Suppression of IL-8 Release by Sweet Olive Ethanolic Extract and Compounds in WiDr Colon Adenocarcinoma Cells.

Oxidative stress can stimulate the secretion of pro-inflammatory cytokines. Interleukin-8 (IL-8) has been implicated in the pathogenesis of inflammatory bowel disease and the metastatic spread of colorectal cancer. The flowers of Osmanthus fragrans (sweet olive) are used to alleviate dysentery with blood in the bowel, as well as stomach ache and diarrhea. However, the evidence of their therapeutic effects on these symptoms remains unclear. In the present study, the protective effects of sweet olive flower ethanolic extract (OFE) against oxidative stress in WiDr cells was assessed by evaluating its 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity. In addition, cellular IL-8 secretion was evaluated. Notably, high-performance liquid chromatography showed verbascoside to be the primary constituent in OFE; it exhibited a DPPH scavenging activity with an IC50 of 8.23 μg/mL. Moreover, OFE (1 to 100 μg/mL) showed a potent, dose-dependent inhibitory effect on H2 O2 -induced IL-8 secretion in WiDr cells. Nine compounds were isolated from OFE based on a protective effect-guided purification process. Of these compounds, 5 phenolic compounds-verbascoside, phillygenin, tyrosol, methyl 4-hydroxycinnamate, and eutigoside A-reduced IL-8 secretion at 10 μg/mL treatment concentrations. Further analysis showed that the anti-inflammatory effects of OFE likely occurred via nuclear factor-κB pathway inhibition, which attenuates IL-8 secretion in cells. Collectively, these data suggest that OFE could be developed as an agent that suppresses IL-8 secretion to treat chronic inflammatory diseases.