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.     

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…     

Triterpenoids and phenolics from the fruiting bodies of Inonotus hispidus and their activations of melanogenesis and tyrosinase

Two new 24-methyl lanostane triterpenoids,hispindic acids A and B(1 and 2),and a new phenolic compound,hispinine(7),along with nine known compounds(3-6,and 8-12),were isolated from the fruiting bodies of Inonotus hispidus.Their structures were elucidated based on the extensive analysis of spectroscopic data(NMR and HRMS).Hispindic acid A(1) possesses an unusual formyl group at C-30.Compounds 1,3-4,and 8 showed stronger activate abilities of melanogenesis and tyrosinase in B16 melanoma cells than those of positive control,8-methoxypsoralen,at 50 μmol/L     

Synthesis of a novel molecularly imprinted polymer based on functionalized multi-walled carbon nanotubes for selective extraction of sulfadiazine prior to spectrophotometric determination

A novel and efficient sulfadiazine imprinted polymer was synthesized via co-precipitation method and successfully grafted on magnetic multi-walled carbon nanotubes. The synthesized magnetic imprinted polymer was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction analysis, thermal analysis and applied as a sorbent for selective magnetic solid-phase extraction of sulfadiazine. The retained sulfadiazine was eluted by 150.0 µL methanol/acetic acid (6:4) solution and quantified by fiber optic linear array spectrophotometry via formation of a detectable azo dye. All parameters affecting the extraction of sulfadiazine were investigated and optimized. Under the optimized conditions, the method exhibited a linear dynamic range of 2.0–50.0 µg L^?1 with a detection limit of 0.56 µg L^?1 and enrichment factor of 300.0. The relative standard deviation at 30.0 µg L^?1 of sulfadiazine (N = 6) was 2.8 and 4.6% for intra-day and inter-day, respectively. The method was successfully applied to determine sulfadiazine in human urine, honey, milk and environmental water samples.     

Synthesis of Dialkyl 2‐(Alkylamino)‐4,9‐dihydro‐9‐oxocyclohepta[b]pyran‐3,4‐dicarboxylates

Dialkyl 2‐(alkylamino)‐4,9‐dihydro‐9‐oxocyclohepta[b]pyran‐3,4‐dicarboxylates are prepared in a one‐pot three‐component reaction of alkyl isocyanide, dialkyl acetylenedicarboxylate, and α‐tropolone (=2‐hydroxycyclohepta‐2,4,6‐trienone). The reaction proceeds smoothly at room temperature and under neutral conditions to afford tropolone derivatives in high yield.     

Optical properties of erbium-doped porous silicon waveguides

Planar and buried channel porous silicon waveguides (WG) were prepared from p⁺-type silicon substrate by a two-step anodization process. Erbium ions were incorporated into pores of the porous silicon layers by an electrochemical method using ErCl₃-saturated solution. Erbium concentration of around 10²⁰ at/cm³ was determined by energy-dispersive X-ray analysis performed on SEM cross-section. The luminescence properties of erbium ions in the IR range were determined and a luminescence time decay of 420 μs was measured. Optical losses were studied on these WG. The increased losses after doping were discussed.