Monoterpene dimers from Lisianthius seemannii

Article abstract of DOI:10.1002/hlca.19980810548

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 spectroscopic analysis (UV, MS, ¹H- and ¹³C-NMR, and 2D-NMR experiments) and chemical 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/¹H-NMR analysis. The active principle, 6, responsible for the antifungal activity of the apolar extract against Cladosporium cucumerinum, has been isolated. Its structure has been established by NMR spectroscopy and X-ray crystallographic analysis as a rare type of aglycone monoterpene dimer.