Five acylphloroglucinols substituted with monoterpenoids (empetrifelixin A–D and empetrikajaforin), three known monocyclic acylphloroglucinols and one monocyclic acylphloroglucinol were isolated from a petrol ether extract of Hypericum empetrifolium after fractionation by flash chromatography on silica gel, RP-18 and subsequent purification by preparative HPLC (RP-18). Their structures were elucidated by 1D, 2D NMR techniques and HREIMS. To determine a possible anti-angiogenic activity, inhibition of cell proliferation was measured using a human microvascular endothelial cell line (HMEC-1). Subconfluent grown HMEC-1 cells were treated with all compounds isolated in sufficient amounts and stained with crystal violet. Highest activity was observed for empetrifelixin A and empetrifelixin D showing a concentration dependent inhibition of cell proliferation with IC50 values of 6.5 ± 0.1 and 7.3 ± 0.4 μM, respectively. Empetrifelixin A also showed activity in a cell migration assay with HMEC-1 cells in low micromolar concentrations.Graphical abstractFive acylphloroglucinols substituted with monoterpenoids were isolated from a petrol ether extract of Hypericum empetrifolium by an 1H NMR guided approach. Inhibition of cell proliferation was measured using a human microvascular endothelial cell line. Most active compounds showed a concentration dependent inhibition of cell proliferation with IC50 values in the lower micromolar range.
Highlights► We isolated five phloroglucinol derivatives from Hypericum empetrifolium. ► We applied a 1H NMR guided approach. ► We found a rare monoterpenoid substitution of the phloroglucinols. ► We found significant inhibition of cell proliferation in endothelial cells.
