Leptocarposide: a new triterpenoid glycoside from Ludwigia leptocarpa (Onagraceae)

A new triterpenoid bidesmoside (leptocarposide) possessing an acyl group in their glycosidic moiety (1), together with the known luteolin‐8‐C‐glucoside (2) and 1‐O‐β‐d ‐glucopyranosyl‐(2S,3R,8E)‐2‐[(2′R)‐2‐hydroxypalmitoylamino]‐8‐octadecen‐1,3‐diol (3) was isolated from the n‐butanol‐soluble fraction of whole plant of Ludwigia leptocarpa (Nutt) Hara (Onagraceae). Structure of compound 1 has been assigned on the basis of spectroscopic data (¹H and ¹³C NMR, ¹H‐¹H COSY, HSQC, HMBC, and ROESY), mass spectrometry, and by comparison with the literature. This compound was further screened for its potential antioxidant properties by using the radical scavenging assay model 2,2‐diphenyl‐1‐picrylhydrazyl and reveals non‐potent antioxidant activities, while compound 2 shows SC₅₀ of 0,038 mM. Copyright © 2013 John Wiley & Sons, Ltd.     

Self-assembly of fatty acid-alkylboladiamine salts

Long-chain fatty acids are insoluble in aqueous solution and form crystal precipitates. It is then of particular importance to determine the physicochemical parameters allowing their dispersion in water to improve their bioavailability and their utilization as surfactants. Herein, we report a study on salt-free catanionic systems in aqueous solution made of mixtures between palmitic or stearic fatty acids and alkylboladiamines (Abd's) differing by their alkyl chain length. Phase contrast microscopy, solid-state NMR, Fourier transform infrared spectroscopy, and small-angle neutron scattering were used to characterize the phase behavior of these systems at molar ratio of fatty acid to Abd of 1 and 2. Whatever the Abd and the molar ratio, fatty acids were embedded at low temperature in a bilayer gel phase which crystallizes after a period of rest. At an equimolar ratio, the gel phases transited upon raising the temperature to an isotropic phase made of worm-like micelles except in the case of the ethylenediamine chain for which a lamellar fluid phase was observed. At a molar ratio of 2 and high temperature, fatty acids were embedded in a lamellar fluid phase which self-orients with its stacking axis perpendicular to the magnetic field. However, for a long alkylboladiamine such as spermine, worm-like micelles formed. The phase behavior at high temperature is discussed in terms of molecular volume.     

A nitrogen-15 NMR study of hydrogen bonding in 1-alkyl-4-imino-1,4-dihydro-3-quinolinecarboxylic acids and related compounds

The title compounds contain groups (amine, amide, imine, carboxylic acid) that are capable of forming intramolecular hydrogen bonds involving a six-membered ring. In compounds where the two interacting functional groups are imine and carboxylic acid, the imine is protonated to give a zwitterion; where the two groups are imine and amide, the amide remains intact and forms a hydrogen bond to the imine nitrogen. The former is confirmed by the iminium 15N signal, which shows the coupling of 1J(15N,1H) -85 to -86.8 Hz and 3J(1H,1H) 3.7-4.2 Hz between the iminium proton and the methine proton of a cyclopropyl substituent on the iminium nitrogen. Hydrogen bonding of the amide is confirmed by its high 1H chemical shift and by coupling of the amide hydrogen to (amide) nitrogen [(1J(15N,1H) -84.7 to -90.7 Hz)] and to ortho carbons of a phenyl substituent. Data obtained from N,N-dimethylanthranilic acid show 15N-1H coupling of (-)8.2 Hz at 223 K (increasing to (-)5.3 Hz at 243 K) consistent with the presence of a N... H-O hydrogen bond.     

Analysis of perfluorinated chemicals in sludge: Method development and initial results

A fast, rigorous method was developed to maximize the extraction efficacy for ten perfluorocarboxylic acids and perfluorooctanesulfonate from waste-water-treatment sludge and to quantitate using liquid chromatography, tandem-mass spectrometry (LC/MS/MS). First, organic solvents were tested for extraction efficiency, including acetonitrile (ACN), methanol (MeOH), isopropanol (IPA), tetrahydrofuran (THF), and 50/50 ACN/MeOH (v/v). Among the extractants tested, 50/50 ACN/MeOH yielded the best results for our combined criteria of extraction efficacy and solvent-handling convenience. Second, chemical pretreatment prior to solvent extraction was tested with sodium hydroxide (NaOH), potassium hydroxide (KOH), hydrochloric acid (HCl), and potassium persulfate (K₂S₂O₈). Pretreatment with NaOH and HCl effectively recovered additional PFCs from the sludge, but KOH and K₂S₂O₈ digestion were less effective than no pretreatment. Third, cleanup methods were investigated with solid-phase extraction using HLB (hydrophilic–lipophilic balanced) and WAX (weak-anion exchange) stationary phases, and with ion-pairing. The HLB stationary phase yielded a slight edge over the other two cleanup strategies in terms of recoverable PFCs and chromatographic separation. Finally, the appropriateness of isotopically labeled PFCs for quantitating unlabeled PFCs using isotopic dilution in complex sludge extracts was evaluated by comparison to results obtained with the standard-addition method. A National Institute of Standards and Technology (NIST) domestic sludge (CRM 2781) was analyzed using our finalized method and compared with previously reported results.     

Complexation of lanthanides, actinides and transition metal cations with a 6-(1,2,4-triazin-3-yl)-2,2':6',2'-terpyridine ligand: implications for actinide(III)/lanthanide(III) partitioning

The quadridentate N-heterocyclic ligand 6-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2'?:?6',2'-terpyridine (CyMe(4)-hemi-BTBP) has been synthesized and its interactions with Am(III), U(VI), Ln(III) and some transition metal cations have been evaluated by X-ray crystallographic analysis, Am(III)/Eu(III) solvent extraction experiments, UV absorption spectrophotometry, NMR studies and ESI-MS. Structures of 1:1 complexes with Eu(III), Ce(III) and the linear uranyl (UO(2)(2+)) ion were obtained by X-ray crystallographic analysis, and they showed similar coordination behavior to related BTBP complexes. In methanol, the stability constants of the Ln(III) complexes are slightly lower than those of the analogous quadridentate bis-triazine BTBP ligands, while the stability constant for the Yb(III) complex is higher. (1)H NMR titrations and ESI-MS with lanthanide nitrates showed that the ligand forms only 1:1 complexes with Eu(III), Ce(III) and Yb(III), while both 1:1 and 1:2 complexes were formed with La(III) and Y(III) in acetonitrile. A mixture of isomeric chiral 2:2 helical complexes was formed with Cu(I), with a slight preference (1.4:1) for a single directional isomer. In contrast, a 1:1 complex was observed with the larger Ag(I) ion. The ligand was unable to extract Am(III) or Eu(III) from nitric acid solutions into 1-octanol, except in the presence of a synergist at low acidity. The results show that the presence of two outer 1,2,4-triazine rings is required for the efficient extraction and separation of An(III) from Ln(III) by quadridentate N-donor ligands.     

Superimposition evaluation of ecdysteroid agonist chemotypes through multidimensional QSAR

The EC₅₀ values for a training set of 66 ecdysteroids and 97 diacylhydrazines were measured in the ecdysteroid-responsive Drosophila melanogaster B_II cell line, a prototypical homologous inducible gene expression system. Each of eight superimposition hypotheses for the folded diacylhydrazine conformation was evaluated and ranked on the basis of CoMFA and 4D-QSAR Q² values for the training set and R² values for a 52-member test set comprising randomly-chosen diacylhydrazines and chronologically-chosen ecdysteroids for which data became available after model construction. Both 4D-QSAR and CoMFA rate a common superimposition as the preferred one. Two additional superimpositions, with somewhat weaker 4D-QSAR and CoMFA consensus, nonetheless share several important topological features. The resultant QSAR models address the question of relative binding orientation of the two ligand families and can be useful as a virtual screen for new chemotypes.     

Characterization of low-fouling ethylene glycol containing plasma polymer films

Low-protein-fouling poly(ethylene glycol) (PEG-like) plasma polymer films were prepared using radio frequency glow discharge polymerization of diethylene glycol dimethyl ether (DGpp) on top of a heptylamine plasma polymer primer layer. By varying the plasma deposition conditions, the chemistry of the DGpp film was influenced, especially in regard to the level of ether content, which in turn influenced the relative levels of bovine serum albumin and lysozyme protein fouling. Surface potential measurements indicated that these surfaces carried a net negative charge. While protein fouling remained low ( approximately 10 ng/cm2), there was a slightly higher level of the positively charged protein adsorbed on these films than the negative protein. The interaction forces measured between a silica spherical surface on both "high"- and "low"-protein-fouling DGpp films were all repulsive and short ranged (2-3 nm). There was no correlation between the surface forces measured for high- and low-protein-fouling DGpp films. Thus, it appears that enthalpic effects are very important in reducing protein adsorption. We therefore conclude that it is the concentration of residual, ethylene glycol containing species that are the crucial parameter determining protein resistance due to a combination of both entropic and enthalpic effects.     

Broadening the absorption of conjugated polymers by "click" functionalization with phthalocyanines

Conjugated copolymer derivatives of poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and poly(3-hexylthiophene) (P3HT) containing 10% of alkyne functionalities in the side chains have been prepared using the sulfinyl precursor route and the Rieke method, respectively. With the aim of expanding the absorption range of these conjugated polymers for their use in bulk heterojunction (BHJ) polymer:fullerene solar cells, appropriate phthalocyanine (Pc) molecules have been covalently bound through a post-polymerization "click chemistry" reaction between the alkyne functionalities in the side chains of the copolymers and a Pc functionalized with an azide moiety. The resulting poly(p-phenylenevinylene)-Pc (PPV-Pc) material holds a 9 mol% content of Pcs, while the polythiophene-Pc material (PT-Pc) contains a 8 mol% of Pc-functionalization in the side chains. As expected, the presence of the Pc contributes to the extension of the absorption up to 700 nm. BHJ solar cells have been prepared using PPV-Pc and PT-Pc materials in combination with PCBM. Although the Pc absorption contributes to the generation of photocurrent, the overall power conversion efficiencies (PCE) obtained from these cells are lower than those obtained with BHJ P3HT:PCBM (1:1) and MDMO-PPV:PCBM (1:4) solar cells. A plausible explanation could be the moderate solubility of the PPV-Pc and PT-Pc materials that limits the processing into thin films.     

A multimodal magnetic resonance imaging nanoplatform for cancer theranostics

We describe an innovative multimodal system, which combines magnetic targeting of therapeutic agents with both magnetic resonance and fluorescence imaging into one system. This new magnetic nanoplatform consists of superparamagnetic γFe(2)O(3) nanoparticles, used clinically as an MRI contrast agent, conjugated to therapeutic molecules of the hydroxylmethylene bisphosphonate family (HMBPs): alendronate with an amine function as the terminal group. In vitro tests with breast cancer cells show that the γFe(2)O(3)@alendronate hybrid nanomaterial reduces cell viability and acts as a drug delivery system. We also investigated the anti-tumoural properties in vivo in nude mice xenografted with MDA-MB-231 tumours. We show that the presence of both γFe(2)O(3)@alendronate and a magnetic field significantly reduced the development of tumours. The amine functionalities can be used as precursor groups for the covalent coupling of peptides or monoclonal antibodies for specific biological targeting. The feasibility of this process was demonstrated by coupling rhodamine B, a fluorescence marker, to the γFe(2)O(3)@alendronate nanohybrid. The system showed fluorescent properties and high affinity for cells. Flow cytometry and fluorescence microscopy were used to study the kinetics of γFe(2)O(3)@alendronate uptake by cells. The magnetic and fluorescent nanoparticles are potential candidates for smart drug-delivery systems. Also, the superparamagnetic behaviour of such nanoparticles may be exploited as MRI contrast agents to improve therapeutic diagnostics.     

Reactions in the rechargeable lithium-O2 battery with alkyl carbonate electrolytes

The nonaqueous rechargeable lithium-O(2) battery containing an alkyl carbonate electrolyte discharges by formation of C(3)H(6)(OCO(2)Li)(2), Li(2)CO(3), HCO(2)Li, CH(3)CO(2)Li, CO(2), and H(2)O at the cathode, due to electrolyte decomposition. Charging involves oxidation of C(3)H(6)(OCO(2)Li)(2), Li(2)CO(3), HCO(2)Li, CH(3)CO(2)Li accompanied by CO(2) and H(2)O evolution. Mechanisms are proposed for the reactions on discharge and charge. The different pathways for discharge and charge are consistent with the widely observed voltage gap in Li-O(2) cells. Oxidation of C(3)H(6)(OCO(2)Li)(2) involves terminal carbonate groups leaving behind the OC(3)H(6)O moiety that reacts to form a thick gel on the Li anode. Li(2)CO(3), HCO(2)Li, CH(3)CO(2)Li, and C(3)H(6)(OCO(2)Li)(2) accumulate in the cathode on cycling correlating with capacity fading and cell failure. The latter is compounded by continuous consumption of the electrolyte on each discharge.