LC–MS–MS Development and Validation for Simultaneous Quantitation of Metformin, Glimepiride and Pioglitazone in Human Plasma and Its Application to a Bioequivalence Study

A simple, precise and reproducible liquid chromatography–tandem mass spectrometry method has been developed and validated according to the Food and Drug Administration guidelines for the simultaneous quantitation of antidiabetic drugs metformin, glimiperide and pioglitazone in human plasma using glipizide as an internal standard. Quantitation was performed on a triple quadrupole mass spectrometer employing electrospray ionization technique, operating in multiple reaction monitoring and positive ion mode. Inter-batch and intra-batch coefficient of variation across four validation runs for the quality control samples was less than 7%. The accuracy determined at quality control levels was within 92.81–105.13%. The method was applied to a bioequivalence study.     

Theoretical investigation of helix distortion and dielectric spectrum of antiferroelectric liquid crystals

Landau-Ginzburg equation is utilized to investigate the dielectric spectrum of an antiferroelectric liquid crystal (AFLC). Two collective modes, one associated with the in-phase motion at the low frequency side and the other related with the anti-phase motion at the high frequency side, are discussed in details utilizing the concept of bulk free energy of the material in terms of the pair interactions of two adjacent Smectic layers. The phenomenon of helix distortion related to the in-phase motion is observed theoretically based on the interlayer interactions of the AFLC system. The anti-phase mode related to the degree of the antiferroelectric ordering is also an important phenomenon depending on the layer-to-layer interactions. Finally we have theoretically obtained the critical field for helix unwinding with the model proposed by de Gennes.     

A Phosphate-Based Silver–Bipyridine 1D Coordination Polymer with Crystallized Phosphoric Acid as Superprotonic Conductor

Phosphate-based silver–bipyridine (Ag-bpy) 1D coordination polymer {[{Ag(4,4′-bpy)}₂{Ag(4,4′-bpy)(H₂PO₄)}] ⋅ 2 H₂PO₄ ⋅ H₃PO₄ ⋅ 5 H₂O}_n ( 1 ) with free phosphoric acid (H₃PO₄), its conjugate base (H₂PO₄⁻) and water molecules in its lattice was synthesized by room-temperature crystallization and the hydrothermal method. An XRD study showed that coordinated H₂PO₄⁻, lattice H₂PO₄⁻ anions, free H₃PO₄ and lattice water molecules are interconnected by H-bonding interactions, forming an infinitely extended 2D H-bonded network that facilitates proton transfer. This material exhibits a high proton conductivity of 3.3×10⁻³ S cm⁻¹ at 80 °C and 95 % relative humidity (RH). Furthermore, synthesis of this material from commercially available starting materials in water can be easily scaled up, and it is highly stable under extreme conditions of conductivity measurements. This report inaugurates the usage and design principle of proton-conducting frameworks based on crystallized phosphoric acid and phosphate.     

Catalyst‐free,Knoevenagel–Michael Addition Reaction of Dimedone under Microwave Irradiation: An Efficient One‐pot Synthesis of Polyhydroquinoline Derivatives

Present investigation reports a concise and efficient protocol for the synthesis of polyhydroquinoline derivatives through coupling of four different components viz. aromatic aldehydes, dimedone, ethyl acetoacetate or ethyl cyanoacetate, and ammonium acetate. The same phenomenon can be observed using arylmethylene bis(3‐hydroxy‐2‐cyclohexene‐1‐ones), ethyl acetoacetate, and ammonium acetate in one pot under microwave irradiation. The key advantages of the given protocol include short reaction time, high yields, and simple work‐up and purification procedure. The present method also allows us to synthesize highly functionalized title compounds from simple and readily available starting materials.     

Effect of time-delay on a food chain model

This paper aims to study the effect of discrete time-delay on a tritrophic food chain model with Holling type-II functional responses. Dynamical behaviours such as boundedness, stability, persistence and bifurcation of the model are studied. Our analytical findings are illustrated through computer simulation. Biological implications of our analytical findings are addressed critically.     

Organobismuth(III) Derivatives of Sterically Hindered Bifunctional Tetradentate Schiff Bases: Synthesis and Spectroscopic Characterization

The equimolar reactions of Ph 3 Bi with the bifunctional tetradentate Schiff bases proceed with cleavage of two Bi--C bond of Ph 3 Bi and result in the formation of phenylbismuth(III) derivatives PhBi[RC(NC 6 H 4 S)CH 2 (NC 6 H 4 S)CCOOCH 3 ] where R = C 6 H 5 , 4-ClC 6 H 4 ,4-BrC 6 H 4 , and 4-CH 3 C 6 H 4 . Physico-chemical, IR, and NMR ( 1 H and 13 C) spectral studies have been carried out to investigate the structural aspect of these derivatives which reveal a penta coordination around the central Bi atom.     

Phytochelatins: Peptides Involved in Heavy Metal Detoxification

Phytochelatins (PCs) are enzymatically synthesized peptides known to involve in heavy metal detoxification and accumulation, which have been measured in plants grown at high heavy metal concentrations, but few studies have examined the response of plants even at lower environmentally relevant metal concentrations. Recently, genes encoding the enzyme PC synthase have been identified in plants and other species enabling molecular biological studies to untangle the mechanisms underlying PC synthesis and its regulation. The present paper embodies review on recent advances in structure of PCs, their biosynthetic regulation, roles in heavy metal detoxification and/or accumulation, and PC synthase gene expression for better understanding of mechanism involved and to improve phytoremediation efficiency of plants for wider application.