Abstract
Equisetum arvense, known as common horsetail, is used for the treatment of inflammatory diseases and
is the plant with the highest concentration of silica. Yet it is unknown if the medicinal
properties are mediated by its silica content. In the current study, optimal conditions
for silica-rich horsetail preparations were identified. Bioactivity of the preparations
was analyzed in vitro using flow cytometry-based activity and functionality profiling of primary human
lymphocytes as well as cytokine measurement using a classical ELISA technique. Experiments
revealed that horsetail preparations suppress activation and proliferation of lymphocytes
by an interleukin-2-dependent mechanism. The effect increased with the silica concentration
in the decoctions. Lymphocytesʼ polyfunctionality was also influenced, shown by a
downregulation of IFN-γ. Analytical profiling by HPLC-UV-MS and bioactivity testing revealed relevant immunosuppressive
concentrations of a component that has been identified as isoquercitrin. Our results
show that both silica and isoquercitrin are active compounds of horsetail preparations.
Key words
Equisetum arvense
- Equisetaceae - silica - isoquercitrin - lymphocytes - immune modulation
