Enrichment of the anti‐tumor compound barbigerone along with a rotenoid derivative from Millettia pachycarpa Benth. was performed by a two‐step high‐speed counter‐current chromatography (HSCCC) separation process. In the first step, 155.8 mg of target fraction (Fra6) was obtained from 400 mg ethyl acetate extract of M. pachycarpa Benth. with an increase in barbigerone from 5.1 to 13% via HSCCC using a solvent system of n‐hexane–ethyl acetate–methanol–water (5:4:5:3, v/v) under normal phase head to tail elution. HSCCC was repeated to eliminate the major contaminant in this initial fraction 6. After a separation time of 65 min, 22.1 mg barbigerone of 87.7% purity was obtained from Fra6 with the ternary solvent system of n‐hexane–methanol–water (2:2:1, v/v) under normal phase elution. Finally, preparative HPLC was employed for the further isolation of barbigerone and the rotenoid derivative. The structures were confirmed by ESI‐MS, 1H NMR and 13C NMR. 相似文献
Recycling counter‐current chromatography (CCC) together with step‐gradient CCC and medium‐pressure liquid chromatography (MPLC) was employed to separate nine anthraquinone compounds from Cassia obtusifolia L. in this study. The results showed that recycling CCC is a powerful tool for compounds that are difficult to separate with common elution mode. CCC was the better option for crude material while MPLC had advantage for the final tuning. The combination of recycling CCC and MPLC could simplify the method exploring process in the separation process. The structures of these compounds were identified according to their mass spectra, by 1H‐NMR and compared with standard compounds. 相似文献
Water‐soluble polypeptides bearing 1‐alkylimidazolium (methyl or n‐butyl) and various counter‐anions (i.e., Cl−, I− or BF4−) are prepared by ring‐opening polymerization of γ‐4‐chloromethylbenzyl‐l‐glutamate‐based N‐carboxyanhydride ( 3 ), post‐polymerization of poly(γ‐4‐chloromethylbenzyl‐l‐glutamate) ( 4 ), and ion‐exchange reaction. Circular dichroism (CD) analysis reveals that the resulting polypeptides adopt an α‐helical conformation in water with a fractional helicity in the range of 30%–56% at 20 °C and exhibit good conformational stability against temperature variations. The polypeptides exhibit lower critical solution temperature (LCST)‐type or upper critical solution temperature (UCST)‐type transitions in organic solvents or in water. The UCST‐type transition temperature (Tpt) in water is independent on the molecular weight, yet it decreases upon addition of NaCl and increases upon addition of NaI or NaBF4, suggesting a mainly electrostatic interaction mechanism.
The elution-extrusion counter-current chromatography (EECCC) method was firstly developed by Berthod in 2003 and has been used in natural products separation in recent years. The advantages of this method have been well documented such as reducing the separation time and solvent consumption. In the EECCC method, the time point of the extrusion step is very important during the whole separation process as it directly affects the resolutions, separation time and solvent consumption. However, how to choose a suitable time point to perform the extrusion step without decreasing the resolution has not been studied yet. In the present study, a strategy for systematically calculating the time point for extrusion was developed in theory and five bioactive compounds from the extract of Dendrobium chrysototxum Lindl. were separated and compared using normal CCC and EECCC method. Our results demonstrated that the accurate time point to perform the extrusion could be calculated and reduced both separation time and solvent consumption without losing separation performance. Using this EECCC method, five bioactive compounds were separated and purified with high purity. The separation time and solvent consumption were decreased from 200 min to 100 min and 5-2.5L during the separation process while the resolutions were still acceptable. Finally, 63 mg, 48 mg, 97 mg, 162 mg and 43 mg of hydroxyl phenanthrenes and bibenzyls with the purity of 98.7%, 98.0%, 98.2%, 99.0% and 98.7%, respectively were isolated from 1.2 g crude extract of D. chrysototxum Lindl. initially purified by column chromatography in one step separation. The purities of compounds were determined by HPLC. Their structures were identified by electrospray ionization-mass spectrometry (ESI-MS) and NMR. 相似文献
ABSTRACT The 28?nm system-on-chip (SoC) was irradiated by 12?MeV electron at the China Institute of Atomic Energy (CIAE) for the first time. Soft errors in the on-chip memory (OCM), D-Cache, Register and BRAM blocks were investigated. The obtained device cross sections are almost in the range of 10?13 cm2 to 10?11 cm2 for the blocks. The results demonstrate that electron fluence per pulse and the corresponding prompt dose rates have no influence on the soft errors in 28?nm SoC. The discrepancy was analyzed between proton and electron inducing soft errors in D-Cache and BRAM blocks, too. The secondary electron is considered as the dominant reason for soft errors caused by 12?MeV electron in 28?nm SoC. 相似文献