On-column nitrosation of amines observed in liquid chromatography impurity separations employing ammonium hydroxide and acetonitrile as mobile phase.

The availability of high performance liquid chromatography (HPLC) columns capable of operation at pH values up to 12 has allowed a greater selectivity space to be explored for method development in pharmaceutical analysis. Ammonium hydroxide is of particular value in the mobile phase because it is compatible with direct interfacing to electrospray mass spectrometers. This paper reports an unexpected N-nitrosation reaction that occurs with analytes containing primary and secondary amines when ammonium hydroxide is used to achieve the high pH and acetonitrile is used as the organic modifier.

The relative contributions of CYP3A4 and CYP3A5 to the metabolism of vinorelbine.

Vinorelbine is a semisynthetic vinca alkaloid used in the treatment of advanced breast and non-small cell lung cancers. Vincristine, a related vinca alkaloid, is 9-fold more efficiently metabolized by CYP3A5 than by CYP3A4 in vitro. This study quantified the relative contribution of CYP3A4 and CYP3A5 to the metabolism of vinorelbine in vitro using cDNA-expressed human cytochrome P450s (P450s) and human liver microsomes (HLMs).

Disposition and metabolism of LY2452473, a selective androgen receptor modulator, in humans.

The disposition and metabolism of isopropyl N-[(2S)-7-cyano-4-(2-pyridylmethyl)-2,3-dihydro-1H-cyclopenta[b]indol-2-yl]carbamate (LY2452473; a selective androgen receptor modulator) in humans was characterized after a single 15-mg (100 μCi) oral dose of [¹⁴C]LY2452473 to six healthy male subjects. LY2452473 was absorbed rapidly (time to reach maximum plasma concentration for both LY2452473 and total radioactivity was 2-3 h) and cleared slowly (plasma terminal t(½) of 27 h for LY2452473 and 51 h for the total radioactivity). LY2452473 and metabolites S5 (acetylamine) and S12 (hydroxylation on the cyclopentene) were major circulating entities in plasma, accounting for approximately 42, 21, and 35% of the total radioactivity exposure, respectively, as calculated from relative area under the concentration versus time curves from zero to 48 h derived from the plasma radiochromatograms.

The fate of 4-hydroxycarbazole metabolite: metabolism and carcinogenicity assessment of a β-adrenergic receptor modulator containing carbazole structure.

LY377604 has a potential to form 4-hydroxycarbazole, which was reported in the literature as a mutagen. This safety concern led to our investigation of the metabolism and carcinogenicity of LY377604. In in vitro studies with LY377604, 4-hydroxycarbazole was detected in the presence of liver microsomes prepared from different species.

Disposition and metabolism of semagacestat, a {gamma}-secretase inhibitor, in humans.

Semagacestat is a functional gamma-secretase inhibitor that has been shown to reduce the rate of formation of amyloid-beta in vitro and in vivo. This study was conducted to characterize the disposition of semagacestat in humans. After a single 140-mg dose of [(14)C]semagacestat administered as an oral solution to six healthy male subjects, semagacestat was rapidly absorbed (T(max) approximately 0.

Identification of human UDP-glucuronosyltransferases catalyzing hepatic 1alpha,25-dihydroxyvitamin D3 conjugation.

The biological effects of 1alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) are terminated primarily by P450-dependent hydroxylation reactions. However, the hormone is also conjugated in the liver and a metabolite, presumably a glucuronide, undergoes enterohepatic cycling. In this study, the identity of human enzymes capable of catalyzing the 1,25(OH)2D3 glucuronidation reaction was investigated in order to better understand environmental and endogenous factors affecting the disposition and biological effects of vitamin D3.

The disposition and metabolism of naveglitazar, a peroxisome proliferator-activated receptor alpha-gamma dual, gamma-dominant agonist in mice, rats, and monkeys.

Naveglitazar [LY519818; benzenepropanoic acid, alpha-methoxy-4-[3-(4-phenoxyphenoxy)propoxy], (alpha-S)-] is a nonthiozolidinedione peroxisome proliferator-activated receptor alpha-gamma dual, gamma-dominant agonist that has shown glucose-lowering potential in animal models and in the clinic. Studies have been conducted to characterize the disposition, metabolism, and excretion of naveglitazar in mice, rats, and monkeys after oral and/or i.v.

In vivo metabolism of [14C]ruboxistaurin in dogs, mice, and rats following oral administration and the structure determination of its metabolites by liquid chromatography/mass spectrometry and NMR spectroscopy.

Ruboxistaurin (LY333531), a potent and isoform-selective protein kinase C beta inhibitor, is currently undergoing clinical trials as a therapeutic agent for the treatment of diabetic microvascular complications. The present study describes the disposition and metabolism of [14C]ruboxistaurin following administration of an oral dose to dogs, mice, and rats. The study revealed that ruboxistaurin was highly metabolized in all species.

Determination by NMR of the binding constant for the molecular complex between alprostadil and alpha-cyclodextrin. Implications for a freeze-dried formulation.

A binding constant was determined for the complexation reaction between alprostadil (PGE1) and alpha-cyclodextrin (alpha-CD). This constant was used to calculate the fraction PGE1 free upon reconstitution of Caverject dual chamber syringe, indicated for the treatment of erectile dysfunction. The determination was based on the measurement of the chemical shift of the C20 methyl protons of PGE1.

A band-selective composite gradient: application to DQF-COSY.

We describe a unique band-selective method that utilizes a selective composite gradient to simultaneously achieve band selection and coherence pathway selection. This element is similar to the composite gradient known as the CLUB sandwich except the original broadband pulses have been replaced with selective pulses and the strengths of the antipolar gradients have been unbalanced. In this way, only the signals within the inversion band will continue to dephase throughout the duration of the element and satisfy the proper encoding-to-decoding gradient ratio necessary for coherence selection.

Adiabatic pulses in 1H-15N direct and long-range heteronuclear correlations.

The application of adiabatic inversion pulses to the detection of (1)H-(15)N heteronuclear correlations is described. The pulse sequences studied were gHSQC, CRISIS-gHSQC, gHMBC and CRISIS-gHMBC. The poor inversion quality of rectangular 180 degrees X pulses can lead to a loss of signal at the peripheries of the spectrum.

Selective reduction of N-oxides to amines: application to drug metabolism.

Phase I oxidative metabolism of nitrogen-containing drug molecules to their corresponding N-oxides is a common occurrence. There are instances where liquid chromatography/tandem mass spectometry techniques are inadequate to distinguish this pathway from other oxidation processes, including C-hydroxylations and other heteroatom oxidations, such as sulfur to sulfoxide. Therefore, the purpose of the present study was to develop and optimize an efficient and practical chemical method to selectively convert N-oxides to their corresponding amines suitable for drug metabolism applications.

Novel rearrangement of a 2-aryl-3-alkyl-3H-indol-3-ol to a 1,4,5,6-tetrahydro-2,6-methano-1-benzazocin-3(2H)-one with implications for the biosynthesis of aspernomine.

[reaction: see text] Nominine (1) and aspernomine (2) are two biologically important indole diterpenoids that arise from a common digeranylindole precursor. The skeletal relationship of these two natural products was not heretofore understood. We have observed a novel rearrangement of 2-(2-bromophenyl)-3-(3-butenyl)-3H-indol-3-ol (5) to 7, which contains the uncommon 1,4,5,6-tetrahydro-2,6-methano-1-benzazocin-3(2H)-one ring system, under acidic conditions.