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.     

Thermodynamic Study of the Three Isomers of Bromobenzoic Acid

The enthalpies of sublimation and fusion and triple-point temperatures of 2-bromo-. 3-bro-mo- and 4-bromobenzoic acids have been determined precisely by sublimation calorimetry, drop calorimetry and differential thermal analysis. The measurements of sublimation enthalpy of the three acids were made at 333, 348 and 363 K, respectively, using a Tian-Calvet microcalorimeter equipped with Knudsen effusion cells. The derived standard molar enthalpies of sublimation at 298.15 K are (95. 94±0. 41), (99. 20± 0.18), and (103. 08±0. 59) kJ · mol-1for the 2-bromo-, 3-bromo- and 4-bromobenzoic acids, respectively. In addition, the saturated vapour pressure of these compounds was also calculated on the basis of the sublimation experiments. The enthalpy of fusion, the triple-point temperatures and the mole fraction purities of the samples of the investigated substances were measured using the mean temperature version DTA apparatus developed by the CTM of the CNRS in Marseille. The triple-point temperature and the     

What Is the Structure of Pterodonoic Acid?

EudesmaneacidsandeudesmanelactoneshavebeendrawingattentionduetotheirwidespectrUmofbi0l0gicalpr0perties,particularlyantifeedant,cellgrowthinhibitoryandplantgr0wthregulatingactivities.l'2Inl994,Zha0andWeirep0rted'theisolationofpterodonoicacidfromLaggerapterodonta(DC)Benth,whichtheyclaimedasanewcomPoundwiththesthectureof3-oxoeudesma-4,ll-dien-l2-oicacid1.Infact,comPoundlisnotanewcomPoundandithasaPpearedinliteratureseveraltimes.hi1977,lwasfirstisolated4byBohlmannetalfromMexicangenusEuPat0riu…     

Studies on the Thioglycosides of N-Acetylneuraminic Acid 1: Synthesis of Alkyl α-Glycosides of 2-Thio-N-Acetylneuraminic Acid

Methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-2-S-acetyl-3,5-di-deoxy-2-thio-D-glycero-α-D-galacto-2-nonulopyranosonate (2) was prepared via methyl 5-acetamTdo-4,7,8,9-tetra-O-acetyl-2-chloro-2,3,5-trideoxy-D-glycero-α-D-galacto-2-nonulopyranosonate (1) and was converted into the sodium salt (3). Condensation of 3 with n-alkyl bromides gave the corresponding methyl (alkyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-α-D-galacto-2-nonulo-pyranosid)onates, which were converted, via O-deacetylation and hydrolysis of the methyl ester group, into the title compounds.     

The Influence of Temperature on the Heat Effects of Acid—Base Interaction in Aqueous Solutions of Citric Acid

The heat effects of interaction of a solution of citric acid with solutions of HNO₃ and KOH at 288.15, 298.15, and 308.15 K and ionic strength values 0.5, 1.0, and 1.5 (KNO₃) were measured calorimetrically. The heat effects of acid dissociation were calculated using the HEAT program. The standard thermodynamic characteristics of step dissociation of citric acid were determined.     

Synthesis and Characterization of the Terpolymer of Itaconic Acid with Acrylamide and 2-Acrylamido-2-methylpropanesulfonic Acid

The thermal stability of the polymer is of great significance in paper, ceramics and oil industry1. Conventional polymers such as polyanionic cellulose can not meet high temperature limitations2-4. Aggour5-6 and Collette7 etc. have conducted extensive research on synthesis and characterizations of the copolymer or terpolymer containing 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS). Till now, very few research works have been reported on the terpolymer of itaconic acid (IA), acrylamid…     

Investigation on the Inverse Emulsion Polymerization of Acrylic Acid

An aqueous solution of the hydrophilic monomer such as acrylic acid is dispersed in a continuous lipophilic medium using surfactants, which promote the formation of a water- in-oil (W/O) emulsion. The water-in-oil (W/O) emulsion polymerization process has shown superior characteristics1 such as the low viscosity of the dispersion, easy removal of the reaction heat2 and the high molecular weight of the obtained polymer3 etc. And it is attractive to investigate the reaction system because the…     

Dielectric Relaxation of the β-Cyclodextrin Complexes with Tridecanoic Acid and 1,13-Tridecanedioic Acid

The frequency and temperature dependence of the real (') and imaginary (') parts of the dielectric permittivity of the polycrystalline complex-cyclodextrin-tridecanoic acid in two hydration forms (with 16.2 and 10.7 water molecules) and -cyclodextrin-1,13-tridecanedioic acid with 16.4 and 10.5 water molecules have been investigated, in the frequency range 0.1–100 kHz and temperature range 120–310 K. The dielectric behavior is described well by Debye-type relaxation dispersion. All systems except for the complex of partially dehydrated monocarboxylic acid, exhibit an additional -dispersion, at low frequencies (f < 1000 Hz). Only one-step was found in the ' vs. Tplots of both complexes in the two hydration forms, a fact indicating that the watermolecules cannot be divided into strongly bound and easily movable molecules. The'vs. T plots, at a fixed frequency (200 Hz), show the characteristic peakattributed to a transition between ordered and disordered -CD hydroxyl groupsand water molecules. The transition temperature was 202.7 K for all systems examinedexcept for the complex -CD-tridecanoic acid.16.2 H₂O (214.5 K). This means that the order to disorder transformation process was unaffected by the dehydration process in the case of the dicarboxylic acid complex, whereas in the case of the monocarboxylic acid, it was unexpectedly facilitated. The relaxation time varies with temperature, in a like curve (in the range 8–14 s), with maximum values located at the corresponding order-disorder transition temperatures. The activation energies of the fully hydrated complexes have absolute values of 5 kJ/mol in the range 1.98–3.82 K_{BT transition} which are higher than the corresponding values of :2 kJ/mol of the dehydrated complexes. A thermal hysteresis observed in all complexes is a result of the order-disorder transformation.     

Ab Initio Study of the Excited State Decomposition Reactions of Monothioformic Acid

IntroductionTherehasbeenconsiderableinterestinrecentyearsinthetheoreticalstudyofthemonothioformicacid1ed.However,mostofthemhaveconcentIatedontheelectronicproperties,isomerizationandintramolecularhydrogenshiftreactionsoftheacid,andstudiesonitschemicalreactionshaverarelybeenrepofted.Recently,wereportedonthetheoreticalstudyofthegroundstateunimolecularpyrolysisofmonothioforndcacid,andtheresultsshowedthathightemperatureisneededforitsgroundstatedecompositionreactions.Asapotentialinterstellarcompoun…     

An NMR Study of the Equilibration of d‐Glucaric Acid with Lactone Forms in Aqueous Acid Solutions

The aqueous solution equilibration of d‐glucaric acid with its lactone forms was studied by NMR with and without acid catalysis. The kinetics of the approach to equilibrium were simulated, and approximate equilibrium and rate constants were obtained.     

Radiation-Induced,Solid-State Polymerization of Derivatives of Methacrylic Acid. XI. Aspects of the Polymerization of Methacrylic Acid by γ-Irradiation

Aspects of the radiation-induced polymerization of methacrylic acid in the crystalline state have been investigated and utilized to evaluate the mechanism of polymerization. In particular, results for post-irradiation polymerization at 0°C after radiation doses of 0.1 to 2.0 Mrad support the concepts of Lando and Semen that chain initiation essentially all commences at the same time, that chain propagation continues without termination, and that termination of nonpropagating radicals proceeds simultaneously.     

Influence of the Br?nsted and Lewis Acid Sites in Platinum/Solid Acid Catalysts on the Hydrogenation of Benzene and Toluene

The hydrogenation of benzene and toluene was investigated over US-SSY, -Al₂O₃, and Ha1-MCM-41 supported platinum catalysts. The acidity of catalyst supports was measured by IR spectra of pyridine adsorption. On the Brönsted acid supported catalyst, both the hexacyclic saturation product and the pentacyclic one, the hydroisomerization product, were observed, and these two products were revealed to be primary reaction products. The two products were proposed to be formed competitively on Brönsted acid sites with carbonium ions as the reaction intermediate. By contrast, no hydroisomerization product was found on Lewis acid supported catalysts. It was inferred that the electron-deficient reaction intermediate formed on Lewis acids could not undertake any skeletal isomerization process to give a pentacyclic saturation product.     

A New Diterpene Acid from the Flowers of Heteropappus altaicus

A new compound, named heteraltaic acid was isolated from the flowers of Heteropappus altaicus (willd) Novopokr. The compound was elucidated as (5R, 6S, 8aS) -5-[2-(3-furyl) ethyl-5, 6, 8a-trimethyl-4a, 5, 6, 7, 8, 8a -hexahydro-l-naphthalenecarboxylic acid] by the combination of 1D and 2D NMR techniques (HSQC, HMBC) and X-ray analysis.     

Efficient Method for Synthesis of the Derivatives of 5‐Arylidene Barbituric Acid Catalyzed by Aminosulfonic Acid With Grinding

Aminosulfonic acid is an environmentally friendly catalyst. Grinding a mixture of aromatic aldehydes, barbituric acid, and H₂NSO₃H at room temperature (without any solvent) gave 5‐arylidene barbituric acid in high yields, providing a simple and efficient route to synthesis of these compounds.     

Glycine Imine—The Elusive α-Imino Acid Intermediate in the Reductive Amination of Glyoxylic Acid

Simple unhindered aldimines tend to hydrolyze or oligomerize and are therefore spectroscopically not well characterized. Herein we report the formation and spectroscopic characterization of the simplest imino acid, namely glycine imine, by cryogenic matrix isolation IR and UV/Vis spectroscopy. Glycine imine forms after UV irradiation of 2-azidoacetic acid by N₂ extrusion in anti-(E,E)- and anti-(Z,Z)-conformation that can be photochemically interconverted. In matrix isolation pyrolysis experiments with 2-azidoacetic acid, glycine imine cannot be trapped as it further decarboxylates to aminomethylene. In aqueous solution glycine imine is hydrolyzed to hydroxy glycine and hydrated glyoxylic acid. At higher concentrations or in the presence of Fe^IISO₄ as a reducing agent glycine imine undergoes self-reduction by oxidative decarboxylation chemistry. Glycine imine may be seen as one of the key reaction intermediates connecting prebiotic amino acid and sugar formation chemistry.     

Modification of the Ultrastable Y Zeolite with Citric Acid in the Unbuffered System

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Improving the Selectivity of the Phosphoric Acid β-Elimination on a Biotinylated Phosphopeptide

This study aims at improving the MALDI-TOF detection of a phosphorylated peptide containing a cysteine residue by ??-elimination of H₃PO₄ hardly enriched by classical methods. The experimental conditions were optimized on this phosphopeptide (biot-pAdd) and its nonphosphorylated counterpart (biot-Add). The major side-reactions were H₂S elimination on the cysteine residues and H₂O elimination on the non phosphorylated serine residue of biot-Add. The former dilutes the MALDI-TOF signal for the desired species. The latter gives a product similar to what is obtained by H₃PO₄ elimination and should prompt to caution when working with a mixture between phosphorylated and non phosphorylated peptides. Modifications on the solvent, the reaction temperature and time, the nature, and concentration of the base were made. Major improvement of the selectivity of the reaction was observed in 30?% ACN, at room temperature for 4?h. However, these optimizations are specific to these sequences and should be performed anew for different peptides. The selectivity of the reaction towards H₃PO₄ elimination is improved, but the persistence of side-reactions renders a previous sample fractionation necessary. In these optimized conditions, the ionization enhancement is 3-fold and the detection limits for biot-pAdd are similar to biot-Add (100?fmol).     

Polymerization of Methyl Methacrylate in the Presence of N-Acetyl-ε-aminocaproic Acid Acetylamide

The effect of N-acetyl--aminocaproic acid acetylamide on radical polymerization of methyl methacrylate initiated with lauroyl peroxide was studied.     

Effect of the Acid–Base Properties of the Support on the Activity of Pd–Zeolite Catalysts for CO Oxidation

The effect of the acid–base properties of zeolite Y on the activity of palladium–zeolite catalysts for CO oxidation was studied. The modification of the support with basic additives was found to improve the catalyst activity. A linear correlation between the ratio between the amounts of O₂and CO adsorbed on the surface of palladium and the catalyst activity was established.     

Voltammmetric Determination of Uric Acid in the Presence of Ascorbates Using Overoxidized Polypyrrol

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