title: Identification of isomeric tropane alkaloids from Schizanthus grahamii by HPLC-NMR with loop storage and HPLC-UV-MS/SPE-NMR using a cryogenic flow probe.
abstract: Two fully automated HPLC-NMR methods are reported and compared for the structure elucidation of four isomeric tropane alkaloids from the stem-bark of an endemic Chilean plant, Schizanthus grahamii Gill. (Solanaceae). The first approach interfaced a conventional HPLC column to NMR by means of a loop storage unit. After elution with a mobile phase consisting of deuterated water and standard protonated organic solvents, the separated analytes were momentarily stored in a loop cassette and then transferred one-at-a-time to the NMR flow probe for measurements. The second strategy combined HPLC with parallel ion-trap MS detection and NMR spectroscopy using an integrated solid-phase extraction (SPE) unit for post-column analyte trapping. The SPE cartridges were dried under a gentle stream of nitrogen and analytes were sequentially eluted and directed to a cryogenically cooled flow-probe with an NMR-friendly solvent. The structures of the four isomeric alkaloids, 3alpha-senecioyloxy-7beta-hydroxytropane, 3alpha-hydroxy-7beta-angeloyloxytropane, 3alpha-hydroxy-7beta-tigloyloxytropane and 3alpha-hydroxy-7beta-senecioyloxytropane, were unambiguously determined by combining NMR assignments with MS data.
authors.affiliation: Laboratory of Pharmaceutical Analytical Chemistry, School of Pharmaceutical Sciences EPGL, University of Geneva, 20 Bd d'Yvoy, 1211 Geneva 4, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Bieri
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Varesio
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Veuthey
authors.forename: Orlando
authors.initials: O
authors.lastname: Muñoz
authors.forename: Li-Hong
authors.initials: LH
authors.lastname: Tseng
authors.forename: Ulrich
authors.initials: U
authors.lastname: Braumann
authors.forename: Manfred
authors.initials: M
authors.lastname: Spraul
authors.forename: Philippe
authors.initials: P
authors.lastname: Christen
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015394:Molecular Structure; D024301:Plant Bark / Q000737:chemistry; D018547:Plant Stems / Q000737:chemistry; D012680:Sensitivity and Specificity; D019657:Solanaceae / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D014326:Tropanes / Q000032:analysis* / Q000737:chemistry*
chemical_list: D014326:Tropanes