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961.
962.
Xiao Hong YAN Yue Wei GUO* State Key Laboratory of Drug Research Institute of Materia Medica Shanghai Institutes for Biological Sciences Chinese Academy of Sciences Shanghai 《中国化学快报》2005,16(3)
Marine organisms have been found to be a storehouse of steroids, particularly in term ofunique side-chain structures and unusual functionalization. Marine steroids are oftenfound in highly oxygenated forms and possessing various biological activities1.Previously, we reported the isolation and structural elucidation of three new marinesteroids, nanjiols A-C, which showed cytotoxicity against HL-60 and BEL 7402 celllines, from a soft coral Nephthea bayeri in East China Sea2. In continuation … 相似文献
963.
964.
Xiao‐Chi Ma Xiulan Xin Bao‐jing Zhang Sha Deng Ji‐hong Yao Chang‐yuan Wang Jian Cui Yan Tian Ke‐xin Liu 《Journal of separation science》2010,33(15):2272-2277
An efficient separation method of using high‐speed counter‐current chromatography was successfully established to directly purify cytotoxic transformed products of cinobufagin by Cordyceps militaris. The two‐phase solvent system composed of n‐hexane–ethyl acetate–methanol–water (4:6:3:4, v/v) was used in high‐speed counter‐current chromatography. A total of 9 mg of 4β,12α‐dihydroxyl‐cinobufagin ( 1 ), 15 mg of 12β‐hydroxyl‐cinobufagin ( 2 ), 8 mg of 5β‐hydroxyl‐cinobufagin ( 3 ), 12 mg of deacetylcinobufagin ( 4 ) and 6 mg of 3‐keto‐cinobufagin ( 5 ) were obtained in a one‐step separation from 400 mg of the crude extract with purity of 98.7, 97.2, 90.6, 99.1 and 99.4%, respectively, as determined by HPLC. Their chemical structures were identified on the basis of 1H‐NMR and 13C‐NMR technology. All products ( 1 – 5 ) showed the potent activities against human carcinoma cervicis (Hela) and malignant melanoma (A375) cells in vitro. 相似文献
965.
A simple, rapid and sensitive method for the determination of pirimicarb in tomato and pear using polymer monolith microextraction (PMME) based on the molecularly imprinted polymer (MIP) monolith combined with high-performance liquid chromatography-photodiodes array detector (HPLC-PAD) was developed. By optimizing the polymerization conditions, such as the nature of porogenic solvent and functional monomer, the molar ratio of the monomer and cross-linker, an pirimicarb MIP monolith was synthesized in a micropipette tip using methacrylic acid (MAA) as the functional monomer, ethylene dimethacrylate (EGDMA) as the cross-linker and the mixture of toluene-dodecanol as the porogenic solvent. The MIP monolith showed highly specific recognition for the template pirimicarb. The monolith was applied for the selective extraction of pirimicarb in tomato and pear. Several parameters affecting MIP-PMME were investigated, including the nature and volume of extraction solvent, sample volume, flow rate and sample pH. Under the optimum PMME and HPLC conditions, the linear ranges were 2.0-1400 μg/kg for pirimicarb in tomato and pear with the correlation coefficient of above 0.999. The detection limits (s/n=3) were both 0.6 μg/kg. The proposed method was successfully applied for the selective extraction and determination of pirimicarb in tomato and pear. 相似文献
966.
A simple and efficient microwave-assisted extraction of polyphenols from industrial apple pomace was developed and optimized by the maximization of the yield using response surface methodology. A Box-Behnken design was used to monitor the effect of microwave power, extraction time, ethanol concentration and ratio of solvent to raw material (g/mL) on the polyphenols yield. The results showed that the optimal conditions were as follows: microwave power 650.4?W, extraction time 53.7?s, ethanol concentration 62.1% and ratio of solvent to raw material 22.9:1. Validation tests indicated that the actual yield of polyphenols was 62.68±0.35?mg gallic acid equivalents per 100?g dry apple pomace with RSD=0.86% (n=5) under the optimal conditions, which was in good agreement with the predicted yield and higher than those of reflux and ultrasonic-assisted extraction methods. HPLC analysis indicated that the major polyphenols of apple pomace consisted of chlorogenic acid, caffeic acid, syrigin, procyanidin B2, (-)-epicatechin, cinnamic acid, coumaric acid, phlorizin and quercetin, of which procyanidin B2 had the highest content of 219.4?mg/kg. 相似文献
967.
Xiaojun Zou Yuemei Cui Xiangbing Zhu Zheng Hu Xijun Chang 《Journal of Sol-Gel Science and Technology》2009,50(1):35-43
Morin was successful as a chemical modifier to improve the reactivity of the nanometer SiO2 surface in terms of selective binding and extraction of heavy metal ions. This new functionalized nanometer SiO2 (nanometer SiO2-morin) was used as an effective sorbent for the solid-phase extraction (SPE) of Cd(II), Cu(II), Ni(II), Pb(II), Zn(II) in
solutions prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Experimental conditions
for effective adsorption of trace levels of metal ions were optimized with respect to different experimental parameters using
static and dynamic procedures in detail. The pH 4.0 was chosen as the optimum pH value for the separation of metal ions on
the newly sorbent. Complete elution of the adsorbed metal ions from the nanometer SiO2-morin was carried out using 2.0 mL of 0.5 mol L−1 of HCl. Common coexisting ions did not interfere with the separation and determination at pH 4.0. The maximum static adsorption
capacity of the sorbent at optimum conditions was found to be 22.36, 36.8, 40.37, 33.21 and 25.99 mg metal/g SiO2-morin for Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II), respectively. The time for 95% sorption for Cu(II) and Ni(II) and 70%
sorption for Cd(II), Pb(II) and Zn(II) was less than 2 min. The relative standard deviation (RSD) of the method under optimum
conditions was lower than 5.0% (n = 11). The procedure was validated by analyzing the certified reference river sediment material (GBW 08301, China), the results
obtained were in good agreement with standard values. The nanometer SiO2-morin was successfully employed in the separation and preconcentration of trace Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II)
from the biological and natural water samples yielding 75-folds concentration factor. 相似文献
968.
脂肪族氨基酸二肽与水团簇的理论研究 总被引:1,自引:0,他引:1
用ABEEMσπ/MM模型和MP2/6-31+G(d)//B3LYP/6-31G(d)方法研究水合效应对脂肪族氨基酸二肽的影响.从结构和能量两方面说明Leu残基在蛋白质中起成旋作用,Val和Ⅱe残基在蛋白质中起解旋作用.同时得出:水分子严重影响了二肽分子的骨架二面角;对于结合相同数目水分子的团簇倾向于形成含有环状氢键的结构,并且含有环状氢键团簇的结合能大于含有链状氢键团簇的结合能. 相似文献
969.
970.
克拉霉素在不同条件下水解,分别生成3-羟基克拉霉素(2)和3-羟基-8,9,10,11-二脱水-9,12-半缩酮克拉霉素(3),用乙酸酐保护2的C(2')-OH得到2'-乙酰基-3-羟基克拉霉素(4),用Ⅳ-氯代琥珀酰亚胺(NCS)氧化4的C(3)-OH合成了2'-乙酰基-3-氧代克拉霉素(5),采用MS,IR,1H NMR,13C NMR等对这些化合物进行了表征.用X射线单晶衍射法测定了化合物2和5的晶体结构,其均属于正交晶系,P212121空间群.化合物2的晶胞参数a=1.3657(3)nm,6=1.4783(3)nm,c=1.6510(3)nm,Z=4,V=3.3332(12)am3,Dc=1.175 g/cm3,F(000)=1288,μ=0.087mm-1;化合物5的晶胞参数a=1.5124(3)nm,b=1.5247(3)nm,c=1.5288(3)nm,Z=4,V=3.5254(12)nm3,Dc=1.187g/cm3,F(000)=1368.0,μ=0.088 mm-1. 相似文献