Chromatographic separation of (E)- and (Z)-isomers of entacapone and their simultaneous quantitation in human plasma by LC–ESI-MS/MS

A selective, sensitive and high throughput liquid chromatography–tandem mass spectrometry (LC–ESI-MS/MS) method has been developed and validated for the chromatographic separation and quantitation of (E)-entacapone and (Z)-entacapone in human plasma. Sample clean-up involved liquid–liquid extraction (LLE) of both the isomers and carbamazepine used as internal standard from 500 μL of human plasma. Both the analytes were chromatographically separated with a resolution factor of 3.0 on a Gemini C18 (50 mm × 4.6 mm, 5 μm particle size) analytical column using 1% formic acid and methanol (50:50, v/v) as the mobile phase. The selectivity factor (α) of the column for the separation was 2.0, based on the capacity factors of 2.6 and 1.3 for (E)- and (Z)-isomers respectively. The parent → product ion transitions for both the isomers (m/z 306.1 → 233.0) and IS (m/z 237.3 → 194.2) were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) and positive ion mode. The method was validated over the concentration range of 24.3–6076 ng/mL and 23.8–5960 ng/mL for (E)-entacapone and (Z)-entacapone respectively. Matrix effect was assessed by post-column analyte infusion experiment and the process/extraction efficiency found was 94.3% and 89.3% for (E)- and (Z)-isomers respectively. The method was successfully applied to a pivotal bioequivalence study in 36 healthy human subjects after oral administration of 200 mg (E)-entacapone tablet formulation under fasting conditions.     

Chitosan-Stearic Acid Based Polymeric Micelles for the Effective Delivery of Tamoxifen: Cytotoxic and Pharmacokinetic Evaluation

Chitosan is a widely employed polysaccharide with positive zeta-potential and better tissue/cell adhesion. Its hydrophilicity, high viscosity, and insolubility at physiological pH are major hurdles in proper utilization of this macromolecule. Therefore, it was conjugated with biocompatible stearic acid and the conjugate was employed to develop polymeric micelles for delivery of tamoxifen to breast cancer cells. The conjugate was characterized by FT-IR and NMR, and the nanocarrier was characterized for micromeritics, surface charge, drug loading, and morphological attributes. The efficacy was evaluated by in vitro MTT studies, safety by erythrocyte compatibility, and biodistribution by in vivo pharmacokinetic studies. Despite better drug loading and sustained drug release, cytotoxicity on MCF-7 breast cancer cells was substantially enhanced and the pharmacokinetic profile was significantly modified. The AUC was enhanced manifolds along with reduced clearance. The findings are unique and provide an alternative to the conventional lipid-based nanocarriers for better dose delivery, tissue adhesion, and desired pharmacokinetic modulation.     

Protective effects of L-pGlu-(2-propyl)-L-His-L-ProNH2, a newer thyrotropin releasing hormone analog in in vitro and in vivo models of cerebral ischemia

In the present study, the newly synthesized TRH analog (l-pGlu-(2-propyl)-l-His-l-ProNH₂; NP-647) was evaluated for its effects in in vitro (oxygen glucose deprivation (OGD)-, glutamate- and H₂O₂-induced injury in PC-12 cells) and in vivo (transient global ischemia) models of cerebral ischemic injury. PC-12 cells were subjected to oxygen and glucose deprivation for 6 h. Exposure of NP-647 was given before and during OGD. In glutamate and H₂O₂ induced injury, exposure of NP-647 was given 1, 6 and 24 h prior to exposure of glutamate and H₂O₂ exposure. NP-647, per se found to be non-toxic in 1-100 μM concentrations. NP-647 showed protection against OGD at the 1 and 10 μM. The concentration-dependent protection was observed in H₂O₂- and glutamate-induced cellular injury. In in vivo studies, NP-647 treatment showed protection of hippocampal (CA1) neuronal damage in transient global ischemia in mice and subsequent improvement in memory retention was observed using passive avoidance retention test. Moreover, administration of NP-647 resulted in decrease in inflammatory cytokines TNF-α and IL-6 as well as lipid peroxidation. These results suggest potential of NP-647 in the treatment of cerebral ischemia and its neuroprotective effect may be attributed to reduction of excitotoxicity, oxidative stress and inflammation.     

Systematic study of photoluminescence,lyoluminescence and mechanoluminescence in Ce3+‐ and Eu3+‐activated Li3PO4 phosphors

Li₃PO₄ phosphor was prepared using a modified solid‐state diffusion technique. In this work, photoluminescence, lyoluminescence and mechanoluminescence studies were carried out in a Li₃PO₄ microcrystalline powder doped with different rare earths. In photoluminescence studies, characteristic emission of Ce and Eu was observed. The lyoluminescence glow curves of Li₃PO₄ microcrystals show that lyoluminescence intensity initially increases with time and then decreases exponentially. The decay time consists of two components for all masses. The dependence of decay time, especially the longer component, on mass has been investigated. Experiments on γ‐irradiated crystals have proved that the light emission originates from the recombination of released F‐centres with trapped holes (V₂‐centres) at the sulfuric acid–solid interface. Incorporation of bivalent alkali in solid lithium phosphate leads to an enhancement of lyoluminescence. A possible explanation for the experimental results has been attempted. The phosphor has a mechanoluminescence single glow peak. Mechanoluminescence intensity under various loading conditions was investigated. It is observed that mechanoluminescence intensity increases with increasing impurity concentration and increasing piston impact velocity. The results may be considered as only being of academic interest in solid‐state materials. Copyright © 2013 John Wiley & Sons, Ltd.     

Role of Novel Multidrug Efflux Pump Involved in Drug Resistance in Klebsiella pneumoniae

Background

Multidrug resistant Klebsiella pneumoniae have caused major therapeutic problems worldwide due to the emergence of the extended-spectrum β-lactamase producing strains. Although there are >10 major facilitator super family (MFS) efflux pumps annotated in the genome sequence of the K. pneumoniae bacillus, apparently less is known about their physiological relevance.

Principal Findings

Insertional inactivation of kpnGH resulting in increased susceptibility to antibiotics such as azithromycin, ceftazidime, ciprofloxacin, ertapenem, erythromycin, gentamicin, imipenem, ticarcillin, norfloxacin, polymyxin-B, piperacillin, spectinomycin, tobramycin and streptomycin, including dyes and detergents such as ethidium bromide, acriflavine, deoxycholate, sodium dodecyl sulphate, and disinfectants benzalkonium chloride, chlorhexidine and triclosan signifies the wide substrate specificity of the transporter in K. pneumoniae. Growth inactivation and direct fluorimetric efflux assays provide evidence that kpnGH mediates antimicrobial resistance by active extrusion in K. pneumoniae. The kpnGH isogenic mutant displayed decreased tolerance to cell envelope stressors emphasizing its added role in K. pneumoniae physiology.

Conclusions and Significance

The MFS efflux pump KpnGH involves in crucial physiological functions besides being an intrinsic resistance determinant in K. pneumoniae.     

Helminth Induced Suppression of Macrophage Activation Is Correlated with Inhibition of Calcium Channel Activity

Helminth parasites cause persistent infections in humans and yet many infected individuals are asymptomatic. Neurocysticercosis (NCC), a disease of the central nervous system (CNS) caused by the cestode Taenia solium, has a long asymptomatic phase correlated with an absence of brain inflammation. However, the mechanisms of immune suppression remain poorly understood. Here we report that murine NCC displays a lack of cell surface maturation markers in infiltrating myeloid cells. Furthermore, soluble parasite ligands (PL) failed to induce maturation of macrophages, and inhibited TLR-induced inflammatory cytokine production. Importantly, PL treatment abolished both LPS and thapsigargin-induced store operated Ca²⁺ entry (SOCE). Moreover, electrophysiological recordings demonstrated PL-mediated inhibition of LPS or Tg-induced currents that were TRPC1-dependent. Concomitantly STIM1-TRPC1 complex was also impaired that was essential for SOCE and sustained Ca²⁺ entry. Likewise loss of SOCE due to PL further inhibited NFkB activation. Overall, our results indicate that the negative regulation of agonist induced Ca²⁺ signaling pathway by parasite ligands may be a novel immune suppressive mechanism to block the initiation of the inflammatory response associated with helminth infections.