Abstract
Five new flavones possessing a fully substituted A-ring with C-6 and C-8 methyl groups,
bougainvinones I – M (1–5), along with three known congeners, 2′-hydroxydemethoxymatteucinol (6), 5,7,3′,4′-tetrahydroxy-3-methoxy-6,8-dimethylflavone (7) and 5,7,4′-trihydroxy-3-methoxy-6,8-dimethylflavone (8), were isolated from the EtOAc extract of the stem bark of Bougainvillea spectabilis. Their structures were established by means of spectroscopic data (ultraviolet, infrared,
high-resolution electrospray ionization mass spectrometry, and one-dimensional and
two-dimensional nuclear magnetic resonance) and single-crystal X-ray crystallographic
analysis. The in vitro cytotoxicity of all isolated compounds against five cancer cell lines (KB, HeLa S-3,
MCF-7, HT-29, and HepG2) was evaluated. Compound 5 showed promising cytotoxic activity against the KB and HeLa S-3 cell lines, with
IC50 values of 7.44 and 6.68 µM. The other compounds exhibited moderate cytotoxicity against
the KB cell line.
Key words
Bougainvillea spectabilis
- flavones - bougainvinone - cytotoxicity - Nyctaginaceae