Iridoid Derivatives with Cytotoxic Activity from Pedicularis uliginosa Bunge

Three new iridoids, rel‐ (4a R ,7 S ,7a S )‐7‐hydroxy‐7‐methyl‐1,4a,5,6,7,7a‐hexahydrocyclopenta[ c ]pyran‐4‐carbaldehyde ( 1 ), 1‐methoxy‐7‐methyl‐1,3,5,6‐tetrahydrocyclopenta[ c ]pyran‐4‐carbaldehyde ( 2 ), and rel‐ (1 R ,4 S ,4a S ,7 R ,7a R )‐7‐methylhexahydro‐1,4‐(epoxymethano)cyclopenta[ c ]pyran‐3(1 H )‐one ( 3 ), together with seven known analogues, were isolated from the 95 % EtOH extract of the whole plants of Pedicularis uliginosa Bunge . Their structures were elucidated via extensive NMR spectroscopy and mass spectral data. In terms of inhibitory effects on human tumor cells, compounds 1 , 2 , 6 , 7 , and 8 exhibited better inhibitory activities against ACHN cells than the positive control (vinblastine).