Journal of Chromatography B: Biomedical Sciences and Applications最新文献

An RP-HPLC method with photodiode array detection was established for the determination of major constituents (rutin, hyperoside, isoquercitrin, quercitrin, quercetin, pseudohypericin, hyperforin and hypericin) in St. John’s Wort dietary supplements. The samples were extracted with methanol by means of sonication in low temperature. The extraction was rapid, with two steps of sonication (30 min each) recovering more than 99% of the major constituents in St. John’s Wort samples. The major components were separated by RP-18 chromatography column using a 60-min water–acetonitrile–methanol–trifluoroacetic acid gradient. The quantification was performed by using external standards. Sample preparation and stability of methanolic extract of St. John’s Wort were extensively explored. It is worth noting that the major constituents in the methanolic extract of St John’s Wort, especially hypericin and pseudohypericin, might be retained by some filter cartridges during the filtration. The current method may serve as a valuable tool for the QA/QC of St. John’s Wort dietary supplements.

A liquid chromatographic procedure with electrospray ionization tandem mass spectrometric detection has been developed and validated for LSD and iso-LSD determination. A one-step liquid–liquid extraction on 1 ml blood or urine was used. The lower limit for quantitative determination was 0.02 μg/l for LSD and iso-LSD. The analytical procedure has been applied in two positive cases (case 1: LSD=0.31 μg/l, iso-LSD=0.27 μg/l in plasma and LSD=1.30 μg/l, iso-LSD=0.82 μg/l in urine; case 2: LSD=0.24 μg/l, iso-LSD=0.6 μg/l in urine). LSD metabolism was investigated using MS–MS neutral loss monitoring for the screening of potential metabolites. The main metabolite was 2-oxo-3-hydroxy-LSD (O–H–LSD) present in urine at the concentrations of 2.5 μg/l and 6.6 μg/l, respectively, for case 1 and 2, and was not present in plasma. Nor-LSD was also found in urine at 0.15 and 0.01 μg/l levels. Nor-iso-LSD, lysergic acid ethylamide (LAE), trioxylated-LSD, lysergic acid ethyl-2-hydroxyethylamide (LEO) and 13 and 14-hydroxy-LSD and their glucuronide conjugates were detected in urine using specific MS–MS transitions.

A chiral separation using carboxymethyl-β-cyclodextrin and methyl-β-cyclodextrin for the direct assay of tramadol in human urine by capillary electrophoresis (CE) with laser-induced native fluorescence detection was developed. Furthermore, the phase II metabolite O-demethyl tramadol glucuronide was determined from the urine samples and the ratio of the diasteromers was determined. The chiral method was validated. Correlation coefficients were higher than 0.999. Within day variation showed accuracy in the range 96.1–105.8% with a RSD less than 6.00%. Day to day variation present an accuracy ranging from 100.2 to 103.5% with a RSD less than 5.4%. After oral administration of 150 mg tramadol hydrochloride to a healthy volunteer, the urinary excretion was monitored during 24 h. About 11.4% of the dose was excreted as 1S,2S-tramadol, 16.4% as 1R,2R-tramadol and 23.7% as O-demethyl tramadol glucuronide. The amount of 1S,2S O-demethyl tramadol glucuronide was more than three fold higher as 1R,2R-O-demethyl tramadol glucuronide. The enantiomeric ratio of tramadol and the diastereomeric ratio of O-demethyl tramadol glucuronide was deviated from 1.0 showing that a stereoselective metabolism of tramadol occurs.

Hyperforin, hypericin and pseudohypericin are the main ingredients of St. John’s wort extract, which is available over the counter for treatment of mild to moderate depression. To facilitate clinical studies we developed two sensitive HPLC methods for determination of hypericin/pseudohypericin and hyperforin, respectively, in human plasma samples. The achieved limits of quantitation of 0.25 ng/ml for hypericin and pseudohypericin and 10 ng/ml for hyperforin were low enough to allow determination of pharmacokinetic parameters of the substances. Following liquid–liquid extraction of human plasma the samples were separated by isocratic reversed-phase HLPC and analyzed using fluorimetric detection for hypericin/pseudohypericin and UV detection for hyperforin.

The phase I and phase II metabolism of the anabolic steroid methandrostenolone was investigated following oral administration to a standardbred gelding. In the phase I study, metabolites were isolated from the urine by solid-phase extraction, deconjugated by acid catalysed methanolysis and converted to their O-methyloxime trimethylsilyl derivatives. GC–MS analysis indicated the major metabolic processes to be sequential reduction of the A-ring and hydroxylation at C6 and C16. In the phase II study, unconjugated, β-glucuronidated and sulfated metabolites were fractionated and deconjugated using a combination of liquid–liquid extraction, enzyme hydrolysis, solid-phase extraction and acid catalysed methanolysis. Derivatization followed by GC–MS analysis revealed extensive conjugation to both glucuronic and sulfuric acids, with only a small proportion of metabolites occurring in unconjugated form.