Cytotoxicity and anti-hepatitis B virus activities of saikosaponins from Bupleurum species.

Saikosaponins, the main active constituents of Bupleurum spp., have been shown to possess immunomodulatory, hepatoprotective, anti-tumor and anti-viral activities. In this study, saikosaponins a, c and d were evaluated for cytotoxicity and anti-hepatitis B virus ( HBV) activities. Results showed that, with the exception of saikosaponins a and d, HBV-transfected human hepatoma cells (2.2.15 cells) cultured with saikosaponin c showed a significantly lower level of HBeAg in culture medium. Saikosaponin c also possessed activity in inhibiting HBV DNA replication; this inhibitory effect was not due to the cytotoxicity of saikosaponin c or its effect on 2.2.15 cell proliferation. Although saikosaponin d exhibited cytotoxicity on 2.2.15 cells, it failed to inhibit HBV multiplication. The cytotoxicity of saikosaponin d against HepG2 human hepatocellular carcinoma cells was due to the induction of apoptosis through the activation of caspases 3 and 7, which subsequently resulted in poly-ADP-ribose-polymerase (PARP) cleavage. DNA fragmentation was clearly noted at more than 6 h after HepG2 cells exposure to saikosaponin d. The present study concludes that saikosaponin c exhibits anti-HBV activity and saikosaponin d possesses potent cytotoxicity against human hepatocellular carcinoma cells.