Supercritical carbon dioxide extraction of ethyl p-methoxycinnamate from Kaempferia galanga L. rhizome and its apoptotic induction in human HepG2 cells

In this study, supercritical carbon dioxide extraction of ethyl p-methoxycinnamate from Kaempferia galanga L. rhizome and its apoptotic induction in human HepG2 cells are reported for the first time. By using supercritical carbon dioxide extraction, the yield of ethyl p-methoxycinnamate identified by gas chromatography mass spectrometry (GC-MS) was as high as 2.5% with respect to the raw materials. In the anticancer assay, it was found that ethyl p-methoxycinnamate could inhibit the proliferation of the human hepatocellular liver carcinoma HepG2 cell line in a dose-dependent manner and induce the significant increase of the subG0 cell population. After treatment with ethyl p-methoxycinnamate, phosphatidylserine of HepG2 cells could significantly translocate to the surface of the membrane. The increase of an early apoptotic population was observed by both annexin-fluorescein isothiocyanate (FITC) and propidium iodide (PI) staining. It was concluded that ethyl p-methoxycinnamate not only induced cells to enter into apoptosis, but also affected the progress of the cell cycle.