3,4,5-Trimethoxycinnamic acid is a phenylpropanoid isolated from the roots of Polygala tenuifolia WILLD, with anti-stress effect, prolonging the sleeping time in animals[1][2]. 3,4,5-Trimethoxycinnamic acid increases expression of GAD65 and gamma-subunit of GABAA receptor, but shows no effect on the amounts of alpha-, beta-subunits[2].