Baicalin induces apoptosis via mitochondrial pathway as prooxidant.

Baicalin is a flavonoid and a major component of a herbal medicine, Sho-saiko-to, which is commonly used for treatment of chronic hepatitis in Japan and China. Flavonoids including baicalin have been reported to not only function as anti-oxidants but also cause cytotoxic effect. We investigated the mechanism of baicalin-induced cytotoxicity in leukemia-derived T cell line, Jurkat cells. When cells were cultured with 50-200 microg/ml baicalin for 6h, caspase-3 was activated and then cells fell into apoptosis. Induction of apoptosis by baicalin was accompanied with the marginal generation of intracellular reactive oxygen species (ROS), the increase of the cytosolic fractions of cytochrome c, and the disruption of mitochondrial transmembrane potential (DeltaPsi(m)) prior to the activation of caspase-3. The pre-culture with 5 mM of buthionine sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, facilitated baicalin-induced disruption of DeltaPsi(m) and induction of apoptosis. The pre-culture with N-benzyloxycarbonyl-valyl-alanyl-aspartyl fluoromethylketone (Z-VAD-fmk), a pan-caspase inhibitor, partially suppressed the induction of apoptosis. On the other hand, baicalin showed little toxic effect on peripheral blood mononuclear cells (PBMCs) from healthy volunteers. These results indicate that baicalin acts as a prooxidant and induces caspase-3 activation and apoptosis via mitochondrial pathway.