Purpurin-18 is a chlorophyll-derived dihydroporphyrin, serves as a key precursor for photosensitizers like purpurinimides, which absorb light in the 700–850 nm range. It demonstrate potent photodynamic anti-tumor activity and generates ROS, disrupting mitochondrial membrane potential and inducing apoptosis against triple-negative breast cancer both in vitro and in vivo.