Rapid screening of lignans from Phyllanthus myrtifolius and stilbenoids from Syagrus romanzoffiana by HPLC-SPE-NMR

Abstract

Application of on-line solid-phase extraction (SPE) as an interface between HPLC and NMR has gained great improvement in solving sensitivity problems and signal interferences by the eluents. Rapid analysis and characterisation by HPLC-SPE-NMR and LC/MS of the arylnaphthalene-type lignans present in Phyllanthus myrtifolius and the minor stilbenoids present in the polyphenol-rich fraction from the ethanol extract of the seeds of Syagrus romanzoffiana. Pretreatment of fractions by liquid-liquid partitioning, followed by Sephadex LH-20 fractionation, was found very useful to facilitate the focusing and analysis of the polyphenolic fraction. HPLC-DAD-SPE-NMR (400 MHz and 600 MHz) analysis was carried out using an Agilent 1100 liquid chromatography, followed by a Prospekt 2 automated solid-phase extraction unit, containing 96 HySphere-Resin GP cartridges (10 × 2 mm, 10-12 µm), which was connected to a 120 or 60 µL LC probe. Seven arylnaphthalene-type lignans from the chloroform-soluble fraction of P. myrtifolius and nine stilbenoids from a polyphenol-rich butanol-soluble fraction of the seeds of S. romanzoffiana were characterised. HPLC-SPE-NMR associated with HR-ESI/MS, which consumed only analytical amounts of partially purified mixtures, was demonstrated to be a good tool for rapid screening of both known and new natural products.