Iridoid Derivatives from Pedicularis uliginosa Bunge and Their Cytotoxic Activity.

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