Sensitive SPE–HPLC method to determine a novel angiotensin-AT1 antagonist in biological samples

Pharmacokinetic study of a new angiotensin-AT1 antagonist by HPLC

Recently an innovative novel class angiotensin-AT1 antagonist has been developed by Rottapharm. In this study, we present a validated method for detecting CR 3834 in biological matrices using high-performance liquid chromatography (HPLC) with diode array detection. After oral administration (30mg/kg) to Wistar rats, the plasma and urine concentrations of CR 3834 and its potential metabolic products were determined. Moreover, the plasmatic time course in rats has been determined after intravenous (IV) administration of CR 3834 (5mg/kg). Biological samples (0.5ml of plasma and 1ml of urine) were purified using solid-phase extraction (SPE) of analytes and the internal standard Idebenone, 2,3-dimethoxy-5-methyl-6-(10-hydroxydecyl)-1-4-benzoquinone. A chromatographic separation was performed on an Adsorboshere C18 at 25 degrees C, with a pre-column of the same matrix; the eluent was made up of acetonitrile/acidified water with CF3COOH (pH 2.01) in ratio of 75:25 (v/v); the flow rate was 1.0ml/min and a 100microl loop. The lower limit of detection (LOD) was taken as 25ng/ml in plasma and 50ng/ml in urine samples. The lower limit of quantification (LOQ) was taken as 0.1 and 0.2microg/ml in plasma and urine samples, respectively. The procedures were validated according to international standards with a good reproducibility and linear response (r=0.9916 in plasma; r=0.9997 in urine). The coefficients of variation inter assay ranged between 2.579 and 4.951% in plasma, and between 0.813 and 2.460% in urine. Mean recovery for CR 3834 was 79% in plasma and 97% in urine samples. The experiments performed demonstrated that the method presented was suitable for determining this new angiotensin-AT1 antagonist in rat plasma and urine.

New materials in sorptive extraction techniques for polar compounds

This paper provides an overview of the new developments in material and format technology that improve the extraction of polar compounds in several extraction techniques. They mainly include solid-phase extraction, but there are also other sorptive extraction techniques, such as stir bar sorptive extraction and solid-phase microextraction that use either fibers or in-tube devices. We focus on new synthesised materials that are both commercially available and "in-house". Most novel materials that enhance the extraction of polar compounds are hydrophilic and have large specific surface area; however, we also cover other leading technologies, such as sol-gel or monolith. We describe the morphological and chemical properties of these new sorbents so that we can better understand them and relate them to their capability of retaining polar compounds. We discuss the extraction efficiency for polar compounds when these polymers are used as sorptive material and compare them to other materials. We also mention some representative examples of applications.

Further studies on imidazo[4,5-b]pyridine AT1 angiotensin II receptor antagonists. Effects of the transformation of the 4-phenylquinoline backbone into 4-phenylisoquinolinone or 1-phenylindene scaffolds

The 4-phenylquinoline fragment of novel AT(1) receptor antagonists 4 based on imidazo[4,5-b]pyridine moiety was replaced by 4-phenylisoquinolinone (compounds 5) or 1-phenylindene (compounds 6) scaffolds to investigate the structure-activity relationships. Binding studies showed that most of the synthesized compounds display high affinity for the AT(1) receptor. Because of the in vitro high potency of carboxylic acids 5b,f, they were evaluated in permeability (in Caco-2 cells) and in pharmacokinetic studies in comparison with quinoline derivatives 4b,i,j,k. The studies showed that these compounds are characterized by rapid excretion, low membrane permeability, and low oral bioavailability. The structure optimization of the indene derivatives led to compounds 6e,f possessing interesting AT(1) receptor affinities. Optimization produced polymerizing AT(1) receptor ligand 6c, which forms a thermoreversible polymer (poly-6c) and is released from the latter by a temperature-dependent kinetics. The results suggest the possibility of developing novel polymeric prodrugs based on a new release mechanism. Finally, a set of 34 AT(1) receptor antagonists was used as a new test for the evaluation of the predictive capability of the previously published qualitative and quantitative pharmacophore models.