Isolation, structure elucidation, synthesis and cytotoxic activity of polyacetylenes and polyenes from Echinacea pallida

This study focuses on presenting an overview of recent results
on the cytotoxic activity of polyacetylenes and polyenes
isolated from Echinacea pallida. In a search for biologically
active compounds from plants of the genus Echinacea, the
lipophilic extract from E. pallida roots was characterized by a
higher cytotoxic activity if compared with the other tested
species. A subsequent bioassay-guided fractionation allowed
the isolation and structure elucidation of ten polyacetylenes and
polyenes from E. pallida roots. The isolated secondary
metabolites were tested for their cytotoxic activity on selected
human cancer cell lines and (8Z,13Z)-pentadeca-8,13-dien-11-yn-2-one was the most active constituent, particularly on the
colonic COLO320 cancer cells (IC50 = 2.3 ± 0.3 μM) and
breast carcinoma MCF-7 cancer cells (IC50 = 2.5 ± 0.7 μM).
Arrest of cell cycle in the G1 phase and induction of apoptosis
were found to be involved in its mechanism of action. Due to
the difficult purification of this compound from the plant
material, its first total synthesis was also described. A HPLC
stability study of this natural product finally indicated that its
cytotoxic activity can be mainly attributed to the genuine, not
oxidized, molecule. These results indicated that polyacetylenes
and polyenes from E. pallida are effective in inhibiting cancer
cell proliferation and incorporation of enriched fractions of
these compounds in the diet may be useful for cancer
prevention. The most active compound represents also an
interesting lead structure for the development of new
antiproliferative agents.