Inhibitors of cholesterol biosynthesis. 6. trans-6-[2-(2-N-heteroaryl-3,5-disubstituted- pyrazol-4-yl)ethyl/ethenyl]tetrahydro-4-hydroxy-2H-pyran-2-ones

Exploration of virtual candidates for human HMG-CoA reductase inhibitors using pharmacophore modeling and molecular dynamics simulations

3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is a rate-controlling enzyme in the mevalonate pathway which involved in biosynthesis of cholesterol and other isoprenoids. This enzyme catalyzes the conversion of HMG-CoA to mevalonate and is regarded as a drug target to treat hypercholesterolemia. In this study, ten qualitative pharmacophore models were generated based on chemical features in active inhibitors of HMGR. The generated models were validated using a test set. In a validation process, the best hypothesis was selected based on the statistical parameters and used for virtual screening of chemical databases to find novel lead candidates. The screened compounds were sorted by applying drug-like properties. The compounds that satisfied all drug-like properties were used for molecular docking study to identify their binding conformations at active site of HMGR. The final hit compounds were selected based on docking score and binding orientation. The HMGR structures in complex with the hit compounds were subjected to 10 ns molecular dynamics simulations to refine the binding orientation as well as to check the stability of the hits. After simulation, binding modes including hydrogen bonding patterns and molecular interactions with the active site residues were analyzed. In conclusion, four hit compounds with new structural scaffold were suggested as novel and potent HMGR inhibitors.

Identification of unknown impurities in simvastatin substance and tablets by liquid chromatography/tandem mass spectrometry

Unknown impurities were detected in simvastatin substance and tablets at a 0.2% level using the liquid chromatography technique with UV (DAD) detection. The impurity structures were elucidated by a direct hyphenation of liquid chromatograph to high-resolution mass spectrometer with electrospray ionisation interface using solutions of formic acid in water and in acetonitrile as the mobile phase. Peak tracking was performed using the column-switching technique. Accurate mass measurements by quadrupole time-of-flight mass spectrometer equipped with lock-spray provided information about elemental composition of intact molecules and fragments of impurities. Measurement accuracy for precursor ions was around 3 ppm and for fragment ions between 4 and 13 ppm. Mass resolving power was around 6500. Deduced molecular formulae for A1, A2 and A3 impurities were C(27)H(44)O(6), C(26)H(43)O(6) and C(26)H(41)O(5), respectively. The structures proposed for all three impurities revealed modifications of simvastatin molecule on the lactone ring. Impurity A1, detected in simvastatin tablets, was identified as ethyl ester, while the impurities A2 and A3, detected in simvastatin substance, were identified as methyl ester and methyl ether of simvastatin. The impurity from tablets was synthesized and its structure confirmed by LC-UV, LC-MS/MS, and NMR techniques.

7-(Disubstituted thiazolyl)-3,5-dihydroxy-6-heptenoic/heptanoic acid derivatives as HMG-CoA reductase inhibitors

A series of disubstituted thiazoles, functionalized with the essential 3,5-dihydroxy-6-heptenoic or heptanoic chain, were prepared and evaluated for their ability to inhibit the enzyme HMG-CoA reductase in vitro. All the synthesized compounds 46-61 showed a moderate inhibitory potency.

Subacute toxicity of a halogenated pyrrole hydroxymethylglutaryl-coenzyme A reductase inhibitor in Wistar rats

Wistar rats received an hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor, a halogenated pyrrole designated PD 123244-15, orally by gavage for 14 days at 10, 50, 150, 300, and 600 mg/kg. Doses of 150-600 mg/kg caused death and marked systemic toxicity involving stomach, esophagus, liver, gonads, lymphoid tissues, and skeletal muscle. Histopathologic findings included hyperkeratosis in esophagus and forestomach, increased hepatic mitotic activity, ovarian follicular necrosis, testicular atrophy and arrested spermatogenesis, and skeletal muscle necrosis and regeneration. Elevated serum aspartate aminotransferase correlated with muscle necrosis and hepatocellular damage. Marked systemic effects associated with high plasma concentrations were consistent with toxicity defined for other HMG-CoA reductase inhibitors, with the exception of pathologic alterations in the esophagus and ovaries. Direct mucosal irritation may have contributed to forestomach and esophageal lesions induced by this halogenated pyrrole.