Cytotoxic chalcones of flavonoids from the leaves of Muntingia calabura

Two new dihydrochalcones, 2',4'-dihydroxy-3'-methoxydihydrochalcone, (-)-3'-methoxy-2,4',beta-trihydroxydihydrochalcone, a new flavanone, (2S)-(-)-5'-hydroxy-7,3',4'-trimethoxyflavanone, and a new flavonol derivative, muntingone, along with sixteen known compounds, were isolated from the leaves of Muntingia calabura. The structures of these new compounds were determined using spectral analyses including extensive 2D NMR data. Among the isolates, (2S)-5'-hydroxy-7,3',4'-trimethoxyflavanone, 4'-hydroxy-7-methoxyflavanone, 2',4'-dihydroxychalcone, and 2',4'-dihydroxy-3'-methoxychalcone exhibited cytotoxicity (IC50 values < 4 mu g/mL) against P-388 and/or HT-29 cell lines in vitro.