Growth inhibitory indole acetic acid polyacetylenic ester from Japanese ivy (Hedera rhombea Bean)

Polyacetylenes 1 and 2 were isolated from extracts of Japanese ivy (Hedera rhombea Bean) flower buds, with their chemical structures established on the basis of extensive 1D and 2D NMR and MS analyses. The absolute configurations of compounds 1 and 2 were determined by both chemical means, and by using the modified Mosher's method. Compound 1 is the first polyacetylene having an ester linkage between falcarindiol (3) and indole-3-acetic acid (IAA) moieties and 2 also had an unique substructure containing a conjugated diene adjacent to a hydroxy group. Polyacetylenes 1, 2, and 3 were also subjected to assessment of growth inhibition against the shoot and root growth of the monocotyledon plants, rice and perennial ryegrass, as well as the dicotyledons, cockscomb, lettuce, cress, and fenugreek. The most bioactive compound appeared to be compound 1, while 2 showed no activity. Compound 1 selectively showed growth inhibitory activity against dicotyledons.