title: On-line identification of unstable iridoids from Jamesbrittenia fodina by HPLC-MS and HPLC-NMR.
abstract: HPLC-UV-MS analysis of the methanol extract of Jamesbrittenia fodina (Wild) O. M. Hilliard (Scrophulariaceae) revealed the presence of different iridoid cinnamic esters; however, isolation of these constituents was prevented by instability problems. HPLC-UV-MS and HPLC-NMR analysis of the mixtures obtained after a tentative isolation indicated that, in the first instance, instability was due to a light-induced cis/trans isomerisation of the cinnamic moieties. Further investigation of related compounds showed an additional instability problem linked to other chemical transformations. A detailed HPLC-NMR-MS study of these fractions demonstrated that the modifications occurred on the rhamnose moiety of these iridoids. It could be concluded that the second type of instability was attributable to transesterification of the cinnamic moiety on the rhamnose unit. The recording of stop-flow HPLC-NMR spectra for specific HPLC peaks permitted the direct monitoring of these transformations. Based on these on-line data, six new unstable aucubin derivatives were efficiently characterised.
authors.affiliation: Laboratoire de Pharmacognosie et Phytochimie, Ecole de Pharmacie Genève-Lausanne, Section des Sciences Pharmaceutiques, Université de Genève, Switzerland.
authors.forename: A L
authors.initials: AL
authors.lastname: Cogne
authors.forename: E F
authors.initials: EF
authors.lastname: Queiroz
authors.forename: A
authors.initials: A
authors.lastname: Marston
authors.forename: J L
authors.initials: JL
authors.lastname: Wolfender
authors.forename: S
authors.initials: S
authors.lastname: Mavi
authors.forename: K
authors.initials: K
authors.lastname: Hostettmann
mesh_terms: D002851:Chromatography, High Pressure Liquid; D039823:Iridoids / Q000032:analysis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D015394:Molecular Structure; D009862:Online Systems; D028083:Scrophulariaceae / Q000737:chemistry*
chemical_list: D039823:Iridoids