Current Pharmaceutical Analysis - Volume 7, Issue 2, 2011

This paper describes a stripping method for the determination of oseltamivir (Tamiflu) at the submicromolar concentration level. This method is based on controlled adsorptive accumulation of oseltamivir at the thin-film mercury electrode followed by a linear cyclic scan voltammetry measurement of the surface species. Optimum experimental conditions consist of a NaOH solution (pH 7-8) as supporting electrolyte, an accumulation potential of -0.40 V, and a scan rate of 100 mV s-1. The response of oseltamivir is linear over the concentration range from 0.0 - 0.5 ppm using lower accumulation time. When there was an accumulation time of 15 minutes, the detection limit was found to be 1.66 ppb (5.3 x 10-9 mol L-1). More convenient methods to measure the oseltamivir in the presence of the didanosine, acyclovir, nevirapine, nelfinavir, efavirenz, lamivudine and zidovudine were also investigated in this experiment. The utility of the method is demonstrated by the presence of oseltamivir together with hypoxanthine, ATP or DNA.

Nadolol and propranolol are beta-blockers used to prevent the onset of migraines. Two simple and rapid High Performance Liquid Chromatographic (HPLC) methods with ultraviolet detection were evaluated in order to establish their efficacy for detecting nadolol and propranolol hydrochloride in samples obtained from in vitro transdermal absorption studies. Both methods were validated for specificity, linearity, precision, accuracy, limit of detection, limit of quantification and robustness. Moreover, the stability of both drugs in a buffered solution was assessed. Separation was carried out on a 250 mm Kromasil® C18 column at room temperature. When nadolol was analysed, the detector response at 269 nm was found to be linear in a concentration range of 0.17 to 167 μM. In the case of propranolol hydrochloride, a fixed wavelength of 291 nm for quantification corresponded with calibration lines in the range of 0.11 to 113 μM. The limits of detection (LOD) and quantification (LOQ) were 0.058 and 0.038 μM and 0.171 and 0.115 μM for nadolol and propranolol hydrochloride, respectively. The maximum relative error and relative standard deviation detected were 5.19% and 6.08% respectively for nadolol and 3.57% and 6.44% respectively for propranolol hydrochloride. The results of robustness were highly satisfactory.

The electrochemical behaviors of eugenol [1-hydroxy-2-methoxyl-4-allylbenzene] on the gold and platinum electrodes were investigated in a Britton-Robinson buffer (pH 1.60-10.44), acetate buffer, phosphate buffer solutions (pH 2.11 and 3.67) and methanol or acetonitrile containing various supporting electrolytes. The detection cell consisted of a gold wire electrochemical signal obtained with a supporting electrolyte containing 60 % methanol-1.0 mM of potassium dihydrogen phosphate (pH 2.40) as the mobile phase. The limit of quantification of the method was found to be 0.02 ng for eugenol. When eugenol was determined in commercial essential oils and pharmaceutical products with the method proposed the results obtained were comparable with those obtained by high-performance liquid chromatography with ultraviolet detection.

A rapid and sensitive liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of asiaticoside in beagle dog plasma. Plasma samples were extracted by protein precipitation with methanol. The chromatographic separation was performed on a C18 column with the isocratic mobile phase comprising of 78% methanol in water and 10 mM ammonium acetate buffer. Asiaticoside and the IS were detected with a triple-quadrupole tandem mass spectrometer in the negative ion mode for drug quantification. The total analytical run time was relatively short (4 min), and the limit of assay quantification (LLOQ) was 2.4 ng/mL using 300 μL of dog plasma. Asiaticoside and the internal standard (nimodipine) were monitored in the multi-reaction-monitoring (MRM) mode as follows: m/z 957.4→469.4 and m/z 417.2→122.0, respectively. The standard curve was linear over a concentration range from 2 to 190 ng/mL, and the correlation coefficients were greater than 0.998. The recoveries of asiaticoside from plasma were larger than 81.7%, and RSD of inter-day and intra-day assay were below 8.2%. The validated method was firstly applied to investigate the pharmacokinetics of asiaticoside in dogs.

A static headspace gas chromatographic (sHS-GC) method for quantitative determination of residual organic solvents in eprosartan mesylate drug substance is developed. SE-30 capillary column (30 m x 0.25 mm i.d., 0.5 μm film thickness) and FID detector are adopted. Response surface methodology (RSM) has been successfully applied to obtain the optimum headspace conditions: the equilibrium temperature is set at 80 °C, equilibrium time at 40 min and the ionic strength (K2CO3) at 4.0 mol/L. Injection is carried out in split mode, with a split ratio of 15. A 0.1 mol/L NaOH solution is proposed as the sample solvent to obtain good sensitivity and recovery. The method of internal standard is used for quantitative analysis of three solvents utilized in the synthesis of eprosartan mesylate: methanol, dichloromethane and pyridine. Validation is performed within the requirements of ICH validation guidelines Q2A and Q2B. System suitability requirements described in the Chinese Pharmacopoeia are checked. Limits of detection and quantitation, precision, linearity and accuracy are determined, and acceptable results are obtained. The proposed method is demonstrated to be simple, accurate and sensitive, and can be used to determine the residual organic solvents in eprosartan mesylate drug substance.

Natural matrices comprise a continuous resource of immeasurable biological activities and chemical entities. The diversity of marine ecosystems has provided a unique source of chemical compounds with potential bioactivities that could lead to new drug candidates. In fact, as many marine-living organisms are soft bodied and/or sessile, over evolutionary time marine eukaryotes have developed an array of metabolites and strategies by which they protect themselves against external aggressions. Research involving marine natural products revealed a broad spectrum of pharmacological activities, as anti-inflammatory, antimicrobial, antitumor and cytotoxic, and the capacity to affect the cardiovascular, immune and nervous system, among others. Fatty acids (FA) are metabolites universally present in all organisms, where they play a number of biological roles, such as building blocks in biological membranes and signalling molecules. In addition to the known set of FA, marine organisms usually display molecules with a very rich chemistry and have been the source of many novel structures that frequently display marked pharmacological properties. As pharmacological research with marine chemicals continues to be extremely active, this review will focus the biological role and potential applications of fatty acids from marine organisms, such as sponges, echinoderms and molluscs, with particular emphasis on their application in cancer, inflammation, tuberculosis and malaria.

Curcumin is the active ingredient of turmeric which is widely used as a yellow spice and food additive in Asia, India and western world. It is a complex natural extraction with various biological target points and different cellular activities including anti-inflammation, antioxidant, decreasing blood lipid, regulating human immunity function and antitumor effect. Recently, its anti-tumor mechanisms have been thoroughly investigated. Accumulating evidences show that curcumin holds a promising efficacy at very low concentration through its interaction with multiple molecular targets. In a phase 2 study, the clinical benefits of curcumin as a single agent were significant in patients with advanced pancreatic cancer. The present review delineates the molecular mechanism of the anti-tumor activities of curcumin in hematological malignancies. Our research shows that the multiple and broad biological effects of curcumin are mediated through its interaction with target proteins including cell proliferation pathway(p27KIP1, p21WAF1, pRbp- and cyclinD3), cell survival pathway (Mcl-1, Bax, Bak and STAT3,5), caspase activation pathway(caspase-8,caspase-9) and angiogenesis pathway( VEGF,VEGFR), as well as epigenetic modulation of target genes through interaction with histone deacetylases and histone acetyltransferases in hematological malignancies.

Background: Tabernaemontana divaricata (L.) R. Br. (Apocynaceae) is an evergreen usually glabrous tree found throughout the India, Australia and Polynesia. Plant roots are chewed for the relief of tooth rubbed into a thin paste and administered as vermicide, also used with lime juice to clear opacity of cornea, juice of leaves used as cooling application for wounds to prevent inflammations. The tree species has special interest because the indole alkaloids, which are commonly, used for anti-inflammatory, antifertility and antioxidant activities. The active sub-fractions and seven indole alkaloids obtained from aerial parts of T. divaricata were investigated first time for their antimicrobial, antineoplastic and cytotoxic activities. Methods: The indole alkaloids obtained from the ethanolic extract of T. divaricata were analyzed by thin layer chromatography, high performance liquid chromatography, and mass spectroscopy. Indole alkaloids were screened for antineoplastic, cytotoxic and antimicrobial activities by using packed cell volume and microdilution methods. Results: The observed results indicated that the strong antibacterial activity was showed by 5-oxocoronaridine at 50 μg/ml dose against K. pneumoniae and coronaridine demonstrated maximum antifungal activity against P. chrysogenum at the dose of 60 μg/ml. The tabernaemontanine and coronaridine demonstrated activity at 10 μg/kg/day and 5 μg/kg/day of 73.40% and 69.34% inhibition against Sarcoma 180. The chloroform sub-fraction (5.0 μg/ml) and coronaridine (3.0 μg/ml) showed selective cytotoxic effect against Chinese hamster V79 cells. Conclusion: The isolated indole alkaloids exhibited antineoplastic and antimicrobial activity thus have great potential as a source of ayurvedic and allopathic products.

Herbal medicine is becoming more and more popular and has been widely used in the world. However, the quality control is a major issue for different types of herbal products. In this study, a combination of high performance liquid chromatography (HPLC) and gas chromatography (GC) analytical methods was successfully employed for the pharmaceutical analysis and quality control of herbal medicine. Five different brands of a popular Chinese herbal medicine “Yin Qiao Jie Du” tablets were chosen as the model products for the purpose of analysis and quality control. After optimization and validation, HPLC and GC methods were applied to quantify the contents of nonvolatile bioactive compounds glycyrrhizin, chlorogenic acid, and volatile ingredient menthol, respectively. The results revealed significant content variations of active ingredients among different brands of tablets. Glycyrrhizin ranges from 0 to 2.672 mg in one tablet, chlorogenic acid ranges from 0.416 to 2.453 mg, while menthol ranges from 0 to 0.1666 mg, indicating different quality of the same product from various manufacturers. This study demonstrated that the combination of HPLC and GC methods can be used to quantify both the nonvolatile and volatile active ingredients in herbal medicines and thus control their quality.