Current Pharmaceutical Analysis - Volume 11, Issue 1, 2015

Spectinomycin, a tricyclic aminoglycoside antibiotic with peculiar chemical structure and pharmacological profile was characterized in terms of microscopic protonation constants. ¹H-¹⁵N HMBC-pH titrations were carried out to allocate the order of basicities of the two similar methylamino functions of spectinomycin, and ¹H NMR-pH titrations were performed on spectinomycin and actinamine, its symmetrical model compound to determine the basicity of the amino sites. It was found that the methylamino moiety in position 3 is of some 60% higher basicity than its counterpart in position 1, and protonation at one site decreases the basicity of the other site by 1.17 logk units. Both secondary amino sites as such are of relatively low basicity, due to the adjacent, electron-withdrawing 7 oxygens. At the pH of blood nearly equal amounts of di- and monocationic species coexist, while less than 1% of neutral spectinomycin occurs at this pH. The pHdependent distribution of the microspecies is depicted.

Hydrophile-lipophile balance method is one of the requirements which can complete the existing guidelines, thereby making the most stable emulsion. The aim of present work was to determine the required hydrophile-lipophile balance of lemon essential oil in oil-in-water emulsions. Paraffin oil and its known required hydrophile-lipophile balance were used as a standard. Span 80 and Tween 80 or Gelucire 44/14 blend were applied as emulsifying agents. Emulsions were evaluated by droplet size distribution and turbidity measurements. Based on the estimated stability of emulsion series and according to the droplet size analysis with lower variations, the required hydrophile-lipophile balance of lemon oil was measured approximately 12 in oil-in-water systems.

40wt.% polyaniline/CuGeO3 nanowires have been used as the glassy carbon electrode (GCE) modified materials for the electrochemical determination of cyanuric acid. The effect of scan rate, cyanuric acid concentration and electrolytes on the electrochemical behaviors of cyanuric acid has been analyzed. Polyaniline content on the electrochemical determination of cyanuric acid has also been discussed. The intensities of the cyclic voltammogram (CV) peaks vary linearly with the increase of the scan rate and cyanuric acid concentration. The detection limit is 1.9 μM and 1.1 μM for cvp1 and cvp2, respectively and linear range is 0.005-2 mM using 40wt.% polyaniline/CuGeO3 nanowire modified GCE. The detection limit decreases with increasing the polyaniline content.

A simple, sensitive, precise and reliable gradient HPLC method was developed and validated for simultaneous quantitative determination of losartan potassium and its eleven related impurities and degradation products in a tablet formulation. Among them B, C, D, E, F, I and G were related impurities and J, K, L and M were degradation products. Optimum chromatographic separation was carried out on an ACCHROM ODS-C18 (250 mm×4.6 mm, 5 μm) column using mobile phases consisting of acetonitrile and 0.1% phosphoric acid under a gradient elution program. The UV detection wavelength was performed at 220 nm with a flow rate of 1.0 mL/min. The column temperature was maintained at 35 °C. All standard curves obtained exhibited good linear regression (r > 0.9995) within the tested range. All the average recovery rates were in the range of 97.00-103.00% and RSD was less than 2.00% (n = 3). Limits of detection and quantification were determined in the level of ng/mL. The results demonstrated that the validated method was suitable for the simultaneous quantification of losartan potassium and its eleven related impurities and degradation products in a tablet formulation.

A highly sensitive and selective LC-MS/MS assay was developed and validated for determination of a novel antitubercular compound S006-830 in rat plasma. The analyte and internal standard (IS) were extracted from plasma by a two step liquid–liquid extraction procedure using 2% isopropanol in n-hexane. Chromatographic separation was achieved on a Phenomenex, Luna C-18 column (3μm, 100mm x 2mm i.d.) under isocratic condition [92:8 (v/v); ACN (0.1% formic acid) : ammonium acetate buffer (10 mM, pH 4)] at a flow rate of 0.450 ml/min. The quantification was performed on Qtrap 5500 LC-MS/MS coupled with ekspert ultra LC 100-XL system (AB Sciex). The detection was performed in positive electrospray mode using multiple reaction monitoring. The precursor to production of ion transitions selected for quantification of S006-830 and IS was m/z 424.353/203.00 and 330.300/267.400 respectively. LC-MS/MS method was found sensitive and reproducible over a linearity range of 0.15-40 ng/ml. Recoveries of S006-830 from spiked plasma samples were consistent and found to be more than 70%. Further, the applicability of this method has been described by determining pharmacokinetic (PK) profile and plasma protein binding of S006-830 in rats. Irregular plasma-concentration time profile was observed. Oral PK profile of S006-830 at 50 mg/Kg demonstrated that mean (±SEM) T1/2 and mean residence time were 8.30 ± 1.30 h and 8.44 ± 0.57 h, while Cmax and AUC0-last were 1.94 ± 0.30 μg /ml and 6.25± 1.66 μg.h /ml respectively. Plasma protein binding for S006-830 was found to be 58.63 ± 3.4 %.

Sensitive LC/MS/MS method was developed and validated to evaluate the bioavailability of cardiovascular formulation- Atorvastatin (ATSV) and Olmesartan (OLM), after administration of its combined formulation to hypertensive patients to mark the drug interaction. Blood samples (ATVS+OLM) were collected, centrifuged at 3000 rpm, at 4°C for 20min and stored at -20 °C until analysis. To the thawed 0.5 mL of sample, 50 μl IS (Rosuvastatin) solution of 50 ng/mL was added and vortex mixing was conducted for 30 sec. To 10Mm solution, about 2 μl of 10% Tris Buffer was added, then it was sonicated (1 min), extracted with adding 5mL of ethyl acetate, hand mixed (10 min) and centrifuged at 5000 rpm for 15 min. The upper organic layer (4 ml) was separated and evaporated to dryness at 45°C, using a gentle stream of N2 atmosphere. The residue was reconstituted in 200 μL of the mobile phase and was injected to the LC-MS/MS system. The developed method was validated for specificity, accuracy, precision, stability, linearity, sensitivity and recovery. It was successfully applied to detect the drug interaction of ATSV & OLM, where OLM conc. was significantly higher in its combination treatment as compared to the single OLM treatment. Thus, ATSV+OLM is least effective in combination instead of its expected synergistic activity.

Human serum albumin is the most abundant protein in the blood serum. Albumin determines the protein binding characteristics for majority of drugs. It is a common practice that the human albumin is replaced by the cheaper and safer bovine albumin, with the assumption that they have identical binding properties, in the binding studies. We here report a case in which the anti-inflammatory drug ibuprofen exhibited different effects on displacing the calcium channel blocker nifedipine from its binding to bovine and human albumins. Ultrafiltration technique was used to separate free from bound nifedipine, and HPLC method was used to analyze its concentrations. The binding parameters were calculated using Scatchard analysis. Nifedipine binding profile to bovine albumin, with no ibuprofen, revealed that the drug has only one class of specific binding sites with n=1 and k = 5.4 x 10⁴ M^-1. However, binding studies of nifedipine in presence of ibuprofen revealed significant difference in the binding profile between bovine and human albumins. Moreover, the interaction of nifedipine with bovine albumin was found to be dependent on the ibuprofen concentration. In presence of lower ibuprofen concentrations, up to 83 μM, nifedipine molar binding ratio (r) was found to initially increase rather than decreasing. At higher Ibuprofen concentrations, r started to decrease. On the other hand, the displacement of nifedipine from human albumin exhibited no such initial increase in the molar binding ratio. This displacement-profile difference was observed at two different nifedipine concentrations of 10 and 20 μM.

It is now recognized that inflammatory processes regulate all stages of atherosclerosis, from disease initiation to thrombotic complications. C-reactive protein (CRP) is a plasmatic protein used as a general marker of inflammation. The high sensitivity C-reactive protein (hsCRP) refers to the measurement of CRP in blood samples using assays with sufficient sensitivity to quantify low (baseline) levels of this biomarker. Low-grade chronic inflammatory processes are linked to atherosclerosis and may be screened with the use of hsCRP, thus providing additional information in cardiovascular risk prediction. This review elaborates the role of CRP in atherogenesis and the value of hsCRP as a biomarker in cardiovascular risk prediction in both primary and secondary prevention setting.

Vitamin E (VE) is one category of important fat-soluble vitamins for human normal growth, which consists of eight isomers known as α-, β-, γ- and δ-tocopherol and α-, β-, γ- and δ-tocotrienol. Each of the isomers has unique and potent physiological functions, thus it is important to analyze VE isomers respectively. This review briefly introduces physiological functions of tocopherols and tocotrienols, and presents the progress of sample pretreatment and analysis of these compounds in pharmaceuticals and foods in the last decade, then makes a comparison in the aspects of sensitivity, selectivity and simplicity of the various analytical methods. Due to their high efficiency, speedness, inexpensiveness and environmental friendliness, nano-LC and capillary electrophoresis including non-aqueous capillary electrophoresis (NACE), capillary electrochromatography (CEC) and microemulsion electrokinetic chromatography (MEEKC) have been applied in the analysis of VE family, which will also be discussed in this review.