First-time Isolation of Flavonoids and Cytotoxic Potential of the Amazonian Shrub Ptychopetalum olacoides Benth

: In the present study three flavonoids, 3- O -methylquercetin ( 1 ), 3,4'- O -dimethylquercetin ( 2 ) and 3,7- O -dimethylquercetin ( 3 ) were isolated and characterized for the first time from a methanol extract obtained from the species Ptychopetalum olacoides . The structures of compounds were identified by spectroscopic methods (1D-, 2D-NMR, MS and UV) and confirmed by comparison with the respective literature data. The cytotoxic effect of crude extract was evaluated in vitro against three human cancer cell lines. Results showed a mild cytotoxic activity (IC 50 = 45.16 µg/mL) against breast cancer (MCF-7), however crude extract did not exhibit any cytotoxic effect against normal cell human fibroblast (MRC-5).