Quantitative major polyacetylenes of carrots (
falcarinol and
falcarindiol) and American ginseng roots (
falcarinol and
panaxydol) were isolated and tested in human intestinal epithelial cells of normal (FHs 74 Int.) and
cancer (Caco-2) origin. A hormesis effect was seen for all isolated polyacetylenes when added to Caco-2 cells in concentrations ranging from 1 ng/mL to 20 microg/mL. The relative inhibitory potency was
falcarinol >
panaxydol >
falcarindiol. No hormesis effect was observed when adding the polyacetylenes to FHs 74 Int. cells. Instead, an inhibitory growth response was observed above 1 microg/mL. The relative inhibitory potency was
panaxydol >
falcarinol >
falcarindiol. Maximal inhibition at 20 microg/mL corresponded to approximately 95% and 80% inhibition of cell proliferation in normal and
cancer cells, respectively. Combinations of
falcarinol and
falcarindiol added to normal and
cancer cells showed a synergistic response for the inhibition of cell growth. Furthermore, the oxidized form of
falcarinol, falcarinon, showed a significantly less growth inhibitory effect in intestinal cells of both normal and
cancer origin; hence, a
hydroxyl group at C-3 may be important for activity of
falcarinol-type polyacetylenes. Extracts of carrots, containing different amounts of
falcarinol,
falcarindiol, and
falcarindiol 3-acetate had significant inhibitory effects on both normal and
cancer cell proliferation. In
cancer cells, the extract containing the highest concentration of
falcarinol tended to have the highest growth inhibitory effect, in accordance with a higher potency of
falcarinol than
falcarindiol. The present study demonstrates that aliphatic C(17)-polyacetylenes are potential anticancer principles of carrots and related vegetables and that synergistic interaction between bioactive polyacetylenes may be important for their bioactivity.