Enantioselective determination of R- and S-(alpha-bromoisovaleryl)urea in plasma using high-performance liquid chromatography after solid-phase extraction

Simultaneous determination of bromvalerylurea and allylisopropylacetylurea in human blood and urine by gas chromatography-mass spectrometry

We devised a sensitive and simple method to simultaneously determine bromvalerylurea and allylisopropylacetylurea in human blood and urine by gas chromatography-mass spectrometry. Bromvalerylurea and allylisopropylacetylurea were extracted using an Extrelut column with an internal standard, 2-bromohexanoylurea, followed by derivatization with heptafluorobutyric anhydride. The derivatized extract was submitted to GC-MS analysis of EI-SIM mode. The calibration curves of both compounds were linear in the concentration range from 0.01 to 10 microg/ml in both blood and urine samples. The lower limits of detection of bromvalerylurea and allylisopropylacetylurea were 0.005 and 0.005 microg/ml, respectively. This method proved most useful in accurately identifying these drugs in blood and urine from an autopsied individual.

Reviewing mobile phases used on Chiralcel OD through an application of data mining tools to CHIRBASE database

During the past decade, thousands of compounds have been resolved on Chiralcel OD (a cellulose-based chiral stationary phase) under diverse eluting conditions. Many researches have documented the effects of mobile phase on enantioselectivity for a given family of samples but today no comprehensive study aimed at identifying the associations between the structural features present on solute and appropriate mobile phase conditions has yet been proposed. In this review of mobile phases used on Chiralcel OD, we try to go far beyond a simple enumeration of eluting conditions and an effort is made to explore the utility of data mining tools for assessing the knowledge contained in CHIRBASE database. We have extracted from CHIRBASE the chemical features of 2363 chiral compounds separated on Chiralcel OD and their corresponding mobile phases. This data set was submitted to data mining programs for molecular pattern recognition and mobile phase predictions for new cases. Some substructural characteristics of solutes were related to the efficient use of some specific mobile phases. For example, the application of CH3CN/salt buffer at pH 6-7 was found convenient for reversed-phase separation of compounds bearing a tertiary amine functional group. Furthermore, a cluster analysis allowed the arrangement of the mobile phases according to similarity found in molecular patterns of solutes. A decision tree, which may lead to a more rational choice of the mobile phase under reversed-phase conditions, is also proposed.

Enantioselective determination of bromoisovalerylurea by liquid chromatography on chiral stationary phase in reversed- or normal-phase partition mode

Bromoisovalerylurea (bromvalerylurea) is a sedative-hypnotic given orally as a racemate. Enantiomers of this drug could be separated by high-performance liquid chromatography on the three chiral stationary phases (a vancomycin-bonded, beta-cyclodextrin derivative-bonded, or urea derivative-bonded phase). Biological fluids of human subjects who had ingested toxic or therapeutic doses of the racemate were chromatographed after liquid-liquid extraction. The (+)-enantiomer concentration was almost equal to the (-)-enantiomer concentration in the serum of one overdosed patient. In all the other subjects, the (+)-enantiomer was less than the (-)-enantiomer in their sera and saliva. The data suggest that the drug is absorbed non-stereoselectively from the gastrointestinal tract and eliminated from the blood stereoselectively.

Abnormal glutathione conjugation in patients with tyrosinaemia type I

Previous studies have suggested that tyrosinaemia type I may be associated with reduced glutathione availability due to conjugation of tyrosinaemia-associated reactive intermediates with glutathione. In the present study, the glutathione/ glutathione S-transferase system of two tyrosinaemia patients and three healthy controls were characterized by administering the racemic sedative drug bromisoval, a probe drug for assessing glutathione conjugation activity in vivo. Furthermore, concentrations of glutathione and glutathione S-transferase class alpha (GSTA) isoenzymes as well as the glutathione S-transferase class mu phenotype were assessed in the blood of six tyrosinaemia patients. The excretion of bromisoval mercapturates in healthy children was comparable to that observed in healthy adults. Tyrosinaemia patients were found to have a very high urinary recovery of bromisoval mercapturates (> or = 60% of the dose compared to about 30% for healthy, age-matched children and adults), which could be attributed mainly to a higher urinary excretion of the mercapturate derived from S-bromisoval. Healthy children and adults predominantly excrete the (R)-bromisoval mercapturate. The differences in amount excreted as well as in stereoselectivity of the urinary excretion of bromisoval mercapturates in tyrosinaemia patients are possibly related to an increased activity of specific glutathione S-transferase isoenzymes. Plasma glutathione and blood cell glutathione disulphide concentrations in tyrosinaemia patients were normal. Low blood cell glutathione concentrations were in general found only in two patients with a poor clinical condition. These results indicate that, in contrast to previous suggestions, reduced glutathione availability is not a generalized problem in (stabilized) tyrosinaemia patients.