Background: Cancer is a serious life-threatening disease often thought of as a deadly and painful disease with no permanent cure. With the advancement of medical science, there have been several clinically approved treatment options developed over the past decade. Photodynamic therapy (PDT) is one such approved minimally invasive light-based therapeutic option for many cancers. Selection of a suitable photosensitizer (PS) is an important step in PDT for improved therapeutic outcomes. Efforts to discover more efficient PSs continue for optimal PDT. Objective: This review discusses the available natural PS of plant origin, the role of phytochemicals in the application of PDT of cancer, specific localization of PS in various cell organelles, and photochemical reactions. Materials and methods: Owing to the substantial side effects, many biomedical research fields are currently focusing on natural compounds with chemotherapeutic potential with environmentally sustainable green approaches. Medicinal plant extracts have been used since ancient times for the treatment of various ailments. Plants are a natural source of many bioactive compounds with pharmaceutical potential and there have been some efforts made to discover potential new compounds from plants with photosensitizing properties for effective PDT outcomes. Results and conclusions: The PDT application in the current scenario raises some questions, such as most effective PS, its administration, the time of irradiation, light source, sensitivity of cells toward PS, and so forth. PDT effects can be direct or indirect. Owing to the direct effect of the PDT, most of the tumoral mass is destroyed. In the cancer cells that were not directly affected, secondary effects such as vascular effects, apoptosis induction, inflammation, and generation of an immune response may occur; however, the complex nature of PDT tissue response is not fully established.
Keywords: cancer; photochemical reactions; photodynamic therapy; photosensitizers; phytochemicals; subcellular localization.