Cytotoxic sesquiterpene lactones from Centaurothamnus maximus and Vicoa pentanema

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Abstract
The aerial parts of Centaurothamnus maximus yielded three cytotoxic guaianolides, chlorojanerin (1), cynaropicrin (2) and janerin (3). The structure elucidation of 1–3 was based on 1H and 13C NMR data, mainly 2D‐NMR 1H‐1H COSY and 1H‐13C HETCOR experiments. Compounds 1–3 showed in vitro cytotoxic activity against human cancer cell lines of malignant melanoma (SK‐MEL), epidermoid (KB), ductal (BT‐549) and ovarian (SK‐OV‐3) carcinomas with IC50 values of 2–6 μg/mL. In addition, 12 sesquiterpene lactones (4–15), isolated previously from the aerial parts of Vicoa pentanema, were evaluated for cytotoxic and antimicrobial activities. 2α‐ Acetoxy‐3β‐hydroxyalantolactone (10) and 8β‐hydroxyparthenolide (14) were found to be the main cytotoxic agents (IC50 values of 2–6 μg/mL against SK‐MEL, BT‐549 and SK‐OV‐3), while lactones 4, 5, 11 and 15 selectively inhibited the growth of human malignant melonoma (IC50 value of 3.6–7.3 μg/mL). Cell aggregation and cell adhesion assays, using HL‐60 and HeLa cell lines, evaluated the effect of cytotoxic constituents 1–3, 10 and 14 on immune response and inflammation. Copyright © 2003 John Wiley & Sons, Ltd.