The sesquiterpene lactone chemistry of Helianthus sect. Ciliares (asteraceae: heliantheae)

Abstract

A total of 40 HPLC peaks tentatively considered to be sesquiterpene lactones was detected from a survey of the six species of Helianthus sect. Ciliares, with individual species exhibiting between 14 and 20 compounds. Comparison with available reference compounds allowed assignment of structures to 26 of the compounds. Although the chemistry of the section is not distinctive within Helianthus, the two series of the section are well distinguished by sesquiterpene lactone features, with series Ciliares characterized by compounds of the budlein type (1-oxo-2(3)-en-3,10-furanoheliangolides) whereas series Pumili lacks budlein type compounds and exhibits several distinctive compounds of the eupasserin type (2-alpha-hydroxy-,trans, transgermacra-1(10),4(5)-dien-12,6-olides). The sesquiterpene lactone profile of the polyploid, H. ciliaris, exhibits similar numbers of shared compounds to the additive patterns of H. arizonensis combined with either H. laciniatus or Hgracilentus, but the lack of major compounds from the latter suggests that H. laciniatus is more likely to be involved in the ancestry of H. ciliaris together with H. arizonensis.