Inhibitory effects of crude extracts from some edible Thai plants against replication of hepatitis B virus and human liver cancer cells

Background Edible plants such as Cratoxylum formosum (Jack) Dyer, Curcumin longa Lin, Momordica charantia Lin and Moringa oleifera Lam have long been believed in Thai culture to relieve ulcers and the symptoms of liver disease. However, little is known about their anti-liver cancer properties and antiviral activity against hepatitis B virus (HBV). The aim of this study was to investigate the anti-liver cancer and anti-HBV activities of crude extracts from these edible plants on human liver cancer cells. Methods Plant samples were prepared and extracted using buffer and hydro-alcoholic solvents. The MTT assay was performed to investigate the effects of the plant extracts on the cell viability of HepG2 cells. The inhibitory effect on replication of HBV was analysed by determining the level of HBV covalently closed circular DNA (cccDNA) in transiently transfected HepG2 cells with the DNA expression plasmid of the HBV genome using a quantitative real-time PCR. Results Buffer and hydroalcoholic extracts from C. formosum (leaf) reduced cell viability of HepG2 cells and they also inhibited HBV cccDNA. Crude extracts from C. longa (bulb) in both solvents did not have any cytotoxic effects on the HepG2 cells, but they significantly decreased the level of HBV cccDNA. Buffer extracts from the leaves of M. charantia and the fruits of M. oleifera showed to have anti-HBV activity and also a mild cytotoxicity effect on the HepG2 cells. In addition, leaves of M. Oleifera extracted by hydroalcoholic solvent drastically decreased the level of cccDNA in transiently transfected HepG2 cells. Conclusion Some crude extracts of edible plants contain compounds that demonstrate anti-liver cancer and anti-HBV activities.