*2.5. Cell Culture*

The human colon cancer cell (HCT-116) was purchased from the ATCC (American Type Culture Collection, Manassas, VA, USA). The cell was maintained and grown in RPMI 1640 medium (Roswell Park Memorial Institute 1640; Corning, Manassas, VA, USA) contained with 10% FBS (fetal bovine serum; Gibco BRL, Carlsbad, MD, USA) and penicillin/streptomycin (Life Technologies, Waltham, MA, USA). The condition of the incubator was 37 ◦C and humidified atmosphere containing 5% CO2.

#### *2.6. Cell Viability Assay*

The cell viability assay was assessed using an Ez-Cytox Kit (Dail Lab Service Co., Seoul, Korea) based on the manufacturer's instructions [19]. Briefly, the cells were seeded in a 96-well plate at 1 × 10<sup>4</sup> cells/well and then incubated. After 24 h, the cells were treated with the indicated concentrations of each sample, and the cells were then incubated for 24 h. Following incubation, Ez-Cytox solution was mixed with medium in each well and incubated for 1 h. The absorbance at 450/600 nm was determined using a SPARK 10M (Tecan Group Ltd., Männedorf, Switzerland). The cell viability of 100% was calculated from control cells.

#### *2.7. Hoechst 33342 Cell Staining*

Sample-induced nuclear condensation of HCT-116 cells was observed using Hoechst 33342 staining (Sigma Aldrich, St. Louis, MO, USA) [20]. Briefly, the cells were seeded in a 6-well plate at 4 × 10<sup>5</sup> cells per well. Following incubation for 24 h, the cells were treated with various concentrations of each sample, and the cells were then incubated for 24 h. Following incubation, Hoechst 33342 solution was added to the cells and incubated for 10 min. The stained cells were observed using a CCD camera conjugated IX50 fluorescent microscope (Olympus, Tokyo, Japan).
