Abstract: The anti-tumor effect of betulonic acid in vivo and in vitro and the preliminary mechanism of action were studied.The survival time of mice bearing H₂₂ was used to observe the potency in vitro and the effect of betulonic acid on human hepatoma cell line(HepG-2) in vitro was studied. The morphology of H₂₂ tumor cells treated with betulonic acid was observed by transmission electron microscopy.The effect of betulonic acid on the cell cycle was adopted by flow cytometry. The results showed that betulonic acid had certain effect on survival time of mice in vitro and HepG-2 in vitro. In the experiments of tumor transplantation in vivo, it could be observed that betulonic acid had some therapeutic effect on H₂₂, it could significantly extend the survival time of the mice vaccinated by H₂₂. This showed that betulonic acid also showed good tumor inhibition in vivo experiments. The values of IC₅₀ and TC₅₀ are 110.77 and 683.57μmol/L, respectively.The apoptosis of tumour cells can be observed by electronmicroscopy. Therefore, betulonic acid had anti-tumor effect by promoting tumor cellapoptosis.Increasing the dosage of betulonic acid, H₂₂ cells in S phase and G₂ phase gradually increased. It can be speculated that when betulonic acid acted on cells, the cells were blocked in S and G₂ phases.

Key words: betulonic acid, tumour cells, apoptosis, cell cycle