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281.
《Arabian Journal of Chemistry》2022,15(1):103507
Syzygium brachythyrsum is an important folk medicinal and edible plant in Yunnan ethnic minority community of China, however, little is known about the chemical and bio-active properties. The present study is aimed to identify the bioactive constituents with antioxidant and anti-inflammatory properties by an integrating approach. First, two new bergenin derivatives, brachythol A (1) and brachythol B (2), together with eleven known phenolic compounds (3–13) were isolated from bioactive fractions by phytochemical method. Among these isolated chemicals, five bergenin derivatives, along with 3 phenolics were found in Syzygium genus for the first time. Then, a further chemical investigation based on ultra-high-performance liquid chromatography-Q Exactive Orbitrap mass spectrometry resulted in a total of 107 compounds characterized in the bio-active fractions, including 50 bergenin derivatives, among which 14 bergenin derivatives and 14 phenolics were potential new natural chemicals. Most of the isolated compounds showed obvious antioxidant activities, while compounds 11, 12, and 13 had favorable performance. Eight compounds (2–5, 7, and 9–11) showed good inhibitory activity on nitric oxide (NO) production in macrophage RAW 264.7 cells. The structure–activity correlation analysis indicated that the antioxidation and anti-inflammatory activities enhanced when bergenin was esterified with gallic acid, caffeic acid or ferulic acid. This is the first report of bergenins in Syzygium genus and the richness in new bio-active bergenins and gallic acid derivatives indicated that Syzygium brachythyrsum is a promising functional and medicinal resource. 相似文献
282.
283.
多评价特征基元可拓集研究 总被引:20,自引:2,他引:20
杨春燕 《数学的实践与认识》2005,35(9):203-208
在单评价特征基元可拓集的基础上,研究多评价特征基元可拓集的构造方法及其关联函数的建立方法,为多特征综合评价和多特征不相容问题求解提供理论依据和可操作的形式化、定量化方法,使多特征不相容问题的智能化处理成为可能. 相似文献
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285.
In this paper, we have analyzed the Jeffrey fluid with pressure‐dependent viscosity. The equations of Jeffrey fluid model have been modelled when viscosity is a function of pressure. Two types of flow problem, namely, Poiseulle flow and Couette flow have been solved numerically for Jeffrey fluid. The velocity field for different physical parameters has been discussed through graphs. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
286.
Indirubin, present in extracts of Isatis tinctoria and some other plant species, has promising cytotoxicity against a variety of cell lines by inhibition of cyclin‐dependent kinases. Chemical synthesis of its derivatives relies on the combination of isatins and 2,3‐dihydro‐1H‐indol‐3‐one (‘indoxyl’) derivatives and usually yields indigo as well as other by‐products. Inspection of the hydrolysis of the long‐known condensation products of 2‐thioxothiazolidin‐4‐one with isatins gave useful hints for an improved synthesis of indirubins: this reaction does not yield quinoline derivatives but 2‐(2,3‐dihydro‐2‐oxo‐1H‐indol‐3‐ylidene)‐2‐sulfanyl acetic acids. By substitution of the sulfanyl group in this oxindoles with anilines and straightforward cyclization under Nazarov conditions, a broad variety of indirubins substituted in the indoxyl ring system are thus available, usually in very good purity and yield. Use of naphthylamines in this reaction sequence yields various fluorescent substances with λfl at ca. 630 nm. 相似文献
287.
Maurizio Manzo 《Journal of Polymer Science.Polymer Physics》2017,55(10):789-792
In this article, a new technique for building temperature compensated microscale lasers that are based on the morphology dependent resonances phenomenon is presented. The dome shaped resonator is made with a mixture of NBA 107 UV curable polymer and rhodamine 6 g dissolved in ethanol solution. Since polymers usually exhibit linear thermal expansion and thermo‐optic coefficients that are opposite in sign but similar in order of magnitude, it is possible to compensate for temperature over the dome shaped resonator by tuning the dye concentration and the ratio between the polymer and dye solution. Experiments with dye concentration between 10?2 to 10?3 M and polymer and dye solution ratios between 1:1 and 4:1 are conducted. The sensitivity for all cases is presented, and the quality factor Q is investigated. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 789–792 相似文献
288.
Tohoru Takeda Jin Wu Qingkai Huo Tetsuya Yuasa Kazuyuki Hyodo Takao Akatsuka 《Journal of synchrotron radiation》2008,15(5):528-531
Fluorescent X‐ray computed tomography (FXCT) enables visualization of myocardial fatty acid metabolism by using non‐radio‐iodinated I‐5‐(p‐iodophenyl)‐3‐(R,S)‐methylpentadecanoice acid (BMIPP). In this experiment, age‐dependent myocardial metabolic impairment was successfully imaged and analyzed quantitatively in J2N‐k cardiomyopathic hamster using FXCT. 相似文献
289.
In this paper existence and regularity results for a class of degenerate nonlinear parabolic equations are proved. Indeed,
the diffusion operator may degenerate as the solution diverges and may depend on space and time variables in a non–regular
way, too. Some estimates on the behaviour of the solutions for t → +∞ are also given. 相似文献
290.