A new labdane diterpenoid glycoside and other constituents from Inula nervosa (Asteraceae) and their chemotaxonomic importance

The chemical investigation of the Inula nervosa Wall. (Asteraceae) led to the isolation of a new labdane diterpenoid glycoside, maoxiucaioside A (1), and ten known compounds including seven steroids (2–8), one triterpenoid (9), and two flavonoids (10 and 11). Their structures were elucidated based on NMR, HRESIMS and ECD data analysis as well as literature data. Moreover, the anti-inflammatory activities of all isolates were evaluated by measuring their inhibitory effects on inflammatory cytokines (IL-1β, IL-6, and TNF-α) production in LPS-stimulated RAW 264.7 macrophages. Among them, compound 1 demonstrated significant inhibition effects of TNF-α, IL-6 and IL-1β release with IC50 values of 17.90 ± 2.29, 19.45 ± 2.16 and 18.54 ± 1.30 μM, slightly inferior to positive control drug (dexamethasone). All the above compounds except 7 were isolated from I. nervosa for the first time and seven compounds (1, 3, 4, 6, and 9–11) were first reported from the genus Inula. Furthermore, the chemotaxonomic significance of these compounds was also discussed.