Bougainvinones A-H, Peltogynoids from the Stem Bark of Purple Bougainvillea spectabilis and Their Cytotoxic Activity

Eight new peltogynoids, named bougainvinones A-H (1-8), were obtained from the stem bark of Bougainvillea spectabilis. Their structures were elucidated by means of physical data (1D and 2D NMR, HRESIMS) and single-crystal X-ray crystallographic analyses. The peltogynoids, a rare type of modified flavonoids, are reported for the first time from this species of the genus Bougainvillea. All isolated compounds were evaluated for their cytotoxic effects against five cancer cell lines including KB, Hela S-3, HT-29, MCF-7, and HepG2. Among them, compound 7 showed cytotoxicity against five cancer cell lines with IC50 values in the 7.4-9.7 mu M range, and compounds 2 and 3 exhibited cytotoxicity against the KB cell line with IC50 values of 6.6 and 9.0 mu M.