*3.6. Cell Apoptosis Analysis*

Human CRC cells were treated with PN at 0.1, 0.5, 1, 2, or 4 μg/mL for 48 h, harvested, stained with Annexin V-FITC and PI for 15 min in the dark, according to the manufacturer's instructions (BD Biosciences, San Jose, CA, USA). Apoptotic cells were analyzed by flow cytometry (FC 500, Beckman Coulter, Indianapolis, IN, USA). The experiments were performed in triplicate.
