Displaying publications 1 - 20 of 686 in total

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  1. Jones CR, Ovenell SM
    J. Chromatogr., 1979 Jun 11;163(2):179-85.
    PMID: 541369
    A high-performance liquid chromatographic method was developed to enable dapsone, monoacetyl dapsone and pyrimethamine to be measured simultaneously in plasma samples from volunteers in England and Malaysia who had been dosed with Maloprim. Mean half-lives of 25 and 80 h were calculated for dapsone and pyrimethamine, respectively, but there was wide individual variation. All subjects were found to be classifiable as "slow acetylators".
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods*
  2. Lacombe C, Arous N, Pontet F, Blouquit Y, Bardakdjian J, Riou J, et al.
    Hemoglobin, 1987;11(2):173-6.
    PMID: 3114176
    Matched MeSH terms: Chromatography, High Pressure Liquid
  3. Sim SM, Back DJ, Breckenridge AM
    Br J Clin Pharmacol, 1991 Jul;32(1):17-21.
    PMID: 1909542
    1. Zidovudine (3'-azido-3'-deoxythymidine; AZT) is the drug of proven efficacy available for the treatment of patients with AIDS or ARC. It is eliminated mainly by hepatic glucuronidation. Therefore, interference with this metabolic pathway may lead to enhancement of AZT effect or to increased toxicity of the drug. We have examined the effect of a number of drugs which themselves undergo glucuronidation on AZT conjugation by human liver microsomes in vitro. 2. AZT glucuronidation followed Michaelis-Menten kinetics. The apparent Km and Vmax values (mean +/- s.d., n = 5), were 2.60 +/- 0.52 mM and 68.0 +/- 23.4 nmol h-1 mg-1, respectively, as determined from Eadie-Hofstee plots. 3. Dideoxyinosine, sulphanilamide and paracetamol were essentially non-inhibitory at concentrations up to 10 mM (4 times the concentration of AZT in the incubation). The most marked inhibitory effects were seen with indomethacin, naproxen, chloramphenicol, probenecid and ethinyloestradiol, with enzyme activity decreased by 97.7, 94.9, 88.7, 83.4% and 79.0%, respectively, at a concentration of 10 mM. Other compounds producing some inhibition of AZT conjugation were oxazepam, salicylic acid and acetylsalicylic acid. 4. Further studies are necessary to characterise the inhibition observed but the method described enables a screen of potentially important drug interactions to be carried out.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  4. Pang T, Devi S, Puthucheary S, Pawlowski N
    Microbiol. Immunol., 1991;35(3):267-71.
    PMID: 1870442
    Mouse macrophages pre-labeled with [3H]arachidonic acid (20:4) were shown to release metabolites generated by the lipoxygenase and cyclo-oxygenase pathways following in vitro addition of heat-killed Salmonella typhi. These metabolites were maximally released after 60-90 min of incubation and consisted of prostaglandins (85%), leukotriene C (6%), di-HETEs, leukotrienes D and E (4%), mono-HETEs (2%) and other metabolites (3%). Of the metabolites generated by the cyclo-oxygenase pathway (prostaglandins), 6-keto PGF1 alpha and PGE2 were generated at a ratio of 1.2 to 1. The significance and importance of these results are discussed.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  5. Tan GH, Chong CL
    Environ Monit Assess, 1993 Feb;24(3):267-77.
    PMID: 24227384 DOI: 10.1007/BF00545983
    The Klang River Basin is located in the most densely populated region in Malaysia, with its heavy concentration of industries and population. A systematic study of the pollution to this river system caused by phenolic compounds have been carried out under this project. Analyses of water samples from the Klang River by high performance liquid chromatography (HPLC) with an ultraviolet (UV) detector at 280 nm have shown the presence of some priority phenolic pollutants.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  6. Yuen KH, Desmukh AA, Newton JM
    Pharm Res, 1993 Apr;10(4):588-92.
    PMID: 8483843
    A novel multiparticulate sustained-release theophylline formulation, which consisted of spherical drug pellets coated with a rate-controlling membrane, was evaluated in vivo. Two preparations that differ solely in the coat thickness, and hence rate of in vitro drug release, were studied in comparison with a solution of the drug. Both preparations produced serum concentration profiles that are reflective of a slow and sustained rate of absorption. The in vivo release versus time profiles calculated using a deconvolution procedure showed that the two preparations differed in the rate but not the extent of drug release. Satisfactory correlation was also obtained between the in vivo and the in vitro results. When the two preparations were further compared using the parameters, time to reach peak concentration (Tp), peak concentration (Cp), and total area under the serum concentration versus time curves (AUC), a statistically significant difference was observed in the Tp and Cp values but not the AUC values, suggesting that the preparations differed in the rate but not the extent of absorption. In addition, the extent of absorption from both preparations was comparable to that obtained with the drug solution.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  7. Ramanathan S, Nair NK, Mansor SM, Navaratnam V
    J. Chromatogr., 1993 Jun 02;615(2):303-7.
    PMID: 8335708
    A rapid and selective high-performance liquid chromatographic assay for simultaneous quantitative determination of a new antifilarial drug (UMF-058, I) and mebendazole (MBZ) is described. After a simple extraction from whole blood, both compounds were analysed using a C18 Nova Pak reversed-phase column and a mobile phase of methanol-0.05 M ammonium dihydrogenphosphate (50:50, v/v) adjusted to pH 4.0, with ultraviolet detection at 291 nm. The average recoveries of I and MBZ over a concentration range of 25-250 ng/ml were 92.0 +/- 7.7 and 84.4 +/- 4.4%, respectively. The minimum detectable concentrations in whole blood for I and MBZ were 7 and 6 ng/ml, respectively. This method was found to be suitable for pharmacokinetic studies.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  8. Malini M, Kwan TK, Perumal R
    Biochem. Mol. Biol. Int., 1994 Feb;32(2):279-90.
    PMID: 8019433
    In vivo studies involved monitoring the effect of morphine administration on catecholamine biosynthesis by the brain while in vitro studies involved studying the effect of morphine on the uptake of tritiated tyrosine by synaptosomes and its subsequent incorporation into the catecholamines. The extremely low levels of these endogenous compounds required the use of High Performance Liquid Chromatography with electrochemical detection. Intra-peritoneal injection of morphine at a dosage of 10 mg/kg did not produce appreciable changes in the catecholamine levels but a dosage of 30 mg/kg morphine was found to elevate dihydroxy phenylacetic acid content. At a dosage of 60 mg/kg, dopamine levels were elevated while noradrenaline was depleted. Morphine, at a concentration of 1 x 10(-5)M increases the incorporation of tritiated tyrosine into dopamine and dihydroxy phenylacetic acid in synaptosomal preparations.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  9. Ramanathan S, Nair NK, Mansor SM, Navaratnam V
    J Chromatogr B Biomed Appl, 1994 May 13;655(2):269-73.
    PMID: 8081473
    A rapid and selective high-performance liquid chromatographic (HPLC) method for the simultaneous determination of the antifilarial drug UMF-078 (I) and its metabolites UMF-060 (II) and flubendazole (III) is described. After a simple extraction from whole blood, the compounds were determined by HPLC using a C18 Inertsil ODS-2 reversed-phase column with methanol-0.05M ammonium acetate (pH 4.0) as the mobile phase and ultraviolet detection at 291 nm. The average recoveries of I, II and III over the concentration range 20-500 ng ml-1 were 69.9 +/- 4.7, 85.6 +/- 4.4 and 85.1 +/- 6.0%, respectively. The minimum detectable concentrations in whole blood for I, II and III were 10, 7 and 7 ng ml-1, respectively. This method was found to be suitable for pharmacokinetic studies.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods*; Chromatography, High Pressure Liquid/statistics & numerical data
  10. Usup G, Kulis DM, Anderson DM
    Nat. Toxins, 1994;2(5):254-62.
    PMID: 7866660
    Toxin production of a Malaysian isolate of the toxic red tide dinoflagellate Pyrodinium bahamense var. compressum was investigated at various stages of the batch culture growth cycle and under growth conditions affected by temperature, salinity, and light intensity variations. In all the experiments conducted, only 5 toxins were ever detected. Neosaxitoxin (NEO) and gonyautoxin V (GTX5) made up 80 mole percent or more of the cellular toxin content and saxitoxin (STX), GTX6 and decarbamoylsaxitoxin (dcSTX) made up the remainder. No gonyautoxins I-IV or C toxins were ever detected. In nutrient-replete batch cultures, toxin content rapidly peaked during early exponential phase and just as rapidly declined prior to the onset of plateau phase. Temperature had a marked effect on toxin content, which increased 3-fold as the temperature decreased from the optimum of 28 degrees C to 22 degrees C. Toxin content was constant at salinities of 24% or higher, but increased 3-fold at 20%. Toxin content decreased 2-fold and chlorophyll content increased 3-fold when light intensity was reduced from 90 to 15 microE m-2 s-1. This accompanied a 30% decrease in growth rate. Toxin composition (mole % individual toxin cell-1) remained constant throughout the course of the nutrient-replete culture and during growth at various salinities, but varied significantly with temperature and light intensity changes. At 22 degrees C, GTX5 was 25 mole % and NEO was 65 mole %, while at 34 degrees C, GTX5 increased to 55 mole % and NEO decreased proportionally to 40 mole %. When light intensity was reduced from 90 to 15 microE m-2 s-1, NEO decreased from 55 to 38 mole %, while GTX5 increased from 40 to 58 mole %. These data suggest that low light and high temperature both somehow enhance sulfo-transferase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
    Matched MeSH terms: Chromatography, High Pressure Liquid
  11. Harrison LJ, Sia GL, Sim KY, Tan HT, Connolly JD, Lavaud C, et al.
    Phytochemistry, 1995 Apr;38(6):1497-500.
    PMID: 7786481
    A novel derivative of sucrose, beta-(3,6-di-O-feruloyl)-fructofuranosyl-alpha-(2,3,4,6-tetra-O-ac etyl)- glucopyranoside, was isolated from the wood of Bhesa paniculata. Its structure was determined by a combination of 2D 1H-1H and 1H-13C correlation NMR spectroscopy. The known compounds, glycerol 1-9',12'-octadecadienoate, beta-sitosterol, (+/-)-pinoresinol, methyl 3,4-dihydroxybenzoate, 4-hydroxy-3-methoxybenzoic acid, anofinic acid and 2-(1'-methylethenyl)-benzofuran-5-carboxylic acid were also isolated.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods
  12. Navaratnam V, Mansor SM, Chin LK, Mordi MN, Asokan M, Nair NK
    J Chromatogr B Biomed Appl, 1995 Jul 21;669(2):289-94.
    PMID: 7581905
    A selective reproducible high-performance liquid chromatographic assay for the simultaneous quantitative determination of the antimalarial compound artemether (ARM), dihydroartemisinin (DQHS) and artemisinin (QHS), as internal standard, is described. After extraction from plasma, ARM and DQHS were analysed using a Lichrocart/Lichrosphere 100 CN stainless-steel column and a mobile phase of acetonitrile-0.05 M acetic acid (15:85, v/v) adjusted to pH 5.0, and electrochemical detection in the reductive mode. The mean recovery of ARM and DQHS over a concentration range of 30-120 ng/ml was 81.6% and 93.4%, respectively. The within-day coefficients of variation were 0.89-7.01% for ARM and 3.45-8.11% for DQHS. The day-to-day coefficients of variation were 2.06-8.43% and 3.22-6.33%, respectively. The minimum detectable concentration for ARM and DQHS in plasma was 2.5 and 1.25 ng/ml for both compounds. The method was found to be suitable for use in clinical pharmacological studies.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods*
  13. Zakiah I, Ashikin YN, Aisiah SM, Ismail HI
    PMID: 8629092
    The Malaysian level of health care has greatly improved so that many of the infectious diseases are now under control. However, perinatal death or death due to unknown childhood diseases remains high (10.3%) being second on the list of causes of death amongst Malaysians. Could inborn metabolic diseases be the main cause of death among these children? Recently, with our success in the development of confirmatory techniques for amino acid disorders using high performance liquid chromatography (HPLC), we have examined 404 samples received from all over the country in 1993. Each specimen with abnormal findings from screening tests by one-dimensional thin layer chromatography was confirmed using HPLC. 41% had generalized aminoacidurias and 4.2% had maple syrup urine disease (MSUD). Patients were aged between 11 days to 6 years. Most of them were Malay males and presented with a history suggestive of MSUD. With this preliminary finding, further studies will be carried out in order to have an investigation and management protocol for the diseases and more importantly to formulate a strategy of screening for the country.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods
  14. Yahya NA, Ismail Z, Embong KH, Mohamad SA
    PMID: 8629091
    High performance liquid chromatography (HPLC) with phenylisothiocyanate (PITC) is recently used for confirming the diagnosis of inborn errors of metabolism (IEM) especially amino acid disorders in Malaysian children. The method of HPLC used is a precolumn derivatization of amino acids with phenylisothiocyanate and is separated by reversed phase chromatography using 3.9 x 300 mm free amino acid columns and is detected by a UV/Vis detector. The samples are obtained from cases suspected of inborn errors of metabolism, especially of amino acid disorders, which are detected clinically by pediatricians. Initially, samples from patients suspected of inborn errors of metabolism, either urine or serum, are run on one-dimensional thin layer chromatography and supplementary chemical tests to detect the abnormal bands and associated abnormalities respectively. Positive samples are further run on HPLC to determine the specific amino acids abnormality. An examples of a case of maple syrup urine disease is discussed, based on the thin layer chromatography findings and HPLC findings.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods
  15. Mansor SM, Navaratnam V, Yahaya N, Nair NK, Wernsdorfer WH, Degen PH
    J Chromatogr B Biomed Appl, 1996 Jul 12;682(2):321-5.
    PMID: 8844426
    A rapid and selective high-performance liquid chromatographic assay for determination of a new antimalarial drug (benflumetol, BFL) is described. After extraction with hexane-diethyl ether (70:30, v/v) from plasma, BFL was analysed using a C18 Partisil 10 ODS-3 reversed-phase stainless steel column and a mobile phase of acetonitrile-0.1 M ammonium acetate (90:10, v/v) adjusted to pH 4.9 with ultraviolet detection at 335 nm. The mean recovery of BFL over a concentration range of 50-400 ng/ml was 96.8 +/- 5.2%. The within-day and day-to-day coefficients of variation were 1.8-4.0 and 1.8-4.2%, respectively. The minimum detectable concentration in plasma for BFL was 5 ng/ml with a C.V. of less than 10%. This method was found to be suitable for clinical pharmacokinetic studies.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods*
  16. Chan KL, Yuen KH, Jinadasa S, Peh KK, Toh WT
    Planta Med, 1997 Feb;63(1):66-9.
    PMID: 9063097
    A high-performance liquid chromatography assay equipped with a glassy carbon electrode for electrochemical detection (HPLC-ECD) was developed at reductive mode for the analysis of artemisinin, the antimalarial drug from Artemisia annua (Asteraceae) in human plasma. This method was selective, sensitive, and produced satisfactory recovery, precision, and accuracy. Analysis of plasma samples from 8 male volunteers given 10 mg kg-1 of artemisinin orally as an aqueous suspension showed a mean peak plasma concentration (Cmax) of 580.89 ng ml-1 +/- 88.64 SD at 2.5 h +/- 0.5 SD after dosing, and the mean area under the plasma concentration-time curve (AUC0-infinity) was 2227.57 ng h ml-1 +/- 677.22 SD. In addition, the elimination rate constant (Ke), elimination half-life (t1/2), and apparent volume of distribution (Vd) were calculated to be 0.2971 h-1 +/- 0.0644 SD, 2.42 h +/- 0.46 SD, and 16.26 l kg-1 +/- 3.44 SD, respectively.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods*
  17. Jayaraman SD, Ismail S, Nair NK, Navaratnam V
    J Chromatogr B Biomed Sci Appl, 1997 Mar 07;690(1-2):253-7.
    PMID: 9106050
    A method is described for the determination of pyronaridine in plasma using high-performance liquid chromatography with fluorescence detection. The method involves liquid-liquid extraction with phosphate buffer (pH 6.0, 0.05 M) and diethyl ether-hexane (70:30%, v/v) and chromatographic separation on a C18 column (Nucleosil, 250 x 4.6 mm I.D., 5 microns particle size) with acetonitrile-0.05 M phosphate buffer pH 6.0 (60:40%, v/v) as the mobile phase (1 ml/min) and detection by fluorescence (lambda ex = 267 nm, lambda em = 443 nm). The detector response is linear up to 1000 ng and the overall recoveries of pyronaridine and quinine were 90.0 and 60.3%, respectively. The assay procedure was adequately sensitive to measure 10 ng/ml pyronaridine in plasma samples with acceptable precision (< 15% C.V.). The method was found to be suitable for use in clinical pharmacological studies.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  18. Mordi MN, Mansor SM, Navaratnam V, Wernsdorfer WH
    Br J Clin Pharmacol, 1997 Apr;43(4):363-5.
    PMID: 9146847
    AIMS: To determine the pharmacokinetics of artemether (ARM) and its principal active metabolite, dihydroartemisinin (DHA) in healthy volunteers.

    METHODS: Six healthy male Malaysian subjects were given a single oral dose of 200 mg artemether. Blood samples were collected to 72 h. Plasma concentrations of the two compounds were measured simultaneously by reversed-phase h.p.l.c. with electro-chemical detection in the reductive mode.

    RESULTS: Mean (+/- s.d.) maximum concentrations of ARM, 310 +/- 153 micrograms l-1, were reached 1.88 +/- 0.21 h after drug intake. The mean elimination half-life was 2.00 +/- 0.59 h, and the mean AUC 671 +/- 271 micrograms l-1 h. The mean Cmax of DHA, 273 +/- 64 micrograms l-1 was observed at 1.92 +/- 0.13 h. The mean AUC of DHA was 753 +/- 233 micrograms h l-1'. ARM and DHA were stable at < or = -20 degrees C for at least 4 months in plasma samples.

    CONCLUSIONS: The relatively short half-life of ARM may be one of the factors responsible for the poor radical cure rate of falciparum malaria with regimens employing daily dosing. In view of the rapid loss of DHA in plasma samples held at room temperature (26 degrees C) it is recommended to store them at a temperature of < or = -20 degrees C as early as possible after sample collection.

    Matched MeSH terms: Chromatography, High Pressure Liquid
  19. Navaratnam V, Mordi MN, Mansor SM
    J Chromatogr B Biomed Sci Appl, 1997 Apr 25;692(1):157-62.
    PMID: 9187395
    A selective reproducible high-performance liquid chromatographic assay for the simultaneous quantitative determination of the antimalarial compound artesunic acid (ARS), dihydroartemisinin (DQHS) and artemisinin (QHS), as internal standard, is described. After extraction from plasma, ARS and DQHS were analysed using an Econosil C8 column and a mobile phase of acetonitrile-0.05 M acetic acid (42:58, v/v) adjusted to pH 5.0 and electrochemical detection in the reductive mode. The mean recovery of ARS and DQHS over a concentration range of 50-200 ng/ml was 75.5% and 93.5%, respectively. The within-day coefficients of variation were 4.2-7.4% for ARS and 2.6-4.9% for DQHS. The day-to-day coefficients of variation were 1.6-9.6% and 0.5-8.3%, respectively. The minimum detectable concentration for ARS and DQHS in plasma was 4.0 ng/ml for both compounds. The method was found to be suitable for use in clinical pharmacological studies.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  20. Peh KK, Yuen KH
    J Chromatogr B Biomed Sci Appl, 1997 May 23;693(1):241-4.
    PMID: 9200543
    A simple high-performance liquid chromatographic method using fluorescence detection was developed for the determination of acyclovir in human plasma. The method entailed direct injection of the plasma sample after deproteination. It is both specific and sensitive with a detection limit of 30 ng/ml at a signal-to-noise ratio of 3:1, and is thus suitable for use in pharmacokinetic studies of acyclovir. The method had a mean absolute recovery of 96%, while the within-day and between-day coefficients of variation and percentages error were all less than 8%. The calibration curve was linear over a concentration range of 62.5-4000 ng/ml.
    Matched MeSH terms: Chromatography, High Pressure Liquid
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