Sweet Olive Extract Attenuates Dextran Sulfate Sodium-Induced Colitis in Mice

Sweet olive (Osmanthus fragrans flowers) is used to treat dysentery and reduce phlegm and stasis in traditional Chinese medicine. Recently, we found that verbascoside, the major component in the sweet olive ethanolic extract (OFE), inhibited IL-8 secretion in human colorectal adenocarcinoma WiDr cells. However, evidence-based treatment of inflammatory bowel disease (IBD) with the extract is yet to be performed. To evaluate the therapeutic effect of OFE, we measured IL-8 suppression by OFE and verbascoside in a WiDr cell culture assay. In the IL-8 secretion assay, both OFE (100 μg/mL) and verbascoside (10 μM) significantly inhibited IL-8 production in WiDr cells. Furthermore, we designed cotreated (dextran sulfate sodium [DSS]+OFE-treated) and post-treated (DSS-OFE-treated) protocols to access the therapeutic effects of OFE in vivo. Mice treated with 500 mg/kg per day OFE exhibited significant improvement in IBD symptoms, including disease activity index score, body weight, and colon length maintenance. The suppressive effects on myeloperoxidase expression and lower histopathology scores (including neutrophil infiltration) for the colon were also found. These findings suggest that OFE exerts anti-inflammatory effect on DSS-induced colitis.