Two new 19-hydroxy bufadienolides with cytotoxic activity from the skins of <i>Bufo melanosticus</i>

Abstract

Two new 19-hydroxy bufadienolides, named bufohydrolide A (<b>1</b>) and bufohydrolide B (<b>2</b>), and four known analogs (<b>3-6</b>) were isolated from the aqueous extracts of the skins of <i>Bufo melanosticus</i>. Their structures were established by spectral data analyses, such as UV, IR, 1 D/2D NMR and mass spectra. Compounds <b>1-6</b> were evaluated for their cytotoxic activity against SMMC-7721, HT-29 and A549 cells. Noteworthily, all six isolates exhibited various levels of anti-proliferative activities with IC₅₀ values ranging from 0.02 ± 0.0002 to 25 ± 0.5 μM.