Reprosil 100 c 18

All chemicals were purchased from Merck KGaA (Darmstadt, Germany), VWR International GmbH (Langenfeld, Germany), Carl Roth GmbH and Co. KG (Karlsruhe, Germany) or Thermo Fisher Scientific (Schwerte, Germany). Water was purified by an ELGA PURELAB system (Veolia Water Technologies, Celle, Germany). Mixed gender HLM of 150 donors were purchased from Corning (Wiesbaden, Germany). RLM, PLM and PLC were prepared according to established protocols [39 ]. Determination of protein content was carried out as described by Bradford [40 (link)]. Liver cytosol and liver microsomes were stored at −80 °C prior to usage. Hac and DHac were isolated from (385 g) dried and powdered Arnica montana flowerheads by Soxhlet extraction with dichloromethane. Afterwards, flash chromatography on silica gel and ambient pressure column chromatography was performed with hexane and ethylacetate. From various subfractions, Hac (89 mg) and DHac (7 mg) were obtained by preparative HPLC (Jasco, Groß-Umstadt, Germany) with preparative reverse phase column Reprosil 100 C18 (5 μm, 250 mm, 20 mm, Macherey-Nagel, Düren, Germany). The identity and purity (>95%) of both STLs was assessed by ¹H NMR spectroscopy.

Analytical TLC was developed on silica gel plates 60 F ${}_{254}$ (Merck Chemicals GmbH, Darmstadt, Germany) with EtOAc-hexane 2:1 (1.5% acetic acid) as the mobile phase. TLC plates were observed under UV-light at wavelengths of 254 nm and 360 nm, then sprayed with anisaldehyde-sulfuric acid reagent and heated on a hot plate [39 ]. Preparative HPLC separations were undertaken with a Jasco (Gross-Umstadt, Germany) prep.HPLC system (pump: PU-2087 plus; diode array detector MD 2018 plus; column thermostat CO 2060 plus; autosampler AS 2055 plus; LC Net II ADC Chromatography Data Solutions; sample injection loop: 2000 $\mathsf{\mu }$ L). Separations were performed using a preparative reverse phase column Reprosil 100 C-18 (5 $\mathsf{\mu }$ m, 250 mm × 20 mm, Macherey-Nagel, Düren, Germany) with binary gradients of the mobile phase. A flow rate of 12 mL/min and a column-thermostat temperature of 40 ${}^{\circ }$ C were used in all HPLC preparative separations. Chromatograms were recorded at 210–220, 254 and 280 nm. Optical rotations were recorded in CHCl ${}_2$ on a Jasco P-2000 polarimeter. UV spectra were extracted from the HPLC-UV-DAD chromatograms. CD spectra were recorded with a Jasco J-815 CD-spectropolarimeter in MeOH.