Chemical constituents from Lonicera japonica flower buds and their anti-hepatoma and anti-HBV activities

Three new naturally occurring monoterpenoids, japopenoid A (1), japopenoid B (23) japopenoid C (24), and one new caffeoylquinic acid derivative (28), together with thirty-one known compounds (2–22, 25–27, 29–35), were isolated and identified from the flower buds of Lonicera japonica Thunb. Their structures were determined by extensive 1D and 2D NMR spectroscopic methods, high-resolution mass spectrometry, and the absolute configurations of 1, 23, 24 were determined by comparison of their electronic circular dichroism (ECD) spectrum with literature and theoretical calculation. Structurally, compound 1 is a monoterpenoid featured with an unusual tricyclic skeleton. All compounds (1–35) were evaluated for their cytotoxicities against human liver cancer cell lines (HepG 2 and SMMC-7721). Compound 12 exhibited the most potent activity with IC50 values of 26.54 ± 1.95 and 8.72 ± 1.57 μg/ml against HepG 2 and SMMC-7721, and the IC50 values of compound 13 were 26.54 ± 1.95 and 12.35 ± 1.43 μg/ml, respectively. Western blot results further proved that compound 13 induces hepatoma cell apoptosis via the intrinsic apoptosis pathway. In addition, most terpenoids showed inhibitory activity against HBsAg and HBeAg secretion, and HBV DNA replication. In particular, 25 μg/mlof compound 11 inhibits HBsAg and HBeAg secretion, and HBV DNA replication by 39.39 ± 5.25, 15.64 ± 1.25, and 16.13 ± 4.10% compared to the control (p < 0.05). These results indicated that L. japonica flower buds could be served as functional food for anti-hepatoma and anti-HBV activities.