Vincent Aroulmoji
Research interests
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InterestsMetabonomics, Biomass Energy, Solar Energy Conversion, NMR Spectroscopy
Publications
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0.75Impact points
Herbicide activity of extracts from Ailanthus altissima (Simaroubaceae).
Natural product communications. 05/2011; 6(5):593-6.
The purpose of the present study was to isolate and characterize ailanthone-rich materials from the bark of the deciduous tree Ailanthus altissima (Mill.) Swingle and to assess their herbicide activity on selected herbaceous species. Ailanthone-rich fractions were obtained from A. altissima bark by ... [more] The purpose of the present study was to isolate and characterize ailanthone-rich materials from the bark of the deciduous tree Ailanthus altissima (Mill.) Swingle and to assess their herbicide activity on selected herbaceous species. Ailanthone-rich fractions were obtained from A. altissima bark by extraction with dichloromethane and ethyl acetate and subsequent purification of these crude extracts, and of the remaining water mixture after solvent extraction, by means of gel permeation chromatography. A number of fractions were isolated and characterized for ailanthone content. A dichloromethane fraction was shown to contain 92% w/w of ailanthone, as demonstrated by HPLC and NMR analysis. A significant pre-emergence herbicide activity was found for most of the extracts which was directly correlated to ailanthone concentration. A remarkable combined pre- and post-emergence herbicide activity was found for a specific fraction. These results indicate that the bark of A. altissima may represent an interesting source for the production of natural herbicides for use in agriculture.
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1.57Impact points
Experimental and theoretical investigation of the molecular and electronic structure of anticancer drug camptothecin.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy. 03/2011; 78(3):1058-67.
The Fourier Transform Infrared spectrum of (S)-4 ethyl-4-hydroxy-1H-pyrano [3',4':6,7]-indolizino-[1,2-b-quinoline-3,14-(4H,12H)-dione] [camptothecin] was recorded in the region 4000-400 cm(-1). The Fourier Transform Raman spectrum of camptothecin (CPT) was also recorded in the region 3500-5... [more] The Fourier Transform Infrared spectrum of (S)-4 ethyl-4-hydroxy-1H-pyrano [3',4':6,7]-indolizino-[1,2-b-quinoline-3,14-(4H,12H)-dione] [camptothecin] was recorded in the region 4000-400 cm(-1). The Fourier Transform Raman spectrum of camptothecin (CPT) was also recorded in the region 3500-50 cm(-1). Quantum chemical calculations of geometrical structural parameters and vibrational frequencies of CPT were carried out by MP2/6-31G(d,p) and density functional theory DFT/B3LYP/6-311++G(d,p) methods. The assignment of each normal mode has been made using the observed and calculated frequencies, their IR and Raman intensities. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. Most of the computed frequencies were found to be in good agreement with the experimental observations. The isotropic chemical shifts computed by (13)C and (1)H NMR analysis also show good agreement with experimental observations. Comparison of calculated spectra with the experimental spectra provides important information about the ability of computational method to describe the vibrational modes of large sized organic molecule.
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Hyaluronan–Carbon Nanotube Derivatives: Synthesis, Conjugation with Model Drugs, and DOSY NMR Characterization
European Journal of Organic Chemistry. 01/2011; 28:5617-5625.
Carbon nanotube (CNTs) derivatives are nowadays under thorough investigation as biomedically interesting materials. In this paper we describe a method for the preparation of water-soluble CNTs by condensation of the carboxylic groups introduced onto the carbon framework and the primary amine moietie... [more] Carbon nanotube (CNTs) derivatives are nowadays under thorough investigation as biomedically interesting materials. In this paper we describe a method for the preparation of water-soluble CNTs by condensation of the carboxylic groups introduced onto the carbon framework and the primary amine moieties inserted in the naturally occurring biopolymer hyaluronan (HA). The covalent conjugation between CNTs and HA should merge the biocompatibility and further processability of the HA chains with the well-known cellular penetration properties of the CNT derivatives to produce novel drug delivery platforms. In fact, thanks to the primary amino groups introduced in the HA chains, HA–CNT derivatives can be further covalently modified with model drugs like ibuprofen and methotrexate. We describe also the monitoring of all the CNT derivatization steps by diffusion-ordered NMR spectroscopy (DOSY), a technique that allows fast and reliable characterization of these novel derivatives.
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Hydration properties and proton exchange in aqueous sugar solutions studied by time domain nuclear magnetic resonance
Food Chemistry. 01/2011;
Proton NMR relaxation rates (R1 and R2) were measured in aqueous solutions of sucrose, d-glucose and d-fructose with increasing concentration. The measurements were carried out using Bruker PC 20 NMR Process Analyzer. Inversion recovery and CPMG pulse sequences are used for the measurement of relaxa... [more] Proton NMR relaxation rates (R1 and R2) were measured in aqueous solutions of sucrose, d-glucose and d-fructose with increasing concentration. The measurements were carried out using Bruker PC 20 NMR Process Analyzer. Inversion recovery and CPMG pulse sequences are used for the measurement of relaxation rates. Results show that the values of relaxation rate increase as the concentration of the sugar is increased. The relaxation rate appears to be higher for sucrose solutions as compared to glucose or d-fructose solutions. These results were discussed on the basis of molecular association between sugar and water molecules through hydrogen bonding. The water self diffusion coefficient was measured in these sugar solutions by using pulse field gradient NMR method. As expected, the water self-diffusion coefficient was reduced with increased sugar concentrations. The results of translational mobility exhibited a higher mobility for fructose than glucose or sucrose in aqueous solutions. The dependence of R2 on the inter-pulse delay of the CPMG sequence gives information on the proton exchange mechanism involved. The mechanism of exchange was studied using R2 with increasing inter pulse delay of 0.05–2.0 ms in aqueous solutions of 10%, 20% and 35% (w/v) of the above sugar solutions. From the plots of relaxation rates (R2) versus the 90°–180° pulse spacing it was possible to calculate the proton exchange rate (kb) of the different sugar solutions. Relaxation rates show characteristic variations with CPMG pulse spacing which can be interpreted on the basis of chemical exchange between solute and solvent molecules. The experimental results namely relaxation rates and CPMG pulse spacing data show the importance of water interactions with sweet molecules and this can lead to a better understanding of the effect of hydration water in taste chemoreception.
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1.57Impact points
Molecular structure, vibrational spectra and DFT molecular orbital calculations (TD-DFT and NMR) of the antiproliferative drug Methotrexate.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy. 09/2010; 77(1):264-75.
The FT-IR and FT-Raman spectral studies of the Methotrexate (MTX) were carried out. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of MTX have been investigated with the help of B3LYP density functional theory (DFT) using 6-31G(d) as basis set. Detailed analy... [more] The FT-IR and FT-Raman spectral studies of the Methotrexate (MTX) were carried out. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of MTX have been investigated with the help of B3LYP density functional theory (DFT) using 6-31G(d) as basis set. Detailed analysis of the vibrational spectra has been made with the aid of theoretically predicted vibrational frequencies. The vibrational analysis confirms the differently acting ring modes, steric repulsion, conjugation and back-donation. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results complement with the experimental findings. The calculated HOMO and LUMO energies show that charge transfer occur within the molecule. Good correlations between the experimental (1)H and (13)C NMR chemical shifts in DMSO solution and calculated GIAO shielding tensors were found.
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7.49Impact points
Two-dimensional diffusion-ordered NMR spectroscopy as a tool for monitoring functionalized carbon nanotube purification and composition.
ACS nano. 04/2010; 4(4):2051-8.
Functionalized carbon nanotube (CNT) derivatives are currently under thorough investigation in different biomedical investigations. In this field of research, the composition of sample either in terms of covalently attached or physisorbed moieties can greatly affect the observed results and hamper t... [more] Functionalized carbon nanotube (CNT) derivatives are currently under thorough investigation in different biomedical investigations. In this field of research, the composition of sample either in terms of covalently attached or physisorbed moieties can greatly affect the observed results and hamper the comparison between different studies. Therefore, the availability of a fast and reliable analytical technique to assess both the type of interaction (covalent vs noncovalent) and the composition of CNT conjugates is of great importance. Here we describe that the two-dimensional diffusion-ordered (DOSY) NMR spectroscopy is extremely useful to discriminate between conjugated and unconjugated polyethylene glycol groups in samples obtained by condensation with oxidized single-walled carbon nanotubes (SWNTs). This fast and nondestructive technique allows us to follow the removal of unconjugated polyethylene glycol chains during the purification. In particular, DOSY analysis reveal that about 1/3 (wt %) of the polyethylene glycol used for the condensation remained physisorbed to functionalized SWNTs after dialysis. Complete elimination of physisorbed polyethylene glycol was achieved using diafiltration.
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1.57Impact points
Hydration and self-association of caffeine molecules in aqueous solution: Comparative effects of sucrose and beta-cyclodextrin.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy. 08/2009; 73(1):6-10.
The UV-spectra of pure caffeine were measured and two quite differentiated hyper- or hypo-chromic effects were observed as concentration was increased. The first one was explained as due to caffeine-water molecule interaction and the second as originating from dimer formation and staking of caffeine... [more] The UV-spectra of pure caffeine were measured and two quite differentiated hyper- or hypo-chromic effects were observed as concentration was increased. The first one was explained as due to caffeine-water molecule interaction and the second as originating from dimer formation and staking of caffeine molecules. The effects of sucrose and beta-cyclodextrin on the hydration and the self-association of caffeine were also examined by UV spectroscopy. Sucrose was found to enhance the self-association of caffeine molecules by attracting and structuring water molecules around itself. The caffeine-caffeine hydrophobic interactions were promoted in such hydrophilic environment and so was the stacking. The molecular aggregation leads to reducing the electronic mobility and so is the case for the mesomeric effect in the heterogeneous cycle. This could explain the hypo-chromic phenomenon observed when sucrose concentration was increased. beta-Cyclodextrin shows a distinct behaviour because of its ability to form inclusion complexes with various hydrophobic guest molecules. This ability enhances the solubility of caffeine molecules throughout the inclusion interactions and prevents the caffeine self-association.
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8.58Impact points
Diffusion-Ordered NMR Spectroscopy in the Structural Characterization of Functionalized Carbon Nanotubes.
Journal of the American Chemical Society. 06/2009;
The emerging applications of functionalized carbon nanotubes (CNTs) in various research domains necessitate the use of many different analytical techniques to confirm their structural modifications in a fast and reliable manner. Thus far, NMR spectroscopy has not been among the main tools for charac... [more] The emerging applications of functionalized carbon nanotubes (CNTs) in various research domains necessitate the use of many different analytical techniques to confirm their structural modifications in a fast and reliable manner. Thus far, NMR spectroscopy has not been among the main tools for characterization of organically modified carbon nanostructures. (1)H analysis is limited because the signals in these derivatives are typically weak and broad, resulting in uncertainties of a few parts per million, and because of the strong interference of residual solvent signals. To overcome these limitations, we investigated the applicability of proton NMR spectroscopy based on gradient-edited diffusion pulse sequences (1D diffusion-ordered spectroscopy, DOSY) in the characterization of CNT derivatives. In general, diffusion NMR experiments allow the separation of NMR signals of different species present in a mixture, according to their own diffusion coefficients, merging spectroscopy information with size analysis. In the present study, a selected set of CNT derivatives was synthesized and analyzed using 1D DOSY experiments by applying strong magnetic field gradients (up to 42.6 G cm(-1)). Colorimetric tests (i.e., Kaiser test) and TGA analysis support the NMR findings, which are related to isolated and/or bundled short SWNTs, on the basis of TEM and AFM characterization. The overall results show that the diffusion-based NMR spectroscopy is a fast and promising approach for the characterization of covalently modified CNT derivatives.
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0.75Impact points
Synthesis and characterization of novel cardanol based benzoxazines.
Natural product communications. 05/2009; 4(4):521-8.
Benzoxazines are a class of phenolic compounds extensively studied in polymer science because of their properties as fiber reinforcements, fire-retardants and curing agents. In this article is described a solvent-less process, based on a Mannich reaction involving a primary amine and an aldehyde, fo... [more] Benzoxazines are a class of phenolic compounds extensively studied in polymer science because of their properties as fiber reinforcements, fire-retardants and curing agents. In this article is described a solvent-less process, based on a Mannich reaction involving a primary amine and an aldehyde, for the preparation of new benzoxazines deriving from cardanol (a well known phenol obtained as a renewable organic resource and harmful by-product of the cashew industry). Particular attention is given to the synthesis and chemical characterization (both by 1H NMR spectroscopy and HPLC), while the thermal polymerization process has been monitored by differential scanning calorimetry.
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2.03Impact points
Synthesis of 6-amino-6-deoxyhyaluronan as an intermediate for conjugation with carboxylate-containing compounds: application to hyaluronan-camptothecin conjugates.
Carbohydrate research. 11/2008;
A novel methodology for making drug conjugates using hyaluronan as a carrier was developed. This strategy involves a completely regioselective two-step synthesis of 6-amino-6-deoxyhyaluronan, which is then easily functionalized with drugs through a suitable linker. The case of hyaluronan-camptotheci... [more] A novel methodology for making drug conjugates using hyaluronan as a carrier was developed. This strategy involves a completely regioselective two-step synthesis of 6-amino-6-deoxyhyaluronan, which is then easily functionalized with drugs through a suitable linker. The case of hyaluronan-camptothecin conjugates is described, making use of a simple succinate linker. The antitumor activity of new hyaluronan derivatives prepared is at present under evaluation.
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2.03Impact points
Synthesis of 6-O-methotrexylhyaluronan as a drug delivery system.
Carbohydrate research. 10/2008;
Selective halogenation of hyaluronan and partial halogen substitution by methotrexate led to 6-chloro-6-deoxy-6-O-methotrexylhyaluronan, a potential antitumor drug. The remaining halogen could be further substituted by a second organic carboxylate, leading to mixed esters. 6-O-Acetyl-6-O-methotrexyl... [more] Selective halogenation of hyaluronan and partial halogen substitution by methotrexate led to 6-chloro-6-deoxy-6-O-methotrexylhyaluronan, a potential antitumor drug. The remaining halogen could be further substituted by a second organic carboxylate, leading to mixed esters. 6-O-Acetyl-6-O-methotrexylhyaluronan and 6-O-butyryl-6-O-methotrexylhyaluronan were thus synthesized and characterized by NMR spectroscopy.
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3.02Impact points
Effect of sucrose on the properties of caffeine adsorption layers at the air/solution interface.
Journal of colloid and interface science. 09/2004; 276(2):269-76.
Sweet and bitter tastes are known to be mediated by G-protein-coupled receptors. The relationship between the chemical structure of gustable molecules and their molecular organization in saliva (aqueous solution) near the surface of the tongue provides a useful tool for elucidating the mechanism of ... [more] Sweet and bitter tastes are known to be mediated by G-protein-coupled receptors. The relationship between the chemical structure of gustable molecules and their molecular organization in saliva (aqueous solution) near the surface of the tongue provides a useful tool for elucidating the mechanism of chemoreception. The interactions between stimulus and membrane receptors occur in an anisotropic system. They might be influenced by the molecular packing of gustable molecules within an aqueous solvent (saliva) close to the receptor protein. To investigate the molecular organization of a sweet molecule (sucrose), a bitter molecule (caffeine), and their mixture in an aqueous phase near a "wall", a hydrophobic phase, we modeled this using an air/liquid interface as an anisotropic system. The experimental (tensiometry and ellipsometry) data unambiguously show that caffeine molecules form an adsorption layer, whereas sucrose induces a desorption layer at the air/water interface. The adsorption of caffeine molecules at the air/water interface gradually increases with the volume concentration and is delayed when sucrose is added to the solution. Spectroscopic ellipsometry data show that caffeine in the adsorption layer has optical properties practically identical to those of the molecule in solution. The results are interpreted in terms of molecular association of caffeine with itself at the interface with and without sucrose in the subphase, using the theory of ideal gases.
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2.47Impact points
Hydration properties and the role of water in taste modalities of sucrose, caffeine, and sucrose-caffeine mixtures.
Journal of agricultural and food chemistry. 09/2001; 49(8):4039-45.
Solution properties of sapid molecules are informative on their type of hydration (hydrophobic or hydrophilic) and on the extent of the hydration layer. Physicochemical properties (intrinsic viscosity and apparent specific volume) and nuclear magnetic resonance (NMR) relaxation rates R(1) and R(2) f... [more] Solution properties of sapid molecules are informative on their type of hydration (hydrophobic or hydrophilic) and on the extent of the hydration layer. Physicochemical properties (intrinsic viscosity and apparent specific volume) and nuclear magnetic resonance (NMR) relaxation rates R(1) and R(2) for pure sucrose, bitter molecule caffeine, and their mixture were found to be relevant in the interpretation of the effects of these solutes on water mobility. Likewise, surface tension, contact angles with a hydrophobic surface, and the adhesion forces to this type of surface of the aqueous solutions of sapid molecules were found to discriminate between their effects on water cohesion and also between their taste qualities. The interpretation of the two sets of independent experimental results, namely physicochemical and spectroscopic data, helps in the elucidation of the role of water in sweet and bitter taste chemoreception.
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Hydration properties of Na, K, Mg gluconates and gluconate/sucrose mixtures and their possible taste effect
Food Chemistry. 01/2000; 70:471-482.
Density and ultrasonic velocity were measured in aqueous solutions of sodium, potassium and magnesium gluconate as a function of increasing concentration. Apparent molar volume (AMV), apparent specific volume (ASV), isentropic apparent molar (IAMC) compressibility and hydration numbers were calculat... [more] Density and ultrasonic velocity were measured in aqueous solutions of sodium, potassium and magnesium gluconate as a function of increasing concentration. Apparent molar volume (AMV), apparent specific volume (ASV), isentropic apparent molar (IAMC) compressibility and hydration numbers were calculated from the experimental data. The results show that AMV and ASV increase as the concentration of gluconates is increased. This is interpreted on the basis of molecular interaction between solute and solvent molecules. These measurements were repeated by adding Na, K and Mg gluconates to 10 and 20% sucrose solution with the aim of understanding the influence of gluconates on water association in sucrose solutions. The results show that the values of IAMC decrease as the concentration is increased. Moreover, Mg gluconate shows more negative IAMC than Na and K gluconates. The observed results are explained on the basis of the hydration of gluconates in the sucrose-water system. NMR relaxation rates (R1 and R2) show an increase as the concentration of the gluconate is increased. On the other hand, the results of Na, K and Mg gluconate in 10 and 20% sucrose solutions demonstrated that the effect of Mg gluconate enhances the hydration properties of sucrose water mixtures more than Na and K gluconate. The overall results show the importance of water interactions with sapid molecules and this can lead to a better understanding of their tastes.
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2.37Impact points
Solution conformation of alpha, beta or gamma-methylglutamyl-containing derivatives as probes of vitamin K-dependent carboxylase using molecular modelling and nuclear magnetic resonance.
International journal of biological macromolecules. 05/1997; 20(2):131-59.
In the present study, the conformational behaviour of methyl substituted N-BOC glutamic acid methyl esters (2M, 3T, 3E, 4T, 4E) has been completely characterized through combined NMR and molecular modeling studies. Hetero- and homonuclear coupling constants were measured in order to assign the remai... [more] In the present study, the conformational behaviour of methyl substituted N-BOC glutamic acid methyl esters (2M, 3T, 3E, 4T, 4E) has been completely characterized through combined NMR and molecular modeling studies. Hetero- and homonuclear coupling constants were measured in order to assign the remaining diastereotopic methylene protons at C(3) and/or C(4), and used for comparison with theoretical data. In parallel, the complete conformational analysis of these analogues has been achieved using molecular mechanics and molecular dynamics (MD) methods. The conformation of the glutamyl residue is established by the excellent agreement between the experimental and calculated side chain scalar coupling constants. The theoretical NMR data were calculated taking into account all the accessible conformations and using the averaging methods appropriate for internal motions. There is a significant influence of the methyl group on the conformational behaviour and on the biological relevance of these structures. Steric effect or electrostatic interaction may also have a considerable influence in stabilizing a conformational population in D2O solution. The conformational preferences of those different analogues in aqueous and methanol solution are discussed in the light of biological results obtained on the vitamin K-dependent carboxylase system.
Following (11)
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Sarathkumar Ramalingan
Maharaja Institutions -
Francesca Romana Delvecchio
Advanced Research Centre for Health, Environment and Space - ARCHES -
Giuseppe Vecchio
Istituto Italiano di Tecnologia (IIT) -
Shishir Gupta
Universität Heidelberg -
Massimo Bergamin
Istituto di Ricerca Protos
