P. Ficarra

Improvement in solubility and dissolution rate of flavonoids by complexation with β-cyclodextrin

The inclusion into the beta-cyclodextrin is used to improve pharmacokinetic characteristics of hesperetin and naringenin. Solubility of hesperetin and naringenin with increasing concentrations of beta-cyclodextrin grows as long as the temperature increased. Stability constants were determined by the solubility method by Higuchi and Connors at different temperatures, and the thermodynamic parameters were calculated for inclusion complex formation in aqueous solution. The solid complexes were obtained in a molar ratio of 1:1 and their dissolution behavior at different pH was examined.

Study of flavonoids/β-cyclodextrins inclusion complexes by NMR, FT-IR, DSC, X-ray investigation☆

Flavonoids are natural substances with a lot of biological activities, including the antioxidant one. Their use in pharmaceutical field is, however, limited by their aqueous insolubility. As the formation of the inclusion complexes can improve their solubility in water, the flavonoids hesperetin, hesperidin, naringenin and naringin have been complexed with beta-cyclodextrin (beta-CD) by the coprecipitation method and studied in solution and in solid state by NMR, FT-IR, differential scanning calorimetry and X-ray techniques. The effects of complexation on the chemical shifts of the internal and external protons of beta-CD in the presence of each flavonoid were observed.

Study of the extraction procedure by experimental design and validation of a LC method for determination of flavonoids in Citrus bergamia juice.

A reversed-phase high-performance liquid chromatographic (HPLC) separation with photo-diode array detection was developed for the simultaneous determination of flavonoids extracted from Citrus bergamia juice. It employs a C18 reversed-phase column and a linear gradient elution system with methanol/water with 5% acetic acid (v/v), as mobile phase. The method was validated in terms of detection limits (LOD), quantitation limits (LOQ), linearity, precision and accuracy. Limits of detection ranged from a low of 0.007 mg ml(-1) (narirutin) to a high of 0.018 mg ml(-1) (didymin). The limits of quantitation were between a low of 0.011 mg ml(-1) (7-OH flavanone) and a high of 0.024 mg ml(-1) (didymin). An excellent linear response was observed over the range specified for all analytes, as confirmed by the correlation coefficient with ranged from 0.9982 and 0.9999. The intra-day R.S.D.% ranged from 0.11 to 3.64%. The intermediate precision R.S.D.% were not higher than 7.62%. The accuracy of the method was confirmed with an average recovery ranging, except for neoeriocitrin, between 88.07% and 102.45%. Since the extraction conditions can affect analyte recovery, a suitable optimization strategy of the procedure was needed. The experimental parameters optimized were extraction time, temperature, and solvents. A multivariate approach was used to provide direct evaluation of the selected variables and related interactions. The D-optimal design was constructed by applying the exchange algorithm. All experimental results were computed by NEMROD-W software. This methodology led us to obtain the best recovery for all the flavonoids in the least number of experiments.

Comparative photodegradation studies on 3-hydroxyflavone: influence of different media, pH and light sources

3-Hydroxyflavone (3-OH-F) photochemistry in solution has been rationalized in terms of an excited state intramolecular proton transfer (ESIPT), which involves the free 3-hydroxy group interacting with the ortho-carbonyl. This photo-rearrangement occurs rapidly and is strongly influenced by the physico-chemical properties of the solvent, which plays an essential role in determining whether a photo-oxidation or a photo-induced molecular rearrangement takes place. 3-OH-F photoreactivity has been deeply investigated and the related mechanisms elucidated, as affected by various solvents, pH values and irradiation wavelengths, leading to different photodegradation rates and pathways. Moreover, the influence of molecular encapsulation upon alpha- and beta-cyclodextrins (alpha- and beta-CyD) on the molecule photoreactivity has been examined, as a potential tool for increasing molecule photostability as well as minimizing photoinduced toxic effects on biosubstrates.

Study of β-blockers/β-cyclodextrins inclusion complex by NMR, DSC, X-ray and SEM investigation ☆

Abstract The formation of inclusion complexes between β-cyclodextrin with the two β-blockers, atenolol and celiprolol, have been studied in the aqueous environment and in the solid state by nuclear magnetic resonance (NMR) spectroscopy, X-ray, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) techniques. The magnitude of the chemical shifts of the interior and exterior β-cyclodextrin protons in the presence of each β-blocker indicated that these are included within the β-cyclodextrin cavity. In aqueous solution they form 1:1 complexes. In the solid state the formation of the β-cyclodextrin/atenolol (celiprolol) complexes is confirmed by X-ray, DSC and SEM, also employed to characterize pure substances and their physical mixtures.

Physico-chemical characterization of an amphiphilic cyclodextrin/genistein complex.

Specific recognition of cell-targeting systems as host-carriers modified with receptor targeting groups, is a major ambition in the application of supramolecular science to medicine and life science. Genistein (Gen), an isoflavone belonging to the class of phytoestrogens, is of great interest because it has been considered as potential remedy for many kinds of disease. In this work, genistein in aqueous medium and in the presence of an host nanocarrier as amphiphilic cyclodextrin (CyD) modified in the upper rim with oligoethylene hydroxyl groups [(2-oligo(ethyleneoxide)-6-hexylthio)-beta-CyD, SC6OH] at 1:1 molar ratio, has been firstly investigated by UV-vis measurements coupled with circular dichroism data, in order to characterize the drug/macrocycle binding affinity through the formation of the complex. Furthermore, FTIR-ATR technique has been used to detect the complex formation in solid phase and to characterize the functional groups responsible of the solid Gen/SC6OH complex stability. The infrared absorbance spectra of the complex, collected in a wide range of wavenumber and around the physiological temperature, have been analysed and compared with the spectra of the pure compounds and their physical mixture. By monitoring the most significant changes in the shape and position of the absorbance bands of the Gen functional groups, we showed that the formation and/or modification of polar bonds play the main role in the interaction of the drug with the amphiphilic CyD. From the results, Gen is shown to be entangled in SC6OH nanoaggregates, establishing hydrogen bonding with the hydrophilic PEG chains.

Validation of a LC method for the analysis of zafirlukast in a pharmaceutical formulation.

A reversed-phase high-performance liquid chromatographic (HPLC) method was developed and validated for estimation of zafirlukast in a pharmaceutical formulation. Assay samples were extracted utilizing acetonitrile. Drug and internal standard were chromatographed on reversed-phase C18 columns, using mixtures of acetonitrile/water and the eluents were monitored at different wavelengths. The method was validated statistically for its linearity, accuracy, robustness and precision. Experimental design was used during validation to evaluate method robustness and for the determination of intermediate precision. Factors examined for statistical approaches include laboratory, day, analyst, instrument, different percentage of organic modifier, temperature, wavelength and flow-rate. Due to its simplicity and accuracy, the method may be used for routine quality control analysis.

Validation of a LC method for the analysis of oxaliplatin in a pharmaceutical formulation using an experimental design

A rapid and sensitive RP-HPLC method with UV detection for routine control of oxaliplatin in a pharmaceutical formulation (Eloxatin) was developed. Quantitation was accomplished with the internal standard method. The procedure was validated by linearity (correlation coefficient=0.999948), accuracy, robustness and intermediate precision. Experimental design was used during validation to calculate method robustness and intermediate precision. For robustness test three factors were considered: percentage v/v of acetonitrile, flow rate and temperature; an increase in the flow rate results in a decrease of the drug found concentration, while the percentage of organic modifier and temperature have no important effect on the response. For intermediate precision measure the considered variables were: analyst, equipment and days. The RSD value (2.27%, n=24) indicated a good precision of the analytical method.

UV–vis and FTIR-ATR characterization of 9-fluorenon-2-carboxyester/(2-hydroxypropyl)-β-cyclodextrin inclusion complex

In this work, the usefulness of (2-hydroxypropyl)-beta-cyclodextrin (HP-beta-CyD) as a tool to form an inclusion complex with 9-fluorenonic derivative (AG11) has been investigated, in pure water, by UV absorption. Phase-solubility diagrams allowed the determination of the association constant between AG11 and HP-beta-CyD. At the same time, solid binary systems between AG11 and HP-beta-CyD have been prepared in 1:1 stoichiometry by co-precipitation method. In order to confirm the complexation, FTIR spectroscopy in ATR geometry measurements have been performed and the results have been compared with the free compounds and the corresponding physical mixture in the same molar ratio. The nature of the interactions between AG11 and HP-beta-CyD has been elucidated also by applying mathematical procedures such as deconvolution and curve fitting. Improvement of the aqueous solubility is expected to improve the bioavailability of the drug in oral administration.

Amphiphilic Cyclodextrins as Nanocarriers of Genistein: A Spectroscopic Investigation Pointing Out the Structural Properties of the Host/Drug Complex System

Nanoggregates of nonionic amphiphilic cyclodextrin (ACyD) modified with hydrophobic chains of intermediate length [(2-oligo-ethyleneoxide-6-hexylthio)-beta-CyD, SC6OH] were prepared by emulsification-diffusion method. They are able to entrap an isoflavone, genistein (Gen), and the complexed species are studied at different host/guest molar ratio. The increased isoflavone solubility in the presence of the aggregates of SC6OH is investigated by UV-Vis spectroscopy, whereas size, charge, and structure of aggregates and their complexes with Gen are measured by means of static and quasi-elastic light scattering, and electrophoretic mobility measurements. On the other hand, preparing samples by the conventional method used for liposomes (hydration of an organic film of SC6OH and sonication) gives rise to aggregates with different sizes and lower colloidal stability. It is shown that the improved stability in water of ACyD aggregates both in the absence and in the presence of Gen, obtained by emulsification-diffusion is due to the existence of nanodomains of organic solvent (R(H) congruent with 120 nm) which cannot be completely removed by evaporation and freeze-drying and in which host/guest complexes are contained. This result shows that residues of organic solvent from preparation step favor the colloidal stability of the aggregate, but their presence must be taken into account in designing systems for drug delivery.