Anti‐arthritic effect of scopoletin,a coumarin compound occurring in Erycibe obtusifolia Benth stems,is associated with decreased angiogenesis in synovium

Scopoletin is the main constituent of coumarin found in the stems of Erycibe obtusifolia Benth, a traditional Chinese medicine used in the treatment of rheumatoid arthritis. We have previously demonstrated that scopoletin is able to decrease the serum level of uric acid in hyperuricemic mice induced by potassium oxonate, and attenuate croton oil‐induced inflammation. In the present study, we evaluated the anti‐arthritic effects of scopoletin in rat adjuvant‐induced arthritis by assessing paw swelling, pathology, and synovial angiogenesis. It was found that scopoletin, injected intraperitoneally at doses of 50, 100 mg/kg, reduced both inoculated and non‐inoculated paw swelling as well as articular index scores, and elevated the mean body weight of adjuvant‐induced arthritic rats. Rats treated with higher dose of scopoletin showed a near‐normal histological architecture of the joints and a reduced new blood vessel formation in the synovial tissues. Furthermore, scopoletin downregulated the overexpression of vascular endothelial growth factor, basic fibroblast growth factor and interleukin 6 in the synovial tissues of adjuvant‐induced arthritic rats. In conclusion, scopoletin is capable of ameliorating clinical symptoms of rat adjuvant‐induced arthritis, by reducing numbers of new blood vessels in the synovium and the production of important endogenous angiogenic inducers. Therefore, this compound may be a potential agent for angiogenesis‐related diseases and could serve as a structural base for screening more potent synthetic analogs.