The present invention describes extracts of Polygonum cuspidatum and related compositions that are capable of photodynamic inactivation (PDI) of microorganisms such as bacteria, viruses, fungi, and protozoa, and capable of killing or inactivating cancer cells. The present invention further describes methods of using said Polygonum cuspidatum extracts and photodynamic inactivation (PDI) as a therapy for the treatment of microbial infection and as well as the use of Polygonum cuspidatum extract and related compositions as photodynamic therapy agents for the treatment of cancer.
