Direct thrombin inhibitors built on the azaphenylalanine scaffold provoke degranulation of mast cells

The main structural feature of direct thrombin inhibitor LK-732 responsible for the appropriate interaction at the thrombin active site is a strong basic group. A possibility that a strong basic group of LK-732 might contribute to the mast cell degranulation effect and consequent reduction of tracheal air flow (TAF) and fall of mean arterial blood pressure (MAP) in rats was investigated in the present study. At doses up to5 mg/kg (i. v.), LK-732 did not cause significant changes of TAF and MAP. At 7 mg/kg (i. v.),a sudden reduction of TAF and a fall of MAP was observed within 5 min after LK-732 administration (75% mortality, p=0. 007). A less basic direct thrombin inhibitor LK-658 (21 mg/ kg, i. v.) did not significantly disturb TAF and MAP. A reduction of TAF and a fall of MAP caused by LK-732 (7 mg/kg, i. v.) was almost completely abolished in rats with degranulated mast cells (0% mortality, p=0. 008). LK-732 concentration-dependently degranulated rat peritoneal mast cells in vitro (pEC50=1. 92±0. 05 µM). A structure-activity relationship (SAR) study revealed that the terminal basic groups attached to the aromatic ring are responsible for the mast cell degranulation effect. A good correlation was observed between mast cell degranulation and pKb of analogues of LK-732 (R2=0. 49), but not between mast cell degranulation and thrombin Ki (R2=0. 23). LK-732-induced reduction of TAF, the fall of MAP and high mortality originate from LK732-induced mast cell degranulation. As judged by the SAR study, this effect could be overcome by reducing the basicity of LK-732.

The design, synthesis, and antioxidant activity of amphiphilic oximes and amidoximes

New amphiphilic benzamidoxime, benzoxime, and aliphatic oxime derivatives of glycolipid mimetics were synthesized. The total antioxidant capacity of these amphiphilic derivatives was evaluated using DPPH assay. The observed antioxidant activity was the highest for benzamidoxime derivatives and glycolipid mimetics with two oxime functionalities, followed by benzoxime derivatives, glycolipid mimetics with one oxime group, and dimers of oxime. Due to their amphiphilic structure, which was a guidance for compound design and synthesis, these novel amphiphilic compounds can be proposed as potential antioxidants for tackling oxidative processes in two-phase systems, either biological (cell membranes) or artificial (emulsions).

Review of operating principle and applications of the charged aerosol detector

Recently a new detection method, based upon aerosol charging (the charged aerosol detector (CAD)) has been introduced as an alternative to evaporative light-scattering detector (ELSD), chemiluminescent nitrogen detector and refractive index detector for detection of non-ultraviolet and weakly ultraviolet active compounds and for UV-absorbing compounds in the absence of standards. The content of this review article includes description of operation principle, advantages and disadvantages of CAD system, and short reports of selected applications of this detector. The main advantages of CAD detector are unique performance characteristics: better sensitivity than ELSD system, a dynamic range of up to 4 orders of magnitude, ease of use and constancy of response factors. Both detectors are mass dependent and the response generated does not depend on the spectral or physicochemical properties of the analyte. This attractive feature of a detection technique generating universal response factors is the potential use of a single, universal standard for calibration against which all other compounds or impurities can be qualified. CAD also has the same limitation as ELSD, namely, the response is affected by mobile-phase composition. This problem has been resolved by using inverse gradient compensation as is done for high pressure liquid chromatography and supercritical fluid chromatography. CAD has been applied for the analysis of structurally diverse compounds used in the pharmaceutical, chemical, food, and consumer products industries and in life science research. They include nonvolatile and semivolatile neutral, acidic, basic, and zwitterionic compounds, both polar and nonpolar (e.g. lipids, proteins, steroids, polymers, carbohydrates, peptides).

Design, synthesis and molecular modelling of 1-amidinopiperidine thrombin inhibitors

Design, synthesis and biochemical evaluation of a series of novel non-covalent thrombin inhibitors with a 1-amidinopiperidine moiety are presented. Replacement of the planar benzamidine group in azaphenylalanine derivatives with 1-amidinopiperidine resulted in lower activity but higher selectivity for this type of compounds. The binding conformation of inhibitors in the active site of thrombin was revealed by molecular modelling studies.

Physical properties and dissolution behaviour of nifedipine/mannitol solid dispersions prepared by hot melt method

Solid dispersions of nifedipine (NIF) with mannitol in preparations containing 10 and 50% (w/w) of drug were manufactured by the hot melt method. Physical properties and the dissolution behaviour of binary systems as physical mixtures and solid dispersions were investigated. In all samples, the crystal structure of NIF was confirmed using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) revealed, there was no interaction between drug and carrier, however, FTIR spectra indicated formation of thermodynamically less stable polymorph of mannitol. The dissolution rate of NIF from solid dispersions was markedly enhanced, the effect being stronger at higher drug loading (50%, w/w, NIF). The dissolution rate enhancement was attributed to improved wetting of NIF crystals due to mannitol particles, attached on the surface, as inspected by means of SEM. Thermal stability of NIF, mannitol and two other potential carbohydrate carriers (lactose and saccharose) during the hot melt procedure was investigated using 1H NMR. NIF was found to be thermically stable under conditions applied. As expected, among carriers only mannitol demonstrated suitable resistance to high temperature used in experiments.

Synthesis and in vitro evaluation of new azaphenylalanine derivatives as serine protease inhibitors

New inhibitors of serine proteases with azaphenylalanine scaffold were synthesized and their activity was evaluated in vitro. We studied the effect of different substituents in the part of a molecule that binds in the distal pocket of the thrombin active site. Modifications generally led to decreased activity, however two derivatives are promising lead compounds as new thrombin and dual thrombin-factor Xa inhibitors.

Novel non-covalent azaphenylalanine thrombin inhibitors with an aminomethyl or amino group at the P1 position

Design, synthesis and biological evaluation of a series of novel non-covalent azaphenylalanine thrombin inhibitors are presented. Replacement of the basic benzamidine moiety in azaphenylalanine derivatives by benzylamine (P1 part of a molecule) and the introduction of a N-cyclopentyl-N-methylamine moiety in the P2 part of a molecule resulted in the thrombin inhibitor LK-733 with greatly increased selectivity against trypsin and an in vitro Ki of 31 nM.

Abuse of clenbuterol and its detection

Clenbuterol and other beta-agonists are commonly misused as repartitioning agents in meat production and as doping substances to improve athletic performance. Numerous reports on food poisoning throughout Europe prompted the EU regulatory offices and FDA to implement a ban on the use of beta-agonists as growth promoters. Several analytical methods have been developed for detecting illegal administration of these compounds, based mainly on chromatography and immunoassay screening. This article deals with the pharmacological aspect of beta-agonists in growth promotion, control of their abuse and methods of analysis.