Direct characterization of drug glucuronide isomers in human urine by HPLC-NMR spectroscopy: application to the positional isomers of 6,11-dihydro-11-oxodibenz[b,e]oxepin-2-acetic acid glucuronide.

In this work, 400 and 600 MHz 1H HPLC-NMR spectroscopic methods were developed and applied to separate and identify the positional glucuronide isomers and anomers of the model nonsteroidal antiinflammatory drug, 6,11-dihydro-11-oxodibenz[b,e]oxepin-2-acetic acid, in whole human urine. The HPLC methods utilized either an isocratic system, comprising 30% acetonitrile in water at pH 2.5, or a gradient elution system increasing from 30% to 60% acetonitrile, in order to achieve improved separation of the 2-, 3-, and 4-O-acylglucuronide isomers from the faster eluting endogenous urinary metabolites. Directly coupled stop-flow 1H HPLC-NMR spectroscopic measurements were made at the retention times indicated by the UV-monitored chromatographic peaks. The glucuronide isomers were identified from the 1H NMR spectra on the basis of their chemical shifts and spin-spin coupling patterns. The elution order was 4-O-acyl-, 3-O-acyl-, and finally 2-O-acylglucuronide, with tR values of 10.04, 11.68, and 12.64 min, respectively. Although the alpha- and beta-anomers of each of the positional isomers could not be separated in these solvent systems, they could be identified in the individual 1H NMR spectra. This work shows for the first time that directly coupled HPLC-NMR spectroscopy can be used directly to isolate and characterize acyl-migrated isomers of drug glucuronides in whole urine. This approach will be of value in the study of glucuronide acyl migration reactions of nonsteroidal antiinflammatory drugs and other xenobiotic ester glucuronides in whole biofluids.

HPLC and 1H-NMR study of chiral recognition in some thromboxane antagonists induced by beta-cyclodextrin.

The interaction of beta-cyclodextrin with a series of structurally related chiral thromboxane antagonists was investigated using NMR and RP-HPLC. HPLC studies used both a cyclodextrin bonded phase (Cyclobond I), and beta-cyclodextrin as a mobile phase additive with an achiral C8 column. Many of the compounds exhibited chiral recognition with beta-cyclodextrin in each technique, but only partial correlations between the three data sets were observed. HPLC and ROESY NMR data suggested the possibility of bimodal inclusion.

Synthesis of N7-hydroxyethylguanine and O6-hydroxyethylguanine. Markers for the reaction of ethylene oxide (EO) with DNA.

O6-Hydroxyethylguanine has been synthesized by reaction of mono-sodium glycolate with 6-chloroguanine. The crystalline product has been characterized using a variety of analytical techniques and compared with a sample of the corresponding N7-hydroxyethyl derivative. These 2 chemicals may prove useful as standards when studying the reaction of ethylene oxide (EO) with DNA.

Identification of mycobactins by nuclear-magnetic-resonance spectroscopy.

Details are given of the n.m.r. spectra of mycobactins F, H, M, N, P, S and T, and resonances are ascribed to all the protons in these molecules. A simplified system is described for identifying known mycobactins by the n.m.r. spectrum alone. This method will not distinguish mycobactins S and T, whose nuclei differ only in the configuration at an asymmetric centre.