Current Pharmaceutical Analysis - Volume 10, Issue 1, 2014

The studies of new anti-cancer drugs are constantly in the centre of scientific interest. This paper provides an overview of the complex compounds of platinum(II) and palladium(II) as anti-cancer drugs. These drugs have been described in dependence on the type of cells which are under the influence of the cytotoxic drug and side effects arising from the use of the drug. In the case of some drugs such as cisplatin or trans-[PtCl2(tz)2] the mechanisms of action in the body are described. Furthermore, in the paper the methods used for cytotoxicity determination of chemical compounds considered to be used as anticancer drugs are described. The MTT, MTS, LDH, BrdU, Alamar Blue and Neutral Red test are examples of such methods.

To treat hypertension around 75% of patients will require combination therapy for which administration of lisinopril and indapamide could be of practical use. Lisinopril has a low oral bioavailability (around 25%) with large intersubject variability (6-60%), due to slow absorption. In order to improve drug permeability, encapsulation of the drugs within nanoparticles (NPs) has demonstrated great potential. For this reason we have prepared hard capsules containing both drugs: indapamide and lisinopril-loaded chitosan (CS) nanoparticles. The mucoadhesive characteristics of CS-NPs will prolong the residence time of lisinopril in contact with the intestinal membrane thereby increasing its oral bioavailability. Moreover, for their quantification a reversed-phase HPLC method is developed and validated using a C18 column. The mobile phase is prepared with methanol:water (50:50, v/v) including triethylamine (0.1% of total volume) and adjusted at pH 3.1. The calibration curves are linear over the ranges 16-24 μg.mL-1 for lisinopril and 8-12 μg.mL-1 for indapamide. Intra-day precision results in %RSD ranging 0.74-1.86 for lisinopril and 0.60-1.91 for indapamide. Recovery results obtained for lisinopril and indapamide range 98.22-102.34% and 97.35-101.00%, respectively. The LOD and LOQ are 0.4 μg.mL-1 and 1.4 μg.mL-1 for lisinopril, and 0.5 μg.mL-1 and 1.5 μg.mL-1 for indapamide. The HPLC method is simple, easy to apply, rapid, with UV detection, and allows for quality control of the new formulation developed. The method can be applied for the quantification of this drug combination in medicinal products.

The influence of addition of dsDNA on the electrocatalytic effect of carbon matrices, e.g. synthetic monocrystalline diamond, fullerenes C60 and multi-walled carbon nanotubes was studied. Three neurotransmitters: dopamine, epinephrine and norepinephrine, which are known as biomarkers that play an important role in transporting and modulating nervous impulses in the synapse were chosen as model analytes. Cyclic voltammetry was used to determine the optimum working conditions with a phosphate buffer solution at a pH=4 with KNO3 as support electrolyte. Differential pulse voltammograms (DPVs) were employed to assess the electrolytic effect of dsDNA on carbon matrices under the optimized conditions, and the potential applications of the biosensors for pharmaceutical and biomedical analysis.

Transporters belonging in the ATP-binding cassette (ABC) family are crucially involved in the determination of the pharmacokinetic behavior of xenobiotics and in the development of drug resistance. The targeting of these transporters has been accepted as a rational option via which to modify the absorption or distribution of pharmaceutical agents and to combat ABC-related inefficiency. Inhibitors of the breast cancer resistance protein (BCRP/ABCG2) multidrug transporter are of interest as chemosensitizers for clinical drug resistance, for improving the pharmacokinetics of substrate chemotherapeutic drugs, and in functional assays of BCRP activity for tailoring chemotherapy. In this study, a reversephase high-performance liquid chromatographic method was developed for the determination of a simplified fumitremorgin C analog, Ko134, a potent ABCG2 inhibitor, in murine serum. The assay involves a simple sample preparation step followed by chromatographic separation on a C8 reversed-phase analytical column. The calibration plots were linear over the range 0.1 to10 μg/ml (r > 0.99). The limits of detection and quantification were 10 ng/ml and 50 ng/ml, respectively. The validation results demonstrated that the method is precise, accurate and selective for the determination of Ko134 in mouse serum. The method was successfully applied to evaluate the pharmacokinetic parameters of Ko134 after different modes of administration in mice.

Capillary electrophoresis (CE) was used to follow Diclofenac tablet dissolution, in very short times and allowing dissolution testing without volume replacement. By using Student´s t test and F-test, this CE method was compared with HPLC. Statistical data show that there are no significant differences among them. The drug release kinetic of diclofenac tablets was described by various mathematical models and equations. Model-Independent Methods: t50% = 10.34 min; t80% = 20 min; DE% = 79.41% and MDT = 10.85 min, show that diclofenac tablet dissolution rate is very high, having 80% drug dissolution within 20 minutes. Model-Dependent Methods. The kinetics models used were: zero order, first order, Hixson–Crowell cube root law, Higuchi model, and Weibull model. Criteria used to choose the best model was by comparisson of r2 and AIC (Akaike Information Criteria). The model that best adjusts diclofenac tablet dissolution profile was the Hixson-Crowell cube root model.

An improved RP- HPLC method with PDA detection has been developed and validated for the simultaneous estimation of artemisinin and dexamethasone in ocular nanodispersion formulations and it has been successfully adopted to check the ex-vivo corneal transport. The chromatographic separation was achieved using phenomenex C18 column (250 × 4.6 mm, 5 μm) analytical column and the mobile phase consisting of acetonitrile: (methanol : water, 4: 6) mixture at the ratio of 45: 55, v/v at a flow rate of 1.0 mL/min and injection volume of 200 μl. The column temperature was maintained at 50°C. The UV detection was carried out at 219 nm using photodiode array detector. The retention times of dexamethasone and artemisinin were found to be 4.5 and 7.9 minutes respectively. Artemisinin and dexamethasone calibration curves were found to be linear with correlation coefficient of 0.9617 and 0.9954 respectively at a dynamic concentration ranging from 250ng/mL to 1250 ng/mL. Recovery was between the ranges of 98.9% - 116.8% for both artemisinin and dexamethasone. The developed method is very selective as both peaks were well separated with a short analysis time of 10 minutes and does not require any preliminary treatment of sample.

With the objective of decreasing analysis time and retaining good efficiency (UPLC-MS/MS) is an outstanding analytical approach for speedy biomedical analysis. The aim of this study was to develop validate a simple, rapid, sensitive and specific UPLC-MS/MS method for quantification of cinacalcet, a calcimimetic agent, which acts on a calcium sensing receptor of the parathyroid gland in human plasma. After following a liquid–liquid extraction procedure with diethyl ether–dichloromethane (70:30, v/v), cinacalcet (CIN) and internal standard (IS) abiraterone with C18 Acquity UPLC BEHTM column. m/z 358.07 > 155.0 and m/z 350.1 > 156.0 where the ion transitions recorded in the positive ion multiple reaction monitoring mode for cinacalcet for IS. The mobile phase consisted of acetonitrile: 10 mM ammonium acetate: formic acid (90:10:0.1% v/v/v) with a flow rate of 0.4 mL/min. The assay exhibited a linear dynamic range of 0.2–100 ng/mL for cinacalcet in human plasma with good correlation coefficient (IQ 0.995) and with an LOQ of 1 ng/mL. The intra- and inter-assay precisions were satisfactory; the relative standard deviations did not exceed 6.98 %. This method was simple, rapid and highly sensitive, hence could be used for analysis of cinacalcet in human plasma.

Robustness tests were performed on a gradient RP-HPLC method that had been developed for rapid simultaneous separation and determination of clarithromycin, norfloxacin, doxycycline, tinidazole and omeprazole in their pharmaceutical dosage forms. Separation was carried out on a 250 x 4.6 mm (i.d.), 5μm ODS column (Inertsil, Tokyo, Japan) and multiwavelength overlay chromatograms at max of 210 and 310 nm were used for quantitative analysis. The standard curve was linear in the concentration range of 100 – 900, 5 – 150, 20 – 220, 10 - 150 and 0.5 - 110 μg ml-1 for clarithromycin, norfloxacin, doxycycline, tinidazole and omeprazole, respectively. Robustness tests were performed using twolevel fractional factorial designs with resolution III, so only main effects can be estimated. Factors chosen for this study were the column temperature (˚C), pH, ion pairing agent concentration (g/l), phosphate buffer concentration (g/l), the fraction of mobile phase B (B% start) at 4 min of the gradient and fraction of mobile B (B% end) at 7 min of the gradient run. The significance of the factor effects was determined statistically, using algorithm of Dong in the calculation of critical effects, and graphically, by means of half-normal plots. Non-significant intervals for significant factors and system suitability limits were calculated based on robustness tests' results. The method was validated according to ICH guidelines. The proposed method was found to be accurate, reproducible, and consistent which is useful for the routine determination of clarithromycin, norfloxacin, doxycycline, tinidazole and omeprazole in combined mixtures and pharmaceutical dosage forms.

DNA methylation is the most common epigenetic tool used by cells to express or silence a gene. Methylation is observed when there is an addition of methyl group at position 5 of cytosine pyrimidine ring or at nitrogen present on 6th position of adenine purine ring. It plays a vital role in many aspects of biology including development and disease. A revolution has been witnessed in DNA methylation analysis technology over the past decade, analysis earlier restricted to specific loci can now be executed on a genome-scale and entire methylomes can be characterized at single-base-pair resolution. Methylation can be detected using bisulfite conversion, methylation sensitive restriction enzymes, methyl binding proteins and anti-methylcytosine antibodies. No single method of DNA methylation analysis is appropriate for every application. By understanding the type of information provided by and inherent potential for bias and artifacts associated with each method, investigators can select method most appropriate for their specic research needs. This article is focused on brief knowledge about DNA methylation, several techniques developed so far and advantages and disadvantages of such techniques.