Izabela Muszalska

Analysis of Sartans: A Review

The risk of cardiovascular diseases is closely related to hypertension, high cholesterol levels, and diabetes. When these risk factors appear together they are referred to as a metabolic syndrome. In the treatment of cardiovascular diseases, a combination of antihypertensive, hypolipemiant, and antidiabetic drugs is often applied. Diuretics (chlortalidone, hydrochlorothiazide, etc.) and angiotensin II receptors antagonist (sartans) are used to control hypertension, whereas statins (fluvastatin, simvastatin, etc.) are used to reduce cholesterol levels. This review is concerned with methods for the analysis of sartans in various matrices, such as pharmaceutical formulations, environmental and biological samples, and discusses the current status of stability studies of sartans . It also presents analytical methods for the simultaneous determination of sartans, diuretics, and statins.

Strategies in the designing of prodrugs, taking into account the antiviral and anticancer compounds

Prodrugs are a wide group of substances of low or no pharmacological activity. The search for prodrugs is aimed at obtaining drugs characterized by better pharmacokinetic properties, pharmaceutical availability and selective activity of the active substance. Prodrug strategies involve chemical modifications and syntheses of new structures as well as the establishment of systems that deliver active substances for therapeutic aims that is prodrug-based treatments. The paper describes decisive factors in prodrug designing, such as enzymes participating in their activation, concepts of chemical modifications in the group of antiviral drugs and new anticancer treatments based on prodrugs (ADEPT, GDEPT, LEAPT). Prodrugs are seen as a possibility to design medicines which are selective for their therapeutic aim, for example a tumorous cell or a microorganism. Such an approach is possible thanks to the knowledge on: pathogenesis of diseases at molecular level, metabolism of healthy and affected cells as well as metabolism of microorganisms (bacteria, fungi, protozoa, etc.). Many drugs which have been used for years are still studied in relation to their metabolism and their molecular mechanism of operation, providing new knowledge on active substances. Many of them meet the criteria of being a prodrug. The paper indicates methods of discovering new structures or modifications of known structures and their synthesis as well as new therapeutic strategies using prodrugs, which are expected to be successful and to broaden the knowledge on what is happening to the drug in the body, in addition to providing a molecular explanation of xenobiotics activity.

Calculation procedures and HPLC method for analysis of the lipophilicity of acyclovir esters.

Abstract Acyclovir (ACV) belongs to a class of drugs with low bioavailability. Selected ACV esters including acetyl (Ac-), isobutyryl (iBut-), pivaloyl (Piv-), ethoxycarbonyl (Etc-) and nicotinoyl (Nic-) were synthesized, and their lipophilicity was determined by the high-performance liquid chromatography (HPLC) RP method. Statistical analyses of the comparative values of log P and clog P were carried out using computational methods. It was proved that the AC log P algorithm can be useful for the analysis of these compounds and has a statistically justified application in the assessment of the quantitative structure–activity relationship. Moreover, the lipophilicity determined by the HPLC method appears as follows: ACV < Ac- < Nic- < Etc- < iBut- < Piv-.

New molecular targets of anticancer therapy - Current status and perspectives.

Molecularly targeted anticancer therapy involves the use of drugs or other substances affecting specific molecular targets that play a part in the development, progression and spread of a given neoplasm. By contrast, the majority of classical chemotherapeutics act on all rapidly proliferating cells, both healthy and cancerous ones. Target anticancer drugs are designed to achieve a particular aim and they usually act cytostatically, not cytotoxically like classical chemotherapeutics. At present, more than 300 biological molecular targets have been identified. The proteins involved in cellular metabolism include (among others) receptor proteins, signal transduction proteins, mRNA thread matrix synthesis proteins participating in neoplastic transformation, cell cycle control proteins, functional and structural proteins. The receptor proteins that are targeted by currently used anticancer drugs comprise the epithelial growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGFR) and vascular endothelial growth factor receptor(VEGFR). Target anticancer drugs may affect extracellular receptor domains (antibodies) or intracellular receptor domains (tyrosine kinase inhibitors). The blocking of the mRNA thread containing information about the structure of oncogenes (signal transduction proteins) is another molecular target of anticancer drugs. That type of treatment, referred to as antisense therapy, is in clinical trials. When the synthesis of genetic material is disturbed, in most cases the passage to the next cycle phase is blocked. The key proteins responsible for the blockage are cyclines and cycline- dependent kinases (CDK). Clinical trials are focused on natural and synthetic substances capable of blocking various CDKs. The paper discusses the molecular targets and chemical structure of target anticancer drugs that have been approved for and currently applied in antineoplastic therapy together with indications and contraindications for their application.

HPLC and HPLC/MS/MS Studies on Stress, Accelerated and Intermediate Degradation Tests of Antivirally Active Tricyclic Analog of Acyclovir.

The degradation behavior of a tricyclic analog of acyclovir [6-(4-MeOPh)-TACV] was determined in accordance with International Conference on Harmonization guidelines for good clinical practice under different stress conditions (neutral hydrolysis, strong acid/base degradation, oxidative decomposition, photodegradation, and thermal degradation). Accelerated [40±2°C/75%±5% relative humidity (RH)] and intermediate (30±2°C/65%±5% RH) stability tests were also performed. For observation of the degradation of the tested compound the RP-HPLC was used, whereas for the analysis of its degradation products HPLC/MS/MS was used. Degradation of the tested substance allowed its classification as unstable in neutral environment, acidic/alkaline medium, and in the presence of oxidizing agent. The tested compound was also light sensitive and was classified as photolabile both in solution and in the solid phase. However, the observed photodegradation in the solid phase was at a much lower level than in the case of photodegradation in solution. The study showed that both air temperature and RH had no significant effect on the stability of the tested substance during storage for 1 month at 100°C (dry heat) as well as during accelerated and intermediate tests. Based on the HPLC/MS/MS analysis, it can be concluded that acyclovir was formed as a degradation product of 6-(4-MeOPh)-TACV.

Determination of adamantane derivatives in pharmaceutical formulations by using spectrophotometric UV-Vis method.

A simple and sensitive extractive spectrophotometric method have been developed and validated for determination of amantadine hydrochloride (AM), memantine hydrochloride (MM) and rimantadine hydrochloride (RM) in pure and pharmaceutical formulations. The method is based on the reaction of these active compounds with bromophenol blue (BB) in acetate buffer (0.1 M) pH 3.5 to form an orange-colored products which have absorption maxima at 408 nm. The procedure of complexation was optimized with regard to such factors as concentrations of BB, pH of medium, a kind of extracting solvents and a number of extractions. Under the optimum conditions, linear relationships A408 = f(c) with good correlation coefficients (≥0.996) and low limit of detection were obtained in the ranges of 50.0–220.0 µg·mL−1, 20.0–150.0 µg·mL−1 or 10.0–110.0 µg·mL−1 for AM, MM and RM, respectively, for the spectrophotometric methods. The proposed method could be applied to the determination of AM, MM and RM in dosage forms. The recovery was 95.3–101.9%. The method was linear, precise and accurate.

Ester Groups as Carriers of Antivirally Active Tricyclic Analogue of Acyclovir in Prodrugs Designing: Synthesis, Lipophilicity - Comparative Statistical Study of the Chromatographic and Theoretical Methods, Validation of the HPLC Method

Knowledge of the lipophilicity of candidate compounds for prodrugs may predict their predetermined course/effect in the body. Acyclovir (ACV) belongs to a class of drugs with low bioavailability. Its tricyclic analogues, the derivatives of 3,9-dihydro-3-[(2-hydroxyethoxy)methyl]-9-oxo-5H-imidazo[1,2-a]purine (TACV) exhibit similar antiviral activities and are more lipophilic as compared with acyclovir itself. In the search for new antiviral prodrugs 6-(4- methoxyphenyl) tricyclic compound (6-(4-MeOPh)-TACV) was modified by esterification of a hydroxyl group in the aliphatic chain. Selected esters (acetyl, isobutyryl, pivaloyl, ethoxycarbonyl and nicotinoyl) were synthesized and their lipophilicity was determined by the HPLC-RP method. The study compared the log kw calculated from the linear and quadratic equations and proved the correctness of the application of the linear relationship log k as a function of the concentration of ACN in the mobile phase (30-60%). Statistical analyses of the comparative values of log kw and clogP were carried out using computational methods. It was proved that the AC logP algorithm can be useful for the analysis of these compounds, which can have a statistically justified application in the assessment of the quantitative structure- activity relationship (QSAR). The lipophilicity determined by the HPLC method appears as follows: 6-(4-MeOPh)-TACV < Ac- < Nic- < Etc- < iBut- < Piv- (log kw = 0.65-2.26). Finally, the HPLC-RP method was developed and validated for simultaneous determination of synthesized esters.

Stability Study of New Analgesic Active Compound, 4‐Methoxy‐2‐[3‐[4‐(2‐methoxyphenyl)‐1‐piperazinyl)]‐propyl] Derivative of Pyrrolo[3,4‐c]pyridine, in Aqueous Solutions Using the HPLC Method

Abstract A high performance liquid chromatographic method which has been applied for the determination of a 4‐methoxy‐2‐[3‐[4‐(2‐methoxyphenyl)‐1‐piperazinyl)]‐propyl]‐6‐methyl‐1H‐pyrrolo[3,4‐c]pyridine‐1,3(2H)‐dione (IV) (a new derivative of 3,4‐pyridinedicarboximide with an analgesic activity), with 4‐hydroxybenzoic acid ethyl ester as an internal standard (i.s.), is described. The samples of solution were chromatographed on LiChrosorb® RP‐8 column (250×4.0 mm I.D., dp=5 µm), using an eluent composed of: acetonitrile–propan‐2‐ol–phosphate buffer pH 2 (0.01 mol/L) (30∶30∶40). Ultraviolet detection was performed at the wavelength of 240 nm. The method was validated with respect to selectivity, linearity, accuracy, and precision. The method was found appropriate for kinetic studies with compound IV. The kinetics of hydrolysis of compound IV in aqueous solutions at 60, 70, 80, and 90°C over the pH range 0.4–7.0 was investigated. The stability of compound IV was found to be dependent on pH. The pH‐rate profile indicated specific acid catalyzed and spontaneous water catalyzed degradation. The ionic strength, effect, and thermodynamic parameters of the reaction were determined.

Stability of Epidoxorubicin Hydrochloride in Aqueous Solutions: Experimental and Theoretical Studies

The first-order degradation kinetics of epidoxorubicin were investigated as a function of pH, temperature, and buffers concentrations. The degradation was followed by HPLC. Buffer catalysis was observed in acetate and phosphate buffers. The pH-rate profiles were obtained at 333, 343, 353, and 363 K. The pH-rate expression was , where , , and are the second-order rate constants (mol−1 L s−1) for hydrogen ion activity and for hydroxyl ion activity, respectively, and and are the first-order constants (s−1) for spontaneous reaction under the influence of water. Epidoxorubicin demonstrates the greatest stability in the pH range 3–5. The electrostatic molecular potential orbitals HOMO-LUMO were also defined in order to determine the cause of the reactivity of particular epidoxorubicin molecule domains in solutions with various pH values.

Forced Degradation and Photodegradation Studies of Pyrrolo[3,4-c]pyridine-1,3-dione Derivatives as Analgesic Active Compounds Using HPLC, UV and IR Spectrometry, and HPLC/MS Methods.

The stress and accelerated tests as well as photostability analysis in solutions and the solid phase of three selected derivatives of pyrrolo[3,4-c]pyridine-1,3-dione were carried out according the International Conference on Harmonization guidelines. For observation of the degradation of tested compounds, the RP-HPLC method was used. The study included the effect of temperature, relative humidity, water, H+ and OH- ions, hydrogen peroxide, and light (6.0×10(6), 1.2×10(6) lux·h) on the stability of pyrrolo[3,4-c]pyridine-1,3-dione derivatives. Studies have shown that these derivatives are photolabile, extremely unstable in an alkaline medium, labile in an acidic medium, and stable in a neutral medium. Their sensitivity to oxidizing agents depends on the chemical structure. The shortening of the aliphatic chain leads to an increase in the sensitivity to hydrolytic and oxidizing factors. The presence of the 1,3,4-tetraisoquinoline group promotes an increase in the susceptibility to photodegradation. The introduction of a carbonyl group to the aliphatic chain and the tetrafluoromethyl group to the phenyl ring stabilizes the molecule in the case of hydrolysis and oxidation and also increases sensitivity to light. The analysis of observed photodegradation products using the HPLC-diode array detector, HPLC/MS, and UV and IR spectrometry techniques showed degradation targeted at the breaking of the pyrrolo[3,4-c]pyridine-1,3-dione, piperazine, and/or tetrahydroisoquinoline rings.