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Inula aucheriana DC is a member of the family Asteraceae which is known to produce cytotoxic secondary metabolites noted as sesquiterpene lactones. In the present study, sesquiterpene lactones inuchinenolide B, 6-deoxychamissonolide (stevin) and 14-acetoxy-1β,5α,7αH-4β-hydroxy-guai-9(10),11(13)-dien-12,8α-olide were isolated from I. aucheriana. Inuchinenolide B and 14-acetoxy-1β,5α,7αH-4β-hydroxy-guai-9(10),11(13)-dien-12,8α-olide were further evaluated by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay to demonstrate cytotoxic activity with IC50 values of (56.6, 19.0), (39.0, 11.8), and (55.7, 15.3) μg/mL against HepG-2, MCF-7 and A-549 cells, respectively. The cytotoxic activity of the two evaluated sesquiterpene lactones partly explains the cytotoxic activity that was previously observed for the extracts of Inula aucheriana. The isolated compounds could be further investigated in cancer research studies.

Inula aucheriana n-hexane, CHCl3 and MeOH extracts were evaluated for their anti-proliferative activity against HepG-2, MCF-7, MDBK and A-549 cells. The CHCl3 extract exhibited cytotoxic activity to the above cell lines with IC50 values of 13.5, 23.4, 10.5, and 26.9 microg/mL, respectively. The sesquiterpene lactone britannin was isolated from the above extract. This was further evaluated in the MTT assay to demonstrate strong cytotoxicity to the mentioned cell lines (IC50: 2.2, 5.9, 5.4, and 3.5 microg/mL, respectively), and the apoptotic inducing properties of britannin were evaluated on human breast adenocarcinoma (MCF-7) cells through the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay.

Inula oculus-christi L. (Compositae) extract was chromatographed and three sesquiterpene lactones ergolide, gaillardin and pulchellin C were isolated. The structures of these compounds were determined by analysis of their spectroscopic data, and their crystal structures were defined using X-ray crystallography; the isolation of ergolide and pulchellin C is reported for the first time from this species. These three compounds were evaluated for their in vitro cytotoxic activity against MDBK, MCF7 and WEHI164 cells; ergolide and gaillardin exhibited lower and significantly different IC50 values compared with pulchellin C (p<0.001).