title: Combining HPLC-PDA-MS-SPE-NMR with circular dichroism for complete natural product characterization in crude extracts: levorotatory gossypol in Thespesia danis.
abstract: Despite recent demonstration of the power of HPLC-PDA-MS-SPE-NMR (high-performance liquid chromatography-photodiode-array detection-mass spectrometry-solid-phase extraction-nuclear magnetic resonance) in structure determination of natural products directly from minute amounts of crude extracts, this technique leaves chirality of the compounds uncharacterized. In this work we demonstrate that postcolumn SPE is a useful method of analyte concentration and accumulation not only for NMR but also for CD (circular dichroism) spectroscopy. Thus, use of HPLC-PDA-MS-SPE-NMR in combination with CD allowed rapid detection of ( R)-(-)-gossypol [( R)- 1] in Thespesia danis, providing a very rare example of the predominance of the levorotatory enantiomer of gossypol. Enantioselectivity of the in vitro antiplasmodial activity of gossypol was also demonstrated; the IC50 value of ( R)- 1 was 4.5 +/- 0.2 microM, with the eudismic ratio of about 2.5. No gossypol was detected in Gossypioides kirkii.
authors.affiliation: Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
authors.forename: Kennett
authors.initials: K
authors.lastname: Sprogøe
authors.forename: Dan
authors.initials: D
authors.lastname: Staek
authors.forename: Hanne L
authors.initials: HL
authors.lastname: Ziegler
authors.forename: Thomas Høgh
authors.initials: TH
authors.lastname: Jensen
authors.forename: Søren B
authors.initials: SB
authors.lastname: Holm-Møller
authors.forename: Jerzy W
authors.initials: JW
authors.lastname: Jaroszewski
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000032:analysis* / Q000737:chemistry / Q000494:pharmacology; D001688:Biological Products / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006072:Gossypol / Q000032:analysis* / Q000737:chemistry / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D007630:Kenya; D019660:Malvaceae / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods*; D015394:Molecular Structure; D010946:Plants, Medicinal / Q000737:chemistry*; D010963:Plasmodium falciparum / Q000187:drug effects; D013237:Stereoisomerism
chemical_list: D000962:Antimalarials; D001688:Biological Products; D006072:Gossypol