• Biomolecules & Therapeutics
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• v.19 no.2
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• pp.255-260
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• 2011

The purpose of this study was to investigate the effect of ticlopidine on the pharmacokinetics of diltiazem and its active metabolite, desacetyldiltiazem, in rats. Pharmacokinetic parameters of diltiazem and desacetyldiltiazem were determined in rats after oral administration of diltiazem (15 $mg{\cdot}kg^{-1}$) with ticlopidine (3 or 9 $mg{\cdot}kg^{-1}$). The effects of ticlopidine on P-glycoprotein (P-gp) and cytochrome P450 (CYP) 3A4 activities were also evaluated. Ticlopidine inhibited CYP3A4 enzyme activity in a concentrationdependent manner with a 50% inhibition concentration ($IC_{50}$) of 35 ${\mu}M$. In addition, ticlopidine did not significantly enhance the cellular accumulation of rhodamine-123 in NCI/ADR-RES cells overexpressing P-gp. Compared with the control (given diltiazem alone), ticlopidine significantly altered the pharmacokinetic parameters of diltiazem. The peak concentration ($C_{max}$) and the area under the plasma concentration-time curve (AUC) of diltiazem were significantly (9 $mg{\cdot}kg^{-1}$, p<0.05) increased in the presence of ticlopidine. The AUC of diltiazem was increased by 1.44-fold in rats in the presence of ticlopidine (9 $mg{\cdot}kg^{-1}$). Consequently, the absolute bioavailability (A.B.) of diltiazem in the presence of ticlopidine (9.3-11.5%) was signifi cantly higher (9 $mg{\cdot}kg^{-1}$, p<0.05) than that in the control group (8.0%). Although ticlopidine significantly (p<0.05) increased the AUC of desacetyldiltiazem, the metabolite-parent AUC ratio (M.R.) in the presence of ticlopidine (9 $mg{\cdot}kg^{-1}$) was significantly decreased compared to that in the control group, implying that ticlopidine could effectively inhibit the metabolism of diltiazem. In conclusion, the concomitant use of ticlopidine significantly enhanced the oral bioavailability of diltiazem in rats by inhibiting CYP3A4-mediated metabolism in the intestine and/or liver rather than by inhibiting intestinal P-gp activity or renal elimination of diltiazem.

• Archives of Pharmacal Research
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• v.19 no.6
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• pp.475-479
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• 1996

Diethylcarbamazine (DEC, 1-diethylcarbamyl-4-methylpiperazine) is an antiparasitic piperazine derivative used in the treatment of lymphatic filariasis caused by Wuchereria bancrofti, Brugia malayi or grugia timori. DEC-N-oxide is a major metabolite in humans and has antifilarial activity. In carrying out pharmacokinetic studies, gas chromatographic analysis of DEC in plasma can be complicated by the presence of the metabolite, since the thermally unstable DEC-N-oxide is converted back to a material which coelutes with DEC under the conditions of the analysis. We now report a method to separate DEC-N-oxide from DEC in plasma using solid phase extraction with subsequent gas chromatographic analysis using a nitrogen specific detector. One-diethylcarbamyl-4-ethylpiperazine (E-DEC) was the internal standard. The standard curve of DEC was linear in the range of 10 to 200 ng/ml as described by Y=0.0350+0.0128X, $R^2=0.999$. The limit of quantitation was 4 ng/mL. Reproducibility at 10, 100 and 200 ng/mL concentration points of the standard curve gave coefficient variations of 6.1%, 7.8% and 1.6%, respectively. The recovery following solid phase extraction was 99.3% for DEC and 94.8% for the internal standard. This sensitive and specific analytical method is suitable for pharmacokinetic studies of DEC.

• Journal of Biomedical and Translational Research
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• v.19 no.4
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• pp.130-139
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• 2018

This study aimed to analyze a high-performance liquid chromatography (HPLC) separation using a pentafluorophenyl column of parent drug hydroxychloroquine (HCQ) and its active metabolite, desethylhydroxchloroquine (DHCQ) applying to determine bioequivalence of two different formulations administered to patients. A rapid, simple, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for bioanalysis of HCQ and its metabolite DHCQ in human whole blood using deuterium derivative $hydroxychloroquine-D_4$ as an internal standard (IS). A triple-quadrupole mass spectrometer was operated using electrospray ionization in multiple reaction monitoring (MRM) mode. Sample preparation involves a two-step precipitation of protein techniques. The removed protein blood samples were chromatographed on a pentafluorophenyl (PFP) column ($50mm{\times}4.6mm$, $2.6{\mu}m$) with a mobile phase (ammonium formate solution containing dilute formic acid) in an isocratic mode at a flow rate of 0.45 mL/min. The standard curves were found to be linear in the range of 2 - 500 ng/mL for HCQ; 2 - 2,000 ng/mL for DHCQ in spite of lacking a highly sensitive MS spectrometry system. Results of intra- and inter-day precision and accuracy were within acceptable limits. A run time of 2.2 min for HCQ and 2.03 min for DHCQ in blood sample facilitated the analysis of more than 300 human whole blood samples per day. Taken together, we concluded that the assay developed herein represents a highly qualified technology for the quantification of HCQ in human whole blood for a parallel design bioequivalence study in a healthy male.

• Analytical Science and Technology
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• v.17 no.4
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• pp.322-336
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• 2004

The improved derivatization technique of tamoxifen metabolite in human urine is described for the acylation method that they are substituted by derivatization reagent like acyl anhydride for use of gas chromatography/mass spectrometry. The hydroxyl group of tamoxifen metabolite was derivatized by trifluoroacetic anhydride (TFAA), pentafluoroacetic anhydride (PFPA) and heptaflorobutylic anhydride (HFBA). It was investigated to the gas chromatography/mass spectrometry (GC/MS) technique use negative ion chemical ionization (NCI), positive ion chemical ionization (PCI) and electron impact (EI). In acylation of the metabolites of tamoxifen, the effective reaction temperature and time were shown to be at $50^{\circ}C$ for 30 min. The 4-hydroxytamoxifen, which is known to major metabolite of tamoxifen, was not detected in human urine, whileas the hydroxymethoxytamoxifen was detected. We thought that this result was from the single dose of tamoxifen.

• Toxicological Research
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• v.5 no.1
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• pp.9-15
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• 1989

The effect of butylated hydroxytoluene (BHT) and its major metabolite, 3, 5-di-tert-butyl-4-hydroxybenzoic acid (BHT-acid) on the uptake of taurocholate into hepatocytes was studied using the primary culture of rat hepatocytes. Hepatocyte were isolated by an in situ collagenase perfusion technique and maintained as a monolayer in serum-free meadia for 24 hours before use. The uptake of taurocholate was saturable with an apparent Km of 12.8+2.8 MuM and Vmax of 0.18+0.01 nmol/mg/min. Both BHT and BHT-acid inhibited the hepatocellular uptake of taurocholate when they were added to the culture.

• Journal of Ginseng Research
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• v.38 no.3
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• pp.203-207
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• 2014

Background: There is limited understanding of the effect of dietary components on the absorption of ginsenosides and their metabolites into the blood. Methods: This study investigated the pharmacokinetics of the ginseng extract and its main constituent ginsenoside Rb1 in rats with or without pretreatment with a prebiotic fiber, NUTRIOSE, by liquid chromatography tandem mass spectrometry. When ginsenoside Rb1 was incubated with rat feces, its main metabolite was ginsenoside Rd. Results: When the intestinal microbiota of rat feces were cultured in vitro, their ginsenoside Rd-forming activities were significantly induced by NUTRIOSE. When ginsenoside Rb1 was orally administered to rats, the maximum plasma concentration (Cmax) and area under the plasma drug concentratione-time curve (AUC) for the main metabolite, ginsenoside Rd, were $72.4{\pm}31.6ng/mL$ and $663.9{\pm}285.3{\mu}g{\cdot}h/mL$, respectively. When the ginseng extract (2,000 mg/kg) was orally administered, Cmax and AUC for ginsenoside Rd were $906.5{\pm}330.2ng/mL$ and $11,377.3{\pm}4,470.2{\mu}g{\cdot}h/mL$, respectively. When ginseng extract was orally administered to rats fed NUTRIOSE containing diets (2.5%, 5%, or 10%), Cmax and AUC were increased in the NUTRIOSE receiving groups in a dose-dependent manner. Conclusion: These findings reveal that intestinal microflora promote metabolic conversion of ginsenoside Rb1 and ginseng extract to ginsenoside Rd and promote its absorption into the blood in rats. Its conversion may be induced by prebiotic diets such as NUTRIOSE.

• The Korean Journal of Pharmacology
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• v.31 no.2
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• pp.165-177
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• 1995

Dissociated cell cultures from rat embryonic ventral mesencephalon were used to evaluate the mechanisms of $MPP^+$ neurotoxicity. The cells were treated with MPTP or $MPP^+$ and the viability of the cells was assessed biochemically; tyrosine hydroxylase (TH) immunoreactivity, protein, intracellular ATP and lactate content and lipid peroxidation. Also the generation of the intracellular oxidants was measured after loading 2', 7‘-dichlorofluorescin diacetate to the cells. When cultures were exposed to 0.1 mM $MPP^+$, at 2 hour incubation lactate was significantly accumulated in the cells and then the intracellular ATP content and TH immunoreactivity were decreased dose- and time-dependently. But, malondialdehyde as an index for lipid peroxidation was not changed even though the generation of the intracellular oxidants was stimulated by the addition of $MPP^+$. On the other hand, 1 mM MPTP significantly reduced the TH immunoreactivity at 24 hour exposure without any change in the intracellular A TP, lactate and MDA content until 6 hour exposure. And also MPTP inhibited the generation of the intracellular oxidants from control cells and $MPP^+$ exposed cells. These results indicate that cytotoxicity of $MPP^+$ is mediated by inhibiting the mitochondrial energy metabolism rather than generating the intracellular oxidants. And MPTP would have direct action in addition to conveting to the toxic metabolite, $MPP^+$ to exert the toxicity on the dopaminergic neurons.

• Archives of Pharmacal Research
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• v.25 no.5
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• pp.647-651
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• 2002

An LC/MS/MS method for the simultaneous determination of a neuroprotective agent for ischemia-reperfusion damage, KR-31378 and its N-acetyl metabolite KR-31612 in human plasma was developed. KR-31378, KR-31612 and the internal standard. KR-31543 were extracted from human plasma by liquid-liquid extraction. A reverse-phase HPLC separation was performed on Luna phenylhexyl column with the mixture of acetonitrile-5 mM ammonium formate (55:45, v/v) as mobile phase. The detection of analytes was performed using an electrospray ionization tandem mass spectrometry in the multiple reaction monitoring mode. The lower limits of quantification for KR-31378 and KR-31612 were 2.0 ng/ml. The method showed a satisfactory sensitivity, precision, accuracy, recovery and selectivity.

• Mycobiology
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• v.42 no.4
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• pp.353-360
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• 2014

Makgeolli is a traditional Korean alcoholic beverage. The flavor of makgeolli is primarily determined by metabolic products such as free sugars, amino acids, organic acids, and aromatic compounds, which are produced during the fermentation of raw materials by molds and yeasts present in nuruk, a Korean fermentation starter. In this study, makgeolli was brewed using the wild yeast strain Saccharomyces cerevisiae Y98-5, and temporal changes in the metabolites during fermentation were analyzed by ultra-high-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry. The resultant data were analyzed by partial least squares-discriminant analysis (PLS-DA). Various metabolites, including amino acids, organic acids, sugar alcohols, small peptides, and nucleosides, were obviously altered by increasing the fermentation period. Changes in these metabolites allowed us to distinguish among makgeolli samples with different fermentation periods (1, 2, 3, 6, 7, and 8 days) on a PLS-DA score plot. In the makgeolli brewed in this study, the amounts of tyrosine ($463.13{\mu}g/mL$) and leucine ($362.77{\mu}g/mL$) were high. Therefore, our results indicate that monitoring the changes in metabolites during makgeolli fermentation might be important for brewing makgeolli with good nutritional quality.

• Microbiology and Biotechnology Letters
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• v.23 no.1
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• pp.24-30
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• 1995

The effects of amino acids in growth media on the biosynthesis of Serratia marcescens biodegradative threonine dehydratase activity were examined. The enzyme activity was decreased by 44 and 34% by 10 mM isoleucine and valine, respectively, whereas it was increased approximately by 20% by 10 mM threonine. Among several metabolites tested, pyruvate increased the enzyme activity by 60% at 5 mM, but decreased the enzyme activity approximately by 20 to 70% above 20 mM. The enzyme activity was increased by 64% by 5 mM glyoxylate, whereas it decreased the enzyme activity approximately by 40 to 70% above 20 mM glyoxylate. The thiamine, monopyrrole derivative, also increased the enzyme activity by 84% at 50 $\mu $g/ml, but did not affected the enzyme activity above 300 $\mu $g/ml. cAMP increased the enzyme activity by 58% at 0.5 mM, but decreased the enzyme activity by 15% at 2 mM. These data suggested that the biosynthesis of Serratia marcescens biodegradative threonine dehydratase is regulated by concentrations of pyruvate, glyoxylate and cAMP.