Semisynthesis and Non-Small-Cell Lung Cancer Cytotoxicity Evaluation of Germacrane-Type Sesquiterpene Lactones from Elephantopus scaber

Two series of germacrane-type sesquiterpene lactones were produced by semisynthetic modulation of scaberol C, which was prepared by a standard chemical transformation from an Elephantopus scaber extract. Their inhibition activities against non-small-cell lung cancer cells were screened, and preliminary structure–activity relationships were also established. Among them, monomeric analog 1u and dimeric analog 3d exhibited superior anti-non-small-cell lung cancer cytotoxic potencies with IC50 values of 4.3 and 0.7 μM against A549 cells, respectively, and were more active than cisplatin and the standard sesquiterpene lactones, parthenolide and scabertopin. Further studies revealed that compounds 1u and 3d cause G2/M phase arrest and induce apoptosis through the activation of mitochondrial pathways in A549 cells. Collectively, the results obtained suggest that compounds 1u and 3d are promising anti-non-small-cell lung cancer lead compounds.