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101.
T Hatano T Yasuhara R Yoshihara I Agata T Noro T Okuda 《Chemical & pharmaceutical bulletin》1990,38(5):1224-1229
The inhibitory effects of hydrolyzable tannins, condensed tannins and related polyphenols on the activity of xanthine oxidase (XOD), catalyzing uric acid formation from xanthine, were investigated. Marked differences in the strength of the inhibition were observed. Some of the differences among the monomeric hydrolyzable tannins were due to their molecular weights, reflecting the number of phenolic hydroxyl groups in the molecule. However, the inhibitory activity of several oligomeric hydrolyzable tannins seemed particularly low in spite of their large molecular size. It was also observed that differences in location of acyl groups on the carbohydrate cores caused differences in the inhibitory activity among monomeric and oligomeric hydrolyzable tannins. A caffeic acid derivative (caffeetannin), 3,5-di-O-caffeoylquinic acid (24), also inhibited this enzyme. Galloylation and the degree of polymerization in proanthocyanidins were also shown to affect remarkably the strength of the inhibition. Among the compounds tested in the present study, valoneic acid dilactone (29), isolated from Mallotus japonicus, inhibited the enzyme most effectively. A kinetic study showed that this dilactone inhibited XOD non-competitively. Comparison of the inhibitory effect on XOD, with the binding activity to hemoglobin, for each tannin, suggests that their inhibition of XOD is not based on non-specific binding to the protein. Similar comparison of the inhibitory effect on XOD with the inhibitory effect on the generation of superoxide anion radical (O2-.) from the hypoxanthine-XOD system revealed that the inhibition of O2-. generation by tannins is due to their radical-scavenging activity, and not due to their inhibitory activity upon the enzyme. 相似文献
102.
Masanori Shinohara Keitaro Iwatsuji Hiromichi Shibata Hiroshi Fujiyama 《Applied Surface Science》2006,252(24):8589-8592
We have investigated the thermal annealing effects of hydrocarbon species on the methane-plasma exposed silicon surface, investigated by in situ infrared absorption spectroscopy (IRAS) in multiple internal reflection (MIR) geometry. The proportion of types of hydrocarbon species is not remarkably changed in the hydrocarbon network that consists of sp-, sp2- and sp3-CHX species by annealing at moderate temperatures. On the other hands, the proportion is drastically changed in the network that is mainly composed of sp3-CHX species by annealing at moderate temperatures. It suggests that excess CH3 species in the film is not stable against thermal annealing and would be converted to sp3-CH1-2 species by annealing at moderate temperatures. And the data also show that sp2-CH species is more stable against the thermal annealing than sp3-hydrocarbon species. 相似文献
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Dobashi T Yoshihara H Nobe M Koike M Yamamoto T Konno A 《Langmuir : the ACS journal of surfaces and colloids》2005,21(1):2-4
Curdlan beads consisting of liquid crystalline gel (LCG) and amorphous gel (AG) in alternating layers in a wide range of diameters were newly prepared by interfacial insolubilization reactions using calcium chloride as the setting reagent. The thickness of the liquid crystalline layer was proportional to the diameter of the gel bead, and the proportional constant agreed with that determined for the cylindrical gel prepared by a dialysis method. The proportional constant initially increased with increasing calcium concentration of the dispersing medium and saturated at a high concentration limit. These results suggest that the mechanisms for forming the alternating LCG/AG structures prepared with different boundary conditions are the same. The LCG/AG structure could be controlled by calcium concentration. 相似文献
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109.
Ryohei Sugita Natsuko I. Kobayashi Atsushi Hirose Yoshimi Ohmae Keitaro Tanoi Tomoko M. Nakanishi 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(2):1411-1416
We have developed a real-time radioisotope imaging system (RRIS) that can nondestructively trace 14C-labeled chemicals in plants. In an experiment, after feeding 14CO2 to a plant, the plant was fixed inside a box where lighting was regulated, and beta rays emitted from the 14C in the plant were intermittently imaged using the developed system. As a first step, using a series of standard sources of 14C, the data depth and detection limits of the 14C images captured by the RRIS were evaluated for various integral times. As a result, the linearity between the 14C activity and signal intensity was determined for the range 103. Next, the linearity was validated using plant (Arabidopsis thaliana) organs, resulting that the linearity was shown in the case of young leaf, but was not maintained in the thick organs, such as a flower, mature leaf, siliques, and stem. Considering the good correlation between the intensity by RRIS and the PSL value by an imaging plate (IP) as well as the relative low energy of beta rays emitted from 14C, the thickness of the organs would easily affect the quantitativity of the RRIS as well as an IP. Our findings prove that sequential images of 14C in a living plant sample in a regulated light and air environment can be nondestructively analyzed using the developed system, whose quantitativity is similar to that of an IP. 相似文献
110.
Nanang Rudianto Ariefta Hasna Tazkia Nikmawahda Takako Aboshi Tetsuya Murayama Keitaro Tawaraya Takuya Koseki Genta Katagi Yoshito Kakihara Yoshihito Shiono 《Tetrahedron》2019,75(10):1371-1377
Four novel compounds with γ-methylidene-spirobutanolide core, fusaspirols A-D, were isolated from the brown rice culture of Fusarium solani B-18. Their structures were established by extensive spectroscopic analyses of 1D/2D-NMR, HRESITOFMS, and chemical derivatization. The absolute configurations of secondary alcohols in fusaspirols A and D were determined using modified Mosher's ester method. Fusaspirol A and 4,9-di-O-acetylfusaspirol A activated a signaling pathway in osteoclastic differentiation of murine macrophage derived RAW264.7?cells. 相似文献