Two new iridoid-sesquiterpene conjugates from Rehmannia glutinosa

Two new iridoid-sesquiterpene conjugates, rehmanniosides E (1) and F (2) along with eight known compounds, jiocaroteniside A1 (3), 6-O-(5′′-O-β-D-quinovopyranosyl)aeginetoylajugol (4), 6-O-vanilloylajugol (5), 6-O-(E)-caffeoylajugol (6), 6-O-trans-feruloylajugol (7), 6-O-(4′′-O-α-L-rhamnopyranosyl)vanilloylajugol (8), rehmaionoside C (9), and jioglutoside B (10) were isolated from the roots of Rehmannia glutinosa (Gaertn.) DC. Their chemical structures were elucidated on the basis of extensive spectroscopic methods, including 1D and 2D NMR, HR ESI MS, and CD spectra.