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Antioxidant Flavone Glycosides from the Root of Pteroxygonum giraldii
Li, Bao-Lin,Yang, Zhan-Jun,Jiang, Lin-Ling,Zhang, Xi-Quan,Gu, Hong-Mei,Wang, Hui-Chun,Tian, Xian-Hua Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.7
Two new flavone glycosides, giraldiin A and B, together with three known compounds, annulatin, myricetin 3-O-$\alpha$- L-rhamnopyranoside and gallic acid, were isolated from the ethanol extract of the root of Pteroxygonum giraldii Damm. et Diels. The structures of giraldiin A and B are designated as 3'-($\alpha$-L-arabinopyranosyloxy)-4',5,5',7- tetrahydroxy-3-methoxyflavone and 4'-($\beta$-D-glucopyranosyloxy)-5,5',7-trihydroxy-2',3-dimethoxyflavone, respectively, on the basis of detailed spectroscopic analyses. The free radical scavenging activity of giraldiin A was evaluated by decolouring spectrophotometry of pentamethine cyanine dye (Cy5) with $Fe^{2+}-H_2O_2$ Fenton radical generating system. The results indicated the hydroxyl free radical scavenging activity of giraldiin A (E$D_{50}$ = 23.7 nmol/mL) is higher than that of some known antioxidants such as rutin, puerarin, daidzein and 2,6-di-tertbutyl-4-methylphenol.
Antioxidant Flavone Glycosides from the Root of Pteroxygonum giraldii
Bao-Lin Li,Lin-Ling Jiang,Hui-Chun Wang,Zhan-Jun Yang,Xi-Quan Zhang,Hong-Mei Gu,Xian-Hua Tian 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.7
Two new flavone glycosides, giraldiin A and B, together with three known compounds, annulatin, myricetin 3-O-α-L-rhamnopyranoside and gallic acid, were isolated from the ethanol extract of the root of Pteroxygonum giraldii Damm. et Diels. The structures of giraldiin A and B are designated as 3'-(α-L-arabinopyranosyloxy)-4',5,5',7-tetrahydroxy-3-methoxyflavone and 4'-(β-D-glucopyranosyloxy)-5,5',7-trihydroxy-2',3-dimethoxyflavone, respectively,on the basis of detailed spectroscopic analyses. The free radical scavenging activity of giraldiin A was evaluated by decolouring spectrophotometry of pentamethine cyanine dye (Cy5) with Fe2+-H2O2 Fenton radical generating system. The results indicated the hydroxyl free radical scavenging activity of giraldiin A (ED50 = 23.7 nmol/mL) is higher than that of some known antioxidants such as rutin, puerarin, daidzein and 2,6-di-tertbutyl-4-methylphenol.
Derivation of hypermethylated pluripotent embryonic stem cells with high potency
Bao, Siqin,Tang, Walfred WC,Wu, Baojiang,Kim, Shinseog,Li, Jingyun,Li, Lin,Kobayashi, Toshihiro,Lee, Caroline,Chen, Yanglin,Wei, Mengyi,Li, Shudong,Dietmann, Sabine,Tang, Fuchou,Li, Xihe,Surani, M Azi Nature Publishing Group 2018 Cell research Vol.28 No.1
<P>Naive hypomethylated embryonic pluripotent stem cells (ESCs) are developmentally closest to the preimplantation epiblast of blastocysts, with the potential to contribute to all embryonic tissues and the germline, excepting the extra-embryonic tissues in chimeric embryos. By contrast, epiblast stem cells (EpiSCs) resembling postimplantation epiblast are relatively more methylated and show a limited potential for chimerism. Here, for the first time, we reveal advanced pluripotent stem cells (ASCs), which are developmentally beyond the pluripotent cells in the inner cell mass but with higher potency than EpiSCs. Accordingly, a single ASC contributes very efficiently to the fetus, germline, yolk sac and the placental labyrinth in chimeras. Since they are developmentally more advanced, ASCs do not contribute to the trophoblast. ASCs were derived from blastocysts in two steps in a chemically defined medium supplemented with Activin A and basic fibroblast growth factor, followed by culturing in ABCL medium containing ActA, BMP4, CHIR99021 and leukemia inhibitory factor. Notably, ASCs exhibit a distinct transcriptome with the expression of both naive pluripotency genes, as well as mesodermal somatic genes; <I>Eomes, Eras, Tdgf1, Evx1, hand1, Wnt5a</I> and distinct repetitive elements. Conversion of established ESCs to ASCs is also achievable. Importantly, ASCs exhibit a stable hypermethylated epigenome and mostly intact imprints as compared to the hypomethylated inner cell mass of blastocysts and naive ESCs. Properties of ASCs suggest that they represent cells at an intermediate cellular state between the naive and primed states of pluripotency.</P>
Jiang Li,Xia-Bing Li,Sha Sha Ma,Juan Liu,Ben Hao Li,Bao-Lin Li 대한화학회 2016 Bulletin of the Korean Chemical Society Vol.37 No.8
A novel chiral ionic liquid containing proline moiety was synthesized. It can be used as a highly efficient and recyclable chiral organocatalyst for Michael addition of cyclohexanone with (E)-β-nitroalkenes in methanol at room temperature. The Michael addition affords the corresponding products in satisfactory yields of isolated products (78–98%) with high diastereoselectivities and excellent enantioselectivities (up to 98% dr and up to 99% ee). The catalyst can be recycled up to five times without any decrease in yields and stereoselectivities.
An Analytical Solution for Voltage Stability Studies Incorporating Wind Power
Lin, Yu-Zhang,Shi, Li-Bao,Yao, Liang-Zhong,Ni, Yi-Xin,Qin, Shi-Yao,Wang, Rui-Ming,Zhang, Jin-Ping The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.3
Voltage stability is one of the most critical security issues which has not yet been well resolved to date. In this paper, an analytical method called PQ plane analysis with consideration of the reactive power capability of wind turbine generator and the wake effect of wind farm is proposed for voltage stability study. Two voltage stability indices based on the proposed PQ plane analysis method incorporating the uncertainties of load-increasing direction and wind generation are designed and implemented. Cases studies are conducted to investigate the impacts of wind power incorporation with different control modes. Simulation results demonstrate that the constant voltage control based on reactive power capability significantly enhances voltage stability in comparison of the conventional constant power factor control. Some meaningful conclusions are obtained.