Immunomodulatory effect of extracts of Hibiscus sabdariffa L. (Family Malvaceae) in a mouse model.

The immunomodulatory activity of water and alcohol extracts (including its fractions) of the dried calyx of the plant was evaluated in mice. The ability of the extracts to inhibit or enhance the production of two cytokines, namely tumor necrosis factor-alpha (TNF- alpha) and interleukin-10 (IL-10), respectively, implicated as proinflammatory and antiinflammatory interleukins were also evaluated. The extracts at doses of 50 mg/kg were found to possess higher immunostimulatory activities in comparison with levamisole (positive control), with significant effects when compared with the vehicle-treated group (p < 0.01). Increased activity was observed with increase in doses of the 50% ethanol and absolute ethanol extracts. The insoluble fraction exhibited a significant dose-dependent immunostimulatory activity (p < 0.05), while the residual water-soluble fraction exhibited activity at 100 mg/kg body weight. The production of tumor necrosis factor-alpha (TNF-alpha), was low in all the extract groups tested, while the production of interleukin 10 (IL-10) was high compared with the control. The production of IL-10 was high in 300 mg/kg aqueous extract. The insoluble fraction exhibited a profound dose-dependent immunostimulatory activity higher than the positive control at 100 mg/kg. This study established the immunoenhancing properties of the extracts of this plant confirming that the immunomodulatory activity is cell mediated and humoral. The insoluble fraction could find use as an immunostimulatory agent in humans.