Essential oil from Siegesbeckia pubescens induces apoptosis through the mitochondrial pathway in human HepG2 cells

Siegesbeckia pubescens (SP) has been used as a traditional medicine for the treatment of and inflammatory diseases. However, the activities of SP against hepatocellular carcinoma and the related mechanisms remain unclear. The present study aimed to examine the effects of the essential oil of SP (SPEO) on the proliferation of hepatocellular carcinoma cells and the possible mechanisms. The growth inhibition of HepG2 cells was analyzed by MTT assay. Hoechst 33258 and fluorescence microscopy were utilized to observe the nuclear morphological changes of apoptotic cells. Flow cytometry was used to detect cell apoptosis and cell cycle. The expressions of the target proteins were detected by Western blotting. The results showed that SPEO obviously inhibited the proliferation of HepG2 cells in a dose-dependent manner. SPEO activated a series of apoptotic proteins in HepG2 cells, increasing expression levels of Bax, caspase-3 and caspase-9, and decreasing the bcl-2 expression level. SPEO displayed promising anti-hepatocellular carcinoma activities in vitro, partly by inducing apoptosis in HepG2 cells through activating the mitochondrial pathway.