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. 113,10a-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 mu M. 1 beta,10 alpha-Epoxyparthenolide and micheliolide potently inhibited NF-kappa B transcriptional activity with IC50 of 13.92 and 8.95 mu M, respectively. The expression levels of NF-kappa B downstream protein p65 and XIAP were clearly down-regulated in 1 beta,10 alpha-epoxyparthenolide and micheliolide treated cells, which demonstrated the inhibition of NF-kappa B signaling pathway.