Marcanine G, a new cytotoxic 1-azaanthraquinone from the stem bark of <i>Goniothalamus marcanii</i> Craib

<p>The ethanolic extract from the stem bark of <i>Goniothalamus marcanii</i> Craib was shown in preliminary brine shrimp lethality data having good cytotoxic activity. Further bioassay guided isolation was done by means of solvent partition, chromatography and precipitation to provide four isolated compounds: a novel compound <b>1</b> with the core structure of 1-azaanthraquinone moiety referred as marcanine G; as well as compounds <b>2–4</b> with known aristolactam structures namely, piperolactam C, cepharanone B and taliscanine. These compounds were characterised by spectroscopic techniques. The assessment of cytotoxicity was established on an SRB assay using doxorubicin as a positive control. Marcanine G (<b>1</b>) was considered the most active compound indicating the IC<sub>50</sub> values of 14.87 and 15.18 μM against human lung cancer cells (A549) and human breast cancer cells (MCF7), respectively. However, <b>2</b> showed mild activity with the IC<sub>50</sub> values of 83.72 and 82.32 μM against A549 and MCF7 cells, respectively.</p>