Further sesquiterpenoids from the rhizomes of Homalomena occulta and their anti-inflammatory activity.

Graphical abstract Highlights • Five new sesquiterpenoids were isolated from the rhizomes of Homalomena occulta. • Compound 5 represented the first example of 1,4-oxa-oppositane sesquiterpenoid. • Compounds 5 , 18 , 19 showed potent anti-inflammatory activity. Abstract The rhizomes of Homalomena occulta are called Qian-nian-jian in Traditional Chinese Medicine (TCM), which is widely consumed in China owing to its health benefits for the treatment of rheumatoid arthritis and for strengthening tendons and bones. A phytochemical investigation on this famous TCM yielded 19 sesquiterpenoids (1 – 19) with various carbocyclic skeletons including isodaucane (2 , 8 , and 9), guaiane (3), eudesmane (4 and 10 – 15), oppositane (5 , 16 , and 17), and aromadendrane (18 and 19) types. The structures of new compounds, Homalomenins A-E (1 – 5), were determined by diverse spectroscopic data. Compound 1 possessed a rare sesquiterpenoid skeleton and compound 5 represented the first example of 1,4-oxa-oppositane sesquiterpenoid. These isolates were evaluated for their inhibitory effects on COX-2 mRNA, COX-2 protein expression, and prostaglandin E2 (PGE2) production in Raw264.7 cells, which demonstrated that compounds 5 , 18 , 19 showed potent anti-inflammatory activity by suppressing LPS-induced COX-2 expression and PGE2 production in a dose-dependent manner. [ABSTRACT FROM AUTHOR]