Recent developments of melatonin related antioxidant compounds

Melatonin is known for its radical scavenger activity, which is related to its ability to protect cells from different kinds of oxidative stress. Oxidative stress has been implicated in the development of neurodegenerative diseases like Parkinson, Alzheimer's disease, Huntington's disease, epileptic seizures, stroke, and as a contributor to aging and some cancer types. The antioxidant properties of melatonin include scavenging free radicals and the regulation of the activity and expression of antioxidant and pro-oxidant enzymes. Due to its free radical scavenger and antioxidant properties, multiple melatonin-related compounds such as melatonin metabolites and synthetic analogues are under investigation to determine which exhibit the highest activity with the lowest side effects. This review addresses recent studies with melatonin and related compounds.     

Equation of state of asymmetric nuclear matter: a VMC study

A Variational Monte Carlo (VMC) method is employed to investigate the properties of symmetric and asymmetric nuclear matter. The realistic Urbana V ₁₄ twonucleon interaction potential of Lagaris and Pandharipande was used to describe the microscopic interactions. Also, many body interactions are included as a density dependent term in the potential. Total kinetic and potential energies per particle are calculated for asymmetric nuclear matter by VMC method at various densities and isospin asymmetry parameters. The results are compared with data found in literature, and it was observed that the results obtained in this study reasonably agree with the results found in the literature. Also, the symmetry energy and incompressibility factor of the nuclear matter were obtained. The results obtained are in good agreement with those obtained by various authors with different methods and techniques.     

Understanding Distributions by Modeling Them

In current curriculum materials for middle school students in the US, data and chance are considered as separate topics. They are then ideally brought together in the minds of high school or university students when they learn about statistical inference. In recent studies we have been attempting to build connections between data and chance in the middle school by using a modeling approach made possible by new software capabilities that will be part of TinkerPlots 2.0 (TinkerPlots is published by Key Curriculum Press and has been developed with grants from the National Science Foundation (ESI-9818946, REC-0337675, ESI-0454754). Opinions expressed here are our own and not necessarily those of the Foundation.). Using a new Sampler object, students build “factories” to model not only prototypical chance events, but also distributions of measurement errors and of heights of people. We provide the rationale for having students model a wide range of phenomena using a single software tool and describe how we are using this capability to help young students develop a robust, statistical perspective.     

Synthesis and Characterization of Novel N-, S-, O-Substituted P-Chloranil Derivatives

A series of novel N-, S-, and O-substituted p-chloranil derivatives were synthesized from the reactions of p-chloranil (1) and related nucleophiles in sodium carbonate (Na₂CO₃) solution of acetonitrile or in chloroform with Et₃N. The structures of novel compounds were characterized by using microanalysis, Fourier transform–infrared, ¹H NMR, ¹³C NMR, and mass spectrometry.     

Simultaneous Determination of Clobetasol Propionate and Calcipotriol in a Novel Fixed Dose Emulgel Formulation by LC-UV

A new, rapid, selective, cheap and simple RP-LC method has been developed and validated for the simultaneous determination of clobetasol propionate and calcipotriol mixtures in bulk drugs (raw materials) and in a novel-fixed dose emulgel formulation. Separation was carried out using a NovaPak C18 column with methanol:water (74:26 v/v) as mobile phase for isocratic elution at a flow rate of 1.0 mL min^?1. The column temperature was set at 25 °C. Calibration curves were established ranging between 0.5 and 20 μg mL^?1 and 0.5 and 10 μg mL^?1 for clobetasol propionate and calcipotriol, respectively. Limit of detection and limit of quantification values of the method was found as 0.16 and 0.48 μg mL^?1 for clobetasol propionate and 0.10 and 0.30 μg mL^?1 for calcipotriol, respectively. The method was validated in accordance with ICH guidelines and obtained results proved that the proposed method was precise, accurate, selective and sensitive for the simultaneous analysis of clobetasol propionate and calcipotriol. The proposed method can be easily applied for the simultaneous determination of clobetasol propionate and calcipotriol in prepared emulgel formulations. The obtained validation results showed that the RP-LC method is suitable for routine quantification of clobetasol propionate and calcipotriol in emulgel formulations with high precision and accuracy.     

Sensitive voltammetric assay of etoposide using modified glassy carbon electrode with a dispersion of multi-walled carbon nanotube

A sensitive electroanalytical method for the determination of anticancer drug etoposide (ETP) using adsorptive stripping differential pulse voltammetry (AdSDPV) at a multi-walled carbon nanotube-modified glassy carbon electrode (MWCNT-modified GCE) is presented. The surface morphology of modified electrode was characterized by scanning electron microscopy. The effects of accumulation time and potential, pH, scan rate, and amount of MWCNT suspension were investigated. The calibration curve was linear in the concentration range of 2.0?×?10^?8–2.0?×?10^?6 M with the detection limit of 5.4?×?10^?9 M. The reproducibility of the peak current was found at 1.55 % (n?=?5) RSD value in pH 6.0 Britton–Robinson buffer for the MWCNT-modified GCE. The method was then successfully utilized for the determination of ETP in pharmaceutical dosage form, and a recovery of 99.55 % was obtained. The possible oxidation mechanism of ETP was also discussed. The proposed electroanalytical method using MWCNT-modified GCE is the most sensitive method for the determination of ETP with lowest limit of detection in the previously published electrochemical methods.     

Electrochemical reduction and oxidation of the antibiotic cefepime at a carbon electrode

The O-methyl oxime grouping in the antibiotic cefepime is reduced in aqueous buffer solution at pH<8 at a carbon electrode. The reduction of the protonated form of the oxime occurs in a single two-electron step. By comparison with anodic wave of 2-aminothiazole it was furthermore shown that the oxidation of cefepime involves the 2-amino group located on the thiazole ring in the side chain on C-7. Both reduction and oxidation peaks can be used for analytical purposes.     

Simultaneous Estimation of Ceftazidime and Ceftizoxime in Pharmaceutical Formulations by HPLC Method

The aim of the present study was to develop a fast, sensitive and reliable method for rapid screening of cephalosporin injectable dosage forms namely ceftazidime and ceftizoxime to the detection of counterfeit and substandard drugs that might be illegally commercialized. Ceftazidime, ceftizoxime and cefixime (IS) were separated in a X-Terra RP-18 column (250 × 4.60 mm ID × 5 ??) and DAD detector set at 290 and 260 nm. The mobile phase consisted of a mixture of methanol:water 20:80 (v/v) at a flow rate of 1.0 mL min^?1. Additionally, in order to find the optimum pH value of separation the pK _a values of studied compounds were determined by using two different methodologies. Aqueous pK _a values of studied compounds have been determined by UV-spectrophotometry and liquid chromatography were used for the determination and direct characterization of the dissociation constants by using the dependence of the capacity factor on the pH of the mobile phase in 20% (v/v) methanol?Cwater binary mixture in which separation was performed. The pH of the mobile phase was adjusted with 25 mM H₃PO₄ to 3.2. The method was shown to be linear, sensible, accurate, and reproducible over the range of analysis and it can be used to pharmaceutical formulations containing a single active ingredient within a short analysis time.     

Optical CO<Subscript>2</Subscript> Sensing with Ionic Liquid Doped Electrospun Nanofibers

The first use of electrospun nanofibrous materials as highly responsive fluorescence quenching-based optical CO₂ sensors is reported. Poly(methyl methacrylate) and ethyl cellulose were used as polymeric materials. Sensing slides were fabricated by electrospinning technique. A fiber-optic bundle was used for the gas detection. CO₂ sensors based on the change in the fluorescence signal intensity of ion pair form of 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS). The sensor slides showed high sensitivities due to the high surface area-to-volume ratio of the nanofibrous membrane structures. The preliminary results of Stern-Volmer analysis show that the sensitivities of electrospun nanofibrous membranes to detect CO₂ are 24 to 120 fold higher than those of the thin film based sensors. The response times of the sensing reagents were short and the signal changes were fully reversible. The stability of ion pair form of HPTS in the employed matrix materials was excellent and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 7 months. Our stability tests are still in progress.