Platinum nanoparticle catalysed coupling of phenol derivatives with 4-aminoantipyrine in aqueous medium

The oxidative coupling of phenols with 4-aminoantipyrine (AmNH₂) has been studied by UV–visible spectroscopy using platinum nanoparticles as catalyst. The rate of antipyrilquinoneimine dye formation depends on the nature of substrates, temperature, pH, and the use of microheterogeneous media such as sodium dodecylsulphate (SDS), cetyl trimethylammonium bromide (CTAB) and Triton X-100 (TX-100). The reactivity trend observed for differently substituted phenols follows the order: 3,5-dimethylphenol > phenol > o-chlorophenol > o-nitrophenol. The rate of dye formation is greater at acid pH than at basic pH and the optimum pH is 5.4. A reaction pathway is proposed, involving the activation of o-chlorophenol with AmNH₂ by metal nanoparticles and concomitant reactions of free radicals. Transmission electron microscopy results show that the particle size is 20 nm for the platinum nanoparticles involved in catalysis. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Green Chemical Synthesis of N-Cholyl-L-Cysteine Encapsulated Gold Nanoclusters for Fluorometric Detection of Mercury Ions

Herein we report a simple, single-step, cost-effective, environmentally friendly, and biocompatible approach using sodium salt of N-cholyl-L-cysteine (NaCysC) capped gold nanoclusters (AuNCs) with green emission properties at above the CMC in aqueous medium under UV-light irradiation. The primary and secondary CMC of NaCysC was found to be 4.6 and 10.7 mM respectively using pyrene as fluorescent probe. The synthesized AuNCs exhibit strong emission maxima at 520 nm upon excitation at 375 nm with a large Stokes shift of 145 nm. The surface functionality and morphology of NCs are studied by fourier transform infrared spectroscopy, dymanic light scattering studies and transmission electron microscopy. The formation of AuNCs was completed within 5 h and exhibit high stability for more than 6 months. The NaCysC templated AuNCs selectively quenches the Hg²⁺ ions with higher sensitivity in aqueous solution over the other metal ions. The fluorescence analysis of Hg²⁺ showed a wide linear range from 15 to 120 µM and a detection limit was found to be 15 nM.

     

Effect of chlorine substitution on triplet state structure of thioxanthone: A time‐resolved resonance Raman study

Substitution plays an important role in determining the triplet state reactivity. In this paper, we have studied the effect of chlorine substitution on the triplet state structure and the reactivity of thioxanthone (TX). We have employed time‐resolved resonance Raman technique to understand the structure of the lowest triplet excited state of 2‐chlorothioxanthone (CTX). The experimental findings have been corroborated with the computational results using density functional theory. Akin to the parent compound (TX), coexistence of two lowest triplet states has been observed in case of CTX, which has been substantiated using resonant probe wavelength dependence study. The relative contribution of ³n–π* to ³π–π* to the equilibrated triplet state has been found to be more for CTX compared to TX suggesting increase in the triplet state reactivity after the substitution. The above observation has been further supported by the flash photolysis experiments. Copyright © 2013 John Wiley & Sons, Ltd.     

Essential oil composition, cytotoxic and antibacterial activities of five Etlingera species from Borneo

Essential oils obtained by hydrodistillation from the rhizomes of Etlingera pyramidosphaera (K. Schum.) R. M. Sm, E. megalocheilos (Griff.) A.D. Poulsen, comb. nov., E. coccinea (Blume) S. Sakai & Nagam, E. elatior (Jack) R. M. Sm, and E. brevilabrum (Valeton) R. M. Sm were analyzed by GCMS. The highest oil yield was obtained from E. pyramidosphaera (0.45%), followed by E. elatior (0.38%), E. coccinea (0.30%), E. brevilabrum (0.28%) and E. megalocheilos (0.25%). The major constituents of the essential oils were oxygenated monoterpenes, followed by sesquiterpenes, oxygenated sesquiterpenes, oxygenated diterpenes and diterpenes. The essential oils from E. pyramidosphaera and E. brevilabrum exhibited the best cytotoxicity against MCF 7 (LC50: 7.5 +/- 0.5 mg mL(-1)) and HL 60 (LC50: 5.0 mg mL(-1)), respectively. Strong inhibition was also observed for the essential oils of E. coccinea and E. megalocheilos against Staphylococcus aureus (MIC: 8.0 +/- 0.5 mg mL(-1), and 5.0 +/- 0.5 mg mL(-1)) and Streptococcus pyrogenes (MIC: 6.0 +/- 0.5 mg mL(-1) and 8.0 +/- 0.5 mg mL(-1)).     

Highly regio- and stereoselective synthesis of tricyclic frameworks using Baylis-Hillman derivatives

A simple and convenient synthetic route for the synthesis of tricyclic chromeno[4,3-b]pyrrolidine frameworks using Baylis-Hillman bromides involving in situ formation of an imine, decarboxylation and a [3+2] cycloaddition sequence is described.     

Metal-free synthesis of aryl esters by coupling aryl carboxylic acids and aryl boronic acids

A facile synthesis of aryl esters is developed by coupling aryl carboxylic acids and aryl boronic acids in the presence of PhI(OAc)₂ and carbonyl diimidazole. A wide range of functional groups were tolerant to the metal-free reaction condition that led to the desired products in good yields.     

Quantification of rosiglitazone in rat plasma and tissues via LC–MS/MS: Method development,validation, and application in pharmacokinetic and tissue distribution studies

A bioanalytical method for the quantification of rosiglitazone in rat plasma and tissues (adipose tissue, heart, brain, bone, and kidney) using LC–MS/MS was developed and validated. Chromatographic separation was achieved on a Gemini C₁₈ column (50 × 4.6 mm, 3 μm) using a mobile phase consisting of 10 mM ammonium formate (pH 4.0) and acetonitrile (10:90, v/v) at a flow rate of 0.8 mL/min and injection volume of 10 μL (internal standard: pioglitazone). LC–MS detection was performed with multiple reaction monitoring mode using target ions at m/z → 358.0 and m/z → 357.67 for rosiglitazone and pioglitazone (internal standard), respectively. The calibration curve showed a good correlation coefficient (r²) over the concentration range of 1–10,000 ng/mL. The mean percentage recoveries of rosiglitazone were found to be over the range of 92.54–96.64%, with detection and lower quantification limit of 0.6 and 1.0 ng/mL, respectively. The developed method was validated per U.S. Food and Drug Administration guidelines and successfully utilized to measure rosiglitazone in plasma and tissue samples. Further, the developed method can be utilized for validating specific organ-targeting delivery systems of rosiglitazone in addition to conventional dosage forms.     

Biological activity of carbazole alkaloids and essential oil of Murraya koenigii against antibiotic resistant microbes and cancer cell lines

A total of three carbazole alkaloids and essential oil from the leaves of Murraya koenigii (Rutaceae) were obtained and examined for their effects on the growth of five antibiotic resistant pathogenic bacteria and three tumor cell lines (MCF-7, P 388 and Hela). The structures of these carbazoles were elucidated based on spectroscopy data and compared with literature data, hence, were identified as mahanine (1), mahanimbicine (2) and mahanimbine (3). The chemical constituents of the essential oil were identified using Gas Chromatography-Mass Spectroscopy (GCMS). These compounds exhibited potent inhibition against antibiotic resistant bacteria such as Staphylococcus aureus (210P JTU), Psedomonas aeruginosa (ATCC 25619), Klebsiella pneumonia (SR1-TU), Escherchia coli (NI23 JTU) and Streptococcus pneumoniae (SR16677-PRSP) with significant minimum inhibition concentration (MIC) values (25.0-175.0 mg/mL) and minimum bacteriacidal concentrations (MBC) (100.0-500.0 mg/mL). The isolated compounds showed significant antitumor activity against MCF-7, Hela and P388 cell lines. Mahanimbine (3) and essential oil in particular showed potent antibacteria and cytotoxic effect with dose dependent trends (≤5.0 μg/mL). The findings from this investigation are the first report of carbazole alkaloids' potential against antibiotic resistant clinical bacteria, MCF-7 and P388 cell lines.     

Label Free Fluorometric Characterization of DNA Interaction with Cholate Capped Gold Nanoparticles Using Ethidium Bromide as a Fluorescent Probe

We demonstrated label free ethidium bromide assisted characterization of DNA interaction with cholate capped AuNPs. Interactions between ss/ds DNA and AuNPs with two different lengths (0.5 and 0.85 kb) were analyzed through fluorescence spectrophotometer and agrose gel electrophoresis analysis. Further results were confirmed by UV–globally visible spectrophotometer, DLS and TEM. As 0.5 and 0.85 kb of ssDNA effectively interacted with AuNPs through the van der Waals interaction which consequently led to the prevention of salt induced aggregation, EtBr intercalations as well as fluorescence shift with less binding constant 0.098 and 0.108 μM, respectively. On the contrary, the same length of dsDNA (0.5 and 0.85 kb) not interacted with AuNPs which led to the NPs aggregation, EtBr intercalation as well as fluorescence shift with increased binding constant 0.166 and 0.599 μM, respectively. This approach helped to understand the mode of interactions of DNA with cholate capped AuNPs without any modifications in a simple method and the results could be readout through the naked eye under the UV transilluminator. Figure

Fluorometric characterization of interaction of different lengths of ss/dsDNA with cholate capped AuNPs using EtBr as fluorescence probe