Immune system evaluation of Echinacea Purpurea root extract in female Harlan Sprague Dawley (Hsd:Sprague Dawley SD) rats

Echinacea is commonly used as a dietary supplement owing to its putative anti-inflammatory, antiviral, and antibacterial activities. Unfortunately, determining risk posed to human health is challenging. A novel combination of chemical and biological characterization was employed for selection of a representative extract sample used for in vivo investigation of the immunomodulatory properties of Echinacea (E.) purpurea. In vitro cytokine profiling showed the extract could stimulate pro-inflammatory cytokine production in the absence of detectable endotoxin. An in-depth in vivo evaluation of the immune response following a 28-day oral exposure to the selected E. purpurea extract was conducted in adult Harlan Sprague Dawley (HSD) female rats at doses up to 2000 mg/kg/day. There was no evidence that E. purpurea caused overt toxicity or effects on humoral immunity. However, cell-mediated immunity was increased but only at low doses and with no evidence of a dose-response. In addition, E. purpurea treatment enhanced natural killer cell activity and the relative percentage of macrophages/monocytes in the spleen of rats from the highest treatment group. These results suggest that E. purpurea may have immunomodulatory properties that support antiviral and antibacterial activity but may also foster an immunostimulatory environment that could exacerbate some immune-mediated conditions.