Anti-inflammatory constituents from the root of Litsea cubeba in LPS-induced RAW 264.7 macrophages

Context Litsea cubeba (Lour.) Pers. (Lauraceae) has long been used as a folk remedy in Traditional Chinese Medicine (TCM) for the treatment of rheumatic diseases. Previous studies from our laboratory indicated that L. cubeba extract showed anti-arthritic activity in rats.

Objective To study L. cubeba chemically and biologically and to find the potential constituents responsible for its anti-arthritic effect.

Materials and methods The compounds were isolated from the root of L. cubeba by column chromatography which eluted with PE:EtOAc gradient system, and the structures were elucidated by detailed spectroscopic data analysis; the anti-inflammatory activity of the isolated compounds was evaluated by lipopolysaccharide (LPS)-induced RAW 264.7 cells and the TNF-α and NO level were measured by ELISA (commercial kit); The iNOS and COX-2 mRNA expression were measured by RT-PCR and the phosphorylation of IκBα, IKKβ, P38 and Akt were determined by western blots.

Results A novel 9-fluorenone, 1-ethoxy-3,7-dihydroxy-4,6-dimethoxy-9-fluorenone (1), together with 4 known compounds, namely pinoresinol (2), syringaresinol (3), 9,9′-O-di-(E)-feruloyl-meso-5,5′-dimethoxysecoisolariciresinol (4) and lyoniresinol (5) were isolated from the root of L. cubeba for the first time. The IC₅₀ for NO inhibition on compounds 1 and 4 were 56.1?±?1.2 and 32.8?±?2.3?μM, respectively. The IC₅₀ for TNF-α inhibition were 28.2?±?0.9 and 15.0?±?1.0?μM, respectively. Both 1 and 4 suppress mRNA expression of iNOS, COX-2 and protein phosphorylation of IκBα, IKKβ in LPS-induced RAW 264.7 cells.

Discussion and conclusion Compounds 1 and 4 isolated from L. cubeba exhibited potent anti-inflammatory activity through the NF-κB signal pathway.