Shigeru Moriyama

Ethyl esterification of docosahexaenoic acid in an organic solvent-free system with immobilized Candida antarctica lipase

Ethyl docosahexaenoate (EtDHA) is regarded as a potentially useful pharmaceutical substance on account of its beneficial physiological activities. We attempted the ethyl esterification of docosahexaenoic acid (DHA) in an organic solvent-free system using Candida antarctica lipase, which acts strongly on DHA and ethanol. Esterification of 88% was attained by shaking a mixture of DHA/ethanol (1:1, mol/mol) and 2 wt% immobilized C. antarctica lipase at 30 degrees C for 24 h. However, even in the presence of an excess amount of ethanol, the extent of esterification could not be raised above 90%. To attain a higher level of esterification, a two-step reaction was found to be effective. The first step was performed in a mixture of DHA/ethanol (1:1, mol/mol), and the reaction mixture was then dehydrated. In the second step, the resulting mixture was shaken at 30 degrees C for 24 h with 5 molar equivalents of ethanol against the remaining DHA using 2 wt% immobilized lipase. By means of this two-step procedure, 96% esterification was attained. Repetition of the first and second reactions showed that the immobilized lipase was reusable for at least 50 cycles. In addition, DHA remaining in the second-step reaction mixture was removed by a conventional alkali refining process, giving purified EtDHA with a high yield.

Autoxidation Kinetic Analysis of Docosahexaenoic Acid Ethyl Ester and Docosahexaenoic Triglyceride with Oxygen Sensor

The application of ω-3 polyunsaturated fatty acids (PUFAs) as food additives is restricted by their chemically quite reactive properties. However, quantitative analyses of the oxidative kinetics of PUFAs are very few compared to other studies on food chemistry. In this study, the autoxidation kinetics of ethyl docosahexaenoate (DHAEE), docosahexaenoic triglyceride (DHA oil), and emulsified DHA oil were investigated with an oxygen sensor. The autocatalytic reaction rate constants for DHAEE, DHA oil, and the emulsified DHA oil with 20%(w/v) GA, 20% SSPS, or 20% SSPS containing 5% soy protein were obtained at 35, 50, and 70°C. A plot of the natural logarithm of the frequency factor, ln ka0, vs. the activation energy, Ea, demonstrated that ln ka0 against Ea fitted well with a single straight line both for the data from this study and for other reported results. This implies that the chemical compensation relationship holds between k a0 and E a for PUFA and emulsified DHA oil.

Purification of docosahexaenoic acid ethyl ester using a silver-ion-immobilized porous hollow-fiber membrane module.

Docosahexaenoic acid ethyl ester (DHA‐Et) was purified by adsorption on Ag‐ion‐immobilized membranes via selective interaction between silver ion and carbon‐carbon double bonds of DHA‐Et. Silver ions were immobilized onto sulfonic‐acid‐group‐containing porous hollow‐fiber membranes at an Ag ion density of 1.4 mol/kg of membrane, and 30 membranes were housed in one module (inner diameter = 18 mm and effective length = 80 mm). The adsorption isotherms of DHA‐Et in various organic solvents revealed that DHA‐Et was adsorbed on the immobilized Ag ions with a DHA‐Et/Ag ion molar binding ratio of 1/5 in methanol, and that acetonitrile was the solvent of choice for the elution of the adsorbed DHA‐Et. Permeation of bonito oil ethyl ester solution in methanol through the Ag‐ion‐immobilized hollow‐fiber membrane module demonstrated that the displacement adsorption of other lower unsaturated fatty‐acid ethyl esters by DHA‐Et proceeded along the membrane thickness. The purity of DHA‐Et was improved to 99 wt % by permeating first bonito oil ethyl ester containing 95 wt % DHA‐Et and then acetonitrile through the module.

補正用CT 画像のピクセルサイズが共役勾配法によるSPECT 再構成画像に与える影響

PURPOSE The frame-of-reference using computed-tomography (CT) coordinate system on single-photon emission computed tomography (SPECT) reconstruction is one of the advanced characteristics of the xSPECT reconstruction system. The aim of this study was to reveal the influence of the high-resolution frame-of-reference on the xSPECT reconstruction. METHODS 99mTc line-source phantom and National Electrical Manufacturers Association (NEMA) image quality phantom were scanned using the SPECT/CT system. xSPECT reconstructions were performed with the reference CT images in different sizes of the display field-of-view (DFOV) and pixel. RESULTS The pixel sizes of the reconstructed xSPECT images were close to 2.4 mm, which is acquired as originally projection data, even if the reference CT resolution was varied. The full width at half maximum (FWHM) of the line-source, absolute recovery coefficient, and background variability of image quality phantom were independent on the sizes of DFOV in the reference CT images. CONCLUSION The results of this study revealed that the image quality of the reconstructed xSPECT images is not influenced by the resolution of frame-of-reference on SPECT reconstruction.