Isolation and cholinesterase activity of Amaryllidaceae alkaloids from Nerine bowdenii

Amaryllidaceae species are known as ornamental plants. Some contain galanthamine, an acetylcholinesterase inhibitor. The chemical composition of the alkaloid extract of bulbs of Nerine bowdenii Watson has been analyzed by means of GC/MS. Twenty-two compounds were detected and nineteen of them identified, one of which was belladine. The alkaloid extract showed promising cholinesterase inhibitory activities against human blood acetylcholinesterase (HuAChE; IC50 = 87.9 +/- 3.5 microg/mL) and human plasma butyrylcholinesterase (HuBuChE; IC50 = 14.8 +/- 1.1 microg/mL). Belladine inhibited HuAChE and HuBuChE in a dose-dependent manner with IC50 values of 781 +/- 12.5 microM and 284.8 +/-4.2 microM, respectively.     

How lipid unsaturation, peroxyl radical partitioning, and chromanol lipophilic tail affect the antioxidant activity of α-tocopherol: direct visualization via high-throughput fluorescence studies conducted with fluorogenic α-tocopherol analogues

The preparation of two highly sensitive fluorogenic α-tocopherol (TOH) analogues which undergo >30-fold fluorescence intensity enhancement upon reaction with peroxyl radicals is reported. The probes consist of a chromanol moiety coupled to the meso position of a BODIPY fluorophore, where the use of a methylene linker (BODIPY-2,2,5,7,8-pentamethyl-6-hydroxy-chroman adduct, H(2)B-PMHC) vs an ester linker (meso-methanoyl BODIPY-6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid, H(2)B-TOH) enables tuning their reactivity toward H-atom abstraction by peroxyl radicals. The development of a high-throughput fluorescence assay for monitoring kinetics of peroxyl radical reactions in liposomes is subsequently described where the evolution of the fluorescence intensity over time provides a rapid, facile method to conduct competitive kinetic studies in the presence of TOH and its analogues. A quantitative treatment is formulated for the temporal evolution of the intensity in terms of relative rate constants of H-atom abstraction (k(inh)) from the various tocopherol analogues. Combined, the new probes, the fluorescence assay, and the data analysis provide a new method to obtain, in a rapid, parallel format, relative antioxidant activities in phospholipid membranes. The method is exemplified with four chromanol-based antioxidant compounds differing in their aliphatic tails (TOH, PMHC, H(2)B-PMHC, and H(2)B-TOH). Studies were conducted in six different liposome solutions prepared from poly- and mono-unsaturated and saturated (fluid vs gel phase) lipids in the presence of either hydrophilic or lipophilic peroxyl radicals. A number of key insights into the chemistry of the TOH antioxidants in lipid membranes are provided: (1) The relative antioxidant activities of chromanols in homogeneous solution, arising from their inherent chemical reactivity, readily translate to the microheterogeneous environment at the water/lipid interface; thus similar values for k(inh)(H(2)B-PMHC)/k(inh)(H(2)B-TOH) in the range of 2-3 are recorded both in homogeneous solution and in liposome suspensions with hydrophilic or lipophilic peroxyl radicals. (2) The relative antioxidant activity between tocopherol analogues with the same inherent chemical reactivity but bearing short (PMHC) or long (TOH) aliphatic tails, k(inh)(PMHC)/k(inh)(TOH), is ~8 in the presence of hydrophilic peroxyl radicals, regardless of the nature of the lipid membrane into which they are embedded. (3) Antioxidants embedded in saturated lipids do not efficiently scavenge hydrophilic peroxyl radicals; under these conditions wastage reactions among peroxyl radicals become important, and this translates into larger times for antioxidant consumption. (4) Lipophilic peroxyl radicals show reduced discrimination between antioxidants bearing long and short aliphatic tails, with k(inh)(PMHC)/k(inh)(TOH) in the range of 3-4 for most lipid membranes. (5) Lipophilic peroxyl radicals are scavenged with the same efficiency by all four antioxidants studied, regardless of the nature of their aliphatic tail or the lipid membrane into which they are embedded. These data underpin the key role the lipid environment plays in modulating the rate of reaction of antioxidants characterized by similar inherent chemical reactivity (arising from a conserved chromanol moiety) but differing in their membrane mobility (structural differences in the lipophilic tail). Altogether, a novel, facile method of study, new insights, and a quantitative understanding on the critical role of lipid diversity in modulating antioxidant activity in the lipid milieu are reported.     

Analysis of isoflavones in soybeans employing direct analysis in real-time ionization-high-resolution mass spectrometry

A direct analysis in real‐time (DART) ion source coupled to a high‐resolution orbitrap mass spectrometer was used for the quantitative analysis of isoflavones isolated from soybeans. For the isolation of genistein, daidzein, glycitein, and their respective acetyl, malonyl, and glucoside forms, an extraction employing 80% aqueous MeOH enhanced by sonication was used. As far as the total isoflavones (expressed as aglycones) were to be determined, an acid hydrolysis with 80% aqueous EtOH and refluxing had to be employed, while in the latter case a good agreement of the results with the data generated by the UHPLC‐orbitrap MS method was achieved, in the case of the analysis of non‐hydrolyzed extracts, some overestimation of the results as compared with those generated by UHPLC‐orbitrap MS was observed. A careful investigation of this phenomenon showed that the free aglycones originated from the conjugated forms of isoflavones in the DART ion source, thus contributing significantly to the “free” genistein/daidzein/glycitein signals during the DART analysis. Good recoveries (95–102%) and repeatabilities (RSD: 7–15%) were obtained at the spiking levels of 0.5, 1, and 0.05 g/kg, for daidzein, genistein, and glycitein, respectively. The limits of detection estimated for the respective analytes were 5 mg/kg.     

Novel methodology for 3D reconstruction of carotid arteries and plaque characterization based upon magnetic resonance imaging carotid angiography data

In this study, we present a novel methodology that allows reliable segmentation of the magnetic resonance images (MRIs) for accurate fully automated three-dimensional (3D) reconstruction of the carotid arteries and semiautomated characterization of plaque type. Our approach uses active contours to detect the luminal borders in the time-of-flight images and the outer vessel wall borders in the T(1)-weighted images. The methodology incorporates the connecting components theory for the automated identification of the bifurcation region and a knowledge-based algorithm for the accurate characterization of the plaque components. The proposed segmentation method was validated in randomly selected MRI frames analyzed offline by two expert observers. The interobserver variability of the method for the lumen and outer vessel wall was -1.60%±6.70% and 0.56%±6.28%, respectively, while the Williams Index for all metrics was close to unity. The methodology implemented to identify the composition of the plaque was also validated in 591 images acquired from 24 patients. The obtained Cohen's k was 0.68 (0.60-0.76) for lipid plaques, while the time needed to process an MRI sequence for 3D reconstruction was only 30 s. The obtained results indicate that the proposed methodology allows reliable and automated detection of the luminal and vessel wall borders and fast and accurate characterization of plaque type in carotid MRI sequences. These features render the currently presented methodology a useful tool in the clinical and research arena.     

Mesoscale simulation of aggregation of imogolite nanotubes from potential of mean force interactions

The aggregation of colloidal clay mineral particles plays an important role in controlling the mechanical and transport properties of soils. Interactions and aggregation of plate-like montmorillonite particles were previously studied with the help of Molecular Dynamics (MD) simulation. This paper investigates the aggregation of cylindrical imogolite-like phyllosilicate nanotubes. Nano-scale MD simulations are carried out to find the potential of mean force between two nanotubes. This PMF is then used in a mesoscale simulation that represents interactions between elemental nanotubes through coarse-graining. We investigate the distribution of water molecules around the curved surfaces, and the effects of the surface charge density and tube length on aggregation. Shorter nanotubes were found to form larger stacks.     

Room‐Temperature,Strain‐Tunable Orientation of Magnetization in a Hybrid Ferromagnetic Co Nanorod–Liquid Crystalline Elastomer Nanocomposite

Hybrid nanocomposites based on magnetic nanoparticles dispersed in liquid crystalline elastomers are fascinating emerging materials. Their expected strong magneto‐elastic coupling may open new applications as actuators, magnetic switches, and for reversible storage of magnetic information. We report here the synthesis of a novel hybrid ferromagnetic liquid crystalline elastomer. In this material, highly anisotropic Co nanorods are aligned through a cross‐linking process performed in the presence of an external magnetic field. We obtain a highly anisotropic magnetic material which exhibits remarkable magneto‐elastic coupling. The nanorod alignment can be switched at will at room temperature by weak mechanical stress, leading to a change of more than 50 % of the remnant magnetization ratio and of the coercive field.     

GC/MS analysis of three Amaryllidaceae species and their cholinesterase activity

Alzheimer's disease (AD), characterized by the death of nerve cells in the cerebral cortex, is the most common subtype of dementia. Despite the exponential growth in the number of AD patients, acetylcholinesterase (AChE) inhibitors are currently used to treat AD. Plants of the Amaryllidaceae family are known to synthesize a particular type of bioactive compounds, named Amaryllidaceae alkaloids, which have shown AChE inhibitory activity. Alkaloid extracts of three species of Amaryllidaceae were studied with respect to their acetylcholinesterase and butyrylcholinesterase inhibitory activity and alkaloid patterns. Eleven alkaloids were identified by GC/MS. Significant cholinesterase inhibitory activity was demonstrated by the alkaloid extract of N. undulata (IC50,(HuAChE) = 14.3 +/- 1.2 microg/mL; IC50,(HuBuChE) = 33.9 +/- 1.9 microg/mL).     

Conformationally restricted calix[8]arenes substituted at all methylene bridges

Reaction under S(N)1 conditions of the octabromocalix[8]arene derivative 2d with alcohols proceeds in nonstereoselective fashion, but all-cis octaryl derivatives are the single major products in the reaction with arenes. The incorporation of aryl substituents at the bridges rigidifies the calix[8]arene skeleton.     

CdS-containing nano-assemblies of double hydrophilic block copolymers in water

Two samples of poly(sodium(sulfamate-carboxylate)isoprene)-block-poly(ethylene oxide) copolymer (SCIEO-1 and SCIEO-2) differing in molecular weight and relative length of polyelectrolyte blocks have been used as templates for the synthesis of cadmium sulfide (CdS) nanoparticles in aqueous media. The double-hydrophilic copolymer SCIEO has very high 1D charge density, and its polymer chain structure mimics that of polysaccharide heparin. It is soluble in aqueous media, but the addition of cadmium acetate (Cd(Ac)₂) to its aqueous solution causes the formation of micellar aggregates with Cd²⁺containing insoluble cores above the threshold Cd²⁺ concentration. The trapped Cd²⁺ ions can be chemically transformed to CdS nanoparticles. The stability of hybrid SCIEO/CdS micelles depends on the ratio of PEO-to-SCI lengths: it was found that the SCIEO-2 copolymer with sufficiently long PEO block behaves as an effective stabilizer for the synthesis of CdS nanoparticles embedded in micelles, while SCIEO-1 does not. The morphology of aggregates varies with the Cd-to-SCI ratios and ranges from spherical to mixture of spherical and necklace-like micellar aggregates. A number of experimental techniques including static and dynamic light scattering, fluorescence correlation spectroscopy, atomic force and transmission electron microscopy, UV-vis, and fluorescence spectroscopy were employed for the characterization of both CdS containing hybrid micelles and embedded CdS nanoparticles.     

Development and validation of a reversed-phase HPLC method for determination of alkaloids from Papaver somniferum L. (Papaveraceae)

An HPLC method for the separation of six target alkaloids from Papaver somniferum L. (morphine, codeine, oripavine, thebaine, papaverine, and noscapine) was developed, optimized, and validated. The chromatographic behavior of these alkaloids was investigated using a reversed-phase chromatography at acidic and alkaline pH. The effects of ion-pairing agents, pH value of the mobile phase, concentration of the buffer components, mobile phase organic modifier, and column temperature were studied. Regardless of the large differences in their pKa values, all alkaloids were separated within a close retention window, and good peak shape was achieved for each of the six alkaloids. The proposed method has adequate selectivity, linearity, accuracy, precision, and reproducibility and is applicable for poppy straw.