HPLC method development and validation of cytotoxic agent phenyl‐heptatriyne in Bidens pilosa with ultrasonic‐assisted cloud point extraction and preconcentration

Extraction and pre‐concentration of a bioactive marker compound, phenyl‐1,3,5‐heptatriyne from Bidens pilosa, prior to HPLC has been demonstrated using both organic and ecofriendly solvents. Non‐ionic surfactants, viz. Triton X‐100, Triton X‐114 and Genapol X‐80, were used for extraction. No back‐extraction or liquid chromatographic steps were required to remove the target phytochemical from the surfactant‐rich extractant phase. The optimized cloud point extraction procedure has been shown to be a potentially useful methodology for the preconcentration of the target analyte, with a preconcentration factor of 4–99. Moreover, the method is simple, sensitive, rapid and consumes lesser solvent than traditional methods. An isocratic chromatographic separation and quantitation was accomplished on a C₁₈ column with acetonitrile–acidified aqueous as mobile phase at a flow rate of 1.0 mL/min, UV detection at 254 nm and specificity with photo diode‐array detector (PDA) and MS. Under the optimum experimental conditions recovery was satisfactory (99.18–100.33%) without interference from the surfactant. The method seems to be reliable with intraday precision and interday precision below 2.0%. Good linearity was obtained in the working range from 7.5 to 30 µg/mL with correlation coefficient >0.99. The limits of detection and quantitation were 1.84 and 6.13 µg/mL, respectively. The method was validated following international guidelines and successfully applied for quantitative assays of cytotoxic compound phenyl‐1,3,5‐heptatriyne in Bidens pilosa. Copyright © 2010 John Wiley & Sons, Ltd.     

Development and validation of a HPLC method for quantification of rivastigmine in rat urine and identification of a novel metabolite in urine by LC‐MS/MS

A sensitive, specific and accurate HPLC method for the quantification of rivastigmine (RSM) in rat urine was developed and validated. The method involves the simple liquid–liquid extraction of RSM and pyridostigmine as an internal standard (IS) from rat urine with tertiary methyl butyl ether. The chromatographic separation of RSM and IS was achieved with 20 mm ammonium acetate buffer (pH 6.5) and acetonitrile (65:35, v/v) delivered at flow‐rate of 1 mL/min on a Kromasil KR‐100. The method was in linear range from 50 to 5000 ng/mL. The validation was done as per FDA guidelines and the results met the acceptance criteria. The method was successfully applied for the quantification of RSM in rat urine. Besides method validation, we have identified two metabolites of RSM in urine. Both the metabolites were characterized by HPLC‐PDA and LC‐MS/MS and it was found that one metabolite is novel. Copyright © 2010 John Wiley & Sons, Ltd.     

Conservation of a prey-predator fishery with predator self limitation based on continuous fishing effort

The paper deals with the problem of selective harvesting in a prey-predator model with predator self limitation. Criteria for local stability and global stability for both the exploited and unexploited system are derived. The effort has been considered as a dynamic variable and taxation as a control instrument to protect the fish populations from over exploitation. Finally, the optimal taxation policy is discussed with the help of control theory.     

Aging effect of diethanolamine derived precursor sol on TiO<Subscript>2</Subscript> films deposited at different annealing temperatures

A diethanolamine stabilized precursor sol has been utilized for studying the effect of sol aging and annealing temperature on key properties of TiO₂ films. X-ray diffraction investigations have shown increased crystallite size in the films as a function of both sol aging and the thermal treatment. Fourier transform infrared studies have elucidated that cleavage of the bond involving diethanolamine and the alkoxide in the films requires high temperature annealing treatment upon the use of aged sol for the deposition of the films. Multiple step chronoamperometry has shown the ion storage capacity of the films increases as a function of sol aging, with the highest extent of Li ion insertion being obtained for films produced from as-prepared and aged sols and subsequently annealed at, 300 and 350 °C, respectively. Films with excellent optical quality were obtained. Ellipsometry revealed that the refractive indices of the films vary from 1.67 to 2.02. The highest thickness obtained in these films was nearly 900 nm. The bandgaps of the films for both direct and indirect transitions decreased as a function of precursor sol’s aging. In addition, although the indirect bandgap values have shown a decrease with increasing annealing temperature, the direct bandgap values reveal a slight increase as a function of annealing temperature.     

Synthesis of novel isoxazole-linked steroidal glycoconjugates—an application of a novel steroidal nitrile oxide

Isoxazole-linked steroidal glycoconjugates are prepared by 1,3-dipolar cycloaddition reactions of an in situ generated and hitherto unknown steroidal nitrile oxide with appropriate propargyl ethers of sugars. The methodology provides a novel vector in the form of an easily accessible nitrile oxide having the ability to couple with many biomolecules, thus offering a new pathway to construct biologically significant novel steroidal conjugates.     

Convex fuzzy mapping with differentiability and its application in fuzzy optimization

The concepts of differentiability, convexity, generalized convexity and minimization of a fuzzy mapping are known in the literature. The purpose of this present paper is to extend and generalize these concepts to fuzzy mappings of several variables using Buckley–Feuring approach for fuzzy differentiation and derive Karush–Kuhn–Tucker condition for the constrained fuzzy minimization problem.