• Isolation of isomangiferin from honeybush (Cyclopia subternata) using high-speed counter-current chromatography and high-performance liquid chromatography.

      de Beer, Dalene; Jerz, Gerold; Joubert, Elizabeth; Wray, Victor; Winterhalter, Peter; ARC Infruitec-Nietvoorbij, Stellenbosch, South Africa. dbeerd@arc.agric.za (2009-05-08)
      Isomangiferin was isolated from Cyclopia subternata using a multi-step process including extraction, liquid-liquid partitioning, high-speed counter-current chromatography (HSCCC) and semi-preparative reversed-phase high-performance liquid chromatography (HPLC). Enrichment of phenolic compounds in a methanol extract of C. subternata leaves was conducted using liquid-liquid partitioning with ethyl acetate-methanol-water (1:1:2, v/v). The enriched fraction was further fractionated using HSCCC with a ternary solvent system consisting of tert-butyl methyl ether-n-butanol-acetonitrile-water (3:1:1:5, v/v). Isomangiferin was isolated by semi-preparative reversed-phase HPLC from a fraction containing mostly mangiferin and isomangiferin. The chemical structure of isomangiferin was confirmed by LC-high-resolution electrospray ionization MS, as well as one- and two-dimensional NMR spectroscopy.
    • Production and modification of bioactive surfactants

      LANGER, Olaf; Palme, Olov; Wray, Victor; Tokuda, Harukuni; Lang, Sigmund (2007-09-20)
    • Structural characterization of 13(2)-hydroxy-(13(2)-S)-phaeophytin-a from leaves and stems of Amaranthus tricolor isolated by high-speed countercurrent chromatography

      Jerz, Gerold; Arrey, Tabiwang N.; Wray, Victor; Du, Qizhen; Winterhalter, Peter; Helmholtz Zentrum für Infektionsforschung GmbH (Elsevier Science, 2007)
    • Structural characterization of the exopolysaccharide PS-EDIV from Sphingomonas pituitosa strain DSM 13101.

      Schultheis, Ellen; Dreger, Michael A; Nimtz, Manfred; Wray, Victor; Hempel, Dietmar C; Nörtemann, Bernd; Institute of Biochemical Engineering, Technical University of Braunschweig, Braunschweig, Germany. (2008-04)
      Members of the bacterial genus Sphingomonas are known to produce highly viscous polysaccharides in solution. The exopolysaccharide PS-EDIV was produced by Sphingomonas pituitosa strain DSM 13101, purified using centrifugation, and precipitation and its structure was elucidated by 1D and 2D NMR techniques and chemical microderivatization combined with various mass spectrometric techniques. The following repeating unit of the polysaccharide could be identified: [formula: see text]. In addition, the polysaccharide also contains acetyl and glyceryl groups whose exact positions were not determined. PS-EDIV is similar in structure to a known exopolysaccharide but differs in being the first bacterial polysaccharide in which two different glucuronic acids are combined. It caused a high viscosity of the culture broth after cultivation for 48 h, although a gelation was not observed.