Both the ethyl acetate fraction and tectoridin activated thyroid-responsive reporters and increased thyroid hormone-dependent proliferation of rat pituitary GH3 cells, indicating modulation of thyroid hormone receptors. In parallel, the estrogenic activity of the fraction and tectoridin were characterized in a transient transfection system using estrogen-responsive luciferase plasmids in MCF-7 cells. The ethyl acetate fraction and tectoridin activated reporter gene expression and decreased the estrogen receptor protein level.
These data indicate that tectoridin acts as a weak phytoestrogen as well as a thyroid hormone-like agent by activating both estrogen and thyroid hormone receptors.
