title: Direct (13)C NMR detection in HPLC hyphenation mode: analysis of Ganoderma lucidum terpenoids.
abstract: Solid phase extraction (SPE) was introduced as a crucial step in the HPLC-SPE-NMR technique to enable online analyte enrichment from which proton-detected NMR experiments on submicrogram amounts from complex mixtures were possible. However, the significance of direct-detected (13)C NMR experiments is indubitable in simplifying structural elucidations. In the current study, we demonstrated direct (13)C NMR detection of triterpenoids from a Ganoderma lucidum extract in hyphenation mode. The combined advantage of a cryogenically cooled probe, miniaturization, and multiple trapping enabled the first reported application of HPLC-SPE-NMR analysis using direct-detected (13)C NMR spectra. HPLC column loading, accumulative SPE trappings, and the effect of different elution solvents were evaluated and optimized. A column loading of approximately 600 μg of a prefractionated triterpenoid mixture, six trappings, and an acquisition time of 13 h resulted in spectra with adequate signal-to-noise ratios to detect all C-13 signals.
authors.affiliation: Department of Molecular Drug Research, Faculty of Pharmaceutical Sciences,  University of Copenhagen , Universitetsparken 2, DK-2100 Copenhagen, Denmark.
authors.forename: Sileshi G
authors.initials: SG
authors.lastname: Wubshet
authors.forename: Kenneth T
authors.initials: KT
authors.lastname: Johansen
authors.forename: Nils T
authors.initials: NT
authors.lastname: Nyberg
authors.forename: Jerzy W
authors.initials: JW
authors.lastname: Jaroszewski
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D020940:Reishi / Q000737:chemistry*; D052616:Solid Phase Extraction / Q000379:methods*; D013172:Spores, Fungal / Q000737:chemistry; D014315:Triterpenes / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D014315:Triterpenes