Cytotoxic Germacranolide Sesquiterpene from Inula cappa

Abstract

A new germacranolide, inulacappolide (1), was isolated from the EtOH extract of the whole plant of Inula cappa along with 16 known compounds. The structure of inulacappolide was a rare 1(10)-saturated type of germacran-6,12-olide, identified as 2α-acetoxy-3β-hydroxy-9β-angeloyloxygermacra-4-en-6α,12-olide by spectral analysis (IR, HR-ESI/MS, ¹H-NMR, ¹³C-NMR, HMQC, HMBC, NOESY). In vitro, it showed antiproliferative effects against human cervical cancer HeLa, human leukemia K562 and human nasopharyngeal carcinoma KB cell lines with IC₅₀ values of 1.2 μM, 3.8 μM and 5.3 μM, respectively.