Immunostimulant properties of Heracleum maximum Bartr.

The root of Heracleum maximum Bartr. (Umbelliferae), known to possess direct antifungal and anti-mycobacterial properties, has been reported anecdotally to possess antiviral properties. It was therefore hypothesized that the plant may have immunostimulant properties. This hypothesis was tested using a macrophage activation assay to evaluate the ability of aqueous extracts of the root of Heracleum maximum to stimulate IL-6 production. All Heracleum maximum extracts were found to stimulate IL-6 and produced a steep dose–response curve. With the assay performed twice in the absence of the macrophage primer, IFN-γ, the mean IL-6 production in the setting of the strongest extract was 3648 pg/ml (95% CI 3361–3935) and 5430 pg/ml (95% CI 4976–5885) as compared to 2722 pg/ml (95% CI 2620–2824) and 6772 pg/ml (95% CI 6282–7262) produced by the LPS positive control, respectively. In the presence of IFN-γ, the strongest extract produced a mean concentration of IL-6 of 21804 pg/ml (95% CI 19755–23854) surpassing the 14893 pg/ml (13159–16628) produced by the LPS + IFN-γ positive control. These positive results confirm the hypothesis of immunostimulation and thus support the anecdotal reports of antiviral activity.