Novel flavonoids from Lonicera japonica flower buds and validation of their anti-hepatoma and hepatoprotective activity in vitro studies

Lonicera japonica, a widely used traditional Chinese medicine, possessed antiviral, hepatoprotective, anti-tumor and other activities. Meanwhile, L. japonica could be used as healthy food, cosmetics, and so on. Herein, four novel flavonoids, japoflavone A-D (2-3, 5, 12), together with ten known flavonoids, were isolated and identified on the basis of spectroscopic evidence from L. japonica. In addition, all isolates were assayed for their anti-hepatoma and hepatoprotective activities in vitro. 5 and 8 showed significant anti-hepatoma activity in SMCC 7721 cell with IC50 values of 13.01 ± 2.62 and 16.69 ± 0.35 μg/ml; Compound 12 showed significant hepatoprotective activity against H2O2-induced injury in SMCC 7721 and HepG 2 cells (p <  0.001). Drop in the levels of catalase and superoxide dismutase caused by H2O2 were remarkably reversed in a dose-dependent manner after treatment with 12. This study provided a phytochemical evidence for further development and utilization of Lonicera japonica in health products.