Preparation and stability of the inclusion complex of astaxanthin with hydroxypropyl-β-cyclodextrin

The inclusion complex of astaxanthin (ASX) with hydroxypropyl-β-cyclodextrin (HP-β-CD) was prepared. Infrared spectroscopy (IR) proved the formation of the inclusion complex. The water solubility of the inclusion complex was >1.0 mg/ml, which is much better than that of ASX. The solid state thermal behaviour of the inclusion complex was investigated by thermogravimetric/differential thermal analysis (TG/DTA). The starting decomposition temperature of ASX was enhanced to about 290 °C. The stability of the inclusion complex in solution was also tested. Forming of the inclusion complex greatly enhanced the stability of ASX against light and oxygen. Furthermore, the release of ASX from the inclusion complex was controlled.     

Characterisation of inclusion complex of trans-ferulic acid and hydroxypropyl-β-cyclodextrin

The inclusion complex of trans-ferulic acid (FA) with hydroxypropyl-β-cyclodextrin (HP-β-CD) was prepared by the freeze-drying method and its characterisation was investigated by different analytical techniques including UV–visible spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffractometry, and scanning electron microscopy. All these approaches indicated that FA was able to form an inclusion complex with HP-β-CD, and the FA/HP-β-CD inclusion compounds exhibited different spectroscopic features and properties from FA. The stoichiometry of the complex was 1:1. The calculated apparent stability constant of the FA/HP-β-CD complex was 166.3 M⁻¹, and the water solubility of FA was significantly improved by phase solubility studies. Moreover, the irradiation-induced decomposition of FA in aqueous solution was markedly reduced by complexation with HP-β-CD. The results showed that HP-β-CD was a proper excipient for increasing solubility and stability of FA.     

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.     

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.     

Na-diclofenac β -cyclodextrin inclusion complex on cotton wound dressing

This paper deals with the production of a wound dressing capable of releasing sodium diclofenac as a drug for curing inflammations. Sodium diclofenac was used as an inclusion compound with β -cyclodextrin and then attached to the cotton wound dressing by a cross-linking agent, namely, dimethyl dihydroxyl ethylene urea (DMDHEU). Here some analyses were performed such as UV spectrophotometry and HNMR spectroscopy to ensure the complex formation of β -cyclodextrin and sodium diclofenac, surface morphology studies by SEM, and dissolution studies for drug release. The results revealed that increasing the amount of complex increases the drug contained in the wound dressing and the cross-linking agent prolongs the drug release time. Also, the existence of ethanol as a solvent for sodium diclofenac increases the drug released during the initial hours of drug release tests.     

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.     

Evaluation of complex forming ability of hydroxypropyl-β-cyclodextrins

The complex forming ability of hydroxypropyl-β-cyclodextrins (HP-β-CDs) is highly influenced by the distribution of substituents and the average degree of substitution (DS), both the size of the cavity and the reactivity of CDs are altered when the hydroxyl groups are substituted. On the other hand, the guests themselves influence these interactions by their sizes and configurations. In the present study, 9 HP-β-CDs with different substitution patterns and DS, which have been investigated by the reductive-cleavage method and methylation analysis, were chosen. The interactions among HP-β-CDs and phenolphthalein (as a model for ‘larger spheriform’ guests) or p-methyl red (as a model for ‘smaller linear’ guests) were studied for determining the complex forming ability of HP-β-CDs. The results indicated that, compared with parent β-CD, HP-β-CDs have a lower ability to form inclusion complexes with the ‘larger spheriform’ guest molecules. With regard to the ‘smaller linear’ guest molecules, HP-β-CDs have a higher complex forming ability, especially the low DS value (<6.5) HP-β-CDs which have a ratio of DS (2 + 3) to DS (6) close to 1.     

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.     

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     

Water dispersibility of the β-carotene source and its effect on the physical,thermal, and in vitro release properties of an inclusion complex

There is a need to understand the effect of in vitro digestion on the release of β-carotene (BC) from inclusion complexes (IC) prepared with water-dispersible (WDBC) or hexane-soluble (HSBC) sources. IC were prepared by co-precipitating WDBC or HSBC with β-cyclodextrin and characterised using imaging, spectral (FTIR) and thermal techniques. Two solvent systems (absolute ethanol, AE and 4:3 ethanol–hexane, EH) were employed to compare extractability of BC during simulated co-digestion with rice as food matrix. WDBC-IC had greater yield (89% vs. 44%) but lower encapsulation efficiency (30% vs. 89%) than HSBC-IC. Imaging, FTIR and thermal data confirm inclusion complex formation. In vitro WDBC release extracted with AE decreased uniformly and was unaffected by rice, whereas HSBC extracted with EH exhibited gradual release towards intestinal digestion but decreased with rice. Fabricated microcapsules with suitable forms of BC may be applied for food fortification purposes.     

Physicochemical and phytochemical properties of cold and hot water extraction from Hibiscus sabdariffa

Hibiscus cold (25 °C) and hot (90 °C) water extracts were prepared in various time-temperature combinations to determine equivalent extraction conditions regarding their physicochemical and phytochemical properties. Equivalent anthocyanins concentration was obtained at 25 °C for 240 min and 90 °C for 16 min. Total phenolics were better extracted with hot water that also resulted in a higher antioxidant capacity in these extracts. Similar polyphenolic profiles were observed between fresh and dried hibiscus extracts. Hibiscus acid and 2 derivatives were found in all extracts. Hydroxybenzoic acids, caffeoylquinic acids, flavonols, and anthocyanins constituted the polyphenolic compounds identified in hibiscus extracts. Two major anthocyanins were found in both cold and hot extracts: delphynidin-3-sambubioside and cyanidin-3-sambubioside. In general, both cold and hot extractions yielded similar phytochemical properties; however, under cold extraction, color degradation was significantly lower and extraction times were 15-fold longer. PRACTICAL APPLICATION: Hibiscus beverages are prepared from fresh or dried calyces by a hot extraction and pasteurized, which can change organoleptic, nutritional, and color attributes. Nonthermal technologies such as dense phase carbon dioxide may maintain their fresh-like color, flavor, and nutrients. This research compares the physicochemical and phytochemical changes resulting from a cold and hot extraction of fresh and dried hibiscus calyces and adds to the knowledge of work done on color, quality attributes, and antioxidant capacity of unique tropical products. In addition, the research shows how these changes could lead to alternative nonthermal processes for hibiscus.     

Comparison tests of hydroxylpropyl β-cyclodextrin (HPβ-CD) and β-cyclodextrin (β-CD) on retrogradation of rice amylose

Retarding effect of hydroxypropyl β-cyclodextrin (HPβ-CD) and β-cyclodextrin (β-CD) on the retrogradation of rice amylose was compared and studied. Size-exclusion high performance liquid chromatography (SE-HPLC) revealed that the degree of amylose retrogradation was reduced more by HPβ-CD than by β-CD. HPβ-CD preferentially interacted with amylose to form the potential amylose-HPβ-CD complex and lessened the stored amylose decrease in molecular weight (Mw). Differential scanning calorimeter (DSC) detected the potential complex formation as well. DSC data was analyzed using Avrami equation. Results showed that HPβ-CD significantly decreased the constant rate (k) and increased the Avrami exponent (n). The X-ray diffraction (XRD) patterns of retrograded amylose were further analyzed. It indicated that HPβ-CD caused an existence of intermediate type (V + B) and retarded the transformation from V- to B-type during the storage of the prepared amylose sample.     

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.     

Effect of polymer concentration on electrospinning of hydroxypropyl-β-cyclodextrins/PEO nanofibres

Hydroxypropyl-β-cyclodextrin (HP-β-CD) is a β-cyclodextrin (β-CD) derivative which is toxicologically harmless to mammals and other animals. In this study, HP-β-CD is electrospun from an aqueous solution by blending with poly(ethylene oxide) (PEO). The aqueous solutions containing different HP-β-CD/PEO blends (50:50–90:10) with varying concentrations (4–12 wt.%) were electrospun at 1 ml/h feed rate, 12 cm working distance and 7 kV applied voltage. The morphology of the nanofibres was investigated by scanning electron microscope. The average diameter of the nanofibres was measured using ImageJ software. It was found from the results that the uniform nanofibres with an average diameter of 264, 244 and 236 nm were obtained from 8 wt.% solution of 50:50, 60:40 and 70:30 HP-β-CD/PEO blends, respectively. The average diameter of the fibre decreases with increasing HP-β-CD/PEO ratio. However, higher proportion of HP-β-CD (i.e. above 70:30 HP-β-CD/PEO blend) in the spinning solution increases the possibility of creating more beads in the fibres. Although the polymer concentrations have not shown a significant effect on fibre diameter, the 8 wt.% solution of 50:50 HP-β-CD/PEO yielded uniform smooth fibres with the narrowest distribution of the diameters. As the aim of this study is to maximize the HP-β-CD content in the fibre, the blend ratio of 70:30 HP-β-CD/PEO and solution concentration of 8 wt.% were optimized to obtain smooth HP-β-CD/PEO nanofibres.     

Effect of hydroxypropyl β-cyclodextrin on physical properties and transition parameters of amylose–lipid complexes of native and acetylated starches

The effect of hydroxpropyl β-cyclodextrin (HPβ-CD) on physical properties and digestibility of wheat, potato, waxy maize and high-amylose maize starches before and after acetylation was studied. Effect of HPβ-CD on amylose–lipid complexes in native and acetylated potato starches synthesized using α-lysophosphatidylcholine was also studied. Acetylation increased swelling factor, amylose leaching, peak viscosity and susceptibility to α-amylase hydrolysis, but decreased gelatinization temperature and enthalpy and gel hardness in all starches. HPβ-CD markedly increased swelling factor and amylose leaching in native and acetylated wheat starches but had little or no impact on other starches. Wheat starch gelatinization enthalpy decreased in the presence of HPβ-CD but gelatinization temperature of all the starches was slightly increased. HPβ-CD had no influence on enzymatic hydrolysis. Melting enthalpy of amylose–lipid complex in both native and acetylated wheat starches was decreased by HPβ-CD. Acetylation also decreased the melting enthalpy of amylose–lipid complex in wheat starch. Similar trend of thermal transitions was observed in the presence of HPβ-CD for the amylose–lipid complexes synthesized in potato starch. Acetylation reduces the complex formation ability of the amylose polymer. Similar to gelatinization, acetylation widened the melting temperature range of amylose–lipid complexes while shifting it to a lower temperature. Higher swelling and amylose leaching, and decreased gelatinization temperature and enthalpy resulting from acetylation of wheat starch is consistent with its influence on starch hydration. Similar effects resulting from the inclusion of HPβ-CD were consistent with the disruption of amylose–lipid complex by HPβ-CD which promotes granular hydration.