71
In Table 4, samples investigated by research teams other than our own groups
are listed. Samples 26–28, 32, 34, and 36 can be grouped to the C type [12, 74, 118,
152, 168, 171–173]. Cacalol (316) and its methyl ether 317 and farfugin B (335)
and its methyl ether 336 were isolated from samples 26 and 27 [169, 171]. Sample
26 also produced cacalolide (547) and epicacalolide (548), which are derived from
cacalol (316), and virgauronin (339) in being related to farfugin B (335).
Compounds 551 and 552 in samples 28 and 32 are interesting [118, 173], because
they have an enol- type triene moiety similar to cacalol (316). Sample 28 produced
pseudoguaiane- type sesquiterpenoids 784 and 785, which were the only examples
of chemical constituents of L. virgaurea. Previously, the dimeric compounds
virgaurin A (615) (vide supra) and adenostin A (570) were isolated from this
species [173]. Compounds 157 and 159 are of the 8,9-seco-cacalol type (sample
32), and the presence of both these isomers indicated that they may be formed
Fig. 9 Secoeremophilanes
Chemical Constituents of Ligularia Species (Asteraceae) and Their Diversity…