Effect of Achillea millefolium L. extract, fractions, and isolated compounds on inflammatory cytokine production in LPS-stimulated human mononuclear cells

Yarrow (Achillea millefolium L.) is traditionally used not only for the treatment of gastro-intestinal and hepato-biliary disorders, but also as an antiphlogistic drug [1]. The production of cytokines (e.g. IL-1, IL-6) is associated with the inflammatory process and plays a role in the genesis of rheumatoid arthritis and other inflammatory diseases [2]. The present study was undertaken to determine whether yarrow has an effect on the interleukin (IL)-6 secretion using a human pro-monocytic cell line (U937). PMA-differentiated cells were incubated with or without different concentrations of the extract and fractions (10, 1, 0.1, 0.01µg/ml) or the positive control diclofenac (10µg/ml), previous to stimulation with 1µg/ml LPS. After designated time points IL-6 levels were measured in supernatants using enzyme-linked immunosorbent assays (ELISA). Yarrow extract (0.1µg/ml) sigificantly decreased the expression of IL-6 (23% inhibition vs. control), as did a caffeic acid (15% inhibition vs. control) and a flavonoid fraction (13% inhibition vs. control) obtained thereof (1µg/ml, respectively); the effects of the extract were comparable to those of diclofenac (28% inhibition vs. control). The role of isolated pure compounds from yarrow on IL-6 secretion need to be further elucidated. Although additional studies are needed to clarify the mode of action of yarrow and to demonstrate a causative relationship between the inhibition of cytokine/chemokine secretion in cell culture and the reported clinical effects of the plant, our in vitro results offer a possible mechanism for the anti-inflammatory effects of yarrow observed in clinical use.

References: [1] Benedek, B. (2007) Dissertation, University of Vienna. [2] Nishimoto, N., Kishimoto, T. (2006) Nat. Clin. Pract. Rheumatol. 2: 619–626. [3] Gabay, C. (2006) Arthritis. Res. Ther. 8 (Suppl 2): S3