Further sesquiterpenoids and phenolics from two species of Taraxacum F.H. Wigg. and cytotoxic activity of taraxinic acid and its derivatives

Abstract

From roots of Taraxacum flavostylum and Taraxacum lucidum, the species included in the section Taraxacum F. H. Wigg. of the genus Taraxacum F. H. Wigg., eight sesquiterpene lactones, including taraxinic acid (1) and 11β,13-dihydrotaraxinic acid (2), taraxinic acid β-glucopyranosyl ester (3) and its 11β,13-dihydroderivative (4), ainslioside (5), deacetylmatricarin (6), 3-epi-11β,13-dihydrodeacylcynaropicrin (7) and ixerin D (8) together with six phenolic metabolites (9‒14) were isolated. 3-Epi-11β,13-dihydrodeacylcynaropicrin (7), 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-1-propanone (9) and 5-methoxy-eugenyl-4-O-β-glucopyranoside (11) were found for the first time in Taraxacum spp. Compounds 1‒14 were isolated from T. flavostylum roots, whereas only three germacranolides (3‒5), a guaianolide (8) and dihydrosyringin (13) were present in the extract from T. lucidum. Structures of the compounds were elucidated based on spectroscopic data.In vitro cytotoxic activity of taraxinic acid (1) and its derivatives (2‒4) against three human melanoma cell lines (A375, HTB140 and WM793), human normal keratinocytes (HaCaT), human normal prostate epithelial cells (PNT-2), and human prostate carcinoma cell line (DU145) was also examined in this study.