Bioactive constituents from Gerbera piloselloides with anti-inflammatory and antiproliferative activities

A phytochemical investigation of the 95% ethanol extract from Gerbera piloselloides obtained fourteen compounds, including three undescribed phenone-monoterpenes (1a/1b and 2), seven undescribed chromone-monoterpenes (3a/3b–5a/5b and 6), and one undescribed coumarin-monoterpene (8). Among them, four pairs of enantiomers (1a/1b and 3a/3b–5a/5b) were successfully isolated by the chiral-phase HPLC resolution. The structures and absolute configurations were unambiguously determined based on comprehensive spectroscopic data, electronic circular dichroism (ECD) data, and X-ray diffraction analysis. Structurally, compound 1 is the first 5-methylphenone monoterpene formed through a circular 6-membered carbocycle. And their anti-inflammatory and antiproliferative activities were evaluated via LPS stimulated RAW 264.7 cells and five human cancer lines (HepG2, MDA-MB-231, SCG-7901, A549 and MCF-7), respectively. Compounds 4b, 5a and 5b showed moderate inhibitory effect against nitric oxide (NO) production with IC50 values ranging from 12.52 to 15.75 μM. Compound 8 significantly inhibited the proliferation of MDA-MB-231 human cancer line in a dose-dependent manner. Furthermore, the connection between phenone-monoterpenes, chromone-monoterpenes, and coumarin-monoterpenes in biosynthesis were also discussed.