The effect of pH dependent molecular conformation and dimerization phenomena of piroxicam on the drug:cyclodextrin complex stoichiometry and its chromatographic behaviour

Rozou, Stavroula; Voulgari, Afrodite; Antoniadou-Vyza, Ekaterini

doi:10.1016/j.ejps.2004.01.007

Cited by 43 publications

(29 citation statements)

References 13 publications

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“…Cyclodextrins are cyclic oligomers of α-D-glucose. They are widely used to increase the solubility and stability of medicinal and biologically active compounds and for chromatographic separation of mixtures of organic compounds because of their unique ability to form inclusion complexes with many organic molecules [1][2][3][4][5]. The application of cyclodextrins for the extraction, concentration, and analysis of toxic metals in environmental samples is promising.…”

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confidence: 99%

Interaction of β-cyclodextrin with mercury(II) nitrate

2008

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546.492+547.458.68The interaction of β-cyclodextrin with mercury(II) nitrate has been studied using UV, IR, and 1 H NMR spectroscopy, elemental analysis, and quantitative chemical analysis. The optimum conditions for complex formation were established. The stability constant of the 1:1 inclusion complex of β-cyclodextrin and nitrate was calculated. The formation of supermolecules of composition C 42 H 70 O 35 ⋅3Hg(NO 3 ) 2 in solution and on a silica surface chemically modified with β-cyclodextrin was shown.Introduction. Cyclodextrins are cyclic oligomers of α-D-glucose. They are widely used to increase the solubility and stability of medicinal and biologically active compounds and for chromatographic separation of mixtures of organic compounds because of their unique ability to form inclusion complexes with many organic molecules [1][2][3][4][5]. The application of cyclodextrins for the extraction, concentration, and analysis of toxic metals in environmental samples is promising. This may explain the vigorously developing research on the preparation of water-insoluble cyclodextrins [6] and their attachment to the surface of inorganic matrices [7-9]. β-Cyclodextrin was previously immobilized chemically on the surface of amorphous wide-pore silica [10][11][12]. The β-cyclodextrin-containing silica exhibited a high affinity for Hg(II) ions. Adsorption equilibrium is attained after only 15 min. The Hg(II) binding constant increases by two orders of magnitude compared with hydroxylated silica. Herein the interaction of β-cyclodextrin with mercury(II) nitrate in aqueous solution is studied in order to find the reasons for the high affinity of β-cyclodextrin-containing silica for Hg(II).Experimental. β-Cyclodextrin (Fluka, 99%) and Hg(NO 3 ) 2 (Khimlaborreaktiv, analytically pure) were used without further purification. UV absorption spectra of Hg(NO 3 ) 2 solutions were recorded on a Specord M-40 spectrophotometer in the wavelength range 260-400 nm in quartz cuvettes (l = 1 cm). The percent content of the various Hg(II) species in solution at pH 1-5 was calculated using the program Chemical Equilibria in AQuatic System. Elemental analyses were performed on an Elemental Analyzer EA 1110. IR spectra of powders were recorded on a Thermo Nicolet NEXUS single-beam Fourier IR spectrophotometer in the frequency range 4000-400 cm -1 . IR spectra were recorded using pressed disks of ~30 mg mass with pressing pressure 10 8 Pa. 1 H NMR spectra were measured at T = 25 o C in DMSO-d 6 on a Varian-VXR-300 (300 mHz) spectrometer with TMS internal standard. The Hg(II) content was determined using back titration with trilon [13].Results and Discussion. A symmetric absorption band with λ max = 302 nm and ε = 300 L/mol⋅cm ( Fig. 1) that belongs to the n → π * -transition of the N=O chromophore in the nitrate ion was recorded in the electronic spectrum of aqueous Hg(NO 3 ) 2 (0.001 M) [14]. Upon addition to the Hg(NO 3 ) 2 solution of given amounts of β-cyclodextrin, which has no characteristic absorption bands in the UV region, the abso...

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Interaction of β-cyclodextrin with mercury(II) nitrate

2008

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“…tolfenamic acid, piroxicam) [12,15]. This methodology has proven quite inefficient in some cases; e.g.…”

Section: Introductionmentioning

confidence: 98%

“…drug substances) when free from the guest:CD complexes [14]. Previously described HPLC methods specific for CD complexes [14,15] demonstrated that drug release from the drug:CD complexes before detection is a crucial parameter, since the fraction of the nondissociated complex causes the detected errors [16].…”

Section: Introductionmentioning

confidence: 99%

New SPE loading material for affinity‐based separation of cyclodextrins from drug:CD complexes in order to overcome Beer's law deviations

Rozou

Raftopoulos

Hatziantoniou

et al. 2009

J of Separation Science

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Molecular inclusion of guest molecules within CDs is known to alter guest molecule spectrophotometric absorptivity, making their determination, based on spectrophotometric data, inaccurate. Therefore specific analytical methods capable of quantifying the drugs as free molecules must be developed and validated. SPE was selected to simplify sample and avoid more time-consuming alternatives. A new solid phase was synthesized and characterized by infrared spectrometry, differential scanning calorimetry and elemental analysis. The competitive complexation of adamantane groups immobilized on the silica substrate facilitates drug:CD complex dissociation and elimination of CD from samples. The drug molecules, now free from CD, can be easily analysed by an already available HPLC method. This new SPE loading material was employed in the determination of ketoprofen in its CD complex as a representative example of the utility of this novel material. The calculated analytical errors were reduced from a maximum of 20.79% (without SPE) to a minimum of 3.99%.

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“…They are widely used for enhancement of solubility and stability of medicines and bioactive compounds due to their unique ability to form inclusion complexes of the "host-guest" type [11,12]. Cyclodextrins also are promising for creation of selective adsorbents, active catalysts and sensors [13][14][15], chromatographic separation and purification of organic compounds of similar structure and composition [16], extraction and concentration of impurities of toxic substances [17]; creation of medicines with prolonged action, and decreasing of toxicity of medicines [18,19].…”

Section: Introductionmentioning

confidence: 99%