Inclusion complexes of eucalyptus essential oil with β-cyclodextrin: preparation,characterization and controlled release

In this study, eucalyptus essential oil (EEO) was encapsulated into β-cyclodextrin (β-CD) by saturated aqueous solution method. The success of EEO encapsulation was confirmed by laser light scatting, scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimeter and thermogravimetric analysis. Releasing characteristics experiments were carried out at various temperatures, relative humidity (RH), storage time and high temperature stability test. Release kinetics of EEO from the inclusion complexes was investigated by zero-order kinetics, first-order kinetics and Avrami’s equation. The result showed that the release model of EEO from inclusion complexes fitted better for Avrami’s equation. Kinetics analysis based on the Avrami’s equation revealed that the release of EEO was accelerated with the increases of RH and temperature. For storage time treatment, the volatilization of EEO was significantly inhibited after encapsulation. High temperature stability test further revealed that EEO was protected after having been encapsulated into β-CD. For all treatments, the release parameter n was between 0.5 and 1.0, which presenting a diffusion-limited and first-order mode. These results indicated that encapsulation enhanced the stability and prolonged the acting time of EEO, and the release rate of EEO can also be passively controlled by the ambient temperature, humidity and storage time.     

Oxidative methylation of α-, β- and γ-picolines with methane vinylpyridines and ethylpyridines over mono- and bialkali promoted magnesia catalysts

The oxidative methylation of -, - and -picolines with methane to the corresponding vinyl- and ethylpyridines was carried out at 750°C and under normal atmospheric pressure, over sodium, cesium or sodium-cesium promoted magnesia catalysts. Among the three picolines, the -picoline was the most reactive, followed by - and -picolines. The (5 mol% Na-5 mol% Cs)/MgO catalyst provided higher yields than the individual promoters, at the same total alkali content of 10 mol%.     

Study on β-cyclodextrin grafting with chitosan and slow release of its inclusion complex with radioactive iodine

β-CD-2-CTS was synthesized by β-cyclodextrin reacting with p-toluenesulfonyl chloride, then grafting with chitosan. The infrared spectra analysis and ¹³C NMR confirmed that β-cyclodextrin reacted with p-toluenesulfonyl chloride at the 2-position carbon atom in the substituted glucose unit of β-cyclodextrin and formed β-CD-2-OTs. In the ¹³C NMR of β-CD-2-OTs, the characteristic peak of the 2-postion carbon atom in the substituted glucose unit of β-cyclodextrin appeared at 78.43 ppm. β-CD-2-CTS was characterized with infrared spectra analysis and X-ray diffraction. In the infrared spectra of β-CD-2-CTS, the characteristic peak of α-pyanyl vibration of β-CD was at 848.6 cm⁻¹. The characteristic peak of β-pyanyl vibration of CTS was at 894.9 cm⁻¹. The X-ray diffraction analysis showed that the peak at 2θ = 20° decreased greatly in β-CD-2-CTS. The polymer inclusion complex of β-CD-2-CTS with iodine was prepared and its inclusion ability was studied. The experimental results showed that a nice bit of iodine was included with β-CD-2-CTS and formed a stable inclusion complex. After the subcutaneous implantation of the polymer inclusion complex of β-CD-2-CTS with ¹³¹I₂ in rats, ¹³¹I₂ exhibited the property of slow release. ¹³¹I₂ in the blood of rats decreased slowly. ¹³¹I₂ in the blood of rats maintained approximately half of maximum for 70 days later, and maintained much higher radioactivity in the organs of rats compared to the inclusion complex of β-CD with ¹³¹ I₂, too. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2414–2421, 2001     

Effect of α-, β-, γ-, and δ-Tocotrienol on the Oxidative Stability of Lard

Despite the structural similarity of tocopherols, the antioxidative activities of tocotrienol homologues have not been studied often. In this study, the antioxidant activities of α-, β-, γ-, and δ-tocotrienols at various concentrations from 100 to 1,000 ppm in lard were evaluated. Headspace oxygen content of the lard without tocotrienol decreased from 21.1 to 10.7 % and the peroxide value increased from 0.4 to 33.4 mequiv/kg after 7 days of storage at 55 °C in the dark. α-Tocotrienol at 100 ppm and β-tocotrienol at 100 and 200 ppm effectively improved the oxidative stability of lard; however, the antioxidative activities of α- and β-tocotrienol reduced as the concentration increased to 1,000 ppm. The γ- and δ-tocotrienols improved the oxidation stability of lard and the effectiveness was essentially same at all concentrations (p > 0.05). The antioxidative activities of tocotrienols in the autoxidation of lard increased in the order of α-, β-, γ-, and δ-tocotrienols. The activities of tocotrienols in lard were different depending on the type of homologues and concentrations.     

Effect of α-, β-, γ-, and δ-Tocotrienol on the Singlet Oxygen Oxidation of Lard

The impacts of four different types of tocotrienol homologues on the singlet oxygen oxidation of lard were evaluated by measuring the headspace oxygen content and the peroxide value. Singlet oxygen oxidation of lard was induced by chlorophyll photosensitization. Samples of 0.100, 0.250, and 0.400 M lard in methylene chloride containing chlorophyll and α‐, β‐, γ‐, or δ‐tocotrienol were prepared and stored under light at 3,000 lux for 4 h. All tocotrienol homologues at 1.20 mM significantly prevented the singlet oxygen oxidation of lard. Chlorophyll under light produced singlet oxygen at 1.09 μmol oxygen/mL headspace/h. A steady state kinetic study showed that tocotrienols reduced the singlet oxygen oxidation of lard by quenching the singlet oxygen. Singlet oxygen reacted with lard at 6.50 × 10⁴M^?1 s^?1. α‐, β‐, γ‐, and δ‐tocotrienol quenched singlet oxygen with the rate of 2.16, 1.99, 2.05, and 0.800 × 10⁷M^?1 s^?1, respectively. Among them, α‐tocotrienol significantly prevented singlet oxygen oxidation of lard.     

Tissue Distribution of α- and γ-Tocotrienol and γ-Tocopherol in Rats and Interference with Their Accumulation by α-Tocopherol

The aim of this study was to evaluate tissue distribution of vitamin E isoforms such as α- and γ-tocotrienol and γ-tocopherol and interference with their tissue accumulation by α-tocopherol. Rats were fed a diet containing a tocotrienol mixture or γ-tocopherol with or without α-tocopherol, or were administered by gavage an emulsion containing tocotrienol mixture or γ-tocopherol with or without α-tocopherol. There were high levels of α-tocotrienol in the adipose tissue and adrenal gland, γ-tocotrienol in the adipose tissue, and γ-tocopherol in the adrenal gland of rats fed tocotrienol mixture or γ-tocopherol for 7 weeks. Dietary α-tocopherol decreased the α-tocotrienol and γ-tocopherol but not γ-tocotrienol concentrations in tissues. In the oral administration study, both tocopherol and tocotrienol quickly accumulated in the adrenal gland; however, their accumulation in adipose tissue was slow. In contrast to the dietary intake, α-tocopherol, which has the highest affinity for α-tocopherol transfer protein (αTTP), inhibited uptake of γ-tocotrienol to tissues including adipose tissue after oral administration, suggesting that the affinities of tocopherol and tocotrienol for αTTP in the liver were the critical determinants of their uptake to peripheral tissues. Vitamin E deficiency for 4 weeks depleted tocopherol and tocotrienol stores in the liver but not in adipose tissue. These results indicate that dietary vitamin E slowly accumulates in adipose tissue but the levels are kept without degradation. The property of adipose tissue as vitamin E store causes adipose tissue-specific accumulation of dietary tocotrienol.     

Chiral adsorption of phenylalanine by α-, β-cyclodextrin modified layered double hydroxides

The chiral adsorption of racemic phenylalanine (Phe) by carboxymethyl-α/β-cyclodextrin-intercalated Zn-Al layered double hydroxides (CM-α/β-CD-LDHs) has been studied. The adsorption isotherms of chiral excess adsorption and the total adsorption of Phe by these CM-α/β-CD-LDHs have been investigated. CM—CD-LDHs were found to be more suitable for chiral recognition of Phe than CM—CD-LDHs. Furthermore, the intraparticle diffusion model is successfully validated in this work. Intraparticle effective diffusivities (D _eff ) of Phe in these CM-α/β-CD-LDHs macroparticles were determined from the homogeneous Fickian diffusion model at various temperatures.     

Dodecenyl succinic-β-cyclodextrin with high degree of substitution: Synthesis,characterization and evaluation

β-cyclodextrin (β-CD) has the characteristics of safety, non-toxicity, and a wide range of sources. It can be used in improving surface activity. However, due to the limitation of molecular polarity and solubility, its surface activity and emulsification ability are weak. Therefore, it is necessary to improve adsorption capacity on phase interface by hydrophobic modification. In this article, dodecenyl succinic-β-cyclodextrin (DDS-β-CD) with different substitution degree was prepared by esterification of β-CD with dodecenyl succinic anhydride (DDSA) as the esterifying agent. The product was characterized by FT-IR, ¹H NMR, SEM, and TGA, respectively. Results showed that DDS was successfully introduced into β-CD. Both the degree of substitution (DS) and productivity (P) increased with the addition of DDSA and can reach 0.283 and 85.8%, respectively, when the molar ratio of DDSA to β-CD was 3:1. The modified cyclodextrin showed lower surface tension and higher foaming ability. Compared with octenyl succinic-β-cyclodextrin (OS-β-CD), it was found that the length of hydrophobic segment had a significant effect on the surface tension. Due to its unique properties, it can be used as a good emulsifier for oil-in-water emulsions and a host material for lavender flavor.     

Preparation,characterization, and drug release properties of poly(2-hydroxyethyl methacrylate) hydrogels having β-cyclodextrin functionality

A new β-cyclodextrin urethane-methacrylate monomer was synthesized from the reaction of toluene-2,4-diisocyanate, 2-hydroxyethyl methacrylate (HEMA), and β-cyclodextrin (β-CD). Based on inclusion character of β-CD, a series of hydrogels were prepared by irradiating the mixtures of β-cyclodextrin urethane-methacrylate monomer (β-CD-UM), poly(ethylene glycol) diacrylate (PEG-DA), HEMA, and the photoinitator. Gel percentages and equilibrium swelling ratios (%) of hydrogels were investigated. It was observed that the equilibrium-swelling ratio increased with increasing β-CD-UM content in the hydrogel composition. SEM images demonstrated that β-CD-UM based hydrogel have porous fractured surface. In this study four different drug molecules, salicylic acid, sulfathiazole, rifampicin, and methyl orange as model drug, which are capable of forming inclusion complexes withβ-CD were chosen. For sulfathiazole and rifampicin, the drug loadings are very low (0.04 and 0.008 mmol/g dry gel), whereas methyl orange and salicylic acid drug uptakes are found as 0.15 and 0.18 mmol/g dry gel, respectively. The incorporation of β-CD-UM comonomer into the gel slightly reduces the methyl orange and salicylic acid releases. However, a significant enhancement was achieved in the case of sulfathiazole delivery. It can be concluded that the inclusion complex formation capability of β-CD moiety increases the drug release by improving the aqueous solubility of hydrophobic drugs. On the other hand, in the case of hydrophilic drugs, the drug release retards by forming strong drug-β-CD complex and reducing the drug diffusivity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Properties of α-, γ-, and δ-tocopherol in purified fish oil triacylglycerols

The effect of α-tocopherol (αTOH) (50–2000 ppm), γ-tocopherol (γTOH) (100–2000 ppm), and δ-tocopherol (δTOH) (100–2000 ppm) on the formation and decomposition of hydroperoxides in purified fish oil triacylglycerols (TAG) was studied. The tests were conducted at 30°C in the dark. Purified fish oil TAG oxidized very rapidly with no apparent induction period. The relative ability of the tocopherols to retard the formation of hydroperoxides decreased in the order αTOH> γTOH>δTOH at a low level of addition (100 ppm), but a reverse order of activity was found when the initial tocopherol concentration was 1000 ppm. This dependence of relative antioxidant activity on tocopherol concentration was caused by the existence of concentrations for maximal antioxidant activity for αTOH and for γTOH. An inversion of activity, on the basis of hydroperoxide formation, was observed for αTOH at 100 ppm and for γTOH at 500 ppm, whereas the antioxidant activity of δTOH increased with level of addition up to 1500–2000 ppm. None of the tocopherols displayed any prooxidant activity. All three tocopherols strongly retarded the formation of volatile secondary oxidation products in a concentration-dependent manner. At concentrations above about 250 ppm there appeared to be a linear relationship between rate of consumption of αTOH and initial αTOH concentration, in accordance with the linear relationship observed between the initial rate of formation of hydroperoxides and the initial αTOH concentration. The rate of consumption of γTOH also increased with initial concentration, but to a lesser extent than for αTOH. At high levels of addition the rate of consumption of δTOH was independent of initial concentration, appearing to reflect the greater stability of this tocopherol homolog and participation in reactions with lipid peroxyl radicals only. Presented in part at the AOCS annual meeting in San Diego, California, April 2000.     

Combustion synthesis of high flexural strength,low linear shrinkage and machinable porous β-Si3N4 ceramics

Porous β-Si₃N₄ ceramics were prepared by combustion synthesis using Si, α-Si₃N₄ and Y₂O₃ powders as raw materials. The effects of α-Si₃N₄ diluent content in pellet on nitriding rate, shrinkage, porosity and flexural strength of porous ceramics were investigated. The results show that porous β-Si₃N₄ ceramic with porosity of 49 % and flexural strength of 151 MPa can be obtained by combustion synthesis when the content of α-Si₃N₄ diluent in raw materials is equal to that of Si, and the linear shrinkage of porous ceramic is only 2.8 %. In addition, the porous ceramic can be drilled and turned by WC drill and turning tool respectively.     

Penetration and distribution of α-tocopherol, α- or γ-tocotrienols applied individually onto murine skin

To evaluate skin penetration of various vitamin E homologs, a 5% solution of either α-tocopherol, α-tocotrienol, or γ-tocotrienol in polyethylene glycol was topically applied to SKH-1 hairless mice. After 0.5, 1, 2, or 4 h (n=four per time point and four per vitamin E homolog), the skin was washed, the animals killed, the skin rapidlly removed, frozen on dry ice, and a biopsy taken and sectioned: stratum corneum (two uppermost, 5-μm sections—SC1 and SC2), epidermis (next two 10μm sections—E1 and E2), papillary dermis (next 100μ, PD), dermis (next 400 μm, D), and subcutaneous fat (next 100 μm, SF). SC1 contained the highest vitamin E concentrations per μ thickness. To compare the distribution of the various vitamin E forms into the skin layers, the percentage of each form was expressed per its respective total. Most surprising was that the largest fraction of skin vitamin E following topical application was found in the deeper subcutaneous layers—the lowest layers, PD (40±15%) and D (36±15%), contained the major portion of the applied vitamin E forms. Although PD only represents about 16% of the total skin thickness, it contains sebaceous glands—lipid secretory organs, and, thus, may account for the vitamin E affinity for this layer. Hence, applied vitamin E penetrates rapidly through the skin, but the highest concentrations are found in the uppermost 5 microns.     

The production of high efficiency Ziegler–Natta catalyst with dual active sites nature using cyclohexyl chloride as promoter with super activity and produced superior polyethylene with controllable molecular weight distribution

In the previous studies, the several halocarbons (HC) were tested as promoters for a Ti-based Ziegler–Natta (ZN) catalyst at different polymerization conditions. The Results showed that chloro cyclohexane has the best operation in catalyst activity, polymer particle size growth, hydrogen responsibility and wax reduction too. For the first time in this study, the effect of Al/Ti ratio on the optimum HC/Ti ratio has been considered and the results showed that the optimum HC/Ti ratio depends on the Al/Ti ratio directly. In the optimum HC/Ti ratio, the catalyst activity and hydrogen responsibility ratio of the catalyst increase up to 125 and 55% respectively. The acceptable growth of polymer powder up to 46%, lower flow rate ratio (FRR) up to 19% and decrease of wax amount up to 12%, completed the promotion results. Furthermore, in the next part of this study and as key note, a little dose of halocarbon was used in the catalyst preparation to produce the special catalysts with dual active sites. In the catalyst preparation, the concentration of each active sites depends on the halocarbon amount and it can control the molecular weight distribution of the produced polyethylene; because each active sites have different response to hydrogen. The halocarbon based catalysts showed the remarkable effect on the catalyst activity, the molecular weight and especially molecular weight distribution (MWD). The flow rate ratio and MWD could be increased up to 77 and 88% respectively as the main result of halocarbon addition during the catalyst preparation.     

An Efficient Method for Determining the α-, β-, and γ-Cellulose Content in Fully Delignified Pulps by Reaction-Based Headspace Gas Chromatography

This article reports on a headspace gas chromatographic (HS-GC) technique for determining the content of α-, β-, and γ-cellulose in fully delignified pulps. In this method, the pulp sample was extracted by 17.5% and 9.45% NaOH solutions (25°C), respectively, to obtain two soluble fractions; i.e., the sum of β- and γ-cellulose and γ-cellulose. By reacting with potassium dichromate in a strong-acidic medium at 100°C for 60 min in a sealed headspace sample vial, these soluble celluloses in the filtrates were quantitatively converted to carbon dioxide. With the headspace equilibration at 60°C for 7 min, the formed carbon dioxide was measured by HS-GC and thus the content of β- and γ-cellulose in the pulp samples can be determined, from which the content of α-cellulose can also be calculated. The results showed that the present method had a good measurement precision (a relative standard deviation <2.1%) and accuracy (relative differences of <10% compared to the reference); the limit of quantification (LOQ) was 1.71%. In summary, the present method is simple, practical, and is particularly suitable for use in the batch sample analysis for determining α-, β-, and γ-cellulose content in fully delignified pulps.     

A porous lanthanide metal–organic framework with luminescent property,nitrogen gas adsorption and high thermal stability

A novel lanthanide metal–organic framework, [Eu₂(BDC)₃(DMF)₂]·(DMF)_1.7(BDC = 1,3-benzenediacarboxylate) 1 has been synthesized under solvothermal condition and characterized by single-crystal X-ray structure determination, luminescent property, nitrogen gas adsorption, powder X-ray diffraction, IR, and TGA.     

The thermal,electrical and mechanical properties of porous α-SiC ceramics bonded with Ti3SiC2 and β-SiC via low temperature in-situ reaction sintering

Porous SiC ceramics have recently attracted wide attention for their applications in the electrically heatable filter. Further improvement of the thermal and electrical conductivity without sacrificing permeability is a critical parameter for such applications. In the present work, porous SiC/Ti₃SiC₂ ceramic composites with Ti₃SiC₂ and micro/nano SiC have been prepared from TiC/Si/α-SiC mixtures at a low sintering temperature (1400 °C). Nano-laminated Ti₃SiC₂ enhanced the electrical conductivity, while the good thermal conductivity was achieved through in-situ formed nano β-SiC and raw coarse α-SiC in the porous ceramics. Along with the increase of initial α-SiC particle size from 0.76 to 16.13 μm, the permeability, thermal and electrical conductivity improved due to the decreased porosity and increased pore size in porous SiC/Ti₃SiC₂ ceramics. The results suggested that the decoupling of the electrical conductivity from the thermal conductivity could be tuned by adjusting the initial α-SiC particle size.