Phenolic glycosides with antimalarial activity from Grevillea "Poorinda Queen"

In search of new antimalarial compounds, three new phenolic glycosides, robustasides E (1), F (2), and G (3), in addition to the known compounds robustaside D (4) and quercetin-7-O-[α-l-rhamnopyranosyl(1→6)-β-d-galactopyranoside] (5), were identified during chemical investigations of the MeOH extract from the leaves and twigs of Grevillea "Poorinda Queen". The chemical structures of the new compounds were elucidated through 2D NMR spectroscopy, while the absolute configuration of the sugar was elucidated through chemical degradation and comparison with an authentic standard. Discussed in detail are the isolation and structure elucidation of 1-3, as well as the associated in vitro anitmalarial activities for 1-5. Also discussed are the in vivo anitmalarial and in vitro cytotoxic activities for 1, 3, and 4.