(+)- and (−)-Ecarlottones, Uncommon Chalconoids from Fissistigma latifolium with Pro-Apoptotic Activity

Four new compounds, (+)- and (−)-ecarlottone (1), (±)-fislatifolione (5), (±)-isofislatifolione (6), and (±)-fislatifolic acid (7), and the known desmethoxyyangonin (2), didymocarpin-A (3), and dehydrodidymocarpin-A (4) were isolated from the stem bark of Fissistigma latifolium, by means of bioassay-guided purification using an in vitro affinity displacement assay based on the modulation of Bcl-xL/Bak and Mcl-1/Bid interactions. The structures of the new compounds were elucidated by NMR spectroscopic data analysis, and the absolute configurations of compounds (+)-1 and (−)-1 were assigned by comparison of experimental and computed ECD spectra. (−)-Ecarlottone 1 exhibited a potent antagonistic activity on both protein–protein associations with Ki values of 4.8 μM for Bcl-xL/Bak and 2.4 μM for Mcl-1/Bid.