Effect of HP-β-cyclodextrins complexation on the antioxidant activity of flavonols

The beneficial effects from phenolic compounds have been attributed to their antioxidant activity. Differences in the chemical structure of flavonols and their degree of substitution will influence phenoxyl radical stability and, thereby, their antioxidant properties. Cyclodextrins (CDs) can be used as a flavonol complexation agent, since they act as a substrate reservoir in a dose-controlled manner. In the present paper, the effect of complexing flavonols, kaempferol, quercetin and myricetin with HP-β-CDs on their antioxidant capacity is studied by means of the oxygen radical absorbance capacity-fluorescein (ORAC-FL) assay. This complexation phenomenon increased the antioxidant activity of the three flavonols, which reached a maximum level when each flavonol had been complexed in the hydrophobic cavity of CDs. The antioxidant activity increased because of the flavonol was protected against rapid oxidation by free radicals.     

Determination of l- and d-carnitine in dietary food supplements using capillary electrophoresis–tandem mass spectrometry

This paper reports the application of a capillary electrophoresis–electrospray ionisation-tandem mass spectrometry methodology for the unequivocal identification and the quantitative determination of the two enantiomers of the non-protein amino acid carnitine (l- and d-Carn) in 22 dietary food supplements, including drinks, biscuits, capsules and tablets. MS/MS experiments were optimised to achieve the high sensitivity and selectivity required for food analysis. A comparison of the slopes obtained by the external standard and the standard additions calibration methods indicated the absence of matrix interferences in these food samples. Good precision (RSDs ranged from 2.3% to 4.3% for migration times, and from 2.1% to 10.5% for corrected peak areas) and acceptable accuracy established by means of recovery studies (from 85% to 102%) were obtained. The limit of detection was about 10 ng/mL (S/N = 3) enabling the determination of enantiomeric impurities (d-Carn) up to 0.025% of Carn in foods. This chiral method illustrated is suitable for routine qualitative and quantitative analyses of Carn in foods. The results showed contents for l-Carn comprised from 47% to 115% with respect to the labelled content of l-Carn. Percentages obtained for the d-enantiomer ranged from 0.4% to 5.9%, except for one of the samples analysed, that contained the racemate (49.3% d-Carn). The use of the racemate is not allowed by legislation, which corroborated the high potential of the developed method in the control of the quality and safety of foods containing Carn.     

Food applications of active packaging EVOH films containing cyclodextrins for the preferential scavenging of undesirable compounds

Novel ethylene-vinyl alcohol copolymer (EVOH) films containing beta-cyclodextrins (βCD) with potential application in active food packaging have been tested as materials for the preferential retention of undesired food components. The films were immersed on pasteurized milk and UHT milk and stored at 4 and 23 °C, respectively. The films containing βCD presented a significant reduction in cholesterol concentration, achieving a 23% reduction in UHT milk exposed to EVOH films containing 30% βCD. Despite the immobilization of the βCD and the large molecular size of cholesterol, 15% of the βCD molecules added to the films were involved in the formation of βCD/cholesterol inclusion complexes. In another set of experiments, the films were used to reduce the presence of aldehydes (substances which develop as a result of oxidative processes) in packaged fried peanuts. The films containing βCD brought a significant reduction in hexanal, reaching a 50% decrease over short periods (1-5 weeks). At longer storage times (10 weeks) the retention capacity of the developed films was exhausted and no differences were observed between the samples.     

The Preparation and Characterization of Small Mesopores in Siloxane‐Based Materials That Use Cyclodextrins as Templates

Porous thin films containing very small closed pores (～ 20 Å) with a low dielectric constant (～ 2.0) and excellent mechanical properties have been prepared using the mixture of cyclic silsesquioxane (CSSQ) and a new porogen, heptakis(2,3,6‐tri‐O‐methyl)‐β‐cyclodextrin (tCD). The pore sizes vary from 16.3 Å to 22.2 Å when the content of tCD in the coating mixture increases to 45 wt.‐% according to positronium annihilation lifetime spectroscopy (PALS) analysis. It has also been found that the pore percolation threshold (the onset of pore interconnectivity) occurs as the ～ 50 % tCD porogen load. The dielectric constants (k = 2.4 ～ 1.9) and refractive indices of these porous thin films decreased systematically as the amount of porogen loading increased in the coating mixture. The electrical properties and mechanical properties of such porous thin films were fairly good as interlayer dielectrics.     

Morphological Control of Nanoporous Films by the Use of Functionalized Cyclodextrins as Porogens

Porous cyclic silsesquioxane (CSSQ) thin films containing nanopores (～ 2 nm) with low dielectric constant (k < 2.2), have been prepared by using various kinds of cyclodextrin (CD) derivatives as porogenic materials. The pore structure, including average pore size and interconnectivity, can be controlled by changing the functional groups of the cyclodextrin derivatives. The pore structure is found to be strongly related to the affinity of the functional groups between CD molecules. The electrical and mechanical properties of the porous thin films were monitored in order to determine the relationship between the pore structure and film properties. The mechanical properties of porous low‐k thin films (total porosity ～ 30 %) prepared with CD derivatives are found to be correlated with the pore interconnection length. The longer the deduced interconnection length in the thin film, the worse the mechanical properties (such as hardness and modulus) of the thin film, even though the porogen‐induced pore diameters are very small (～ 2 nm).     

Evaluation of various processes for simultaneous complexation and granulation to incorporate drug–cyclodextrin complexes into solid dosage forms

Insoluble drugs often formulated with various excipients to enhance the dissolution. Cyclodextrins (CDs) are widely used excipients to improve dissolution profile of poorly soluble drugs. Drug–CD complexation process is complex and often requires multiple processes to produce solid dosage form. Hence, this study explored commonly used granulation processes for simultaneous complexation and granulation. Poorly soluble drugs ibuprofen and glyburide were selected as experimental drugs. Co-evaporation of drug:CD mixture from a solvent followed by wet granulation with water was considered as standard process for comparison. Spray granulation and fluid bed processing (FBP) using drug:CD solution in ethanol were evaluated as an alternative processes. The dissolution data of glyburide tablets indicated that tablets produced by spray granulation, FBP and co-evaporation–granulation have almost identical dissolution profile in water and 0.1% SLS (>70% in water and >60% in SLS versus 30 and 34%, respectively for plain tablet, in 120?min). Similarly, ibuprofen:CD tablets produced by co-evaporation–granulation and FBP displayed similar dissolution profile in 0.01?M HCl (pH 2.0) and buffer pH 5.5 (>90 and 100% versus 44 and 80% respectively for plain tablets, 120?min). Results of this study demonstrated that spray granulation is simple and cost effective process for low dose poorly soluble drugs to incorporate drug:CD complex into solid dosage form, whereas FBP is suitable for poorly soluble drugs with moderate dose.     

Nanostructuring and functionalizing polymers with cyclodextrins

We summarize our recent studies employing the cyclic starches called cyclodextrins (CDs) to both nanostructure and functionalize polymers. Two important structural characteristics of CDs are taken as advantages to achieve these goals. First the ability of CDs to form non-covalent inclusion complexes (ICs) with a variety of guest molecules, including many polymers, by threading and inclusion into their relatively hydrophobic interior cavities, which are roughly cylindrical with diameters of ∼0.5 to 1.0 nm for α-, β-, and γ-CD containing 6, 7, and 8 α-1,4-linked glucose units, respectively. When guest polymers are coalesced from the CD-ICs by removing their host CDs, they are observed to solidify with structures, morphologies, and even conformations that are distinct from bulk samples made from their solutions and melts. Molecularly mixed, intimate blends of two or more polymers that are normally immiscible can be obtained from their common CD-ICs, and the phase segregation of incompatible blocks can be controlled (suppressed or increased) in CD-IC coalesced block copolymers. In addition, additives may be more effectively delivered to polymers in the form of their soluble or crystalline CD-ICs or rotaxanes. Secondly, many -OH groups attached to the exterior rims of CDs, in addition to conferring water solubility, provide an opportunity to covalently bond them to polymers either during their syntheses or via post-polymerization reactions. Polymers containing CDs in their backbones or attached to their side chains are observed to more readily accept and retain additives, such as dyes, fragrances, etc. They may also be further reacted or treated through their CDs to cross-link and form networks or to form blends with other polymers having a propensity to thread through their attached CD cavities.     

Thermal stability of the linoleic acid/α- and β-cyclodextrin complexes

This paper presents a thermal stability study of the linoleic acid/α- and β-cyclodextrin (α- and βCD) complexes. Bionanoparticles were obtained by a solution method and were characterized by differential scanning calorimetry and transmission electron microscopy. The pure linoleic acid, the corresponding thermally (50–150 °C) degraded raw linoleic acid samples or those recovered from the complexes were analyzed by gas chromatography–mass spectrometry, after conversion to the methyl esters. Nanoparticles were obtained with good yields of 88% and 74% for α- and βCD complexes, respectively. The main degradation products (for the thermally degraded raw samples) were aldehydes, epoxy, dihydroxy derivatives, homologues, and isomers of linoleic acid. A good thermal stability of nanoparticles can be observed, especially for the linoleic acid/αCD complex, which contains a relative concentration above 98% fatty acid in the case of temperature degradations of 50 and 100 °C. A lower concentration of 92% can be observed in the case of the linoleic acid/βCD complex but, for the temperature degradation of 150 °C, the linoleic acid was partially converted to more stable geometrical isomers.