http://hdl.handle.net/10366/4174 Tue, 21 Apr 2026 19:01:34 GMT 2026-04-21T19:01:34Z http://hdl.handle.net/10366/171052 [EN]Photophysical properties of a non-steroidal anti-inflammatory drug, Naproxen (6-methoxy a-methyl-2-naphthalene acetic acid sodium salt), were investigated in solvents of different polarity, hydrogen donor ability and also in cyclodextrins. The results indicate that in all cases the emitting state is the ~I~ singlet. In alcoholic solvents, an intermolecular hydrogen bond is responsible for the observed photophysical behaviour of the probe whereas in non-protic solvents (polar and weakly polar) an intramolecular hydrogen bond type is postulated to rationalize the data found. In water, the non-radiative rate constant has a value similar to those found in aqueous solutions of a- and/3- cyclodextrins where the probe form complexes. The behaviour in water is explained by a water-structure enforced hydrophobic effect. The spectroscopic results are interpreted on the basis of a multiple-parameter model that considers specific solute-solvent interactions. These were also observed in the ground state and detected by Fourier transform infrared spectroscopy. Molecular mechanics (MM) and molecular orbital (AM1) calculations also support the existence of two conformations (rotamers) in Naproxen with non-equivalent intramolecular hydrogen bond-like formation. Sun, 01 Jan 1995 00:00:00 GMT http://hdl.handle.net/10366/171052 1995-01-01T00:00:00Z http://hdl.handle.net/10366/171051 [EN]The inclusion of the anti-inflammatory drug, Nabumetone, in α-, β-and hydroxypropylβ-cyclodextrin (CDs) is studied using UV-VIS absorption and steady-state fluorescence emission. Binding constants and thermodynamic parameters of complex formation are determined by spectrofluorimetry. The inclusion phenomena of Nabumetone with the three cyclodextrins is compared with that of the well known similar anti-inflammatory drug Naproxen. In the case of Nabumetone pronounced differences are observed in the complexation process with each cyclodextrin whereas the respective Naproxen complexes are nearly identical. 1H-NMR experiments show that the inclusion process in Nabumetone can occur either through the substituents in the -2 (butanone) or -6 (methoxy) positions in the naphthalene ring. Fri, 01 Jan 1999 00:00:00 GMT http://hdl.handle.net/10366/171051 1999-01-01T00:00:00Z http://hdl.handle.net/10366/171050 [EN]UV-absorption spectroscopy technique enables the determination of the binding constants of some non-steroidal anti-inflammatory drugs to α-, β-, and γ-cyclodextrins. In all cases the stoichiometry of the complex is 1:1 and the drugs have a higher affinity for β-cyclodextrin than for α-cyclodextrin or γ-cyclodextrin. The dielectric constant of the cyclodextrin cavity has also been determined. The values show that the microenvironment of the drugs in β-cyclodextrin is more hydrophobic than the corresponding value for α-cyclodextrin and for γ-cyclodextrin. This fact seems to be due to a greater penetration of the drugs into the β-cyclodextrin cavity. From the changes observed in the C-band of the absorption spectra of the complexed drug, the changes in the structure of the drug included into the cyclodextrin may be analyzed and compared to the structure of the free drug. Mon, 01 Jan 1996 00:00:00 GMT http://hdl.handle.net/10366/171050 1996-01-01T00:00:00Z http://hdl.handle.net/10366/171049 [EN]The characterization and study of the polarity of mixed micelles of sodium decyl and sodium dodecyl sulfate and sodium cholate by fluorescence probing have been carded out. Pyrene and Pyrene-l-carboxaldehyde were used. The obtained results allow the discussion of the changes of micelle structure with composition. Mon, 01 Jan 1990 00:00:00 GMT http://hdl.handle.net/10366/171049 1990-01-01T00:00:00Z http://hdl.handle.net/10366/171035 [EN]Spectroscopic and photophysical properties of a non-steroidal anti-inflammatory drug, Nabumetone, were studied in dioxane/water mixtures, cyclodextrins (α-CD, β-CD and HP-β-CD) and besides that, for comparison, in a wide range of solvents with different polarities, viscosities and hydrogen bonding ability. The fluorescence quantum yields (φf) and lifetimes (τf) in aqueous and in non-aqueous media, present some evidence which points to the existence of two preferred conformations in aqueous media: one with global φf=0.1–0.3 and τf2=7 ns, corresponding to the side chain completely extended and the other one, with lower global φf=0.02–0.08 and τf1=0.7–2 ns, likely associated with a folded conformation responsible for the fluorescence quenching of the naphthalene moiety by the butanone chain. The formation of one or other conformation is not much affected by the physical properties of the solvent. By contrast, the presence of water creates a very favourable environment for the formation of the folded conformation, which is essentially the only one in pure water. This behaviour is explained by a water-structure enforced hydrophobic effect and makes this drug a good water sensitive probe. Inclusion of the drug in the β-cyclodextrin emphasises the existence of two conformations, whereas in α-CD only the extended one is present, with a much higher φf=0.4 and τf=15.7 ns. Molecular mechanics (MM) and molecular orbital (MNDO) calculations also support the existence of two possible conformations in Nabumetone. Sat, 01 Jan 2000 00:00:00 GMT http://hdl.handle.net/10366/171035 2000-01-01T00:00:00Z http://hdl.handle.net/10366/171033 [EN]By using electrical conductivity and static and dynamic light scattering measurements, the behavior of water−oil (w/o) microemulsions formed by Aerosol OT dissolved in toluene has been examined. To study the effect of the droplet volume fraction on the microemulsion behavior, the water and the surfactant concentrations were systematically modified and the temperature dependence was also studied. The scattering intensity and the apparent diffusion coefficients are analyzed with a model involving the Carnahan−Starling hard-sphere model including an attractive term. It was found that attractive interactions become important in w/o microemulsions containing w0 > 37. No percolation threshold is detected at the droplet volume fraction and temperature values used in this work. Mon, 01 Jan 2001 00:00:00 GMT http://hdl.handle.net/10366/171033 2001-01-01T00:00:00Z http://hdl.handle.net/10366/171032 [EN]The structure of CTAB micelles in the presence of α-, β- and hydroxypropyl-β-cyclodextrin has been investigated by means of conductivity and spectroscopic measurements – absorption and steady state fluorescence – using Naproxen, Nabumetone and pyrene as probes. In the presence of the three cyclodextrins, two types of micelles have been detected. The first type is a pure surfactant micelle, while the other is formed by surfactant monomers complexed with cyclodextrins. The presence of cyclodextrins produces a decrease in the cmc of the pure micelle. The second type of micelle is formed at higher cmc* values, 25.6 × 10-4 M, 27.8 × 10-4 M and 38.9 × 10-4 M for α-, β-, and HPβCD respectively. A significant increase in the ionisation degree has been detected. The aggregation number is strongly increased, being 92 ± 3 , 97 ± 3 and 80 ± 2 for for α-, β-, and HPβCD respectively. The polarity of this micelle decreases, indicating that it becomes tighter and its hydrophobic region becomes less polar. Tue, 01 Jan 2002 00:00:00 GMT http://hdl.handle.net/10366/171032 2002-01-01T00:00:00Z http://hdl.handle.net/10366/171031 [EN]The aim of this study was to investigate the effects of the presence of the water-soluble polymer polyvinylpyrrolidone K-25 (MW=24,000 g/mol) on the complexation of the AINE naproxen, in its sodium salt form, with the β-cyclodextrin. The data revealed that the polyvinylpyrrolidone K-25 interacts with the drug as well as with the drug:β-cyclodextrin inclusion complex. The polymer shows more affinity for the inclusion complex, K=(6.67±0.292)×10−5 M−1 than for the free drug, (2.08±0.208)×10−5 M−1. The presence of different proportions of polymer, in a range 0–1% (w/w) of polyvinylpyrrolidone, does not increase the ability of drug–cyclodextrin complexation but important changes in the driving force of complex formation were detected, depending on the percentage of polyvinylpyrrolidone K-25 present. At low polymer concentrations, the complexation process is driven entropically, while at higher PVP proportions it is enthalpically favored. In the ternary system, polyvinylpyrrolidone K-25 partially or totally coats the drug:β-cyclodextrin inclusion complex interacting with the β-cyclodextrin (through hydrogen bonds), and with the naproxen. Wed, 01 Jan 2003 00:00:00 GMT http://hdl.handle.net/10366/171031 2003-01-01T00:00:00Z http://hdl.handle.net/10366/171030 [EN]The aim of this study was to investigate the effect of the presence of the water-soluble polymer polyethylene glycol (PEG)—MW=35000 g/mol—on the complexation of the phototoxic anti-inflammatory drug naproxen, in its sodium salt form, with β-cyclodextrin (β-CD). The data revealed that the polymer does not interact with the uncomplexed naproxen whereas it does with the β-CD. The presence of different proportions of PEG, in the 0–1% (w/w) range, systematically lowers Kapp of the formation of the naproxen:β-CD inclusion complex. The reason for the decrease in the complexed drug is the presence of other competing equilibria, the first one is an interaction of the polymer with the β-CD, which in turn reduces the amount of free CD available for including the naproxen, and the second is the formation of a naproxen:β-CD:PEG ternary complex with lower affinity than the binary complex. The binding constant of these processes are K2=(4.5±1.0)×105 M−1 and K3=870±19 M−1, respectively. In addition the presence of the PEG produces an important change in the driving force of the complex formation. In this case the process is enthalpically unfavoured and entropically favoured; these are typical characteristics of processes governed by hydrophobic interactions. Wed, 01 Jan 2003 00:00:00 GMT http://hdl.handle.net/10366/171030 2003-01-01T00:00:00Z http://hdl.handle.net/10366/171029 [EN]The photolability of the anti-inflammatory drug Nabumetone (4-(6-methoxy-2-naphthyl)-butan-2-one) was studied in water. The photoproducts were followed by UV-Vis absorption, fluorescence and FTIR spectroscopies as well as gas chromatography–mass spectrometry (GC–MS). The photodegradation process in water followed first-order kinetics, with an half-life, t1/2 = 9.7min whereas leading to different products. In this medium, the side chain is photoxidised to 6-methoxy-2-naphthalene aldehyde, as major product, probably via a Nabumetone radical cation formation and the addition of singlet oxygen generated in the drug photolysis. In addition the (4-(6-methoxy-2-naphthyl)-3-buten-2-one) was detected. The most likely origin of the unsaturated compound is the dehydratation of an alcoholic derivative in alpha position of the naphthalene ring, produced via the same radical cation. Wed, 01 Jan 2003 00:00:00 GMT http://hdl.handle.net/10366/171029 2003-01-01T00:00:00Z http://hdl.handle.net/10366/171028 [EN]The photolability of the anti-inflammatory drug Nabumetone was studied in n-butanol. The photoproducts were followed by UV-Vis absorption, fluorescence and FTIR spectroscopies as well as gas chromatography–mass spectrometry (GC/MS). The photodegradation process in this organic medium followed first-order kinetics. In contrast with what was expected on the basis of the changes in the electronic spectra observed, the process seems to be more efficient than in water, with a Φ = 0.47 and a half-life, t1/2 = 3.0min, leading to different products. In this medium, the side chain is photo-oxidised to 6-methoxy-2-naphthaldehyde, as a major product. In addition the (4-(6-methoxy-2- naphthyl)-3-buten-2-one) was detected. The kinetic behaviour suggests that the photoproducts are formed from the singlet excited state (1NB∗) of the drug. Therefore the increase in the rate constant of the degradation of the Nabumetone, may be thought to be due to an increase in the concentration of this excited species via hydrogen bond formation with the solvent. Thu, 01 Jan 2004 00:00:00 GMT http://hdl.handle.net/10366/171028 2004-01-01T00:00:00Z http://hdl.handle.net/10366/171027 [EN]The properties of the interface of vesicles of pure sodium bis-(2-ethyl-hexyl) sulfosuccinate (AOT) and binary mixtures composed of AOT with poly(ethylene) glycol (PEG), poly(sodium 4-styrensulfonate) (PSS) and sodium chloride were investigated using absorption and steady-state fluorescence of nabumetone and electrophoretic mobility measurements. Results confirm those obtained in a previous work indicating that the addition of PEG, PSS, and NaCl stabilizes the AOT vesicles. The stabilization mechanism is the screening of the surface charge in the case of binary mixtures of AOT/PSS and AOT/NaCl and the polymer adsorption on the interface for vesicles of AOT/PEG. Thu, 01 Jan 2004 00:00:00 GMT http://hdl.handle.net/10366/171027 2004-01-01T00:00:00Z http://hdl.handle.net/10366/171026 [EN]The effect of the polyethylene glycol and/or β-cyclodextrin on the photolability of aqueous solutions of the anti-inflammatory drug Naproxen was studied. In all systems studied, the photodegradation process followed zero-order kinetics, leading to the same photoproducts as in the absence of these additives. Kinetic studies revealed that the presence of polyethylene glycol (PEG) reduced drug photodegradation (Φ=0.11 in water and Φ=0.045 in the presence of 1% of PEG). By contrast, the binary inclusion complex, Naproxen:β-CD, did not protect the drug from degradation, Φ=0.11. However, the ternary complex, Naproxen:β-CD:PEG, reduced the efficiency of the photodegradative process to a considerable extent, with Φ=0.022 in this system.In all cases the presence of the different additives elicited a change in the photomixture composition, the alcoholic derivative being the major photoproduct formed.Nevertheless, the change in the efficiency of the process and the amount of the photoproducts formed in the different systems were not related with the biodamage produced by the drug. In this sense, the presence of free Naproxen clearly sensitized the photoperoxidation of linoleic acid. The photosensitizing effect decreased as the PEG concentration increased and was completely abolished by both the binary (Naproxen:β-CD) and ternary (Naproxen:β-CD:PEG) complexes.In light of these observations, it is possible to speculate that in these systems the prevention of biodamage would be due to a decrease in the contact between the short-lived species generated during Naproxen photodegradation and biological structures, rather than to the nature or amount of the photoproducts. © 2004 Elsevier B.V. All rights reserved. Thu, 01 Jan 2004 00:00:00 GMT http://hdl.handle.net/10366/171026 2004-01-01T00:00:00Z http://hdl.handle.net/10366/171025 [EN]The aim of the present study was to investigate the effect of the presence of the water-soluble polymer polyvinylpyrrolidone (PVP) MW=24,000 g/mol, on the complexing of the anti-inflammatory drug nabumetone, with β-cyclodextrin (β-CD). The data show that the polymer interacts with the free nabumetone and with the nabumetone:β-CD inclusion complex, in both cases with a stoichiometry of 1:1. The interaction constants are 1.3×104 M-1 and 1.6×104 M-1, respectively. The presence of PVP, changes the drug:cyclodextrin interaction, a nabumetone:(β-CD)2:PVP complex being formed. In addition, the presence of PVP, produces a strong increase in the global binding constant, β2=(22.12±0.22)×106 M-2 at 1% PVP. In the ternary complex, the nabumetone is wrapped at both ends for the β-CD. In this complex the polymer seems to act as a bridge between both β-CD molecules that bind the nabumetone. Mon, 02 Oct 2006 00:00:00 GMT http://hdl.handle.net/10366/171025 2006-10-02T00:00:00Z http://hdl.handle.net/10366/171024 [EN]The effect of the formation of the naproxen:cyclodextrin inclusion complex on the quenching of the drug by iodide has been studied. The results show that -cyclodextrin ( -CD), -cyclodextrin ( -CD), and hydroxypropyl- -cyclodextrin (HP- -CD) provide good protection for the drug against iodide quenching. The trend of protection is -CD > HP- -CD≈ -CD>H2O, in contrast to the binding constant values and the structure of these complexes. The effect of these cyclodextrins on the quenching process is discussed on the basis of the parameters obtained by fitting the experimental data to the modified Stern–Volmer, and finite-sink approximation models. Wed, 15 Nov 2006 00:00:00 GMT http://hdl.handle.net/10366/171024 2006-11-15T00:00:00Z http://hdl.handle.net/10366/171023 [EN]Dynamic light scattering and Cryo-TEM measurements have allowed us to obtain the size and structure of spontaneous aggregates formed by mixtures of Aerosol OT, AOT, and ethylene glycol polymers of different molecular mass. The results presented in this work show that small unilamellar vesicles predominate in pure Aerosol OT solutions and in dilute polymer solutions mixed with AOT. In the latter case, elongated micelles coexist with unilamellar vesicles. When polymer concentration increases above a certain concentration, the small vesicles disappear and the size of the elongated micelles decreases to a radius compatible with spherical micelles. For PEG concentrations above the overlapping ones, spherical micelles coexist with very large aggregates probably formed by large rod like micelles or by superstructures of elongated micelles embedded in a polymer network. This behavior is consistent with theoretical models based in molecular mean-field theory [M. Rovira-Bru, D.H. Thompson, I. Szleifer, Biophys. J. 83 (2002) 2419]. The properties of the different types of aggregates are obtained by fluorescence spectroscopy and electrophoretic mobility measurements. Mon, 01 Jan 2007 00:00:00 GMT http://hdl.handle.net/10366/171023 2007-01-01T00:00:00Z