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

ABSTRACT

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 PEEtOAc 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, IKKß, 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, IKKß 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.