Studies on Panax Acetylenes: Absolute Structure of a New Panax Acetylene, and Inhibitory Effects of Related Acetylenes on the Growth of L-1210 Cells

A new Panax acetylene, 3-oxo-PQ-1 (1), was isolated from Panax quinquefolium. The absolute configurations of 3-oxo-PQ-1 (1) and PQ-1 (2) were determined to be (9R,10R) and (3R,9R,10R), respectively, by synthesizing 1 and 2 starting from D-(−)-diethyl tartrate, and by synthesizing their stereoisomers from L-(+)-diethyl tartrate. The growth inhibitory effects of Panax acetylenes (1—8) and their stereoisomers against leukemia cells were tested. Unnatural acetylenes having the (3S)-configuration (2, 5, 6, 7, 8; IC50=0.01—0.1 μg/ml) were found to be approximately ten times more potent than natural acetylenes (IC50=0.1—1.0 μg/ml) with the (3R)-configuration. Potency differences due to the configuration at C-9 and C-10 were unrelated to this stereochemistry. The C14-polyacetylenes, PQ-8 (4) and its isomer (IC50=1.0—10.0 μg/ml), were found to exhibit weaker cytotoxicity than the C17-polyacetylenes.