Cytotoxic sesquiterpenoids from the leaves of Magnolia grandiflora.

Nine previously undescribed sesquiterpenoids, named magnograndins A-I, as well as fourteen known ones, were obtained from the 70% acetone extract of the leaves of Magnolia grandiflora. Their structures were ascertained based on the spectroscopic evidences. The assignment of the relative configuration of magnograndin A was further confirmed by single-crystal X-ray diffraction analysis. 1β,10α-Epoxyparthenolide, parthenolide, and micheliolide exhibited potent cytotoxic activity against MDA-MB-468, AGS, HCT116, Hela, and MDA-MB-231 human cancer cell lines with IC50 values ranging from 1.76 to 16.11 μM. 1β,10α-Epoxyparthenolide and micheliolide potently inhibited NF-κB transcriptional activity with IC50 of 13.92 and 8.95 μM, respectively. The expression levels of NF-κB downstream protein p65 and XIAP were clearly down-regulated in 1β,10α-epoxyparthenolide and micheliolide treated cells, which demonstrated the inhibition of NF-κB signaling pathway.