Cytotoxic Iridoid Glycosides from the Aerial Parts of Paederia foetida

Two previously undescribed iridoid glycosides, 6′-O-trans-caffeoyl-(4S,6R)-3,4-dihydro-3α- methylthioasperulosid (1) and 6′-O-trans-feruloyl-(4S,6R)-3,4-dihydro-2′-O-3α-paederosid (2), were isolated from the 90% EtOH extract of the aerial part of Paederia foetida L. The structures of the new compounds were elucidated by spectral methods such as 1D and 2D (¹H–¹H COSY, HMQC, and HMBC) NMR spectroscopy, HR-ESI-MS, as well as ECD data. The isolated compounds were tested in vitro for cytotoxic activity against five tumor cell lines. These results revealed that 2 exhibited some cytotoxicities against all the tested tumor cell lines with IC₅₀ value less than 20.0 μM and provided a scientific basis for further processing and utilization of P. foetida.