Bioactive galloyl flavans from the stems of Helixanthera parasitica.

Three new flavans, (2S)-7-O-galloyl-5,3',4'-trihydroxyflavan (1), (2S)-7,3'-O-digalloyl-5,4'-dihydroxyflavan (2), and (2S)-7,4'-O-digalloyl-5,3'-dihydroxyflavan (3), together with four known compounds, (2S)-5,7,3',4'-tetrahydroxyflavan (4), (-)-epicatechin (5), (-)-syringaresinol (6), and methyl gallate (7) have been isolated from the EtOAc extract of the stems of Helixanthera parasitica. Compounds 2 and 3 were obtained as a mixture of positional isomers. The structures of the isolated compounds were established using extensive spectroscopic data. Compound 1 and the mixture of 2 and 3 exhibited significant antimalarial activity against Plasmodium falciparum, with IC₅₀ values of 0.59 and 1.38 μM, respectively. In addition, flavans 1-3 showed cytotoxicity against KB, MCF-7, and NCI-H187 cancer cell lines, with IC₅₀ values in the range of 11.1-30.0 μM.