Position Of OH Group Research Articles

A float mechanism of retention in reversed-phase chromatography

A float mechanism of retention in reversed-phase HPLC is proposed as an alternative to the known mechanisms of the distribution and hydrophobic expulsion of sorbate to the surface of a sorbent. Experimental data that the sorption of a flavylium structure is poorly sensitive to the position of OH groups, and that the retention of anthocyanins depends on the length of bonded alkyl radicals of reversed phase, form the basis of the proposed hypothesis. It is noted that the retention of anthocyanins depends on the orientation of hydroxyl groups in carbohydrate radicals, due to which the chromatographic behavior of anthocyanins is different for glucosides and galactosides, for arabinosides and xylosides, and so on. In other words, retention is a reliable indicator of the composition of a carbohydrate fragment. It is concluded that carbohydrate radicals serve as unique floats, while flat flavilic ions penetrate into the bonded phase. The existence of floats is the main reason for the lower efficiency (of the number of theoretical plates) of the peaks of anthocyanins. It is shown that if two carbohydrate radicals are present at different sites of aglycone (a two-float sorbate), the peaks of the substance are characterized by substantial additional broadening.

The effects of resonance delocalization and the extent of π system on ionization energies of model fluorescent proteins chromophores

Recent advances in the design and application of redox‐active fluorescent proteins (FPs) stimulated an interest in the electronic structure of the ionized/electron‐detached FP chromophores. Here, we report the results of a computational study of the electron‐detached and ionized states of model chromophores of green and red FPs. We focus on the analysis of the effects of the phenolate OH group position (ortho, meta, and para) on relative energies of the chromophores in the ground as well as in the ionized/detached electronic states. We found that, similarly to the green chromophore, the red chromophores with the OH group in meta position have lower vertical detachment energies (DE) and greater ionization energies relative to the ortho and para forms. Moreover, the effect is stronger for the red anionic chromophores. The differences in DE in meta species relative to their para counterparts are 0.47 and 0.25 eV for the red and green chromophores, respectively. The observed trends are due to a combined effect of resonance stabilization and the electronegativity of the acylimine group in the red chromophores. The analysis is supported by the computed charge and spin density delocalization patterns. © 2014 Wiley Periodicals, Inc.

UV/Visible spectra of a series of natural and synthesised anthraquinones: experimental and quantum chemical approaches.

Root decoctions of anthraquinone-containing plants are often taken as postpartum tonic and aphrodisiac. Anthraquinones are known for their diverse biological activities, especially antioxidant and anticancer. A series of 35 anthraquinones was generated by isolation from Rubiaceae plants and synthesis. Their UV/vis spectrum depends on the nature and relative positions of auxochromic substituents on the basic skeleton. To predict the maximum absorption bands for the current series of anthraquinones, excited sate calculations were performed using TD-DFT, CIS, ZINDO methods. The results showed that the use of PBE0 or its combination with B3LYP and B3P86 hybrid functionals are the most suitable to reproduce accurately the experimental λMAX. The structure–property relationships (SPRs) were established based on structural and electronic properties of the anthraquinones and showed (i) the importance of the number and position of OH groups and (ii) the positive contribution of the electrophilicity and hardness as electronic descriptors on position and amplitude of the maximum absorption bands.

Isolation, structure determination, and antiaging effects of 2,3-pentanediol from endophytic fungus of Curcuma amada and docking studies

An endophytic fungus was isolated from the rhizomes of Curcuma amada (Zingiberaceae), which was identified as Fusarium oxysporum on the basis of its morphological and molecular characters. Chromatographic separation and spectroscopic analysis of the fungal metabolite (chloroform extract) led to the identification of one pure compound having molecular formula C5H12O2, i.e., 2,3-pentanediol (1). Activity analysis of compound 1 demonstrated improved antiaging (antioxidant, thermotolerance) properties against Caenorhabditis elegans, in comparison to a similar, commercially available molecule i.e., 1,5-pentanediol (2). The effective (lower) concentration of 1 significantly showed (28.6%) higher survival percentage of the worms under thermal stress (37 ºC) compared to its higher concentration (25.3%), while similar trends were followed in oxidative stress where (22.2%) higher survival percentage was recorded in comparison to untreated control. The compound 1, however, lacked potential antimicrobial activity, indicating the plausible ramification of the position of OH group in such bioactive molecules. In silico evaluation of these molecules against common as well as unique targets corroborated better antiaging potential of 1 in comparison to that of 2. The results for the first time indicated that the utilization of the endophytic fungi of C. amada could, thus, be a possible source for obtaining non-plant-based bioactive compounds having broader therapeutic applications pertaining to age-related progressions.

Studies of interparticle interactions among some l-α-amino acids and 1,2 (1,3)-propanediols in aqueous solution at 298.15 K

Mixing enthalpies of aqueous glycine, l-α-alanine, l-α-valine, l-α-serine. l-α-threonine and l-α-proline solutions and aqueous 1,2-propanediol and 1,3-propanediol solutions and their dilution enthalpies have been measured with a Thermometric-2277 Thermal Activity Monitor at 298.15K. Experimental data were treated according to the McMillan–Mayer theory and the heterogeneous enthalpic pairwise interaction coefficients (hxy) of the natural amino acids and propanediol molecules in aqueous solution were obtained. Combining the hxy coefficients of amino acids with glycol and glycerol in aqueous solution reported by our previous works, the effects of number and position of OH groups in polyalcohols on the interactions between them and amino acids are discussed in the terms of solute–solute interactions.

Experimental determination and modeling of excess molar volumes, viscosities and refractive indices of the binary systems (pyridine + 1-propanol, +1,2-propanediol, +1,3-propanediol, and +glycerol). New UNIFAC-VISCO parameters determination

Densities, viscosities and refractive indices of four binary systems consisting of pyridine with mono-, di-, and three- hydroxyl alcohols (1-propanol, 1,2-propanediol, 1,3-propanediol, and glycerol) were measured at eight temperatures (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15, and 323.15)K and atmospheric pressure. From these data, excess molar volumes, viscosity deviations and deviations in refractive indices were calculated and fitted to the Redlich–Kister equation. The obtained results have been analyzed in terms of specific molecular interactions and mixing behavior between mixture components, taking into considerations effect of number and position of OH groups in polyols, as well as the influence of temperature on them. The modeling of VE binary data was performed with the Peng–Robinson–Stryjek–Vera cubic equation of state (PRSV CEOS) coupled with the van der Waals (vdW1) and CEOS/GE mixing rule introduced by Twu, Coon, Bluck, and Tilton (TCBT). The refractive indices of binary mixtures were predicted by various mixing rules and compared with experimental data. The viscosity modeling was done by two types of models: predictive UNIFAC-VISCO and correlative Teja–Rice and McAlister equations. In addition, due to the high importance of the prediction models, the experimental values of viscosity were used to determine the interaction parameters of following groups C6H5N–CH3, C6H5N–CH2, C6H5N–OH, C6H5N–CH, CH–CH3, CH–CH2, and CH–OH for their application in the UNIFAC-VISCO model.

Biocompatibility and Alkaline Phosphatase Activity of Phosphorylated Chitooligosaccharides on the Osteosarcoma MG63 Cell Line.

Phosphorylated chitooligosaccharides (P-COS) were prepared using a H3PO4, P2O5, Et3PO4 and hexanol solvent system. The P-COS were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Thermo gravimetric-Differential Thermal Analyzer (TG-DTA), 13C NMR, 31P NMR, X-ray diffraction analysis, solubility studies, biocompatibility and Alkaline Phosphatase Activity (ALP). The results reveal that phosphorylation occurred at the C3 and C6 position of OH groups and the C2 position of NH2 group. FT-IR confirmed no decomposition in pyranose ring in P-COS even with heating and treatment in acidic conditions. The amorphous nature of P-COS was confirmed by X-ray diffraction analysis. Further, the biocompatibility and alkaline phosphatase activity of P-COS were checked against the osteosarcoma MG63 cell line at different concentrations and no cytotoxicity was observed. After 12 h and 24 h of incubation, the ALP activity of P-COS was higher compared with the control group. These results suggest that P-COS is a biocompatible material and in future P-COS could open up a number of promising pharmaceutical and clinical applications to mankind.

Densities, Viscosities, and Refractive Indices of Binary Mixtures of Methyl Ethyl Ketone + Pentanol Isomers at Different Temperatures

Densities, viscosities, and refractive indices of mixing of methyl ethyl ketone with 1-pentanol, 2-pentanol, and 3-pentanol have been measured as a function of composition range at temperatures (298.15, 308.15, and 318.15) K and ambient pressure. Excess molar volumes VmE, viscosity deviations Δη, and refractive index deviations ΔnD were calculated and correlated by the Redlich−Kister-type function to derive the coefficients and estimate the standard error. From the experimental data, partial molar volumes, Vm,i, and partial molar volumes at infinite dilution, Vm,i0, were also calculated. The latter values are interesting from a theoretical point of view since at infinite dilution the only interactions present are solute−solvent interactions. The effect of temperature and −OH group position of pentanol isomers on the excess molar volumes, viscosity, and refractive index deviations of its mixtures with methyl ethyl ketone is discussed in terms of the nature and type of intermolecular interactions in binar...

Speed of Ultrasound and Internal Pressure of Propanediol and Butanediol Isomers under Elevated Pressures

The phase speed of an ultrasound wave depends on the elastic properties of the material. It is a significant source of information on the molecular structure of the liquid and on physical and chemical processes occurring in the liquid phase. Speed of ultrasound measurements carried out as functions of temperature and pressure enable also the determination of pρT relationships. Moreover, the measurements of the speed of ultrasound permit the investigation of very subtle effects such as, for example, stacking effect [1] or the effect of the position of OH groups in diol isomers on the physicochemical and thermodynamic properties of the pure compounds or their mixtures [2]. However, it requires measurements of adequate high accuracy and precision [3–6]. One of the convenient methods for the determination of the internal pressure is the acoustic one, i.e. the use of speed of ultrasound in conjunction with the density, isobaric heat capacity, and isobaric expansibility. The starting point is the combination of the low-frequency speed of ultrasound and density, which yields the isentropic compressibility (the Newton–Laplace equation). Then the latter may be combined with the isobaric expansibility and the isobaric heat capacity to yield the isothermal compressibility and finally the internal pressure (more details can be found elsewhere [7–11]). The so-called direct methods of determination of internal pressure are very inconvenient. Therefore, these methods are rather rarely used.

Bisphenol A Imprinted SiO2‐ZrO2 Mixed Oxide Materials Prepared by Acetic Anhydride Sol‐Gel Method

Silica‐zirconia (SiO2‐ZrO2) materials including bisphenol A (BPA) were prepared by a sol‐gel method using tetraethoxysilane, zirconium complexes and acetic anhydride in organic solution. The removal of BPA from SiO2‐ZrO2 materials is expected to form BPA‐imprinted sites in the solid matrices. Both the molecular shape and the positions of OH groups of BPA were considered to be imprinted. The acidic sites induced by isomorphously substituted Zr atom in silica matrix play the role in recognizing the OH groups of BPA. A BPA imprinted SiO2‐ZrO2 material preferentially adsorbed BPA and steroid hormones from the mixed solution of other reference molecules.

Neutron scattering studies of solid-state polymorphism in dimethyl butanol glass formers

Inelastic incoherent neutron scattering (IINS) and neutron powder diffraction (NPD) studies have been performed for two dimethyl 1-butanols and two dimethyl 2-butanols with CH 3 side molecular groups. Low-temperature vibrational density of states confirmed solid-state polymorphism detected by calorimetric methods, i.e., existence of crystalline and ODIC phases for all isomers, orientationally disordered glass for 2,2-DM 1-B and 3,3-DM 2-B, and glass of isotropic phase for 3,3-DM 1-B. Difference in vibrational density of states between glass and the ordered crystal has shown the so-called Boson peak. Influence of the OH group position in the molecules on their vibrational dynamics up to 50 meV is discussed.

Phase equilibria of vanillins in compressed gases

Solid–liquid phase transitions of vanillin, ethylvanillin, o-vanillin and o-ethylvanillin in compressed hydrocarbons (isobutane and propane), fluorinated hydrocarbons (R23, R134a and R236fa) and sulphur hexafluoride (SF 6) were determined with a modified capillary method in a pressure range between 0.1 and 31.0 MPa. Equilibrium solubilities of vanillins in compressed fluorinated hydrocarbons were determined at temperatures 313.2 and 333.2 K and over a pressure range between 1.1 and 26.0 MPa with a static–analytic method. Experimental solubility data were correlated by a density-based Chrastil model. Results showed that phase equilibria of vanillins in investigated compressed gases are influenced by the type of alchoxy group (methoxy or ethoxy) and the position of OH group (ortho or para), bound to the aromatic ring of solute, as well as the molecular structure of the gas. Three phase SLG curves in p, T-projections mainly exhibited temperature minimums and negative slopes d p/d T, with a maximum melting point depression between 9 and 21 K; all systems with SF 6 exhibited a continuous positive slope d p/d T of approximately 4.5 MPa/K. SLG curves with a temperature maximum at low pressure were observed for systems of o-vanillins with R23. Solubilities of o-vanillins in R23 and R236fa were higher in comparison with p-vanillins, whereas, in the case of R134a, the solubilities were influenced by the alchoxy group bound on aromatic ring: vanillin and o-vanillin with methoxy group are more soluble than vanillins with ethoxy group (ethylvanillin and o-ethylvanillin). The highest solubility of all four vanillins was observed in R236fa.

Antioxidant and Antiradical Activity of Hydroxy‐Substituted 4‐Thiaflavanes

AbstractThe antioxidant activities of several hydroxy‐substituted 4‐thiaflavanes, compounds 1–3, were determined by measuring their ability of inhibiting the autoxidation of styrene or cumene. On this basis, the role played by the number and position of OH groups and by the oxidation state of the S‐atom was quantified and rationalized. With these data, it should be possible to optimize the structural features of these ‘double‐faced’ antioxidants for structureactivity‐relationship studies. A comparison between the kinetic data (kinh) reported in this paper and the previously reported values of the antiradical activities (SC50), measured by the DPPH. bleaching method, for 1–3 is made (Table).

Neutron Scattering in 3,3-Dimethyl-2-Butanol and 2,3-Dimethyl-2-Butanol

Influence of the OH group position in the molecule on solid state polymorphism was found. Dynamics in solid phases of two dimethyl butanols were studied by inelastic incoherent neutron scattering. In glass of plastic crystal the boson peak was detected.

Microscopic Structure of Crystalline Langmuir Monolayers of Hydroxystearic Acids by X-ray Reflectivity and GID: OH Group Position and Dimensionality Effect

Hydroxystearic acid (HSA) molecules at the air-water interface present an interesting bicompetitive adsorption between primary and secondary hydrophilic groups on either end of an alkyl chain, which, depending on the position of the second hydrophilic group, may lead to a sharp transition from an expanded phase to a crystalline condensed morphology as surface pressure is increased. Here we report a set of measurements on a series of hydroxystearic acids in which the position of the secondary competing hydrophilic group position is varied along the whole extent of the alkyl chain from position 2 (i.e., close to the primary hydrophilic group) to positions 7, 9 and 12, the latter being the compounds mostly studied in the literature. We show here direct microscopic evidence, obtained by synchrotron radiation reflectometry and grazing incidence diffraction, that the position of the secondary hydrophilic group not only strongly influences the phase diagram as determined by compression isotherms and ellipsometry but also induces different crystallization patterns in the 2D system of the Langmuir monolayer. In particular, we report for the first time the existence of a turning point in the effects of the hydroxyl position on the monolayers structure at 7-HSA.

Optimization of the separation of flavonoids using solvent‐modified micellar electrokinetic chromatography

In this work the separation of eighteen flavonoids was attempted using reduced-flow micellar elektrokinetic chromatography (RF-MEKC) electrolytes modified by selected solvents with differing properties: methanol (MeOH), acetonitrile (ACN) and tetrahydrofuran (THF). Structural aspects such as unsaturation of the C ring, number and position of OH groups, methylation and glycosylation as well as solvent effects and their impact on the electrophoretic behavior of flavonoids were addressed. By evaluating the electropherograms obtained from mixture-designed electrolytes and searching for changes in the critical pairs, a favorable separation condition was achieved using 20 mmol/L phosphate buffer at pH 2.5 containing 50 mmol/L sodium dodecyl sulfate (SDS), 15% ACN and 5% THF (one critical pair) in less than 12 min with 1.5% coefficient of variation (CV) for retention factor and 3% CV for peak area (n = 5). The applicability of the proposed separation condition was demonstrated by the inspection of flavonoids in herbal extracts of Neem.

Measurement and correlation of excess molar enthalpy [formula omitted] for (1,2-propanediol, or 1,3-propanediol, or 1,4-butanediol + water) at the temperatures (298.15, 323.15, and 343.15) K

The excess molar enthalpies for (1,2-propanediol, or 1,3-propanediol, or 1,4-butanediol + water) have been measured at three different temperatures under atmospheric pressure over the whole composition range using a modified 1455 Parr solution calorimeter. For the temperature range studied all the mixtures exhibit negative values for H m E being less negative with increasing temperature. The obtained values have been correlated by a model [M.Y. Nagamachi, Ph.D. Thesis, Universidade Estadual de Campinas, Brazil, 2001.] in which hydrophobic effects are considered. The calculated values are in good agreement with the experimental ones. The influence of methyl group of alkanediol on hydrophobic hydration as well as the influence of the position of OH groups on hydrophilic hydration is discussed.

Enthalpies of dilution of aqueous solutions of n-butanol, butanediols, 1,2,4-butanetriol, and 1,2,3,4-butanetetrol at 298.15 K

Enthalpies of dilution of aqueous solutions of 1-butanol, butanediols, 1,2,4-butanetriol and 1,2,3,4-butanetetrol (erythritol), were measured at 298.15 K, using a LKB flow microcalorimeter. Experimental data were treated according to the McMillan–Mayer theory, to obtain the enthalpic interaction coefficients. The pair interaction coefficient h xx shows a clear dependence on number and position of OH groups. Results are discussed in terms of molecular interactions.

Effect of the hydroxy group position on the monolayer characteristics of hydroxypalmitic acids

The effect of the OH-group position on the monolayer characteristics of hydroxypalmitic acids is studied by coupling the results of surface pressure–area ( π– A) isotherm measurements and Brewster angle microscopy (BAM). In the present work, the phase behaviour and the domain morphology of 2-, 3- and 9-hydroxypalmitic acid monolayers are investigated. They deviate considerably but in different way from the adequate monolayer characteristics of the usual non-substituted amphiphiles. General differences exist also between the monolayer characteristics of palmitic acid OH-substituted near the COOH-group (in 2- or 3-position) and those when the OH-substitution is in or near the mid-position of the alkyl chain (in 9-position). This is demonstrated by differences in the temperature dependence of the phase transition pressure. The values of enthalpy and entropy change for the main phase transition are discussed and suggest in the case of 9-hyroxypalmitic acid, a structure improvement in the fluid monolayer phase at compression to the phase transition point because of reorientation into a perpendicular position. For the two types in the position of the OH-substitution, large differences in the morphology of the condensed phase domains indicate adequate differences in the long-range orientational order. In the case of OH-substitution near the COOH-head-group, irregular domain growth occurs while at OH-substitution in or near the mid-position of the alkyl chain, regular patterning of the domains indicate a high ordering. The reasons for the differences in the ordering are discussed.

Colorimetric detection and differentiation of fluoride and dihydrogenphosphate anions

Benzylidene malononitrile derivatives 2– 4 with H-bonding donors were synthesized and studied to colorimetrically detect anions. Compound 3 allows selective colorimetric detection of F − and H 2PO 4 − in organic solvents via intermolecular hydrogen binding, and can distinguish H 2PO 4 − from F − by adding a protic polar solvent such as water. In contrast to compound 3, compound 4 exhibits its selectivity to AcO − superior to H 2PO 4 −. This disparity is likely to be related to the different number and position of OH groups in a benzene ring, which lead to different electronic and steric effects.