Effects of an ethanolic salix extract on the release of selected inflammatory mediators in vitro

Salix extracts are in current use for the treatment of pain and inflammation. In order to obtain an insight into the mechanism(s) of action of the ethanolic Salix extract 1520L--which is essentially similar to an extract for which clinical studies have demonstrated analgesic effectiveness--its effects were evaluated in an established in vitro assay test system using primary human monocytes. The IC50-values obtained for the inhibition of lipopolysaccharide (LPS)-induced release of prostaglandin E2 (PGE2) reflecting cyclooxygenase (COX)-2-mediated PGE2 release were 47 microg/ml and 0.6 microg/ml, for the Salix extract 1520L and rofecoxib-like research compound L745337, respectively. There was no effect on COX-1 and COX-2 activity. The Salix extract inhibited the LPS-induced release of tumor necrosis factor-alpha, interleukin-1beta and interleukin-6 with IC50-values of 180.0, 33.0 and 86.0 microg/ml, respectively. Both, salicin and salicylate, had no effect in any of the parameters. Our results indicate that Salix extract 1520L inhibits COX-2-mediated PGE2 release through compounds other than salicin or salicylate. Our data further suggest that the proprietary Salix extract is a weak inhibitor of proinflammatory cytokines.