MONOTERPENE DIMERS FROM LISIANTHIUS-SEEMANNII

A new acylated dimeric secoiridoid glycoside, seemannoside A (2), has been isolated from the aerial parts of Lisianthius seemannii (GRISEB) O. KUNTZE (Gentianaceae). The structure was established by spectroscop ic analysis (UV, MS,H-1- and C-13-NMR, and 2D-NMR experiments) and che mical reactions as (E)-4'-O-(p-coumaroyl)lisianthioside. The structure of the (Z)-isomer (seemannoside B, 3), also present in the plant, was confirmed by LC/UV/H-1-NMR analysis. The active principle, 6, respons ible for the antifungal activity of the apolar extract against Cladosp orium cucumerinum, has been isolated. Its structure has been establish ed by NMR spectroscopy and X-ray crystallographic analysis as a rare t ype of aglycone monoterpene dimer.