Preparation and properties of phytosterols with hydroxypropyl β-cyclodextrin inclusion complexes

In order to enhance the solubility and bioavailability of phytosterols (PS), cyclodextrin–PS (CD–PS) inclusion complexes were prepared and the properties of PS-β-cyclodextrin (PS-β-CD) and the inclusion mechanism of its derivative hydroxypropyl β-cyclodextrin (PS-HP-β-CD) in solution were also evaluated. The effects of crucial parameters on cyclodextrin–sterol inclusion efficiency were optimized, including solvent type, β-CD/PS molar ratio, temperature, PS content and reaction time; 92–98?% inclusion efficiency was achieved under the conditions of HP-β-CD/PS ratio 3:1–4:1, PS concentration 15–20?mM, temperature 50–55?°C, reaction time 12?h. For β-CD host, butanol was a good solvent for PS inclusion reaction. The properties of CD–PS inclusion complexes were characterized by differential scanning calorimetric, scanning electron microscopy, UV–Vis scanning spectrophotometer (UV–Vis) and fourier transform infrared spectroscopy (FT-IR), which demonstrated that there are intermolecular hydrogen bonds between PS and HP-β-CD in inclusion complex, resulting in the formation of amorphous form. To clarify the mechanism of the increase in the solubility and bioactivity of HP-β-CD–PS inclusion complexes, the structure of CD as well as the interaction of the HP-β-CD–PS inclusion formation was elucidated. The conclusions indicated that PS-HP-β-CD showed higher water solubility with greater solubilizing and complexing capabilities than PS-β-CD and PS itself.     

Morphological characterization of encapsulated fish oil with β-cyclodextrin and polycaprolactone

The present study characterized the morphology of fish oil β-cyclodextrin (β-CD) complex or fish oil encapsulated with polycaprolactone (PCL) by transmission electron microscopy (TEM) observation using low or high voltage with or without phosphotungstic acid (PTA) staining. Emulsion–diffusion or self-assembly aggregation methods were used to encapsulate fish oil in PCL or β-CD. PCL spheres averaged 200 nm in diameter. However, β-CD spheres were significantly larger and dependent on host:guest mixing ratio (w:w), being approximately 300 nm and 600 nm at ratios of 10:1 and 10:10, respectively. TEM enabled the visual distinction of core and wall materials, and revealed that fish oil was encapsulated with a different structure depending on whether the self-resembling aggregation of β-CD or emulsion–diffusion method with PCL was used. Hexagonal-type β-CD aggregates were evident at a mixing ratio 10:1 between β-CD and fish oil. The hexagonal arrangement of β-CD enveloped the fish oil with a thick (100–150 nm) membrane. Incorporation of β-CD with fish oil at a 10:10 mixing ratio produced a worm-type of β-CD. It is suggested that the fish oil might be physically blended without wrapping with β-CD. For the PCL formulation, the lower voltage TEM operating condition better enabled the observation of the thin PCL layer (1–2 nm) encapsulating the fish oil. Nanosizer^® and TEM yielded comparable measurements.     

Preparation,physicochemical characterization and release behavior of the inclusion complex of trans-anethole and β-cyclodextrin

Trans-anethole (AT) has a variety of antimicrobial properties and is widely used as food functional ingredient. However, the applications of AT are limited due to its low water solubility, strong odor and low physicochemical stability. Therefore, the aim of this work was to encapsulate AT with β-cyclodextrin (β-CD) for obtaining inclusion complex by co-precipitation method. The measurements effectively confirmed the formation of inclusion complex between AT and β-CD. The results showed that the inclusion complex presented new solid crystalline phases and was more thermally stable than the physical mixture and β-CD. The phase solubility study showed that the aqueous solubility of AT was increased by being included in β-CD. The calculated stability constant of inclusion complex was 1195 M^− 1, indicating the strong interaction between AT and β-CD. Furthermore, the release study suggested that β-CD provided the protection for AT against evaporation. The release behavior of AT from the inclusion complex was controlled.     

Antioxidant activity of β-cyclodextrin inclusion complexes containing trans-cinnamaldehyde by DPPH,ABTS and FRAP

This study was carried out to observed β-cyclodextrin (β-CD) inclusion complexes containing trans-cinnamaldehyde (CIN) by using DPPH, ABTS and FRAP assay. Antioxidative ability was compared between pure CIN and β-CD-CIN inclusion complexes and particle size, encapsulation efficiency, and temperature-dependent release of inclusion complexes were investigated. High concentration of β-CD (1.8%) as well as guest oil 1:3 molar ratio (β-CD:CIN) influenced on particle size bigger during self-assembly process. And particle sizes were increased as storage period. In the antioxidant capacity results, pure β-CD (1.8%) was antioxidative without CIN especially at FRAP assay. Antioxidant activity dramatically increased after 1:1 molar ratio (1.8% β-CD:CIN), especially at DPPH assay and ABTS^•+ assay. In this study, β-CD complexation enhanced CIN solubility and affected increase the antioxidant activity of the CIN. Moreover, we need to consider that molar ratio of between β-CD concentration and CIN is effective manufacturing condition to improve antioxidant activity of β-CD-CIN inclusion complexes.     

Preparation and characterization of β-lactoglobulin hydrolysate-iron complexes

The purpose of this study was to determine the best preparation condition of β-lactoglobulin hydrolysate-iron complexes and characterize its structural transformation both before and after binding using the UV-visible absorption spectrum, Fluorescence spectrum, and Fourier transform infrared spectroscopy. Results showed that β-lactoglobulin hydrolysates obtained with alcalase after hydrolysis for 6h possessed the highest iron-binding capacity. The highest yield of complexes was obtained when the mass ratio between β-lactoglobulin hydrolysate and Fe(3+) reached 40:1, with the optimal pH value of 7.0. All of the spectra indicated that some sites such as amido bonds transformed during chelation, and nitrogen atoms could chelate with Fe(3+) to form coordinate bonds by offering electron pairs. Therefore, β-lactoglobulin hydrolysate-iron complexes may be good carriers for iron and possess great potential to be used as iron supplements.     

Physicochemical and release characterisation of garlic oil-β-cyclodextrin inclusion complexes

Garlic oil (GO), rich in organosulphur compounds, has a variety of antimicrobial and antioxidant activities, however, its volatility and low physicochemical stability limit its application as food functional ingredients. The aim of this study was to investigate the physicochemical and release characterisation of inclusion complexes of GO in β-cyclodextrin (β-CD). The formation of GO/β-CD inclusion complex was demonstrated by different analytical techniques including Fourier transform-infrared spectroscopy, differential scanning calorimetry and X-ray diffractometry. The stoichiometry of the complex was 1:1. The calculated apparent stability constant of GO/β-CD complex was 1141 M⁻¹, and the water solubility of GO was significantly improved by the phase solubility study. Furthermore, the release of GO from the inclusion complex was determined at a temperature range from 25 to 50 °C and in an acidic dissolution medium (pH 1.5), respectively. The release rate of GO from the inclusion complex was controlled.     

Preparation and characterization of β-cyclodextrin grafted silk fabric

ABSTRACT

Silk fabrics were treated by β-cyclodextrin (β-CD) in the presence of citric acid (CA) as crosslinking agent and sodium hypophosphite (SHP) as catalyst using pad dry cure technique. CA is expected to react with β-CD and hydroxyl groups of silk fibroin via esterification reaction. Four independent factors including curing time, curing temperature, β-cyclodextrin, and citric acid concentrations were selected, and effects of these factors on the weight gain of the samples were examined. Fourier transformed infrared spectrometer (FTIR), weight gain, differential scanning calorimetry (DSC), Thermal gravimetric (TGA) and differential thermal analysis (DTA), and field-emission scanning electron microscope (FE-SEM) were employed to confirm the changes of the silk fabrics. The effect of crosslinking reaction on the color changing of samples was investigated by measurement yellowness index of the treated fabrics. The results revealed that the weight gain could reach up to 22% when fabric was treated with 50 g/L β-CD, 100 g/L CA under 170°С for 3 min. FTIR and thermal analysis demonstrated that β-CD had been grafted onto silk fabric successfully.     

Encapsulation of cinnamon and thyme essential oils components (cinnamaldehyde and thymol) in β-cyclodextrin: Effect of interactions with water on complex stability

Thymol and cinnamaldehyde formed inclusion complexes with β-cyclodextrin (β-CD) upon mixing the components in aqueous media and subsequent freeze–drying, as confirmed by differential scanning calorimetry. The samples were stored at constant relative humidities (RH) from 22% to 97%, at 25 °C. The release of encapsulated compounds was determined following the melting enthalpy of each guest. Water sorption isotherms for β-CD and the complexes showed constant and low water sorption at RH < 80%, then the uptake of water increased abruptly. The amount of sorbed water at each RH was smaller for the complexes than for β-CD. The guest molecules displaced water molecules from inside the cavity of β-CD. No thymol or cinnamaldehyde release was detected at RH < 84%, and it increased abruptly from 84% RH, coincidentally with the abrupt increase of sorbed water. Water sorption significantly affects β-CD complexes stability, which is thus governed by the shape of the water sorption isotherm.     

Phase solubility studies and stability of cholesterol/β-cyclodextrin inclusion complexes

BACKGROUND: Cyclodextrins (CDs) are able to enhance the solubility, stability and bioavailability of several bioactive hydrophobic compounds by complex formation. They can also be used for removal of undesired components (such as cholesterol, off‐flavors or bitter components) present in foods. Although many patents account for the use of cyclodextrins for removal of cholesterol from dairy foods, there is no available information on the effect of water on encapsulation efficiency and on the stability of sterols in CDs. The aim of this work was to study the inclusion properties and the factors affecting the encapsulation and stability of cholesterol in β‐cyclodextrin (BCD). The optimum encapsulation conditions (ligand–CD molar ratio, stirring time and temperature), and stability of the complexes as a function of storage time and water content were analyzed. RESULTS: Phase solubility study pointed out the formation of 1:1 stoichiometric complexes between cholesterol and β‐cyclodextrin, which was influenced by temperature variations. The process was shown to be exothermic and energetically favored. The presence of cholesterol greatly modified the BCD water sorption curves, being the amount of adsorbed water smaller in the combined systems. The principal ‘driving force’ for complex formation is the substitution of the high‐enthalpy water molecules by an appropriate hydrophobic ligand. The freeze‐dried complexes probed to be stable at different storage conditions. CONCLUSION: The phase solubility and stability data obtained could be essential for selecting the most suitable conditions when CDs are employed either for removing cholesterol or to incorporate functional ingredients (i.e. sitosterol) in the development of innovative food products. Copyright © 2011 Society of Chemical Industry     

Molecular microcapsules and inclusion interactions of eugenol with β-cyclodextrin and its derivatives

The molecular microcapsules and inclusion interactions of eugenol (EG) with β-cyclodextrin (β-CD) and three derivatives, heptakis-2,6-di-β-CD (DM-β-CD), mono [2-O-(2-hydroxyethyl)]-β-CD (HE-β-CD), and mono [2-O-(2-hydroxypropyl)]-β-CD (HP-β-CD) have been investigated by fluorescence and infrared spectroscopy. The interaction capacities of β-CDs with EG were as the following order: HP-β-CD > DM-β-CD > HE-β-CD > β-CD. Effects of pH value, concentrations of CDs, and temperature on the inclusion interactions were studied to obtain further knowledge on the mechanism of inclusion process. The formation constants were derived by the modified Hildebrand–Benesi equation. The results show that EG with CDs formed 1:1 host–guest complexes. The thermodynamic parameters of inclusion process, ΔG, ΔH and ΔS were determined. Based on the thermodynamic results, the inclusion process was deduced to be an exothermic and enthalphy-driven process. Furthermore, the IR spectra study has been made to confirm the inclusion and to provide information on the geometry of EG inside the cavity of β-CD.     

Preparation and characterization of the inclusion complex of hypocrellin A with hydroxypropyl-β-cyclodextrin

Hypocrellin A (HA) is a naturally occurring perylenequinone pigment with bright red colour. The inclusion complex of HA with hydroxypropyl-β-cyclodextrin was prepared successfully by lyophilization method for the first time. Phase solubility studies indicated that the inclusion complex was formed with possible stoichiometry of 1:1. The apparent stability constants and the thermodynamic parameters such as enthalpy change (∆H), entropy change (∆S) and Gibbs free energy (∆G) were calculated in the range of 25–45 °C. The values of apparent stability constants decrease with the increasing of temperature. The thermodynamic results showed that the inclusion process was an exothermic and enthalpy-driven process accompanied with a negative entropic contribution. The formation of inclusion complex was also conformed by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetry and spectroscopic studies. The inclusion complex showed much better water solubility and dissolution property than the free HA. Therefore, the inclusion complex can be used to expand the application of HA in food, feed and pharmaceutical industries.     

Formation of β-cyclodextrin inclusion enhances the stability and aqueous solubility of natural borneol

The aims of this study were to optimize the preparation conditions of natural borneol/β-cyclodextrin (NB/β-CD) inclusion complex by ultrasound method, and to investigate its improvement of stability and solubility. The complex was characterized by different various spectroscopic techniques including Fourier transform infrared spectroscopy, X-ray diffractometry, and differential scanning calorimetry. The results demonstrate that NB could be efficiently loaded into β-CD to form an inclusion complex by ultrasound method at a molar ratio of 1 : 1 and mass ratio of 1 : 6. The complex exhibited different physicochemical characteristics from that of free NB. Typically, formation of β-CD inclusion significantly enhanced the stability and aqueous solubility of NB. PRACTICAL APPLICATION: Natural borneol (NB) has the potential to be widely used in the fields of medical and functional food, due to its specificity. However, the disadvantages of unstability in the preparation and storage process due to its easy sublimation and the low water solubility limit its application. This research provides an effective way to improve the solubility and stability of NB by preparing NB/β-CD inclusion complex. Furthermore, theoretical basis is also provided for the application development of NB.     

Preparation,characterisation and activity of the inclusion complex of paeonol with β-cyclodextrin

The inclusion complex of β-cyclodextrin (β-CD) and paeonol (2′-hydroxy-4′-methoxyacetophenone, PAE) was synthesised and characterised by thermal gravimetric analysis (TGA) and two-dimensional rotating frame spectroscopy (2D ROESY). The antioxidant activity and tyrosinase inhibition activity were also studied. The TGA results indicated that the thermal stability of PAE was improved when it was included with β-CD. Based on the 2D ROESY analysis, an inclusion structure of the PAE–β-CD complex was proposed, in which PAE penetrated β-CD in a tilted manner due to the interaction of intermolecular hydrogen bonds between PAE and β-CD. The complex of PAE with β-CD increased the antioxidant activity and tyrosinase-inhibiting activity of PAE.     

Release kinetics of ethylene gas from ethylene–α-cyclodextrin inclusion complexes

Ethylene was included into α-cyclodextrin (α-CD) by molecular encapsulation. Characterisation of the ethylene–α-CD inclusion complexes (ICs) using X-ray diffractometry (XRD) and scanning electron microscopy (SEM) confirmed their crystalline structures. Release kinetics of ethylene gas from the ICs was investigated. Release characteristics experiments were carried out at various relative humidities (RH) (52.9%, 75.5%, and 93.6%) and temperatures (45, 65, 85, and 105 °C). The Power Law and Avrami’s equations were used to analyse release kinetics. The latter showed better fit for ethylene release. Kinetics analysis based on Avrami’s equation showed that the release of ethylene was accelerated by increases in RH and temperature. For humidity treatments, the release parameter n represented a diffusive mechanism at 52.9% and 75.5% RH and a first-order mode at 93.6% RH. However, a diffusive mechanism was found in all temperature experiments. Release rate constants increased as a function of increasing temperature. Temperature coefficient (Q₁₀), activation energy (E_a) and half-life release of ethylene gas were also analysed.