On the structures of garcinol,isogarcinol and camboginol

A new polyisoprenylated phenolic pigment, garcinol, and its colourless isomer, isogarcinol, have been isolated from $\text{Garcinia indica}$ and their structures proposed on the basis of chemical and spectral data. A modification is suggested for the recently proposed structure of camboginol.     

Fluorescent aluminum chelate complexes as modified precursors for nano-structured alumina

A series of new mononuclear heteroleptic derivatives of aluminum(III), {[(CH₃COCHCOCH₃)AlL] (1 and 4)}, {[(C₆H₅COCHCOC₆H₅)AlL] (2, 5, and 7)}, and {[(C₉H₆NO)AlL] (3 and 6)}, have been synthesized by reacting Al(OPrⁱ)₃ with tridentate Schiff base H₂L^x (H₂L¹ = C₁₃H₁₀BrNO₂; H₂L² = C₁₄H₁₃NO₃; H₂L³ = C₁₇H₁₃NO₂) and β-diketone/8-hydroxyquinoline (β-diketone = acetylacetone/dibenzoylmethane) in 1?:?1?:?1 stoichiometry using anhydrous benzene and ethanol. All the complexes were characterized by elemental analysis, FTIR, and NMR (¹H and ¹³C) spectral studies. Molecular structures obtained from single-crystal XRD of aqua 1 (1a) and DMSO coordinated 2 (2a) authenticate their existence. Further, nanostructured α-alumina was synthesized from 1 by well-established sol–gel method and was characterized by powder XRD, TEM, and EDX analyses.     

New theoretical considerations in polymer rheology: elastic breakdown of chain entanglement network

Recent experimental evidence has motivated us to present a set of new theoretical considerations and to provide a rationale for interpreting the intriguing flow phenomena observed in entangled polymer solutions and melts [P. Tapadia and S. Q. Wang, Phys. Rev. Lett. 96, 016001 (2006); 96, 196001 (2006); S. Q. Wang et al., ibid. 97, 187801 (2006)]. Three forces have been recognized to play important roles in controlling the response of a strained entanglement network. During flow, an intermolecular locking force f(iml) arises and causes conformational deformation in each load-bearing strand between entanglements. The chain deformation builds up a retractive force f(retract) within each strand. Chain entanglement prevails in quiescence because a given chain prefers to stay interpenetrating into other chains within its pervaded volume so as to enjoy maximum conformational entropy. Since each strand of length l(ent) has entropy equal to k(B)T, the disentanglement criterion is given by f(retract)>f(ent) approximately k(B)Tl(ent) in the case of interrupted deformation. This condition identifies f(ent) as a cohesive force. Imbalance among these forces causes elastic breakdown of the entanglement network. For example, an entangled polymer yields during continuous deformation when the declining f(iml) cannot sustain the elevated f(retract). This opposite trend of the two forces is at the core of the physics governing a "cohesive" breakdown at the yield point (i.e., the stress overshoot) in startup flow. Identifying the yield point as the point of force imbalance, we can also rationalize the recently observed striking scaling behavior associated with the yield point in continuous deformation of both shear and extension.     

New synthetic routes to chain-extended selenium, sulfur, and nitrogen analogues of the naturally occurring glucosidase inhibitor salacinol and their inhibitory activities against recombinant human maltase glucoamylase

Six heteroanalogues (X = S, Se, NH) of the naturally occurring glucosidase inhibitor salacinol, containing polyhydroxylated, acyclic chains of 6-carbons, were synthesized for structure-activity studies with different glycosidase enzymes. The target zwitterionic compounds were synthesized by means of nucleophilic attack of the PMB-protected 1,4-anhydro-4-seleno-, 1,4-anhydro-4-thio-, and 1,4-anhydro-4-imino-D-arabinitols at the least hindered carbon atom of 1,3-cyclic sulfates. These 1,3-cyclic sulfates were derived from D-glucose and D-galactose, and significantly, they utilized butane diacetal as the protecting groups for the trans 2,3-diequatorial positions. Deprotection of the coupled products proceeded smoothly, unlike in previous attempts with different protecting groups, and afforded the target selenonium, sulfonium, and ammonium sulfates with different stereochemistry at the stereogenic centers. The four new heterosubstituted compounds (X = Se, NH) inhibited recombinant human maltase glucoamylase (MGA), one of the key intestinal enzymes involved in the breakdown of glucose oligosaccharides in the small intestine. The two selenium derivatives each had Ki values of 0.10 microM, giving the most active compounds to date in this general series of zwitterionic glycosidase inhibitors. The two nitrogen compounds also inhibited MGA but were less active, with Ki values of 0.8 and 35 microM. The compounds in which X = S showed Ki values of 0.25 and 0.17 microM. Comparison of these data with those reported previously for related compounds reinforces the requirements for an effective inhibitor of MGA. With respect to chain extension, the configurations at C-2' and C-4' are critical for activity, the configuration at C-3', bearing the sulfate moiety, being unimportant. It would also appear that the configuration at C-5' is important but the relationship is dependent on the heteroatom.     

A rapid LC-MS/MS method for quantitation of eszopiclone in human plasma: application to a human pharmacokinetic study

A highly reproducible, specific and cost-effective LC-MS/MS method was developed for simultaneous estimation of eszopiclone (ESZ) with 50 μL of human plasma using paroxetine as an internal standard (IS). The API-4000 LC-MS/MS was operated under the multiple reaction-monitoring mode using the electrospray ionization technique. A simple liquid-liquid extraction process was used to extract ESZ and IS from human plasma. The total run time was 1.5 min and the elution of ESZ and IS occurred at 0.90 min; this was achieved with a mobile phase consisting of 0.1% formic acid-methanol (15:85, v/v) at a flow rate of 0.50 mL/min on a Discover C(18) (50 × 4.6 mm, 5 μm) column. The developed method was validated in human plasma with a lower limit of quantitation of 0.1 ng/mL for ESZ. A linear response function was established for the range of concentrations 0.10-120 ng/mL (r > 0.998) for ESZ. The intra- and inter-day precision values for ESZ were acceptable as per FDA guidelines. Eszopiclone was stable in the battery of stability studies, viz. bench-top, autosampler and freeze-thaw cycles. The developed assay method was applied to an oral bioequivalence study in humans.     

Development and validation of a highly sensitive LC-MS/MS method for quantitation of dexlansoprazole in human plasma: application to a human pharmacokinetic study

A highly sensitive, specific and simple LC-MS/MS method was developed for the simultaneous estimation of dexlansoprazole (DEX) with 50 μL of human plasma using omeprazole as an internal standard (IS). The API-4000 LC-MS/MS was operated under multiple reaction-monitoring mode using electrospray ionization. A simple liquid-liquid extraction process was used to extract DEX and IS from human plasma. The total run time was 2.00 min and the elution of DEX and IS occurred at 1.20 min. This was achieved with a mobile phase consisting of 0.2% ammonia-acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on an X-terra RP 18 (50 × 4.6 mm, 5 μm) column. The developed method was validated in human plasma with a lower limit of quantitation of 2 ng/mL for DEX. A linear response function was established for the range of concentrations 2.00-2500.0 ng/mL (r > 0.998) for DEX. The intra- and inter-day precision values for DEX met the acceptance criteria as per FDA guidelines. DEX was stable in the battery of stability studies, viz. bench-top, auto-sampler and freeze-thaw cycles. The developed assay method was applied to an oral bioequivalence study in humans.     

Phase‐controlled epitaxial growth of iron oxide thin films on MgO(001) and LaAlO3(001) substrates

We have deposited epitaxial iron oxide thin films on MgO(001) and LaAlO₃(LAO)(001) substrates, resulting in different phase stabilities. Atomic force microscopy images revealed a smooth surface. Detailed X‐ray diffraction (XRD) measurements were performed to confirm the epitaxial growth and to analyze the atomic growth configuration. We found that (00l) oriented γ‐Fe₂O₃ was the stable phase on MgO(001) substrates, whereas $ (1\bar 102) $ oriented α‐Fe₂O₃ was stable on LAO(001). Magnetic hysteresis loop measurements revealed typical ferrimagnetic behavior for γ‐Fe₂O₃ on MgO, whereas the magnetization of α‐Fe₂O₃ on LAO was relatively small and consistent with an antiferromagnetic order. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nonquiescent relaxation in entangled polymer liquids after step shear

Large step shear experiments revealed through particle tracking velocimetry that entangled polymeric liquids display either internal macroscopic movements upon shear cessation or rupturelike behavior during shear. Visible inhomogeneous motions were detected in five samples with the number of entanglements per chain ranging from 20 to 130 at amplitudes of step strain as low as 135%.