Use of HPLC in the Determination of the Molar Absorptivity of 4��-Geranyloxyferulic Acid and Boropinic Acid

Natural prenyloxycinnamic acids were shown to exert in vitro and in vivo remarkable and valuable anti-cancer and anti-inflammatory effects. Among these, 4??-geranyloxyferulic acid [3-(4??-geranyloxy-3??-methoxyphenyl)-2-trans-propenoic acid] was discovered as an efficient orally active chemopreventive agent of several types of cancer, and its structural analogue boropinic acid was shown to exert a valuable inhibitory effect both in vitro and in vivo against the growth of Helicobacter pylori. As a continuation of our chemical, chemico-physical, and pharmacological studies on these secondary metabolites, we report herein the comparison between traditional UV/Vis assays and HPLC?CDAD methods for the determination of the molar absorptivity coefficient of 4??-geranyloxyferulic acid (?? ₃₁₀ = 12,950 and ?? ₂₈₈ = 11,910 L mol^?1 cm^?1) and boropinic acid (?? ₃₁₀ = 13,510 and ?? ₂₈₈ = 12,350 L mol^?1 cm^?1). Ferulic acid was merely used as a reference standard to test the possibility of the application of these two assays to the oxyprenylated compounds. The data reported in the present study will represent an essential aid for future studies aimed to better define the pharmacological profile and the mechanism of action of these compounds and are an important starting point to evaluate other natural products where standard powders are not available.     

Comprehensive analysis of maté (Ilex paraguariensis) compounds: development of chemical strategies for matesaponin analysis by mass spectrometry

Ilex paraguariensis (maté) is an important plant from southern Brazil, Paraguay, Uruguay and Argentina, where its leaves are widely used in hot or cold beverages. We now present a comprehensive ULPC-PDA-MS analysis of the compounds found in its leaves. The analysis was rapid, less than 13 min and many compounds were identified, among these, the chlorogenic acid series, and other quinic acid derivatives, xanthines, and several saponins, many of which have not been previously described, including many isomers. The isomerism could occur in the aglycone moiety, namely ursolic or oleanolic acid, or in the carbohydrate moiety. Additionally, many acetylated saponins were detected. The structure of known and novel saponins was determined using per-O-methylation with ESI-MS analysis, as well as with GC-MS of their partially O-methylated alditol acetate (PMAA) derivatives, along with ESI-MS analysis of the O-isopropylidene (IPP) derivatives provided fundamental information on interglycosidic linkages, avoiding the purification steps.     

Self-assembly of gold nanoparticles on functional organic molecular crystals

The utilization of metal nanoparticles (NPs) to fabricate metal electrodes under mild conditions is one of the most studied topic in recent years. In this work, colloidal Au NPs were deposited on two isostructural molecular crystals, namely 1,2,3,4-tetrafluoro-7-thiomethyl-acridine (MeSAcr) and 1,2,3,4-tetrafluoro-7-methoxy-acridine (MeOAcr), exposing S atoms and O atoms, respectively, at their largest crystal faces. The depositions were carried out mainly by drop casting under ambient conditions, increasing the contact time from 1 to 120 min, and the samples were then analyzed by atomic force microscopy (AFM) to evaluate the coverage. Thanks to the affinity between S and Au atoms, Au NPs are observed to adhere on the MeSAcr surface within 1-min contact time, whereas at least 1h is required to find NPs on the MeOAcr surface. NP adsorption is also affected by the substrate surface morphology; indeed, step edges represent preferential adsorption sites even in the absence of Au-S interaction. Experiments under different conditions were performed to maximize the coverage on MeSAcr, reaching values up to 13%. AFM equipped with fluid cell was also employed to simultaneously depositing and imaging NPs, achieving a better understanding of the adsorption mechanism.     

sp hybridization in free carbon nanoparticles--presence and stability observed by near edge X-ray absorption fine structure spectroscopy

The presence and stability of sp hybridized atoms in free carbon nanoparticles was investigated by NEXAFS spectroscopy. The experiments show that a predominant fraction of carbon atoms is found in linear sp-chains and that conversion into sp(2) structures proceeds already at low temperature and in the gas phase.     

Rhenium(IV) compounds inducing apoptosis in cancer cells

The anticancer properties of a series of mononuclear Re(IV) compounds of formula ReCl(4)L (where L is bpy = 2,2'-bipyridine; bpym = 2,2'-bipyrimidine; dmbpy = 4,4'-dimethyl-2,2'-bipyridine; phen = 1,10-phenanthroline) were investigated for the first time. All compounds displayed potent in vitro antiproliferative activity against selected cancer cells.     

Extreme events and entropy: A multiple quantile utility model

This paper introduces a multiple quantile utility model of Cumulative Prospect Theory in an ambiguous setting. We show a representation theorem in which a prospect is valued by a composite value function. The composite value function is able to represent asymmetric attitude on extreme events and a rational prudence on ordinary events.     

Recurrence and Higher Ergodic Properties for Quenched Random Lorentz Tubes in Dimension Bigger than Two

We consider the billiard dynamics in a non-compact set of ℝ ^d that is constructed as a bi-infinite chain of translated copies of the same d-dimensional polytope. A random configuration of semi-dispersing scatterers is placed in each copy. The ensemble of dynamical systems thus defined, one for each global realization of the scatterers, is called quenched random Lorentz tube. Under some fairly general conditions, we prove that every system in the ensemble is hyperbolic and almost every system is recurrent, ergodic, and enjoys some higher chaotic properties.     

A Multifrequency (X-, Q-, and W-band) EPR and DFT Study of a Photopolymerizable Dental Resin

The free radicals generated during the polymerization process of Z100 (3 M ESPE) dental resin were examined by electron paramagnetic resonance (EPR) in X-, Q- and W-bands. Experimental generation and spectra simulations were associated with density functional theory (DFT) calculations to determine the molecular structure and explain the EPR spectrum formation. It was assumed that the EPR spectrum was formed by the sum of two different types of radicals: “propagating” and allylic. The spectra simulations and DFT calculations showed good agreement, indicating that the proposed model fully explained the nine lines of the EPR spectrum in X-band and showed that the spectrum formation is the sum of “9 + 5” lines, rather than the “5 + 4” lines predicted early. Simulations in Q- and W-bands showed very close correlation and were essential to support the proposed model.     

NLO‐X (X = I–III): New Gaussian basis sets for prediction of linear and nonlinear electric properties

New adjusted Gaussian basis sets are proposed for first and second rows elements (H, B, C, N, O, F, Si, P, S, and Cl) with the purpose of calculating linear and mainly nonlinear optical (L–NLO) properties for molecules. These basis sets are new generation of Thakkar‐DZ basis sets, which were recontracted and augmented with diffuse and polarization extrabasis functions. Atomic energy and polarizability were used as reference data for fitting the basis sets, which were further applied for prediction of L–NLO properties of diatomic, H₂, N₂, F₂, Cl₂, BH, BF, BCl, HF, HCl, CO, CS, SiO, PN, and polyatomic, CH₄, SiH₄, H₂O, H₂S, NH₃, PH₃, OCS, NNO, and HCN molecules. The results are satisfactory for all electric properties tested; dipole moment (µ), polarizability (α), and first hyperpolarizability (β), with an affordable computational cost. Three new basis sets are presented and called as NLO‐I (ADZP), NLO‐II (DZP), and NLO‐III (VDZP). The NLO‐III is the best choice to predict L–NLO properties of large molecular systems, because it presents a balance between computational cost and accuracy. The average errors for β at B3LYP/NLO‐III level were of 8% for diatomic molecules and 14% for polyatomic molecules that are within the experimental uncertainty. © 2014 Wiley Periodicals, Inc.     

A Bio‐Inspired Switch Based on Cobalt(II) Disulfide/Cobalt(III) Thiolate Interconversion

Disulfide/thiolate interconversion supported by transition‐metal ions is proposed to be implicated in fundamental biological processes, such as the transport of metal ions or the regulation of the production of reactive oxygen species. We report herein a mononuclear dithiolate Co^III complex, [Co^IIILS(Cl)] ( 1 ; LS=sulfur containing ligand), that undergoes a clean, fast, quantitative and reversible Co^II disulfide/Co^III thiolate interconversion mediated by a chloride anion. The removal of Cl^? from the Co^III complex leads to the formation of a bis(μ‐thiolato) μ‐disulfido dicobalt(II) complex, [Co₂^II,IILSSL]²⁺ ( 2 ²⁺). The structures of both complexes have been resolved by single‐crystal X‐ray diffraction; their magnetic, spectroscopic, and redox properties investigated together with DFT calculations. This system is a unique example of metal‐based switchable Mⁿ₂‐RSSR/2 M⁽ⁿ⁺¹⁾‐SR (M=metal ion, n=oxidation state) system that does not contain copper, acts under aerobic conditions, and involves systems with different nuclearities.