Ipomeanol 4-glucuronide, a major urinary metabolite of 4-ipomeanol in the rat

Urinary excretion and metabolism of 4-ipomeanol was studied in rats injected ip with the radiolabeled compound. There was a rapid elimination of radioactivity in the urine, amounting to 47% of the administrated dose within 4hr. One major metabolite was isolated and purified by HPLC. Analysis by analytical HPLC, beta-glucuronidase hydrolysis, and mass spectrometry identified this material as ipo-meanol 4-glucuronide. The large amount of this metabolite excreted suggests that 4-glucuronidation is an important detoxication reaction in vivo for 4-ipomeanol in rats.

Use of high-performance liquid chromatography-mass spectrometry for the study of the metabolism of ranitidine in man

High-performance liquid chromatography has been used for the qualitative analysis of metabolites and the quantitative analysis of ranitidine in the urine from subjects given oral and intravenous doses of ranitidine. Ranitidine, ranitidine-N-oxide, ranitidine-S-oxide and desmethylranitidine were identified in extracts of the urine obtained by the XAD-methanol procedure. A selected-ion monitoring technique, using [2H3]ranitidine as the internal standard, was used to determine ranitidine. A normal-phase system consisting of methanol-propan-2-ol-5 M ammonium acetate (50:50:1) was used, and because of this the volume of urine which could be injected on-column without deterioration of the chromatography was limited to 10 microliters. This limited the sensitivity of the method to 1.0 microgram of ranitidine per millilitre of urine.

The use of on-line high-performance liquid chromatography-mass spectrometry for the identification of ranitidine and its metabolites in urine

1. Reverse and normal phase h.p.l.c. systems have been developed for separation ranitidine and three metabolites, desmethylranitidine, ranitidine-S-oxide and ranitidine-N-oxide. 2. These h.p.l.c. systems have been evaluated for characterization of ranitidine and metabolites using an h.p.l.c. coupled to a mass spectrometer with a moving belt interface. 3. Ranitidine and its metabolites were thermally degraded under the conditions required to evaporate the reverse phase eluent that contained 40% aq. 0.05 M ammonium acetate. 4. The normal phase eluent was evaporated in the interface at a lower temp. and satisfactory mass spectra were obtained from 1 microgram of ranitidine and each metabolite injected on to the h.p.l.c. column. 5. Normal phase h.p.l.c.-mass spectrometry has been used to identify ranitidine and three of its metabolites in rabbit and human urine obtained after oral administration of ranitidine.

Determination of ranitidine and its metabolites in human urine by reversed-phase ion-pair high-performance liquid chromatography

A method using ion-pair high-performance liquid chromatography is presented for determining ranitidine, ranitidine N-oxide, ranitidine S-oxide and desmethyl ranitidine in the urine from four volunteers, given on separate occasions an intravenous and oral dose of 100 mg ranitidine. This method has been used to study the metabolism and pharmacokinetics of ranitidine by man. It was found that the elimination half-life of ranitidine ranged from 110-246 min. The mean renal clearance of ranitidine in these four volunteers was 512 ml/min.

The definitive identification of the lignans trans-2,3-bis(3-hydroxybenzyl)-gamma-butyrolactone and 2,3-bis(3-hydroxybenzyl)butane-1,4-diol in human and animal urine

The definitive identification of the first lignans to be found in humans and animals is described. Gas chromatography--mass spectrometry, n.m.r. spectroscopy, i.r. spectroscopy and chemical techniques were employed to establish the structures of two lignans as trans-2,3-bis(3-hydroxybenzyl)-gamma-butyrolactone and 2,3-bis(3-hydroxybenzyl)butane-1,4-diol. Both compounds are essetially racemic. Evidence was also found for several methoxy analogues of these lignans in the vervet monkey.

High-pressure liquid chromatographic determination of ranitidine, a new H2-receptor antagonist, in plasma and urine

An assay is described for the determination of a new H2-receptor antagonist, ranitidine, and its desmethyl metabolite in human plasma and urine. Alkalinized plasma or urine was extracted with methylene chloride, the organic phase was evaporated, and the reconstituted residue was analyzed by high-pressure liquid chromatography using a reversed-phase column. Two other identified metabolites of ranitidine, the S-oxide and N-oxide, were separated chromtographically from both ranitidine and the desmethyl metabolite. However, these metabolites could not be quantitative due to poor analytical recovery and interference from endogenous components. The sensitivity limits were 5 ng/ml for ranitidine and 15 ng/ml for desmethylranitidine. Plasma samples from two volunteers who were given oral ranitidine (0.1, 0.2, and 0.4 mg/kg) at 1-week intervals were assayed. Peak levels of 30--130 ng/ml were achieved between 40 and 120 min after dosage, followed by an elimination half-life of 2.9-3.9 hr. Plasma levels of ranitidine were still detectable at 8 hr but were below the sensitivity of the assay by 24 hr. Plasma levels of the desmethyl metabolite were seldom above the threshold sensitivity of the assay. Urinary excretion of unmetabolized ranitidine accounted for 77% of the administered dose, whereas only 4% appeared as desmethylranitidine.

Profiles of volatile metabolities in body fluids

A method for the analysis of volatile metabolites present in plasma, urine, breast milk and amniotic fluid collected from mother-infant pairs has been developed which requires only 100 mul of plasma, 3 ml of urine, 20 mul of breast milk and 500 mul of amniotic fluid. After extraction with diethyl ether, the volatile compounds were absorbed on glass wool in a special concentration tube and subsequently desorbed and transferred to a 100-m nickel capillary column for analysis by gas chromatography and gas chromatography-mass spectrometry. The separations, carried out by temperature programming, were complete in 90 min.

Gas-chromatographic/mass-spectrometric identification and quantitation of tetronic and deoxytetronic acids in urine from normal adults and neonates

Gas chromatographic/mass spectrometric/computer analyses of trimethylsilyl derivatives of urine extracts, prepared by an anion-exchange procedure, reveal the presence of several tetronic and deoxytetronic acids. Identifications were confirmed by comparing gas-chromatographic methylene unit values and mass spectrometric characteristics with those of chemically synthesized samples. In addition, several 1,4-lactones corresponding to the acids were detected in small amounts. The acids were measured in groups of adults and neonates by gas chromatographic/computer determination of peak areas and the use of calculated response factors. In urines from adults, 4-deoxythreonic, threonic, and erythronic acids were present in relatively large amounts. 4-Deoxyerythronic and 2-deoxytetronic acids were present in small to moderate amounts; 3-deoxytetronic and 2-methylglyceric acids were only trace constituents. These latter two acids, in addition to 4-deoxyerythronic, were also trace constituents of several urines from neonates but could not be detected in others. Expressed in terms of creatinine excretion, both groups excreted similar amounts of 4-deoxythreonic acid and neonates excreted significantly more 2-deoxytetronic, erythronic, and threonic acids.