Glycycoumarin (30 μM-0.3 nM; 5 min) has an inhibitory effect on smooth muscle contraction induced by various types of stimulants through the inhibition of PDEs, especially isozyme 3, followed by the accumulation of intracellular cAMP. Glycycoumarin (10 mg/kg; i.p.; once daily for 4 d) enhances tumor growth inhibition in HepG2 xenograft model in mice and shows synergistical effect with ABT-737 .