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871.
Lei Zhang Liang Xu Xiao-Jie Tan Qiong-Feng Liao Wei Guo Xiao-Hui Chen Kai-Shun Bi 《Chromatographia》2007,66(1-2):115-120
A sensitive and reliable ion-paired high-performance liquid chromatographic method has been established for the simultaneous
quantification of six major active ingredients, namely baicalin, baicalein, wogonin, oxysophocarpine, oxymatrine and matrine
in the Chinese herbal preparation, Sanwu-Huangqin-Tang. HPLC analyses were performed on a Phenomenex luna C18 column with mobile phase of methanol–acetonitrile–aqueous phosphoric acid at a flow rate of 0.9 mL min−1. The complete separation was achieved within 35 min for the six target constituents. A good linear regression relationship
between peak-areas and concentrations was obtained over the range of 12.10–242.0 μg*mL−1 for baicalin, 5.05–101.0 μg*mL−1 for baicalein, 0.95–19.0 μg*mL−1 for wogonin, 2.75–55.0 μg*mL−1 for oxysophocarpin, 2.75–55.0 μg*mL−1 for oxymatrine and 4.90–98.0 μg*mL−1 for matrine, respectively. The repeatability was evaluated by intra- and inter-day assays with relative standard deviation
(RSD) being less than 5.1%. The recoveries, measured at three concentration levels, varied from 93.8 to 102.1%. The assay
was successfully applied for determination of six bioactive compounds in Sanwu-Huangqin-Tang. The interaction of chemical
constituents was observed when the herbs were used in compatibility. The results indicated that the developed assay method
was rapid, accurate and could be readily utilized as a quality control method for Sanwu-Huangqin-Tang. 相似文献
872.
《Tetrahedron: Asymmetry》2005,16(22):3682-3689
The results of a reduction of a wide range of ketones using 31 commercially available isolated ketoreductases (KREDs) are presented. All enzymes accepted a wide substrate range. The stereoselectivity of each enzyme was measured for the reduction of benzoyl-hydroxyacetone and ethyl-3-oxobutanoate, and in each case, enzymes which produce enantiomerically pure (R)- and (S)-alcohols were found. The preparative scale reactions were investigated using two ketones with different hydrophobicities (benzoyl-hydroxyacetone and α-tetralone) and using enzymes with varying specific activities for their reduction. Regardless of the hydrophobicity of the substrate, high titers of ketone (0.75–1.4 M) were reduced in high yield using catalytic amounts of enzyme (1–7% g/g relative to substrate) and cofactor (0.1–0.2% equiv. relative to ketone) within 4–24 h. The cofactor was efficiently regenerated in situ via the oxidation of glucose by glucose dehydrogenase, an enzyme that has also been cloned and over-expressed. These results show that isolated ketoreductases can be quickly and easily screened against target ketones, and the reactions can be scaled to produce preparative amounts of chiral alcohols. Ketoreductase enzymes should become a standard addition to the organic chemists toolbox of asymmetric catalysts for stereoselective ketone reduction. 相似文献
873.
单一分散氧化铁-葡聚糖纳米粒子的制备及超顺磁性 总被引:5,自引:0,他引:5
0引言
氧化铁-葡聚糖(Fe3O4-Dextran)复合粒子由于具有良好的生物相容性和优异的靶向性能,被用做药物、细胞、酶的载体广泛应用于生物医学、细胞学、生物工程和工业工程等领域[1~3].目前其制备方法主要有一步法和两步法.一步法中氧化铁是在葡聚糖体系下制备的,葡聚糖在氧化铁成核过程中能隔离和分散磁性粒子,防止磁性粒子的团聚和沉积[5]. 相似文献
874.
《Tetrahedron: Asymmetry》2006,17(23):3265-3272
Starting from protected (S)-3-hydroxyglutarimide 2a, the asymmetric synthesis of (2R,3S)-CP-99,994 8 was achieved. The crucial steps were a neighboring group participation leading to pyrrolidino-aziridinium intermediate 25 and the subsequent regioselective ring-opening reaction. In the case where neighboring group participation was not involved, only the eliminated product 15 was obtained. 相似文献
875.
《Tetrahedron: Asymmetry》2006,17(1):61-67
Two epimeric chiral cyclopentylglycines (−)-16 and (+)-17, functionalised with a carboxy group cis to the amino acid group, were prepared starting from chiral 2-amino-3-oxo-norbornanecarboxylic acid derivative exo-9 by combining two classical reactions such as the Diels–Alder and retro-Claisen reactions. Compounds 16 and 17 are non-proteinogenic amino acids of biological interest containing conformational constraints in which the skeletons of both 2-aminoadipic acid and 2-aminopimelic acid are included. 相似文献
876.
877.
利用溶胶-凝胶分配理论对氢键溶液的模型体系进行研究, 给出了凝胶点后氢键网络中各结构参数的计算方案, 并进行相应的数值计算. 结果表明, 因受体基团本身的性质及两类质子受体基团的数量比不同, 受体基团的竞争作用对网络结构有明显影响, 这提供了控制氢键网络结构特征的可能方法. 相似文献
878.
ZHAO Chun-shen ZHAO Yan-fang CHAI Hui-fang GONG Ping 《高等学校化学研究》2006,22(5):577-583
A series of ethyl 5-hydroxyindole-3-earboxylates 6a-10r was designed and synthesized. The structures of all the compounds were confirmed by IR, ^1H NMR, and MS and their anti-hepatitis B virus (HBV) activities were evaluated in 2.2.15 cells. Among them, compound 7g { ethyl 5-hydroxy-2- [ ( 3-methoxyphenylsulfinyl ) methyl ] -1-methyl-4- [ (4-methylpiperazin-1-yl) methyl ]-1H-indole-3-carboxylate} displays a significant anti-HBV activity, which is more potent than the positive control lamivudine. 相似文献
879.
本文采用脂质体/水分配系统来考察pH、磷脂的种类和荷电性对药物与有序磷脂膜结合的影响. 相似文献
880.