Sesquiterpene lactones from Inula cappa

Three new germacranolides, ineupatolides A-C (1-3), together with six known sesquiterpenoids, were isolated from the aerial parts of Inula cappa (Buch.-Ham.) DC. The structures of new compounds were elucidated by 1D-, and 2D-NMR techniques including HMQC, HMBC, 1H-1H COSY and ROESY spectra. The known compounds were identified by spectroscopic data analyses and data comparison. Compound 2 was finally proved to be converted from 1 with the trace existence of acid. Compounds 2 and 5 showed moderate inhibitory activity against human leukemia cell line HL-60, while compounds 2, 5, 6, 7 and 9 exhibited no antiproliferative activities on human lung cancer cell line A549.

Three new germacranolide sesquiterpenes (1-3) and six known analogues were isolated from Inula cappa, and their structures were elucidated by detailed analyses of MS, 1D-, and 2D-NMR spectroscopic data. A chemical conversion took place between compounds 1 and 2 in the presence of acid.Highlights► Three new germacrane-type sesquiterpenes were reported from Inula cappa. ► Structural elucidations were carried out by analyzing spectroscopic data. ► A chemical conversion took place between compounds 1 and 2 with the existence of acid. ► No compounds showed antiproliferative activity on human lung cancer cell line A549.