Separation/preconcentration and determination of vanadium with dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) and electrothermal atomic absorption spectrometry

A novel dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) for separation/preconcentration of ultra trace amount of vanadium and its determination with the electrothermal atomic absorption spectrometry (ETAAS) was developed. The DLLME-SFO behavior of vanadium (V) using N-benzoyl-N-phenylhydroxylamine (BPHA) as complexing agent was systematically investigated. The factors influencing the complex formation and extraction by DLLME-SFO method were optimized. Under the optimized conditions: 100 μL, 200 μL and 25 mL of extraction solvent (1-undecanol), disperser solvent (acetone) and sample volume, respectively, an enrichment factor of 184, a detection limit (based on 3S_b/m) of 7 ng L⁻¹ and a relative standard deviation of 4.6% (at 500 ng L⁻¹) were obtained. The calibration graph using the preconcentration system for vanadium was linear from 20 to 1000 ng L⁻¹ with a correlation coefficient of 0.9996. The method was successfully applied for the determination of vanadium in water and parsley.     

New Guaipyridine Sesquiterpene Alkaloids from Artemisia rupestris L.

Three new guaipyridine sesquiterpene alkaloids, rupestine A, B, C ( 1 – 3 , resp.), and the new nor‐sesquiterpne alkaloid rupestine D ( 4 ) were obtained from the flowers of Artemisia rupestris L. Their structures were elucidated on the basis of sepectroscopic data and by comparison with those of the related compounds reported in the literature. In addition, the absolute configurations of 2 and 4 were determined by single‐crystal X‐ray diffraction analyses.     

Vernodalidimers A and B, novel orthoester elemanolide dimers from seeds of Vernonia anthelmintica

Two novel elemanolide dimers, vernodalidimers A (1) and B (2), possessing a rare tricyclic ortho ester moiety, were isolated from the seeds of Vernonia anthelmintica. Their structures were elucidated by 1D and 2D NMR data and CD spectra. Vernodalidimers A (1) and B (2) exhibited potent cell growth inhibitory activity against HL-60 cells (IC₅₀ 0.72 and 0.47 μM, respectively).     

Novel Designs for Centrifugal Countercurrent chromatography: V. Comparative Studies on Performance of Various Column Configurations

The conventional toroidal coil in centrifugal countercurrent chromatography has a low level of stationary phase retention, since a half of each helical turn is entirely occupied by the mobile phase. In order to cope with this problem, several new column designs including zigzag, saw-tooth and figure-8 patterns have been introduced and their performance was compared in terms of retention of the stationary phase (Sf), peak resolution (Rs), theoretical plate number (N) and column pressures. Overall results of experiments indicate that the figure-8 column yields the highest Rs when the lower phase is used as the mobile phase. Since the column pressure of all these new columns are much lower than that in the traditional toroidal coil column, the separation efficiency can be improved using a long separation column without a risk of column damage by high back pressure.     

Pyrrole alkaloids from <Emphasis Type="Italic">Alhagi sparsifolia</Emphasis>

The novel pyrrole alkaloid alhagifoline A (1) together with the two known analogs pyrrolezanthine (2) and pyrrolezanthine-6-methyl ether (3) were isolated from the aerial part of Alhagi sparsifolia. Their structures were established based on spectral (HR-ESI-MS, ¹ H and ¹³C NMR, ¹ H–¹ H COSY, HSQC, HMBC) data. Compounds 2 and 3 were isolated from the genus Alhagi for the first time.     

Total Synthesis of (±)-Nocardione A and (±)-Nocardione B, Two Cdc25B Tyrosine Phosphatase Inhibitors

Quinones are biologically important compounds, especially because of their cytotoxic and pharmacological action. The antitumor activities of the quinones, including naphthoquinones1, were revealed more than two decades ago when the National Cancer Institute published a report in which 1500 synthetic and nature quinones were screened. Some natural naphthoquinones were under development for antitumor agents2. The protein tyrosine phosphatases (PTPase) and dual phosphatases (DSPase) are key…