A new sesquiterpenoid and further natural products from Taraxacum portentosum Kirschner & Štěpánek, an endangered species.

The chemical studies of roots and aerial parts of Taraxacum portentosum Kirschner & Štěpánek, a member of the section Palustria (H. Lindb.) Dahlst. (Asteraceae), led to the isolation of one new eudesmanolide and 13 known compounds, including five sesquiterpenoids: taraxinic acid, 11β,13-dihydrotaraxinic acid, taraxinic acid β-glucopyranosyl ester and its 11β,13-dihydroderivative, ixerin D, one apocarotenoid ‒ loliolide and seven phenolics: scopoletin, 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-1-propanone, methyl p-hydroxyphenylacetate, 5-methoxy-eugenyl-4-O-β-glucopyranoside, syringin, dihydroconiferin, and dihydrosyringin. Their structures were established by 1H NMR. The new compound was characterized as 3-oxo-4βH-11,13-eudesmen-12,6-olide-8-O-β-glucopyranoside based on spectroscopic data (1 D and 2 D NMR) and HRESI mass spectrometry.