DFT study on hydroxy acid-lactone interconversion of statins: The case of fluvastatin

Development and Validation of a DLLME-GC-MS-MS Method for the Determination of Benzotriazole UV Stabilizer UV-327 and Its Metabolites in Human Blood

2-(5-Chloro-benzotriazol-2-yl)-4,6-di-(tert-butyl)phenol (UV-327) is used as an ultraviolet (UV) absorber in plastic materials and coatings. To investigate its metabolism and to assess human exposure, analytical methods are necessary for the determination of UV-327 and its metabolites in human biological specimens. The method thus presented targets the determination of UV-327 and several of its predicted metabolites in blood using protein precipitation, dispersive liquid-liquid microextraction (DLLME) and derivatization. The trimethylsilylated analytes and internal standards are separated by gas chromatography and analyzed with tandem mass spectrometry. The DLLME procedure was optimized with respect to the type and volume of disperser and extraction solvents, the pH value of the sample solution and the addition of salt. During method development, an effective ex vivo lactone/hydroxyl carboxylic acid interconversion was observed for two metabolites, each containing a carboxyl group adjacent to the phenolic hydroxyl group. The analytes resulting from interconversion enabled a more sensitive and reliable determination of the metabolites compared to their native structures. Method validation revealed limits of detection between 0.02 and 0.36 µg/L. The mean relative recovery rates ranged from 91% to 118%. Precision and repeatability were demonstrated by relative standard deviations in the range of 0.6-14.2% and 1.1-13.7%, respectively. The presently described procedure enables the sensitive and robust analysis of UV-327 and its metabolites in human blood and allows the elucidation of the human UV-327 metabolism as well as the assessment of exposure in potentially exposed individuals.

Computational studies on statins photoactivity

Statins are popular drugs widely prescribed to control hypercholesterolaemia and to prevent cardiovascular diseases. Synthetic statins constitute a group of pharmaceuticals which are very sensitive to exposure to light in both UVA and UVB ranges. Light, by causing drugs degradation, can essentially change their pharmaceutical properties leading even to the loss of therapeutic activity and/or to the formation of deleterious photoproducts. Drugs which exhibit photochemical reactivity may elicit undesired adverse effects. A detailed understanding of mechanisms involved in molecular basis of these effects origin is very important for evaluating the photobiological risk associated with therapy in which drugs prone to exposure to light are involved. In this work we critically discussed finding regarding the mechanisms of synthetic statins phototransformation. We showed inconsistency of some previously reported facts and revised earlier presented studies. We also completed the lack of information on pitavastatin photobehaviour. This all together resulted in proposal of new schemes for the statins photodecomposition. We reviewed data derived from both experimental and computational methods. Studies of photochemical problems by the use of theoretical methods enable getting insight into areas of some fascinating events that experimental techniques can touch only indirectly. Besides effect of light, phenomenon of statins’ sensitivity to pH and resulting implications were discussed. Statins undergo pH-dependent interconversion between their pharmacologically active hydroxy acid and inactive lactone forms, and it was shown that for both forms, drugs’ interactions should be considered. Knowledge of the statins interconversion mechanisms is important for understanding how differences in the structures of their molecules can affect the drugs’ activity.

Structural Basis for Activation of Human Sirtuin 6 by Fluvastatin

Sirtuins are NAD+-dependent protein lysine deacylases that are considered attractive drug targets for aging-related diseases. Sirt6 deacetylates, e.g., transcription factors and histone H3, and regulates metabolic processes and stress responses. It has been implicated in lifespan extension and tumor suppression. Sirt6 deacetylase activity can be stimulated with small molecules, and fluvastatin, an FDA-approved synthetic statin, was recently described as a novel Sirt6 activator. We studied the molecular details of this effect on Sirt6 in deacylation assays and by solving a crystal structure of a Sirt6/fluvastatin complex. We find that fluvastatin inhibits Sirt1-3 at higher concentrations but has a unique, activating effect on Sirt6. The complex structure reveals that fluvastatin occupies the Sirt6 substrate acyl channel exit, similar to other, unrelated activator families, providing interaction details that will support the development of potent, druglike Sirt6 activators.

Experimental and theoretical studies on fluvastatin primary photoproduct formation

Fluvastatin (FLV) belongs to the group of compounds referred to as statins, also known as 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors. Statins act as cholesterol-lowering agents and are among the most frequently prescribed drugs. They upregulate low-density lipoprotein receptors in the liver by binding to the active site of HMG-CoA reductase, which is the key enzyme in cholesterol biosynthesis. Statins have been detected as contaminants in natural waters and are susceptible to degradation upon exposure to light. Fluvastatin is extremely sensitive to light; upon irradiation it forms a range of photoproducts. In this study the fluvastatin molar absorption coefficient and the quantum yield of the drug photodegradation were determined. The FLV photodegradation quantum yield value determined in this work (Φ = 0.13 ± 0.02) was found to be significantly larger than that previously reported in the literature. Our results also showed that the generation of singlet oxygen is not involved in the drug photodecomposition indicating that the excited triplet state of fluvastatin is not populated efficiently. Moreover, experimental methods and DFT calculations were applied to get insight into the possible mechanisms of fluvastatin primary photoproduct formation. Using the transient absorption spectroscopy technique, the transient species formed immediately after the drug excitation were followed, and the scheme for fluvastatin primary photochemistry was suggested. The primary photoproducts were identified on the basis of spectroscopic and spectrometric methods. A new mechanism for photooxygenation leading to the formation of one of the identified photoproducts (FP2) was proposed and a new approach to the formation of the other photoproduct (FP1) was provided. The theoretical mechanistic explanation of the photoproduct formation is in excellent agreement with the experimental data.

In Vitro Assessment of CYP-Mediated Drug Interactions for Kinsenoside, an Antihyperlipidemic Candidate

Kinsenoside, the herb-derived medicine isolated from the plant Anoect chilus, has diverse pharmacological actions, and it is considered to be a promising antihyperlipidemic drug candidate. This study evaluates the effects of kinsenoside on CYP enzyme-mediated drug metabolism in order to predict the potential for kinsenoside-drug interactions. Kinsenoside was tested at different concentrations of 0.1, 0.3, 1, 3, 10, 30, and 100 µM in human liver microsomes. The c Cktail probe assay based on liquid chromatography-tandem mass spectrometry was conducted to measure the CYP inhibitory effect of kinsenoside. Subsequently, the metabolism profiles of amlodipine and lovastatin in human liver microsomes were analyzed following co-incubation with kinsenoside. The concentration levels of the parent drug and the major metabolites were compared with the kinsenoside-cotreated samples. The effect of kinsenoside was negligible on the enzyme activity of all the CYP isozymes tested even though CYP2A6 was slightly inhibited at higher concentrations. The drug-drug interaction assay also showed that the concomitant use of kinsenoside has a non-significant effect on the concentration of lovastatin or amlodipine, and their major metabolites. So, it was concluded that there is almost no risk of drug interaction between kinsenoside and CYP drug substrates via CYP inhibition.

Translational insight into statin-induced muscle toxicity: from cell culture to clinical studies

Statins are lipid-lowering drugs used widely to prevent and treat cardiovascular and coronary heart diseases. These drugs are among the most commonly prescribed medicines intended for long-term use. In general, statins are well tolerated. However, muscular adverse effects appear to be the most common obstacle that limits their use, resulting in poor patient compliance or even drug discontinuation. In addition, rare but potentially fatal cases of rhabdomyolysis have been reported with the use of these drugs, especially in the presence of certain risk factors. Previous reports have investigated statin-induced myotoxicity in vivo and in vitro using a number of cell lines, muscle tissues, and laboratory animals, in addition to randomized clinical trials, observational studies, and case reports. None of them have compared directly results from laboratory investigations with clinical observations of statin-related muscular adverse effects. To the best of our knowledge this is the first review article that combines laboratory investigation with clinical aspects of statin-induced myotoxicity. By reviewing published literature of in vivo, in vitro, and clinically relevant studies of statin myotoxicity, we aim to translate this important drug-related problem to establish a clear picture of proposed mechanisms that explain the risk factors and describe the diagnostic approaches currently used for evaluating the degree of muscle damage induced by these agents. This review provides baseline novel translational insight that can be used to enhance the safety profile, to minimize the chance of progression of these adverse effects to more severe and potentially fatal rhabdomyolysis, and to improve the overall patient compliance and adherence to long-term statin therapy.

Application of density functional theory in combination with FTIR and DSC to characterise polymer drug interactions for the preparation of sustained release formulations between fluvastatin and carrageenans

In the present study, ι- and λ-carrageenans were used as appropriate carriers for sustained release formulations of fluvastatin drug. From viscosity measurements, it was found that both carrageenans can give miscible blends with fluvastatin due to the interactions between the sulfate groups of carrageenans and hydroxyl groups of fluvastatin. This was predicted by computational analysis using density functional theory and proved by FTIR spectroscopy. These interactions, which are in higher intensity using ι-carrageenan, lead to the formation of complexes between polymeric matrices and fluvastatin drug. DSC experiments also confirmed that miscible blends between carrageenans and fluvastatin can be formed since in all concentrations only one glass transition temperature was recorded. Fluvastatin release depends on the drug content and in all formulations of λ-carrageenans containing 10, 25 and 50 wt% drug, almost sustained release profiles were observed. Fluvastatin/carrageenan complexes have lower dissolution profiles compared with physical mixtures. Polymer swelling seems to be the dominant drug release mechanism. Besides to neat ι- and λ-carrageenans, their blends can be also used as effective matrices for sustained release.

Selective Organic Synthesis for Sustainable Development

The data on the development of selective organic synthesis suitable for obtaining multifunctional organic compounds both linear and cyclic structures using environmentally benign, inexpensive and renewable resources summarized. This article is an extended abstract of a communication presented at the Conference Ecological Chemistry 2012.

New Catalytic System for Preparation of Methyl 2-(3-Hydroxy-2-Oxo-2,3-Dihydro-1H-3- Indolyl)Acrylates

A novel catalyst derived from the nitrile functionalized ionic liquids and DMAP promoted the MoritaBaylis-Hillman reaction of N-substituted isatines and the methyl acrylate with moderate up to high yields.

In-vitro release kinetics and stability of anticardiovascular drugs-intercalated layered double hydroxide nanohybrids

We report the intercalation and characterization of pravastatin and fluvastatin drugs in Mg(II)/Al(III) layered double hydroxides (LDHs) to form novel nanohybrid hydroxides through the coprecipitation technique. powder X-ray diffraction, Fourier transform infrared spectroscopy, and thermal analysis techniques reveal that the drugs are accommodated within the brucite layers. Structural characterization, computed results, and atomic force microscopy image analysis demonstrate that the fluvastatin anions are attached with the brucite as a monolayer, whereas the pravastatin anions form a multilayer. The shift in the stretching frequency of carboxylate anion of statin drugs provides evidence that the drugs are electrostatically bonded to LDHs. X-ray diffraction and thermal analysis studies performed after keeping the nanohybrid particles at 75 +/- 10% relative humidity atmosphere, indicate their physical stability due to proper confinement of drugs within the layers. In-vitro release study of developed nanohybrid particles suggests that the significant reduction in release rate of fluvastatin anions from fluvastatin intercalated LDHs is due to its hydrophobic nature and it can be further controlled by varying the concentration in physiological medium. After release, the data were fitted to the dissolution-diffusion kinetic model. The mechanism of drugs diffusion in hydrophobic nanohybrid is probably due to heterogeneous diffusion via anion exchange, while in a hydrophilic nanohybrid, it is due to intraparticle diffusion via anion exchange with the anions in the physiological medium.

The interactome: predicting the protein-protein interactions in cells

The term Interactome describes the set of all molecular interactions in cells, especially in the context of protein-protein interactions. These interactions are crucial for most cellular processes, so the full representation of the interaction repertoire is needed to understand the cell molecular machinery at the system biology level. In this short review, we compare various methods for predicting protein-protein interactions using sequence and structure information. The ultimate goal of those approaches is to present the complete methodology for the automatic selection of interaction partners using their amino acid sequences and/or three dimensional structures, if known. Apart from a description of each method, details of the software or web interface needed for high throughput prediction on the whole genome scale are also provided. The proposed validation of the theoretical methods using experimental data would be a better assessment of their accuracy.

DFT study on hydroxy acid-lactone interconversion of statins: the case of atorvastatin

Atorvastatin (ATV), the best known HMG-CoA reductase inhibitor family member, undergoes pH-dependent hydroxy acid-lactone interconversion similar to other statins. Although the only active form is a linear one, it was shown that drug interactions should also be considered for the lactone. The ATV lactonisation-hydrolysis mechanism was investigated theoretically using the density functional theory (DFT) method. Under both mildly acidic and basic conditions, the ATV lactone form is less stable than its hydroxy acid form. However, in the presence of a carboxylic acid, the equilibrium was only slightly shifted towards the lactone side (4 kcal mol(-1) difference between the substrate and the product), while energy gain for the hydrolysis under basic conditions amounts to 18 kcal mol(-1). Hydrolysis activation energy barriers were 19 and 6 kcal mol(-1), in acidic and basic conditions, respectively. We determined one-step interconversion as unfavourable under physiological conditions due to a 35 kcal mol(-1) activation energy barrier. All data were compared with analogue ones for fluvastatin (FLV) reported earlier and indicated that ATV is more flexible than FLV, not only due to the fact that it has more rotatable carbon-carbon single bonds, but also because ATV lactonistation-hydrolysis energy barriers are lower.