Corrected Structure of Aglalactone Isolated from Aglaia elaeagnoidea (Meliaceae)

Summary.  The structure of aglalactone, a dihydrobenzofuranone from Aglaia elaeagnoidea, was revised on the basis of 2D NMR data and lanthanide induced shifts (LIS). Received June 29, 2000. Accepted July 11, 2000     

Samarium(II) Iodide Promoted Tandem Reductive Fragmentation and Aldol Reaction

Summary.  We report a new reductive fragmentation/aldol tandem reaction in a 1,4-diketone induced by samarium(II) iodide. Due to the particular stereoelectronic situation in the molecule, an alternative pathway was avoided despite the fact that it would have greatly reduced the strain in the tricyclic molecule. Received February 23, 2001. Accepted March 7, 2001     

Approximate theoretical determination of molecular static polarizabilities

Molecular polarizabilities are computed using ab initio SCF wave functions and second-order perturbation theory with special attention given to the use of a shifted denominator. Rather small basis sets are used, in order to obtain reasonable values at a reduced cost. Results are presented for H₂, CO, H₂O, C₂H₄, OCS, C₆H₆, Cl₂, Br₂, I₂.     

Combination of a new sample preparation strategy with an accelerated high-performance liquid chromatography assay with photodiode array and mass spectrometric detection for the determination of destruxins from Metarhizium anisopliae culture broth

A method is presented allowing the qualitative and quantitative analysis of destruxins (dtxs) in fungal culture broth. Sample preparation was carried out by ultrafiltration over a commercially available acetylated cellulose (CTA) membrane with a Mr 10000 cut-off. The developed high-performance liquid chromatography assay with diode array detection (HPLC-DAD) cuts down the analysis time by 50% compared to most of the currently applied methods (retention times: dtx A = 8.3 min, dtx B = 8.9 min, dtx E= 7.5 min) and enables dtx detection down to sub-ppm range (limits of detection: dtx A = 0.19 mg/l, dtx B = 0.41 mg/l, dtx E = 0.10 mg/l). Stability of dtx E in filtrated culture broth was found to be much lower than anticipated (half-life time = 64.5 +/- 1.7 h). Thus, the detoxification of this metabolite is an abiotic process. Coupling of the HPLC-DAD system to an ion trap mass spectrometer with an electrospray ionization source operating in the positive mode allowed identification of most dtxs encountered by utilizing multiple stage MS-MS experiments and retention time rules.     

Towards eco‐friendly secondary plant metabolite quantitation: Ultra high performance supercritical fluid chromatography applied to common vervain (Verbena officinalis L.)

This report presents the first ultra high performance supercritical fluid chromatography diode array detector based assay for simultaneous determination of iridoid glucosides, flavonoid glucuronides, and phenylpropanoid glycosides in Verbena officinalis (Verbenaceae) extracts. Separation of the key metabolites was achieved in less than 7 min on an Acquity UPC² Torus Diol column using a mobile phase gradient comprising subcritical carbon dioxide and methanol with 0.15% phosphoric acid. Method validation for seven selected marker compounds (hastatoside, verbenalin, apigenin‐7‐O‐glucuronide, luteolin‐7‐O‐glucuronide, apigenin‐7‐O‐diglucuronide, verbascoside, and luteolin‐7‐O‐diglucuronide) confirmed the assay to be sensitive, linear, precise, and accurate. Head‐to‐head comparison to an ultra high performance liquid chromatography comparator assay did prove the high orthogonality of the methods. Quantitative result equivalence was evaluated by Passing‐Bablok‐correlation and Bland‐Altman‐plot analysis. This cross‐validation revealed, that one of the investigated marker compound peaks was contaminated in the ultra high performance liquid chromatography assay by a structurally related congener. Taken together, it was proven that the ultra high performance supercritical fluid chromatography instrument setup with its orthogonal selectivity is a true alternative to conventional reversed phase liquid chromatography in quantitative secondary metabolite analysis. For regulatory purposes, assay cross‐validation with highly orthogonal methods seems a viable approach to avoid analyte overestimation due to coeluting, analytically indistinguishable contaminants.     

Glycodendriproteins: a synthetic glycoprotein mimic enzyme with branched sugar-display potently inhibits bacterial aggregation

The continuing ability of bacteria to resist current antibiotic treatments highlights the need for alternative strategies for inhibiting their pathogenicity. Bacterial attachment is a major factor in infectivity and virulence. This key binding phase of bacteria to any potential host is mediated by adhesin proteins and so these present an attractive therapeutic target for antiinfective blocking strategies. However, the natural ligands to adhesins are large, typically complex molecules that are difficult to mimic with small molecules. We describe here a method that creates precise synthetic mimics of glycoproteins that are designed to bind adhesins. By using protein-degrading enzymes as the basis for these mimics we have created large-molecule protein ligands that inhibit aggregation of pathogenic bacteria at levels greater than a million-fold higher than small-molecule inhibitors of adhesins.