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581.
Chengjian Tan Yingtong Di Ye Wang Suo Gao Ningchuan Kong Jianxin Zhang Chunshun Li Xiaojiang Hao 《Tetrahedron letters》2008,49(21):3376-3379
Oldhamine A, a novel alkaloid with an unusual cyclopentadienyl anion in the fused-pentacyclic skeleton was isolated from the twigs of Daphniphyllum oldhami. The structure of oldhamine A was elucidated based on the spectroscopic data and the single-crystal X-ray diffraction crystallography. It is the first X-ray diffraction of the Daphniphyllum alkaloids with nitrogen-containing two pentacyclic rings. The inter-conversion between cyclopentadienyl anion and conjugated enolic unit was also conducted. 相似文献
582.
Huangbai-Zhimu herb-pair (HBZMHP) is a widely used Chinese traditional medicine formula in treating various diseases; however, its active components have remained unknown. In this paper, serum chemistry and combined high-performance liquid chromatography (HPLC), diode-array detection and mass-spectrometry (MS) techniques were used to study the constituents of HBZMHP extract absorbed into rat serum after oral administration. A total of nine characteristic HPLC peaks in the TIC chromatograms were identified as magnoflorine (1), menisperine (2), palmatine (3), berberine (4), timosaponin N or timosaponin E1 (5), timosaponin D (6), timosaponin BIII, anemarsaponin C or xilingsaponin B (7) timosaponin BII (8) and timosaponin AIII (9). All of the identified peaks were constituents of HBZMHP extract. The results narrow the range of active compounds to be found in HBZMHP extract, and pave the way for the follow-up action mechanism research. 相似文献
583.
Enantioseparation of chiral sulfonates by liquid chromatography and subcritical fluid chromatography
Tert‐butylcarbamoyl‐quinine and ‐quinidine weak anion‐exchange chiral stationary phases (Chiralpak® QN‐AX and QD‐AX) have been applied for the separation of sodium β‐ketosulfonates, such as sodium chalconesulfonates and derivatives thereof. The influence of type and amount of co‐ and counterions on retention and enantioresolution was investigated using polar organic mobile phases. Both columns exhibited remarkable enantiodiscrimination properties for the investigated test solutes, in which the quinidine‐based column showed better enantioselectivity and slightly stronger retention for all analytes compared to the quinine‐derived chiral stationary phase. With an optimized mobile phase (MeOH, 50 mM HOAc, 25 mM NH3), 12 of 13 chiral sulfonates could be baseline separated within 8 min using the quinidine‐derivatized column. Furthermore, subcritical fluid chromatography (SubFC) mode with a CO2‐based mobile phase using a buffered methanolic modifier was compared to HPLC. Generally, SubFC exhibited slightly inferior enantioselectivities and lower elution power but also provided unique baseline resolution for one compound. 相似文献
584.
Gang Fan Meng Ying Zhang Xiang Dong Zhou Xian Rong Lai Qing Hong Yue Ce Tang Wei Zao Luo Yi Zhang 《Analytica chimica acta》2012
Rhizoma coptidis, a broadly used traditional Chinese medicine, derives from the dried rhizomes of Coptis chinensis Franch, Coptis deltoidea C.Y. Cheng et Hsiao and Coptis teeta Wall. Quantitative determination of protoberberine alkaloids in R. coptidis is critical for controlling its quality. In this study, a rapid, simple and accurate quantitative 1H NMR (qNMR) method was developed for simultaneous determination of berberine, jatrorrhizine, epiberberine, coptisine, palmatine and columbamine in R. coptidis from the three species. Method validation was performed in terms of selectivity, precision, repeatability, stability, accuracy, robustness and linearity. The average recoveries obtained were in the range of 96.9–102.4% for all the six alkaloids. In addition, the qNMR data were analyzed with analysis of variance (ANOVA), hierarchical clustering analysis (HCA) and principal component analysis (PCA), and the results showed that the contents of the active alkaloids have significant difference among the three species. Compared with the conventional HPLC approach, the proposed qNMR method was demonstrated to be a powerful tool for quantifying the six alkaloids due to its unique advantages of high robustness, rapid analysis time and no need of standard compounds for calibration curves preparation. These findings indicate that this method has potential as a reliable method for quality evaluation of herb medicines, especially for protoberberine alkaloid-containing ones. 相似文献
585.
《Analytical letters》2012,45(16):2655-2664
Sample preparation technique based on an organic filter membrane (pH-resolved filter membrane microextraction) (pH-RFMME) was developed, coupled with high-performance liquid chromatography, and used to determine protoberberine alkaloids (jatrorrhizine, epiberberine, coptisine, palmatine, and berberine) in Coptis chinensis at different pH values through a one-step procedure. This green procedure provides a desirable sample pretreatment technology. The main variables affecting the extraction such as filter membrane area (or volumes of extraction solvents), sample pH, eluent pH, ionic strength, extraction stirring rate, extraction time, and sample volume were optimized. Under the optimized conditions, the enrichment factors of the analytes were 40.4–52.0, the linear ranges were 3.2–6250 ng · mL?1 for jatrorrhizine and epiberberine, 6.0–12000 ng · mL?1 for coptisine, 1.8–3600 ng · mL?1 for palmatine, and 18.8–18800 ng · mL?1 for berberine, with r 2 ≥ 0.9945. The limits of detection were less than 0.3 ng · mL?1. Satisfactory recoveries (84.8%–115.5%) and precision (1.8%–10.0%) were also achieved. These results confirmed that pH-RFMME is a simple, rapid, practical, and environmentally friendly method to isolate analytes that exhibit significant differences in acidity or alkalinity from complex samples. 相似文献
586.
Determination of Catechins and Purine Alkaloids in Tea by High Performance Liquid Chromatography 总被引:2,自引:0,他引:2
《Analytical letters》2012,45(17):2530-2537
With a novel internal standard, 8-chlorotheophylline, a high-performance liquid chromatography method was successfully developed for simultaneous determination of six catechins, three purine alkaloids, and gallic acid in green tea, oolong tea, and black tea. The analysis was carried out on a C18 column with the temperature of 35°C, and a gradient elution was adopted with a mobile phase composed by aqueous solution (containing 0.2% acetic acid, v/v) and acetonitrile. The optimal detection wavelength was 278 nm, of which both of the analytes and internal standard displayed the highest UV adsorption. Both the internal standard (ISTD) method and external standard (ESTD) method had wide linear range, good precision (coefficients of variation CV ≤ 3.65%), good intermediate precision (CV ≤ 5.82%), and good accuracy (recovery 92%–120%). Compared with the ESTD method, the ISTD method had better precision and lower test costs. 相似文献
587.
Yusuke HirasawaRyo Matsuya Khozirah ShaariNordin Hj Lajis Nahoko UchiyamaYukihiro Goda Hiroshi Morita 《Tetrahedron letters》2012,53(31):3971-3973
Novel C16N2-type Lycopodium alkaloids consisting of a decahydroquinoline with an aminohexyl side chain, lycobelines A-C (1-3), were isolated from the club moss of Huperzia goebelii, and their structures and relative stereochemistry were elucidated on the basis of spectroscopic data and chemical correlations. 相似文献
588.
589.
590.
A new purine nucleoside coupled with an amino acid derivative,N~2-(1-methoxycarbonylethyl)guanosine 1,along withβ-carboline and russulaceramide was isolated from the fruiting bodies of Amanita exitialis,a newly described poisonous mushroom. Its structure was elucidated by spectroscopic methods.This is the first report of naturally occurring nucleosides in which anα-amino acid derivative is bonded through itsα-amino nitrogen to a nucleobase aglycone by a C-N bond.The new compound was found to be toxic in ... 相似文献