Improvement of oxidative stability of conjugated linoleic acid (CLA) by microencapsulation in cyclodextrins

Oxidative stability of conjugated linoleic acid (CLA) encapsulated in alpha-, beta-, and gamma-cyclodextrins (designated CLA/CDs microencapsules) was studied by measuring the headspace-oxygen depletion in airtight serum bottles and by measuring the peroxide values (POV). The rate of oxygen depletion was reduced from 41.0 (control) to 21.5, 2.1, 1.2, and 1.1 micromol/L.h(-)(1) by CLA/alpha-CD microencapsules at 1:1, 1:2, 1:4, and 1:6 mole ratios, respectively, indicating that CLA oxidation was completely protected by a 1:4 mole ratio of CLA/alpha-CD. Such a protective effect by CLA/beta-CD or CLA/gamma-CD microencapsules was achieved at a 1:6 mole ratio, but the effect by CLA/beta-CD was slightly greater than that by CLA/gamma-CD. The protective effect of alpha-, beta-, and gamma-CDs for CLA oxidation was confirmed by their POV-reducing abilities in CLA/CDs. These results suggest that alpha-CD was the most effective for the protection of CLA oxidation by microencapsulation, followed by beta-CD and gamma-CD.     

Interaction of cyclodextrins with aliphatic acetate esters and aroma components of La France pear

The interaction between aliphatic acetate esters, which are the major flavor components of La France pear (Pyrus communis L.), and cyclodextrins (CDs) was studied to obtain fundamental data for preparing powdered pear flavor materials. The complexing abilities of alpha-, beta-, or gamma-CD with six kinds of aliphatic acetate esters were compared. alpha-CD formed the highest numbers of complexes with all of the esters. All of the CDs produced complexes more readily with the more hydrophobic esters. Among our samples of freeze-dried pear juice containing dissolved alpha-, beta-, or gamma-CD, the juice with alpha-CD retained the greatest amount of esters. These data demonstrate that alpha-CD is an effective material with which to prepare powdered pear flavor materials. The nuclear Overhauser effect, measured by (1)H NMR spectra, of an alpha-CD-butyl acetate or alpha-CD-hexyl acetate complex showed that these esters were included in the alpha-CD cavity.     

Formation of natamycin:cyclodextrin inclusion complexes and their characterization

Natamycin is a broad spectrum antimycotic with very low water solubility, which is used to extend the shelf life of shredded cheese products. beta-Cyclodextrin (beta-CD), hydroxypropyl beta-cyclodextrin (HP beta-CD), and gamma-cyclodextrin (gamma-CD) were found to form inclusion complexes with natamycin in aqueous solution. The increase in solubility of natamycin with added beta-CD was observed to be linear (type A(L) phase solubility diagram). The 1:1 stability constant of natamycin:beta-CD complex was estimated from its phase solubility diagram to be 1010 M(-1). The phase solubility diagrams of both gamma-CD and HP beta-CD exhibited negative deviation from linearity (type A(N) diagram) and, therefore, did not allow the estimation of binding constants. The water solubility of natamycin was increased 16-fold, 73-fold, and 152-fold with beta-CD, gamma-CD, and HP beta-CD, respectively. The natamycin:CD inclusion complexes resulted in in vitro antifungal activity nearly equivalent to that of natamycin in its free state.     

Stability of natamycin and its cyclodextrin inclusion complexes in aqueous solution

Aqueous solutions of natamycin and its beta-cyclodextrin (beta-CD), hydroxypropyl beta-cyclodextrin, and gamma-cyclodextrin (gamma-CD) inclusion complexes were completely degraded after 24 h of exposure to 1000 lx fluorescent lighting at 4 degrees C. After 14 days of storage in darkness at 4 degrees C, 92.2% of natamycin remained in active form. The natamycin:beta-CD complex and natamycin:gamma-CD complex were significantly more stable (p < 0.05) than natamycin in its free state in aqueous solutions stored in darkness at 4 degrees C. Clear poly(ethylene terephthalate) packaging with a UV light absorber allowed 85.0% of natamycin to remain after 14 days of storage under 1000 lx fluorescent lighting at 4 degrees C. Natamycin:cyclodextrin complexes can be dissociated for analysis in methanol/water/acetic acid, 60:40:5, v/v/v. Natamycin and its complexes in dissociated form were quantified by reverse phase HPLC with detection by photodiode array at 304 nm.     

Use of natural and modified cyclodextrins as inhibiting agents of peach juice enzymatic browning

Although cyclodextrins (CDs) have been successfully used as antibrowning agents in different fruit juices, no research has studied the effect of these compounds on enzymatic browning in peach juice. In this paper, the color of fresh peach juice was evaluated in the presence of two types of natural (alpha-CD and beta-CD) and a modified (maltosyl-beta-CD) CD, and the effectiveness of these compounds as browning inhibitors was determined using the color space CIELAB system. Moreover, to clarify the mechanism by which CDs inhibit peach juice enzymatic browning, the process was kinetically modeled in the absence and presence of CDs using a colorimetric method; the apparent complexation constants between the mixtures of diphenols present in peach juice and some types of CD were calculated. The results show that the highest affinity constant was presented by alpha-CD (Kc = 18.31 mM-1) followed by maltosyl-beta-CD (Kc = 11.17 mM-1), whereas beta-CD was incapable of inhibiting peach juice enzymatic browning. Keywords: Cyclodextrin; browning; peach; juice; color; polyphenol oxidase.     

Characterization of inclusion complexation between fenoxaprop-p-ethyl and cyclodextrin

Cyclodextrins (CDs) derived from natural starches are capable of forming inclusion complexes with a variety of organic compounds. This work evaluated the complexation role of CDs toward fenoxaprop-p-ethyl (FE) in an attempt to assess their potential as new formulation additives for more efficient FE delivery and better environmental approaches. beta-CD and its two derivatives, randomly methylated beta-CD (RAMEB) and 2-hydroxypropyl beta-CD (HP-beta-CD), were tested. The solubility of FE was enhanced in the presence of the CDs due to the formation of inclusion complexes, with RAMEB being >6 times more effective than the other two. The complexation was confirmed by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD), where the FE melting peaks in DSC, the FTIR bands, and the XRD peaks were generally weakened. Within the tested time up to 60 min, the dissolution of the FE-CD complexes resulted in higher FE concentrations than did that of FE by itself. The dissolution of the FE-RAMEB complex was much faster than other complexes and FE alone. These results indicate that RAMEB was a better inclusion complexation agent for FE in terms of both solubility enhancement and dissolution rate. RAMEB may thus be used to improve FE delivery and to mobilize FE in soil for bioremediation.     

Kinetics of molecular encapsulation of 1-methylcyclopropene into alpha-cyclodextrin

1-methylcyclopropene (1-MCP), an ethylene inhibiting regulator, is commercially available in the form of an inclusion complex with alpha-cyclodextrin (alpha-CD). In this study, molecular encapsulation of gaseous 1-MCP into aqueous alpha-CD was investigated in a closed, agitated vessel with a flat gas-liquid interface. Molecular encapsulation of gaseous 1-MCP by alpha-CD is a simultaneous two-step reaction which involves the aqueous dissolution of gaseous 1-MCP and the encapsulation of the dissolved molecules by alpha-CD. The kinetics and mechanism of molecular encapsulation were analyzed based on the depletion rate of 1-MCP in the headspace of the vessel. The encapsulation rates could be explained quantitatively by the gas absorption theory with a pseudo-first-order reaction between 1-MCP and alpha-CD. The negative value of the calculated apparent activation energy of encapsulation (-24.4 kJ/mol) implied the significant effect of exothermic aqueous dissolution of 1-MCP. An encapsulation temperature of 15 degrees C was optimal; at this temperature, the highest 1-MCP yield and best inclusion ratio of inclusion complex were obtained. Changes in the X-ray diffraction pattern suggested that the crystal lattice structure of alpha-CD was altered upon inclusion of 1-MCP.     

Preparation and characterization of inclusion complex of norflurazon and beta-cyclodextrin to improve herbicide formulations

The formulation of inclusion complexes of the herbicide norflurazon as guest and beta-cyclodextrin (beta-CD) as host has been studied as a first step in the use of cyclodextrins to obtain improved formulations of this herbicide. The interaction of norflurazon with beta-CD produced the formation of an inclusion complex in solution and in solid state. The inclusion of norflurazon in beta-CD in solution was studied by phase solubility, and an apparent stability constant of 360 M(-)(1), a 1:1 stoichiometric ratio for the complex, and up to 5-fold increase in norflurazon solubility were determined. Three processing methods (kneading, spray drying and vacuum evaporation) were used to prepare norflurazon-beta-CD solid inclusion complexes. X-ray diffraction, infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy techniques were used to study the solid complexes. From the different solid systems, an increase of norflurazon aqueous dissolution rate was obtained in comparison to the uncomplexed herbicide. This finding is a first step to obtain controlled release and/or protective formulations of norflurazon, which allow a more rational application of norflurazon, diminishing the use of organic solvents and increasing its efficacy.     

Preparation, stabilization, and bioefficacy of beta-cyclodextrin inclusion compounds of chloramidophos

Cyclodextrins are common compounds capable of forming inclusion complexes with a variety of pesticides to improve their solubility, bioavailability, and stability. In this study, chloramidophos (CP) was inclusion-complexed with beta-cyclodextrin (beta-CD) by a kneading method in an attempt to gain a more stable but equally effecacious formulation compared with CP alone. A 1:1 CP-beta-CD complex with an inclusion constant of 203.0 M(-1) was determined to exist by UV spectrophotometry. The structural identification, thermal stability, and biological assays of the CP-beta-CD complex were then carried out with a product with the maximum guest loading efficiency. The data measured by differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR), and X-ray diffraction (XRD), where the endothermic peaks of beta-CD, the FT-IR bands, and the XRD peaks were generally changed, deduced the formation of complex. Results of the thermal stability assay showed that the degradation rate of CP in 14-day incubation was slowed by a factor of 3.6 when it was complexed with beta-CD. Then, activity and toxicity of CP influenced by the encapsulated process of beta-CD were evaluated by an in vitro acetylcholinesterase (AChE) inhibition assay and an acute aquatic toxicity assay, respectively. No significant differences were found in both the two biological assays by a t-test. This indicated that the encapsulation process greatly improved the thermal stability of the pesticide with no adverse effects on bioefficacy compared to that of CP. There is a promising outlook for CP-beta-CD to be produced as the active ingredient of various formulation additives of CP for its continued application.     

Preparation and characterization of inclusion complex of iprodione and beta-cyclodextrin to improve fungicidal activity

The effect of beta-cyclodextrin (beta-CD) on the improvement of the fungicidal activity of iprodione has been investigated. The inclusion complexation of beta-CD with iprodione has been prepared and characterized by integrating some analytical techniques (such as electrospray ionization-mass spectrometry, differential scanning calorimetry, thermogravimetry, x-ray diffraction, and scanning electron microscopy) and molecular simulation methods. The beta-CD/iprodione inclusion complex has exhibited different spectroscopic features and properties from iprodione. The stoichiometric ratio and stability constant describing the extent of formation of inclusion complexes have been determined by phase solubility studies. The calculated apparent stability constant of the iprodione/beta-CD complex was 407.5 M-1. The obtained inclusion complexes were found to significantly improve the water solubility of iprodione, and there is a 4.7-fold increase in the presence of 13 mM beta-CD as compared with the solubility of iprodione in deionized water in the absence of beta-CD. The bioassay demonstrated that the complex displayed over two-fold increase of the fungicidal activity. In addition, the possible structure of the beta-CD/iprodione complex was proposed according to the results of the molecular dynamic simulation. The present study provided useful information for a more rational application of iprodione, diminishing the use of organic solvents and increasing its efficacy.     

Study on the supramolecular interaction of thiabendazole and beta-cyclodextrin by spectrophotometry and its analytical application

The beta-cyclodextrin-thiabendazole (beta-CD-TBZ) inclusion complex was synthesized and its structure characterized by (1)H NMR and IR. The mechanism of the supramolecular interaction of TBZ and beta-CD has been studied and discussed by spectrophotometry. The results showed that the phenyl ring of TBZ was included in the beta-CD cavity to form a 1:1 host-guest complex with an apparent formation constant of 1.60 x 10(3) mol(-1).L. On the basis of the enhancement of the absorbance of TBZ produced through complex formation, a spectrophotometric method for the determination of TBZ in bulk aqueous solution in the presence of beta-CD was developed. The linear relationship between the absorbance and TBZ concentration was obtained in the range of 8.86 x 10(-7)-1.45 x 10(-5) mol/L. The detection limit was 2.71 x 10(-7)mol/L, and the relative standard deviation was 0.86%. The interference of 48 coexisting substances was slight. The proposed method has been successfully applied to the determination of TBZ in fruits with recoveries of 96-103%.     

Study on the supramolecular interaction of curcumin and beta-cyclodextrin by spectrophotometry and its analytical application

The supramolecular interaction of curcumin and beta-cyclodextrin (beta-CD) has been studied by spectrophotometry. The mechanism of the inclusion was studied and discussed based on the variations of pK(a), absorption intensity, and infrared spectrograms. The results show that beta-CD reacts with curcumin to form a 2:1 host-guest complex with an apparent formation constant of 5.53 x 10(5) mol(-2) x L2. Based on the enhancement of the absorbance of curcumin produced through complex formation, a spectrophotometric method for the determination of curcumin in bulk aqueous solution in the presence of beta-CD was developed. The linear relationship between the absorbance and curcumin concentration was obtained in the range of 0-15 microg/mL, with a correlation coefficient (r) of 0.9991. The detection limit was 0.076 microg/mL. The proposed method was used to determine the curcumin in curry and mustard with satisfactory results.     

Thermal stability of anthocyanin extract of Hibiscus sabdariffa L. in the presence of beta-cyclodextrin

The thermal stability of anthocyanin extract isolated from the dry calyces of Hibiscus sabdariffa L. was studied over the temperature range 60-90 degrees C in aqueous solutions in the presence or absence of beta-cyclodextrin (beta-CD). The results indicated that the thermal degradation of anthocyanins followed first-order reaction kinetics. The temperature-dependent degradation was adequately modeled by the Arrhenius equation, and the activation energy for the degradation of H. sabdariffa L. anthocyanins during heating was found to be approximately 54 kJ/mol. In the presence of beta-CD, anthocyanins degraded at a decreased rate, evidently due to their complexation with beta-CD, having the same activation energy. The formation of complexes in solution was confirmed by nuclear magnetic resonance studies of beta-CD solutions in the presence of the extract. Moreover, differential scanning calorimetry revealed that the inclusion complex of H. sabdariffa L. extract with beta-CD in the solid state was more stable against oxidation as compared to the free extract, as the complex remained intact at temperatures 100-250 degrees C where the free extract was oxidized. The results obtained clearly indicated that the presence of beta-CD improved the thermal stability of nutraceutical antioxidants present in H. sabdariffa L. extract, both in solution and in solid state.     

Sulfluramid volatility reduction by beta-cyclodextrin

Sulfluramid is an expensive active principle of insecticidal baits that is lost by volatilization during the pelletization of baits. To increase the thermal stability of sulfluramid, we tested its molecular encapsulation in beta-cyclodextrin (beta-CD), using molar ratios of 1:1 and 1:2 (sulfluramid:beta-CD), using the complex preparation techniques of coprecipitation and kneading. The physical mixture of sulfluramid and beta-CD was also tested for comparison. The products of complexation were characterized by differential scanning calorimetry, thermogravimetry, and derivative thermogravimetry, indicating the formation of a sulfluramid/beta-CD complex and showing that the release of the complexed sulfluramid occurs in the range of 270-300 degrees C, a temperature range that is well above the temperature at which sulfluramid sublimates (40 degrees C). This result warrants a reduced sulfluramid loss in the preparation of insecticidal baits. The preparation of the complex by kneading with molar ratio of 1:2 gave the highest yield of complex, about 64%, in relation to the theoretical maximum.     

Encapsulation of olive leaf extract in beta-cyclodextrin

Olive leaf extract, rich in oleuropein, formed an inclusion complex with beta-cyclodextrin (beta-CD) upon mixing of the components in aqueous media and subsequent freeze-drying. Inclusion complex formation was confirmed by differential scanning calorimetry (DSC). DSC thermograms indicated that the endothermic peaks of both the olive leaf extract and the physical mixture of olive leaf extract with beta-CD, attributed to the melting of crystals of the extract, were absent in DSC thermogram of inclusion complex. Moreover, DSC studies under oxidative conditions indicated that the complex of olive leaf extract with beta-CD was protected against oxidation, since it remained intact at temperatures where the free olive leaf extract was oxidized. Phase solubility studies afforded A L type diagrams, 1:1 complex stoichiometry, a moderate binding constant ( approximately 300 M (-1)), and an increase of the aqueous solubility by approximately 50%. The formation of the inclusion complex was also confirmed by nuclear magnetic resonance (NMR) studies of beta-CD solutions in the presence of both pure oleuropein and olive leaf extract. The NMR data have established the formation of a 1:1 complex with beta-CD that involves deep insertion of the dihydroxyphenethyl moiety inside the cavity from its secondary side.     

Cyclodextrins as activator and inhibitor of latent banana pulp polyphenol oxidase

The effect of cyclodextrins (CDs) on o-diphenol oxidation catalyzed by banana polyphenol oxidase (PPO) was studied. The oxidation of dopamine, the natural substrate of banana, in the presence of cyclodextrins was unaffected, because this hydrophilic phenol does not form inclusion complexes with CDs. However, when a hydrophobic phenol such as tert-butylcatechol (TBC) was used, a marked inhibition was observed with beta-, hydroxypropyl-beta-, and maltosyl-beta- CDs. This inhibition was due to the complexation of TBC in the CD core, demonstrating that banana pulp PPO worked only toward free substrate and not toward the complex TBC-CDs. In addition, the effect of some inhibitors in the presence of CDs and dopamine as substrate was studied. Increasing concentrations of CDs, in the presence of two inhibitors (4-iodophenol and cinnamic acid) were able to activate the inhibited enzyme to reach the noninhibited level by complexing the inhibitors in the hydrophobic core of the CDs. This dual effect of CDs as activator and inhibitor was tested in crude banana pulp extracts, with surprising activation effects never before described being observed.     

Improvement of antifungal activity of 10-undecyn-1-ol by inclusion complexation with cyclodextrin derivatives

The inclusion complexation behavior between 10-undecyn-1-ol and cyclodextrin (CD) derivatives, namely, randomly methylated beta-CD (RM-beta-CD) and hydroxypropyl-beta-CD (HP-beta-CD), was studied in terms of solubility improvement, apparent stability constant, and the inclusion ratios of the resultant inclusion complexes. The aqueous solubility of 10-undecyn-1-ol was greatly improved through complexation with the CD derivatives. RM-beta-CD is comparatively more efficient in solubilizing 10-undecyn-1-ol with an apparent stability constant outstripping that of HP-beta-CD by about an order of magnitude. Comparative in vitro evaluations of the growth inhibition effects of inclusion complex solutions toward Rosellinia necatrix, a phytopathogenic fungus, were performed. In comparison with the positive control, appreciable improvements of the antifungal activity of 10-undecyn-1-ol through the addition of CD derivatives were observed visually. The improvement was evaluated in terms of area covered by the mycelia of Rosellinia necatrix and their growth rate. RM-beta-CD was proven to be more effective compared to HP-beta-CD with regard to the reduction of both fungal mycelium-covered area and growth rate constant, presumably owing to greater solubility enhancement by RM-beta-CD and thus the bioavailability of 10-undecyn-1-ol. Inclusion complexation of 10-undecyn-1-ol with CD derivatives suggests a potential means for production of an environmentally friendly 10-undecyn-1-ol-based fungicide to counteract R. necatrix.     

ORAC-fluorescein assay to determine the oxygen radical absorbance capacity of resveratrol complexed in cyclodextrins

The effect of the complexation of resveratrol with hydroxypropyl-beta-cyclodextrins (HP-beta-CDs) on the antioxidant capacity of the polyphenol is studied for the first time by means of the oxygen radical absorbance capacity (ORAC) method, using fluorescein (FL) as the fluorescent probe. The method is validated through its linearity, precision, and accuracy for measuring the ORAC of resveratrol in the absence or presence of cyclodextrins (CDs). The complexation of resveratrol in CDs increased the net area under the FL decay curve (net AUC) of resveratrol up to its saturation level, at which the polyphenol showed almost double the antioxidant activity it shows in the absence of CDs. The complexation constant ( K c) between resveratrol and HP-beta-CDs was calculated by linear regression of the phase solubility diagram ( K c = 18048 M (-1)). The antioxidant activity of resveratrol was dependent on the complexed resveratrol because CDs acts as a controlled dosage reservoir that protects resveratrol against rapid oxidation by free radicals. In this way, its antioxidant activity is prolonged and only reaches its maximum when all the resveratrol is complexed.     

Thermodynamic parameters of beta-lactoglobulin-pectin complexes assessed by isothermal titration calorimetry

Isothermal titration calorimetry (ITC) was used to determine the binding constant, stoichiometry, enthalpy, and entropy of beta-lactoglobulin/low- and high-methoxyl pectin (beta-lg-LM- and HM-pectin) complexes at 22 degrees C and at pH 4. The binding isotherms revealed the formation of soluble intrapolymer complexes (C1) further followed by their aggregation in interpolymer complexes (C2). The interaction between beta-lg and LM- or HM-pectin in C1 and C2 occurred spontaneously with a Gibbs free energy around -10 kcal/mol. The C1 were enthalpically driven, whereas enthalpic and entropic factors were involved in the C2 formation. Because ITC did not allow the dissociation of different enthalpic contributions, the values measured as pectin and beta-lg interacted could partially be attributed to conformational changes. The C1 had a binding stoichiometry of 8.3 and 6.1 beta-lg molecules complexed per LM- or HM-pectin molecule, respectively. The C2 had about 16.5 and 15.1 beta-lg molecules complexed per LM- and HM-pectin, respectively.     

Antiatherogenic effects of structured lipid containing conjugated linoleic acid in C57BL/6J mice

Conjugated linoleic acids (CLA) were enzymatically acidolyzed with olive oil to produce structured lipids (SL), and their antiatherosclerotic properties were investigated in C57BL/6J mice. Twenty-eight mice were divided into four groups and fed control diet or atherogenic diets supplemented with high cholesterol and high fat (HCHF) containing 5% of lard, olive oil, or SL based on control diet for 4 weeks. The supplementation of SL diet (0.6% CLA) significantly reduced the levels of serum total cholesterol and total triglyceride and increased high-density lipoprotein cholesterol level as compared to lard and olive oil diet groups (p < 0.05). The activity of liver acyl CoA:cholesterol acyltransferase (ACAT) of mice fed the SL diet was significantly lower than that of mice fed the lard or olive oil diet. A reduced formation of aortic fatty streak was observed in SL group. The extent of CLA incorporation depended on tissues or types of phospholipids. More CLA was incorporated in adipose tissue (1.85 mol %) than in the liver (0.33 mol %). Besides, more CLA was found in phosphatidylethanolamine (PE) (0.47 mol %) than in phosphatidylcholine (PC) (0.05 mol %) of hepatic phospholipids. Hepatic phospholipids (PC and PE) of mice fed the SL diet contained reduced contents of arachidonic and linoleic acid compared with mice fed the olive oil or lard diet. The present study suggests that SL could be considered as a functional oil for preventing risks of atheroscelerosis.