Cotinine, a major metabolite of nicotine, is the most appropriate parameter to evaluate tobacco exposure and smoking status due to its higher stability and half-life when compared to nicotine. The procedure involves liquid,liquid extraction, separation on a RP column (Zorbax® XDB C8), isocratic pump (0.5,mL/min of water,methanol,sodium acetate (0.1,M),ACN (50:15:25:10, v/v/v/v), 1.0,mL of citric acid (0.034,M) and 5.0,mL of triethylamine for each liter) and HPLC-UV detection (261,nm). The analytical procedure proved to be sensitive, selective, precise, accurate and linear (r>0.99) in the range of 5,500.0,ng/mL for cotinine. 2-Phenylimidazole was used as the internal standard. The LOD was 0.18,ng/mL and the LOQ was 5.0,ng/mL. All samples from smoking volunteers were collected simultaneously to establish a comparison between serum, plasma, and urine. The urinary cotinine levels were normalized by the creatinine and urine density. A significant correlation was found (p<0.01) between all matrices. Results indicate that the urine normalization by creatinine or density is unnecessary. This method is considered reliable for determining cotinine in serum and plasma of smokers and in environmental tobacco smoke exposure. [source]

In vitro biotransformation of anabolic steroids in canines

Forensic drug testing of anabolic steroids in racing animals is required because of the potential for steroid abuse. Often when the metabolic products of an administered compound have not been identified, the analysis and verification of the administered compound is difficult. The objective of this study was to qualitatively identify the in vitro phase I biotransformation products of anabolic steroids that have a high potential for abuse in canines. The investigated steroids included testosterone, methyltestosterone, mibolerone and boldenone. Steroid biotransformation products were generated using beagle liver microsomes and analysed by high performance liquid chromatography (HPLC)/mass spectrometry (MS) with an electrospray ionization source. Characterization of steroid metabolites was based on HPLC retention, UV and mass spectra. The major testosterone metabolites were identified as androstenedione and 6,- and 16,-hydroxytestosterone. 6,-Hydroxymethyltestosterone was identified as a major metabolite in the methyltestosterone microsomal incubations. Several mibolerone metabolites were identified as monohydroxylated mibolerones as well as an oxidized mibolerone metabolite. Boldenone metabolites were identified as monohydroxylated boldenones, oxidized boldenone, and testosterone. This information should assist in the determination of anabolic steroid use in canines through the correlation of the urinary metabolites to the administered drug. [source]

Potentially Fatal Interaction Between Azithromycin and Disopyramide

A patient on disopyramide developed disopyramide toxicity when treated concurrently with azithromycin. Evidence of toxicity included an elevated serum disopyramide level and ventricular tachycardia requiring cardioversion. The azalide antibiotic presumably inhibited dealkylation of disopyramide to its major metabolite, mono-N-dealkyldisopyramide. Physicians should avoid using azithromycin in patients on disopvramide. If this drug combination is unavoidable, disopyramide levels must be closely monitored. [source]

Identification of [(GS)2AsSe], in rabbit bile by size-exclusion chromatography and simultaneous multielement-specific detection by inductively coupled plasma atomic emission spectroscopy

Jürgen Gailer
Abstract An arsenic,selenium metabolite that exhibited the same arsenic and selenium X-ray absorption near-edge spectra as the synthetic seleno-bis(S -glutathionyl) arsinium ion [(GS)2AsSe], was recently detected in rabbit bile within 25,min after intravenous injection of rabbits with sodium selenite and sodium arsenite. X-ray absorption spectroscopy did not (and cannot) conclusively identify the sulfur-donor in the in vivo sample. After similar treatment of rabbits, we analyzed the collected bile samples by size-exclusion chromatography (SEC) using inductively coupled plasma atomic emission spectroscopy (ICP-AES) to monitor arsenic, selenium and sulfur simultaneously. The bulk of arsenic and selenium eluted in a single peak, the intensity of which was greatly increased upon spiking of the bile samples with synthethic [(GS)2AsSe],. Hence, we identify [(GS)2AsSe], as the major metabolite in bile after exposure of rabbits to selenite and arsenite. The reported SEC,ICP-AES method is the first chromatographic procedure to identify this biochemically important metabolite in biological fluids and is thus a true alternative to X-ray absorption spectroscopy, which is not available to many chemists. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Pharmacokinetics of TDP223206 following intravenous and oral administration to intact rats and intravenous administration to bile duct-cannulated rats

Yanmin Chen
Abstract The pharmacokinetics of TDP223206 was studied following single intravenous and oral administrations in rats. A mixture of TDP223206 and 14C-TDP223206 were administered to intact and bile duct-cannulated rats. Following intravenous administration, plasma concentrations declined biphasically. The AUCinf increased linearly with dose but was not dose proportional. The PK parameters of TDP223206 indicated low clearance (254,386,ml/h/kg) and a moderate volume of distribution (968,1883,ml/kg). The bioavailability was 32.95% and 24.46% for 10 and 50,mg/kg oral doses, respectively. 14C-TDP223206 was distributed widely into different tissues with small intestine, liver, kidneys and large intestine having large tissue to plasma ratios. 14C-TDP223206 was the major circulating component in the plasma. A total of 91.2% of administered radioactivity of 14C-TDP223206 was recovered in bile indicating that biliary excretion was the major pathway for drug elimination. 14C-TDP223206-acyl glucuronides were the major metabolites in bile. The oxo- 14C-TDP223206 was the major metabolite in plasma and an important metabolite in bile. Two forms of diastereomeric acyl glucuronides of 14C-TDP223206 were detected in bile with similar LC/MS intensities suggesting a similar biotransformation capacity. Only one form of these 14C-TDP223206-acyl glucuronides was detected in plasma suggesting that enterohepatic recirculation was related to the nature of the stereo-isomers. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Ibudilast in healthy volunteers: safety, tolerability and pharmacokinetics with single and multiple doses

Paul Rolan
WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT , Ibudilast is an oral drug approved in Asia for asthma. , Tolerability of 10-mg regimens has been described previously. , Published pharmacokinetics (PK) are limited: single or 7-day repeat oral administration of 10 mg in healthy male Asian volunteers. WHAT THIS STUDY ADDS , Safety/tolerability and PK of a single 30-mg dose and a 30-mg twice daily (b.i.d.) 2-week regimen in male and female healthy volunteers. , Higher-dose regimens are relevant for testing in new neurological indications. , LC-MS/MS analytics for quantification of plasma and urine levels of ibudilast parent and its primary metabolite (6,7-dihydrodiol-ibudilast). AIMS To investigate the safety, tolerability and pharmacokinetics (PK) of ibudilast after a single-dose and a multiple-dose regimen. METHODS Healthy adult male (n = 9) and female (n = 9) volunteers were evaluated over a 17-day stay in a Phase 1 unit. Subjects were randomized 1 : 3 to either oral placebo or ibudilast at 30-mg single administration followed by 14 days of 30 mg b.i.d. Complete safety analyses were performed and, for PK, plasma and urine samples were analysed for ibudilast and its major metabolite. RESULTS Ibudilast was generally well tolerated. No serious adverse events occurred. Treatment-related adverse events included hyperhidrosis, headache and nausea. Two subjects discontinued after a few days at 30 mg b.i.d. because of vomiting. Although samples sizes were too small to rule out a sex difference, PK were similar in men and women. The mean half-life for ibudilast was 19 h and median Tmax was 4,6 h. Mean (SD) steady-state plasma Cmax and AUC0,24 were 60 (25) ng ml,1 and 1004 (303) ng h ml,1, respectively. Plasma levels of 6,7- dihydrodiol-ibudilast were approximately 30% of the parent. CONCLUSIONS Ibudilast is generally well tolerated in healthy adults when given as a single oral dose of 30 mg followed by 30 mg b.i.d. (60 mg day,1) for 14 days. Plasma PK reached steady state within 2 days of starting the b.i.d. regimen. Exposure to ibudilast was achieved of a magnitude comparable to that associated with efficacy in rat chronic pain models. [source]

The insecticide fipronil and its metabolite fipronil sulphone inhibit the rat ,1,2,2L GABAA receptor


Background and purpose: Fipronil is the active ingredient in a number of widely used insecticides. Human exposure to fipronil leads to symptoms (headache, nausea and seizures) typically associated with the antagonism of GABAA receptors in the brain. In this study, we have examined the modulation of the common brain GABAA receptor subtype by fipronil and its major metabolite, fipronil sulphone. Experimental approach: Whole-cell and single-channel recordings were made from HEK 293 cells transiently expressing rat ,1,2,2L GABAA receptors. Key results: The major effect of fipronil was to increase the rate of current decay in macroscopic recordings. In single-channel recordings, the presence of fipronil resulted in shorter cluster durations without affecting the intracluster open and closed time distributions or the single-channel conductance. The ,1V256S mutation, previously shown alleviate channel inhibition by inhibitory steroids and several insecticides, had a relatively small effect on channel block by fipronil. The mode of action of fipronil sulphone was similar to that of its parent compound but the metabolite was less potent at inhibiting the ,1,2,2L receptor. Conclusions and implications: We conclude that exposure to fipronil induces accumulation of receptors in a novel, long-lived blocked state. This process proceeds in parallel with and independently of, channel desensitization. The lower potency of fipronil sulphone indicates that the conversion serves as a detoxifying process in mammalian brain. British Journal of Pharmacology (2008) 155, 783,794; doi:10.1038/bjp.2008.309; published online 28 July 2008 [source]

Promotion of Skin Carcinogenesis by Dimethylarsinic Acid in Keratin (K6)/ODC Transgenic Mice

CANCER SCIENCE, Issue 6 2000
Takashi Morikawa
Dimethylarsinic acid (DMA) is a major metabolite of inorganic arsenicals in mammals, and arsenic exposure is associated with tumor development in a wide variety of human tissues, particularly the skin. Transgenic mice with ornithine decarboxylase (ODC) targeted to hair follicle keratinocytes are much more sensitive than littermate controls to carcinogens. In this study we investigated the promoting effect of DMA on skin carcinogenesis in such K6/ODC transgenic mice. The back skin of female C57BL/6J K6/ODC transgenic mice, 10 to 14 weeks old, was initiated with topical application of 7,12-dimethylbenz[,]anthracene (DMBA) at a dose of 50 ,g or acetone alone on day 1 of the experiment, followed by treatment with 3.6 mg of DMA, 5 ,g of 12-O-tetradecanoylphorbol-13-acetate (TPA) or neutral vehicle (control) twice a week for 18 weeks. Mice were killed 1 week after the end of the treatment. Induction of skin tumors was significantly accelerated in the DMA-treated group, as well as in the TPA-treated group, indicating that DMA has a promoting effect on skin tumorigenesis in K6/ODC transgenic mice. [source]

In vivo Mutational Analysis of the Mupirocin Gene Cluster Reveals Labile Points in the Biosynthetic Pathway: the "Leaky Hosepipe" Mechanism

CHEMBIOCHEM, Issue 9 2008
Ji'en Wu Dr.
Abstract A common feature of the mupirocin and other gene clusters of the AT-less polyketide synthase (PKS) family of metabolites is the introduction of carbon branches by a gene cassette that contains a ,-hydroxy-,-methylglutaryl CoA synthase (HMC) homologue and acyl carrier protein (ACP), ketosynthase (KS) and two crotonase superfamily homologues. In vivo studies of Pseudomonas fluorescens strains in which any of these components have been mutated reveal a common phenotype in which the two major isolable metabolites are the truncated hexaketide mupirocin H and the tetraketide mupiric acid. The structure of the latter has been confirmed by stereoselective synthesis. Mupiric acid is also the major metabolite arising from inactivation of the ketoreductase (KR) domain of module 4 of the modular PKS. A number of other mutations in the tailoring region of the mupirocin gene cluster also result in production of both mupirocin H and mupiric acid. To explain this common phenotype we propose a mechanistic rationale in which both mupirocin H and mupiric acid represent the products of selective and spontaneous release from labile points in the pathway that occur at significant levels when mutations block the pathway either close to or distant from the labile points. [source]

Reactions of {4-[Bis(2-chloroethyl)amino]phenyl}acetic Acid (Phenylacetic Acid Mustard) with 2,-Deoxyribonucleosides

Diana Florea-Wang
Abstract Phenylacetic acid mustard (PAM; 2), a major metabolite of the anticancer agent chlorambucil (CLB; 1), was allowed to react with 2,-deoxyadenosine (dA), 2,-deoxyguanosine (dG), 2,-deoxycytidine (dC), 2,-deoxy-5-methylcytidine (dMeC), and thymidine (T) at physiological pH (cacodylic acid, 50% base). The reactions were followed by HPLC and analyzed by HPLC/MS and/or 1H-NMR techniques. Although the predominant reaction observed was hydrolysis of PAM, 2 also reacted with various heteroatoms of the nucleosides to give a series of products: compounds 5,31. PAM (2) was found to be hydrolytically slightly more stable than CLB (1). The principal reaction sites of 2 with dA, dG, and with all pyrimidine nucleosides were N(1), N(7), and N(3), resp. Also, several other adducts were detected and characterized. There was no significant difference in the reactivity of 1 and 2 with dG, dA or T, but the N(3) dC,PAM adduct was deaminated easier than the corresponding CLB derivative. The role of PAM,2,-deoxyribonucleoside adducts on the cytotoxic and mutagenic properties of CLB (1) is discussed. [source]

Stereoselective pharmacokinetics of clausenamide enantiomers and their major metabolites after single intravenous and oral administration to rats

CHIRALITY, Issue 8 2003
Chuan Jiang Zhu
Abstract The pharmacokinetics of clausenamide (CLA) enantiomers and their metabolites were investigated in Wistar rat. After intravenous and oral administration at a dose of 80 and 160 mg/kg each enantiomer, plasma concentrations of (,)- or (+)-CLA and its major metabolites were simultaneously determined by reverse-phase HPLC with UV detection. Notably, stereoselective differences in pharmacokinetics were found. The mean plasma levels of (+)-CLA were higher at almost all time points than those of (,)-CLA. (+)-CLA also exhibited greater tmax, Cmax, t1/2,, AUC0,12h, and AUC0,, and smaller CL (or CL/F) and Vd (or Vd/F), than its antipode. The (+)/(,) isomer ratios for t1/2,, tmax, AUC0,12 h, and AUC0,,, which ranged from 1.26 to 2.08. The ratio for CL (or CL/F) was about 0.5, and there were significant differences in these values between CLA enantiomers (P < 0.05), implying that the absorption, distribution, and elimination of (,)-CLA were more rapid than those of (+)-CLA. Similar findings for (,)-7-OH-CLA, the major metabolite of (,)-CLA, and (+)-4-OH-CLA, the major metabolite of (+)-CLA, can be also seen in rat plasma. The contributing factors for the differences in stereoselective pharmacokinetics of CLA enantiomers appeared to be involved in their different plasma protein binding, first-pass metabolism and interaction with CYP enzymes, especially with their metabolizing enzyme CYP 3A isoforms. Chirality 15:668,673, 2003. © 2003 Wiley-Liss, Inc. [source]

Selective antibodies to methadone enantiomers: Synthesis of (R)- and (R,S)-methadone conjugates and determination by an immunoenzymatic method in human serum

CHIRALITY, Issue 4 2001
Nassima Chikhi-Chorfi
Abstract Selective antibodies to (R)-methadone (Mtd) and to its racemate were produced in rabbits by immunization with conjugates of (R)- or (R,S)-hemisuccinyl-methadol-bovine serum albumin, respectively. A hapten was first prepared by reduction of (R)- or (R,S)-Mtd with sodium borohydride, followed by esterification with succinic anhydride. The conjugation of hapten with albumin was achieved by the mixed anhydride method. After immunization of rabbits, the titers and specificity of each antibody were determined by ELISA. The antibodies obtained were tested with (R)-, (S)-, (R,S)-Mtd, its major metabolite (EDDP), and some drugs of abuse (morphine, codeine, cocaine). The sensitivities of antibodies to (R)- and (R,S)-Mtd were about 1 and 2 ng/ml, respectively. Selective (R)-antibodies recognized (R)-Mtd about 40 times more avidly than the (S)-isomer, while an antiserum against (R,S)-Mtd recognized (R)- and (S)-isomers to about the same degree. Both selective antibodies showed little interference (about 0.5%) with EDDP metabolite and no crossreactivity with morphine, codeine, and cocaine. These two selective antibodies were used to develop an immunoenzymatic method (ELISA) for the determination of (R)- and (R,S)-Mtd in serum samples of patients under maintenance treatment for narcotic addiction. Chirality 13:187,192, 2001. © 2001 Wiley-Liss, Inc. [source]

Testosterone and dihydrotestosterone, but not estradiol, enhance survival of new hippocampal neurons in adult male rats

Mark D. Spritzer
Abstract Past research suggested that androgens may play a role in the regulation of adult neurogenesis within the dentate gyrus. We tested this hypothesis by manipulating androgen levels in male rats. Castrated or sham castrated male rats were injected with 5-Bromo-2,deoxyuridine (BrdU). BrdU-labeled cells in the dentate gryus were visualized and phenotyped (neural or glial) using immunohistochemistry. Castrated males showed a significant decrease in 30-day cell survival within the dentate gyrus but there was no significant change in cell proliferation relative to control males, indicating that androgens positively affect cell survival, but not cell proliferation. To examine the role of testosterone on hippocampal cell survival, males were injected with testosterone s.c. for 30 days starting the day after BrdU injection. Higher doses (0.5 and 1.0 mg/kg) but not a lower dose (0.25 mg/kg) of testosterone resulted in a significant increase in neurogenesis relative to controls. We next tested the role of testosterone's two major metabolites, dihydrotestosterone (DHT), and estradiol, upon neurogenesis. Thirty days of injections of DHT (0.25 and 0.50 mg/kg) but not estradiol (0.010 and 0.020 mg/kg) resulted in a significant increase in hippocampal neurogenesis. These results suggest that testosterone enhances hippocampal neurogenesis via increased cell survival in the dentate gyrus through an androgen-dependent mechanism. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source]

Validated capillary electrophoresis assay for the simultaneous enantioselective determination of propafenone and its major metabolites in biological samples

Minoo Afshar
Abstract A robust, inexpensive, and fully validated CE method for the simultaneous determination of the enantiomers of propafenone (PPF), 5-hydroxy-propafenone (5OH-PPF) and N -despropyl-propafenone (NOR-PPF) in serum and in in vitro media is described. It is based upon liquid,liquid extraction at alkaline pH followed by analysis of the reconstituted extract by CE in presence of a pH,2.0 running buffer composed of 100,mM sodium phosphate, 19% methanol, and 0.6% highly sulfated ,-CD. For each compound, the S -enantiomers are shown to migrate ahead of their antipodes, and the overall run time is about 30,min. Enantiomer levels between 25 and 1000,ng/mL provide linear calibration graphs, and the LOD for all enantiomers is between 10 and 12,ng/mL. The assay is shown to be suitable for the determination of the enantiomers of PPF and its metabolites in in vitro incubations comprising human liver microsomes or single CYP450 enzymes (SUPERSOMES). Incubations with CYP2D6 SUPERSOMES revealed, for the first time, the simultaneous formation of the enantiomers of 5OH-PPF and NOR-PPF with that enzyme. CE data can be used for the evaluation of the enzymatic N -dealkylation and hydroxylation rates. [source]

Comparison of methanol and acetonitrile as solvents for the separation of sertindole and its major metabolites by capillary zone electrophoresis

Xavier Subirats
Abstract Sertindole (1-[2-[4-[5-chloro-1-(4-fluorophenyl)-1H -indol-3-yl]-1-piperidinyl]ethyl]-2-imidazolidinone), an atypical antipsychotic drug, was separated by capillary electrophoresis from its two main metabolites norsertindole and dehydrosertindole. The low solubility of the analytes in water (octanol-water partition coefficient is about 105) is overcome by the use of methanol (MeOH) and acetonitrile (ACN) as solvents for the background electrolyte (BGE). Mobilities were measured in BGEs with defined pH in a broad range. It was found that in MeOH the mobility of the analytes is mainly governed by acid,base equilibria, whereas in ACN other reactions like ion pairing and homoconjugation play a pronounced role and lead to a complex pattern of the mobility as function of the pH. However, separation can be obtained in less than 10,min in both solvent systems. [source]

Enantioseparation of warfarin and its metabolites by capillary zone electrophoresis

Qingyu Zhou
Abstract A capillary zone electrophoresis (CZE) method with direct ultraviolet (UV)-absorbance detection is presented for the simultaneous enantiomeric separation of warfarin and its main metabolites, including warfarin alcohols, 4'-, 6-, and 7-hydroxywarfarin, using highly sulfated ,-cyclodextrin (HS-,-CD) as the chiral selector. This chiral separation method was optimized in terms of the electrophoretic parameters, which included the concentration of HS-,-CD used, the type and composition of organic modifier added to the background electrolyte (BGE) buffer, and the BGE buffer pH. Chiral separation of warfarin and its major metabolites was achieved with high resolution, selectivity, efficiency, repeatability, and reproducibility. This optimized chiral analysis of warfarin along with its metabolites was completed within a satisfactory electrophoresis time of 20 min. [source]

Human exposure to heterocyclic amine food mutagens/carcinogens: Relevance to breast cancer ,

James S. Felton
Abstract Heterocyclic amines produced from overcooked foods are extremely mutagenic in numerous in vitro and in vivo test systems. One of these mutagens, 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP), induces breast tumors in rats and has been implicated in dietary epidemiology studies as raising the risk of breast cancer in humans. Efforts in our laboratory and others have centered on defining the exposure to PhIP and other dietary mutagens derived from cooked food. We accomplish this by analyzing the foods with a series of solid-phase extractions and HPLC. We have developed an LC/MS/MS method to analyze the four major human PhIP metabolites (sulfates and glucuronides) following a single meal containing 27 ,g of cooking-produced PhIP in 200 g of grilled meat. Although the intake of PhIP was similar for each of eight women, the total amount excreted in the urine and the metabolite profiles differed among the subjects. It appears that adsorption (digestion) from the meat matrix, other foods in the diet, and genetic differences in metabolism may contribute to the variation. The four major metabolites that can be routinely assayed in the urine are N2 -OH-PhIP- N2 -glucuronide, PhIP- N2 -glucuronide, 4,-PhIP-glucuronide, and N2 -OH-PhIP- N3-glucuronide. This work is suited to investigate individual exposure and risk, especially for breast cancer, from these potent dietary mutagens. Environ. Mol. Mutagen. 39:112,118, 2002. Published 2002 Wiley-Liss, Inc. [source]

Degradation of chlorpyrifos, fenamiphos, and chlorothalonil alone and in combination and their effects on soil microbial activity

Brajesh Kumar Singh
Abstract The effects of repeated application and of combinations of pesticides on their degradation rates in soil and on some soil microbial properties were studied. Repeated application of chlorpyrifos did not modify its degradation rate, whereas repeated applications of fenamiphos and chlorothalonil suppressed their own rates of degradation. When applied in combination, the presence of chlorothalonil reduced the degradation rate of both chlorpyrifos and fenamiphos, and the half-life of chlorothalonil was extended in the presence of chlorpyrifos. The dynamics of residues of the major metabolites of the different compounds were also affected by the pesticide combinations and, particularly, by the presence of chlorothalonil. The measured soil microbial parameters (enzyme activities and total microbial biomass) were stable in the pesticide-free control soils throughout the 90-d incubation period, but they were all adversely affected by the presence of chlorothalonil in the soil. The effects from fenamiphos or chlorpyrifos on the soil microbial characteristics were either very small or insignificant. [source]

Relations of clinical features, subgroups and medication to serum monoamines in schizophrenia

Robert D. Oades
Abstract Background Plasma and serum indices of monoaminergic activity reflect partly the illness of schizophrenia (e.g. HVA/deficit syndrome) and sometimes the symptoms (e.g. HVA/anhedonia). But, such studies have rarely taken both metabolites and parent amines or inter-amine activity ratios into account. We hypothesized that comparing the major symptom dimensions to measures of transmitter activity (with and without control for antipsychotic drug treatment) would show differential patterns of activity useful for the design of pharmacological treatments. Methods Dopamine (DA), noradrenaline (NA), serotonin (5-HT), their three major metabolites and prolactin were measured in the serum of 108 patients with schizophrenia and 63 matched controls: DA D2-receptor blocking-activity was estimated from a regression of butyrophenone displacement in striatum in vitro on to PET reports of drug-binding in vivo. Symptoms were factored into four dimensions (disorganized/thought disorder, nonparanoid/negative, ideas-of-reference and paranoid/positive symptoms). Results (1) Patients' DA activity did not differ from controls: but their 5-HT and NA turnovers increased/decreased, respectively, and the DA/5HT-metabolite ratio was lower. Increased DA-D2-receptor occupancy was predicted by decreased DA-metabolism and its ratio to 5-HT-metabolism. (2) Patients had higher levels of NA, DA-metabolites and DA-/5-HT-metabolite ratios on atypical vs typical drugs. (3) Increased D2-occupancy was associated with lower DA metabolism in paranoid patients but was unrelated to relative increases of DA/5-HT- and NA-metabolism in nonparanoid patients. (4) Low DA-/5-HT-metabolite ratios, high prolactin and low DA-metabolism characterized thought-disordered patients. (5) High DA-/5-HT-metabolite ratios paralleled many ideas-of-reference. The metabolites were sensitive, respectively, to control for D2-occupancy and prolactin. Conclusions The role of DA in paranoid, and 5-HT in thought-disordered and ideas-of-reference dimensions point both to the mechanisms underlying the features typical of these subgroups and the type of medication appropriate. Copyright © 2002 John Wiley & Sons, Ltd. [source]

20-O-,-D-Glucopyranosyl-20 (S)-protopanaxadiol (compound K) induces expression of hyaluronan synthase 2 gene in transformed human keratinocytes and fibroblasts and increases hyaluronan in hairless mouse skin

S. Kim
Ginsenosides, the major active ingredient of ginseng, show a variety of biomedical efficacies such as anti-aging, anti-oxidation and anti-inflammatory activities. To understand the effects of 20-O-,-D-glucopyranosyl-20 (S)-protopanaxadiol (compound K), one of the major metabolites of ginsenosides on the skin, we assessed the expression level of approximately 100 transcripts in compound K-treated HaCaT cells using cDNA microarray analysis. Compound K treatment induced differential expression of 40 genes, which have been reported to be involved in the organization of the structure of the extracellular matrix as well as defense responses in human skin cells. One of the most interesting findings is a two-fold increase in hyaluronan synthase2 (HAS2) gene expression by compound K. We found that change in expression of HAS2 gene represents a specific response of HaCaT cells to compound K because hyaluronan synthase 1,3 was not changed by treatment with compound K. We also demonstrated that the compound K effectively induced hyaluronan synthesis in human skin cells and hairless mouse skin. A human clinical study indicated that topical application of compound K containing oil-in-water emulsion showed improvement of xerosis, wrinkle and fine lines in the aged skin. We concluded that compound K has anti-aging effects by the induction of HAS2 gene expression and following hyaluronan synthase. [source]

Synthesis of five nevirapine metabolites

Karl G. Grozinger
Nevirapine (1) is a non-nucleoside reverse transcriptase inhibitor marketed for HIV treatment by Boehringer Ingelheim as Viramune® since 1996. In vitro studies of nevirapine biotransformation using human liver microsomes demonstrated the formation of five major metabolites. This paper describes the syntheses of these metabolites. [source]