Objective: To investigate the components and antitumor activity against human tumor cell lines of fatty oil of Annona squamosa seeds. Method: The samples were derivated by methyl esterification

the components were identified by gas chromatography (GC) analysis and comparison of references

and the relative amount of these components were determined by peak area normalization method. In vitro anti-proliferative activity of the fatty oil against human liver cancer (SMMC-7721 and HepG2)

human uterine cervix cancer (Hela)

human lung cancer (A549) and human breast cancer (MCF-7) cell lines were tested by MTT assay. Result: The major chemical constituents of the fatty oil were fatty acid (80.9%)

and the content of unsaturated fatty acid were 51.1%. The IC50 of the fatty oil against the 5 human cancer cell lines tested above was 10.4

0.57

30.3

44.3

6.7 mg·L-1 respectively. Conclusion: The main components of the fatty oil of A. squamosa seeds were methyl palmitate

methyl stearate

methyl oleate and methyl linoleicacid. They showed high selective inhibitation towards the proliferation of HepG2 cell line.