Ursolic acid

The chemical reference standards silybin (98% pure) and caffeic acid (98% pure) were obtained from Sigma Aldrich (St. Louis, United States), silydianin, chlorogenic acid (97% pure), caftaric acid (90% pure), and chicoric acid (97% pure) from USP (Rockville, United States), and silychristin (97.9% pure), dodec-2-ene-8,10-diynoic acid isobutylamide, and isoferulic acid (97% pure) from Chromadex (Los Angeles, United States). Taxifolin (85% pure) was purchased from Extrasynthese (Genay, France), and β-sitosterol (95% pure), ursolic acid (97% pure), echinacoside (95% pure), dodeca-2E,4E,8Z, 10E/Z-tetraenoic acid isobutylamide (93% pure), cynarin (96% pure), actein (95% pure), and cimifugin (97% pure) from Phytolab (Vestenbergsgreuth, Germany).
Solvents (≥95% pure) and reagents were purchased from Roth (Karlsruhe, Germany), Acros (Gent, Belgium), Fisher Scientific (Hampton, United States), and Merck (Darmstadt, Germany). Silica gel 60 F₂₅₄ HPTLC glass plates (20 × 10 cm) were obtained from Merck (Darmstadt, Germany).
HPTLC instruments from CAMAG (Muttenz, Switzerland) were used, including Automatic TLC Sampler (ATS 4), Automatic Development Chamber (ADC 2) with humidity control, Plate Heater 3, TLC Visualizer 2, and Immersion Device 3.

Maslinic acid, corosolic acid, oleanolic acid, and ursolic acid were obtained from Phytolab (Vestenbergsgreuth, Germany), lithocholic acid (LCA), chenodeoxycholic acid (CDCA), oleic acid, and palmitic acid from Sigma Aldrich (St. Louis, MO, United States), stearic acid and 4-methoxycinnamic acid from Fluka (Buchs, Switzerland), chlorogenic acid from Carl Roth (Karlsruhe, Germany), and linoleic acid from Acros (Geel, Belgium). Eugenol was isolated from clove and the identity and purity tested by ATR-IR spectroscopy. All reference and standard compounds were obtained in a purity of ≥90%. They were dissolved to 1.0 mg/mL in MeOH. The triterpene acids (TTAs) used for the quantification were mixed and diluted to give a standard solution containing 100 μg/mL of each corosolic acid, Maslinic acid, oleanolic acid, and ursolic acid followed by a serial dilution down to 2 μg/mL.