Quality evaluation of Radix Stemonae through simultaneous quantification of bioactive alkaloids by high-performance liquid chromatography coupled with diode array and evaporative light scattering detectors

A high-performance liquid chromatography coupled with diode array detection and evaporative light scattering detection (HPLC-DAD-ELSD) method was developed to simultaneously quantify six major bioactive alkaloids belonging to different structure types in Radix Stemonae, Bai-Bu in Chinese, a traditionally used antitussive and insecticidal medicinal material in China and other countries of Southeast Asia. Diode array detector (DAD) with the wavelengths at 307 and 260 nm was used to monitor the conjugated system of protostemonine (2) and maistemonine (4), respectively, whereas evaporative light scattering detector (ELSD) was employed to detect croomine (1), stemoninine (3), neotuberostemonine (5) and tuberostemonine (6), the other four analytes with no or poor chromophores. The assay was validated to be sensitive, precise and accurate, with a detection limit of 3.64-0.04 microg/mL depending on the individual analytes. The overall intra- and inter-day variations were less than 9.3%, and the overall recoveries higher than 91.2%, respectively. The correlation coefficients of the calibration curves were better than 0.996 for all analytes. The newly established method was successfully utilized to determine six major components in the genuine sources of Radix Stemonae: Stemona japonica, S. sessilifolia and S. tuberosa. Significant variations of contents of these components were demonstrated in samples of these three species. This simple, rapid, low-cost and reliable method is suitable for the routine quality control of herbal medicines containing bioactive components with different structure types such as Radix Stemonae.     

Corrected Structure of Aglalactone Isolated from Aglaia elaeagnoidea (Meliaceae)

 The structure of aglalactone, a dihydrobenzofuranone from Aglaia elaeagnoidea, was revised on the basis of 2D NMR data and lanthanide induced shifts (LIS).     

Quantum and Classical Radiation Reaction from Lightfront QED

We examine dynamical radiation reaction in lightfront QED. We take the classical limit and compare with predictions from various classical equations of motion.     

Complete 1H and 13C NMR data assignment of new constituents from Severinia buxifolia

Phytochemical analysis of different organs of the rutaceaeous plant Severinia buxifolia led to the isolation of a new limonoid, a new acridone alkaloid, and a new flavone. Structure elucidation and signal assignment were achieved by the extensive use of 1D and 2D NMR experiments (selective 1D NOE, COSY, NOESY, HSQC, HMBC). Copyright © 2009 John Wiley & Sons, Ltd.     

Case studies of CSEARCH supported structure elucidation strategies: lupeol and a new germacrane derivative

The NMR based structure elucidation of secondary natural products can be supported by the CSEARCH database system. In the case of the triterpene lupeol the correct identification was performed without further experiments. The structure proposal for the new germacrane derivate hydroxygermacrene-D was proven by isomer generation and subsequent ranking of the eight isomers obtained by weighted spectrum estimation.     

Naturally occurring sesquiterpene-coumarin ethers,VI. New sesquiterpene-isofraxidin ethers fromAchillea depressa

The roots ofAchillea depressa afforded in addition to known sesquiterpene-isofraxidine ethers three new derivatives: the bicyclic drimenol derived albartol and the monocyclic derivatives deparnol and acetyldeparnol. The compounds were characterized by¹H-NMR, MS, UV, IR, and CD data.Herrn Prof. Dr.U. Schmidt mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Anisotropic water diffusion in macroscopically oriented lipid bilayers studied by pulsed magnetic field gradient NMR

The anisotropy, D(parallel)/D( perpendicular ), of water diffusion in fully hydrated bilayers of dimyristoylphosphatidylcholine at 29 degrees C has been measured by pulsed magnetic field gradient (pfg) NMR. By using NMR imaging hardware to produce magnetic field gradients in an arbitrary direction with respect to a stack of macroscopically aligned lipid bilayers, translational diffusion of water was measured as a function of the angle between the direction of the magnetic field gradient and the normal of the lipid membrane. The observed diffusion coefficient is found to depend strongly on this angle. The anisotropy cannot be accurately determined due to the very small value of D( perpendicular ), but a lower limit of about 70 can be estimated from the observed diffusion coefficients. The results are discussed in terms of the relatively low permeability of water across the lipid bilayer, instrumental limitations, and/or possible defects in the lamellae.