Pheophorbide A is a product of chlorophyll breakdown in plants. It is an active component of the Chinese medicinal herb Scutellaria barbata. Others report on extraction of the drug from sources as varied as spinach leaves and silkworm excreta, and on its confounding appearance in the digestive tracts of animals fed chlorophyll-containing food. Pheophorbide A acts as a photosensitizer in photodynamic therapy. Photoactivated pheophorbide A induces lipid peroxidation, arrests cell growth by activating apoptosis and/or necrosis. In vitro and animal studies have suggested some efficacy for pheophorbide A-mediated photodynamic therapy of cancers.