High performance liquid chromatographic analysis of a new proton pump inhibitor KR60436 and its active metabolite O-demethyl-KR60436 in rat plasma samples using column-switching

Characterization of human liver cytochrome P450 enzymes involved in the metabolism of a new H+/K+-ATPase inhibitor KR-60436

KR-60436 ([1-(4-methoxy-2-methylphenyl)-4-[(2-hydroxyethyl)amino]-6-trifluoromethoxy-2,3-dihydropyrrolo [3,2-c]quinoline]) is a new reversible H+/K+-ATPase inhibitor. The isoforms of human liver cytochrome P450 (CYP) responsible for the hepatic transformation of KR-60436 is identified. Dihydropyrrole oxidation and O-demethylation are major pathways for the metabolism of KR-60436 in human liver microsomes, whereas N-dehydroxyethylation and hydroxylation are minor pathways. The specific CYP isozymes responsible for KR-60436 oxidation to four major metabolites, pyrrole-KR-60436, O-demethylpyrrole-KR-60436, N-dehydroxyethyl-KR-60436 and an active metabolite, O-demethyl-KR-60436 were identified using the combination of correlation analysis, immuno-inhibition, chemical inhibition in human liver microsomes and metabolism by expressed recombinant CYP enzymes. The inhibitory potency of KR-60436 on clinically major CYPs was investigated in human liver microsomes. The results show that CYP3A4 contributes to the oxidation of KR-60436 to pyrrole-KR-60436, O-demethylpyrrole-KR-60436 and N-dehydroxyethyl-KR-60436, and CYP2C9 and CYP2D6 play roles in demethylation of KR-60436 to form the active metabolite, O-demethyl-KR-60436. KR-60436 was found to inhibit potently the metabolism of CYP1A2 substrates.

Restricted access materials and large particle supports for on-line sample preparation: an attractive approach for biological fluids analysis

An analytical process generally involves four main steps: (1) sample preparation; (2) analytical separation; (3) detection; and (4) data handling. In the bioanalytical field, sample preparation is often considered as the time-limiting step. Indeed, the extraction techniques commonly used for biological matrices such as liquid-liquid extraction (LLE) and solid-phase extraction (SPE) are achieved in the off-line mode. In order to perform a high throughput analysis, efforts have been engaged in developing a faster sample purification process. Among different strategies, the introduction of special extraction sorbents, such as the restricted access media (RAM) and large particle supports (LPS), allowing the direct and repetitive injection of complex biological matrices, represents a very attractive approach. Integrated in a liquid chromatography (LC) system, these extraction supports lead to the automation, simplification and speeding up of the sample preparation process. In this paper, RAM and LPS are reviewed and particular attention is given to commercially available supports. Applications of these extraction supports, are presented in single column and column-switching configurations, for the direct analysis of compounds in various biological fluids.

LC-MS/MS identification of in vitro metabolites of a new H+/K+ ATPase inhibitor, KR-60436 produced by rat and human liver microsomes

The metabolism of a new H+/K+ ATPase inhibitor, KR-60436 [1-(4-methoxy-2-methyl-phenyl)-4-[(2-hydroxyethyl)amino]-6-trifluoromethoxy-2,3-dihydropyrrolo[3,2-c]quinoline] has been studied by LC-electrospray mass spectrometry. In vitro incubation of KR-60436 with rat and human liver microsomes in the presence of NADPH produced seven metabolites (M1-M7). M3-M6 were identified as O-demethyl-KR-60436, O-demethyl-pyrrole-KR-60436, N-dehydroxyethyl-KR-60436 and pyrrole-KR-60436, respectively, based on LC/MS/MS analysis with authentic standards. M1, M2 and M7 were tentatively identified as monohydroxylated-KR-60436, monohydroxylated-pyrrole-KR-60436 and N-dehydroxyethyl-pyrrole-KR-60436, respectively. The four principal metabolic pathways are characterized in KR-60436 metabolism: oxidation of dihydropyrrole ring to pyrrole, O-demethylation of methoxy group, hydroxylation of quinoline moiety and N-dealkylation of hydroxyethylamino group.