Diastereomeric identification of neolignan rhamnosides from Trochodendron aralioides leaves by LC-SPE-NMR and circular dichroism

Trochodendron aralioides is an old-existing relic plant with limited availability and only a few identified compounds. Accumulative analysis on the methanolic extract from its leaf part by LC-SPE-NMR resulted in the identification of seven new compounds, including three neolignan α-rhamnosides [(7R,8S)-dihydrodehydrodiconiferyl alcohol- 9-O-α-rhamnopyranoside (2) and 9′-O-α-rhamnopyranoside (3), and (7S,8R)-dehydrodiconiferyl alcohol-9′-O-α-rhamnopyranoside (4)], two isomeric oxyneolignan α-rhamnosides [(7R,8S)- (5) and (7R,8R)-icariside E8 (6)), and (7R,8S)- (10) and (7R,8R)-icariside E9 (11)], and two isomeric acylated fructofuranosyl mevalonolactones (13, 14), along with five known compounds (1, 7–9 and 12). The absolute configuration of the C-7 and C-8 positions for the new compounds 2–6 and 10–11 was assigned by comparison of the reported ECD spectra. Compounds 2, 3, 4, and 6 were further isolated by semi-preparative column chromatography for structure confirmation by 2D NMR spectroscopic analysis.