Characterizing the mechanism for ginsenoside-induced cytotoxicity in cultured leukemia (THP-1) cells

Pure ginsenoside standards (saponins Rh2, PD, and PT), along with an Rh2-enhanced North American ginseng (Panax quinquefolius) leaf extract (LFRh2), were tested for cytotoxic activity in cultured THP-1 leukemia cells. Thermal treatment of ginseng leaf resulted in production of both Rh2 and Rg3 content that was confirmed by liquid chromatography - mass spectrometry (LC-MS). Flow cytometry of cells stained with annexin V - fluorescein isothiocyanate and propidium iodide showed that the LFRh2 significantly (p < or = 0.05) increased apoptosis (18% +/- 0.4%) after 23 h at a concentration that inhibited cell viability by 50% (LC50 (72 h) = 52 microg/mL. In comparison, a similar significant (p < or = 0.05) increase in apoptotic cell numbers occurred at 41 h of exposure for pure ginsenoside standards, PD (LC50 (72 h) = 13 microg/mL), PT (LC50 (72 h) = 19 microg/mL), and Rh2 (LC50 (72 h) = 15 microg/mL). Although no further increase in apoptosis was observed in THP-1 cells after exposure to increasing concentrations of LFRh2 and pure Rh2, PD, and PT standards, a significant (p < 0.05) increase in the percentage of necrotic cells did occur after exposure of cells to different ginsenosides at elevated concentrations. THP-1 caspase-3 activity was greatest (p