Scoparone from Artemisia capillaris Thunb. induces apoptosis in HepG2 cells via activation of both intracellular and extracellular pathways

Six separated compounds were identified from Artemisia capillaris Thunb., and they were 7-methoxycoumarin (1), 6,7-dimethoxycoumarin (2), 7-hydroxy-6-methoxycoumarin (3), quercetin (4), chlorogenic acid (5) and caffeic acid (6). Among them, 6,7-dimethoxycoumarin, as known as scoparone, was the most effective on scavenging ABTS free radicals (IC50 = 0.97 μΜ) and was then tested by cytotoxic activity and pro-apoptotic activity against HepG2 cells. Scoparone dose-dependently and time-dependently inhibited the cell proliferation. Furthermore, scoparone induced the expression of Bax, concurrently suppressing the expression of Bcl-2, resulting in a noteworthy elevation in the Bax/Bcl-2 ratio to up-regulate Caspase-3 activity, thus inducing cell apoptosis via the intracellular pathway. Meanwhile, scoparone promoted the expression of Fas, FasL, FADD, Caspase-8 and Caspase-3, indicating that scoparone also triggered apoptosis via the extracellular pathway. In a word, scoparone demonstrated remarkable antitumor capability to induce apoptosis of HepG2 cells through both intracellular and extracellular pathways.