Sambulin A and B, non-glycosidic iridoids from Sambucus ebulus, exert significant in vitro anti-inflammatory activity in LPS-induced RAW 264.7 macrophages via inhibition of MAPKs's phosphorylation

Abstract

Ethnopharmacological relevance: The leaves of Sambucus ebulus L. (Adoxaceae) are widely used in Turkish folk medicine particularly against inflammatory disorders. The fresh leaves after wilted over fire or the poultices prepared are directly applied externally to heal burns, edema, eczema, urticarial and abscess. Two iridoids were recently isolated (sambulin A, sambulin B) from the leaves of S. ebulus. Aim of the study: This study aims to investigate the in vitro anti-inflammatory activities of these iridoids on LPS-induced RAW 264.7 macrophages. Materials and methods: Raw 264.7 macrophages were treated with 12.5, 25 and 50 mu g/ml Sambulin A and 6.25, 12.5 and 25 mu g/ml Sambulin B and induced with 1 mu g/ml lipopolysaccaharides (LPS). Effect of the compounds on nitric oxide (NO) production and cytoldnes (TNF alpha, IL-6) were determined by Griess and ELISA assays respectively. iNOS and the phosphorylation levels of MAPKs (ERK, JNK) were examined by Western Blot. Results: Sambulin A and sambulin B inhibited 52.82% and 72.88% of NO production at 50 and 25 mu g/ml concentrations respectively. The levels of iNOS were significantly decreased by both molecules, sambulin B at 25 mu g/ml almost completely decreased iNOS levels (97.53%). Both molecules significantly inhibited TNF alpha productions. However, only sambulin B inhibited IL-6 production. Consequently, it was shown that sambulin B exerted its effect through the inhibition of ERK and JNK phosphorylations. Conclusion: The prominent bioactivities exerted by two iridoids will contribute to explanation of the usage of S. ebulus in traditional medicine against rheumatoid diseases.