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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
Author(s) -
Bieri Stefan,
Varesio Emmanuel,
Veuthey JeanLuc,
Muñoz Orlando,
Tseng LiHong,
Braumann Ulrich,
Spraul Manfred,
Christen Philippe
Publication year - 2006
Publication title -
phytochemical analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 72
eISSN - 1099-1565
pISSN - 0958-0344
DOI - 10.1002/pca.889
Subject(s) - chemistry , tropane , chromatography , high performance liquid chromatography , organic chemistry
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, 3 α ‐senecioyloxy‐7 β ‐hydroxytropane, 3 α ‐hydroxy‐7 β ‐angeloyloxytropane, 3 α ‐hydroxy‐7 β ‐tigloyloxytropane and 3 α ‐hydroxy‐7 β ‐senecioyloxytropane, were unambiguously determined by combining NMR assignments with MS data. Copyright © 2005 John Wiley & Sons, Ltd.