Application of high-performance liquid chromatography–nuclear magnetic resonance coupling to the identification of limonoids from mahogany tree (Switenia macrophylla, Meliaceae) by stopped-flow 1D and 2D NMR spectroscopy

Separation and characterization of limonoids from Switenia macrophylla (Meliaceae) by HPLC–NMR technique has been described. Analyses were carried out using reversed-phase gradient HPLC elution coupled to NMR (600 MHz) spectrometer in stopped-flow mode. Separated peaks were collected into an interface unit prior to NMR measurements, which were performed with suppression of solvent signals by shaped pulses sequences. Structure elucidation of the limonoids was attained by data obtained from 1H NMR, TOCSY, gHSQC and gHMBC spectra without conventional isolation that is usually applied in natural products studies.