Cytotoxic anthraquinone dimers from Melandrium firmum

Two new anthraquinone dimers, melrubiellin A (1) and melrubiellin B (2), were isolated from the aerial part of Melandrium firmum Rohrbach, along with seven known compounds (3–9). The structures of these compounds were elucidated by spectral analyses, including 1D and 2D NMR (COSY, HMQC, HMBC and NOESY) experiments. Compound 1 and 2 exhibited significant cytotoxicity towards HeLa, NCI-H460, Hep G2, Hep 3B and MKN-28 cell lines with IC50 values ranging from 5.26 to 81.16 μM.