A Review on the Therapeutic Potential of Nature derived Cholrin Photosensitizer and its Synthetic Counterparts for Photodynamic Therapy in the control of Neoplastic Diseases

In the past three decades, photodynamic therapy (PDT) has accepted as an alternative modality for the management of wide variety of diseases including cancer, skin and bacterial, viral and fungal infections. It is minimally invasive treatment, which involves the interaction of a non-toxic photosensitizer (PS), light of an appropriate wavelength and tissue oxygen to remove unwanted cells by generating free radicals mediated by light receptors, which is more prevalent when the plant-produced metabolites are heterocyclic/polyphenols in nature. Until date, more than hundred photosensitizers or photosensitive drugs were identified various natural sources including plants. Many bioactive principles have shown in recent years to be potential photosensitizers, i.e. their toxic activities against various microorganisms, insects or cells are dependent on or are augmented by light of certain wavelengths. PDT considered often as selective and target specific, which led to the novel concept of therapeutic prospects in the control of infectious and other diseases including cancer. Photosensitization mechanisms commonly involve singlet oxygen and radicals, which causes photo damage to membranes or macromolecules. Although many existing PSs developed in the last 30 years, only a handful of them employed in human clinical applications. The main classes of natural photosensitizers reviewed in this chapter are chlorins and their synthetic counterparts because of their therapeutic efficacy by employing various search engines such as PubMed, Scifinder, and Web of Science. The continued progress in the development of novel photochemical is essential to advance targeted delivery of PS and efficacy of PDT, which consequently expands the range of clinical applications. The constant development of new photosensitizers is required to improve site-specific delivery for therapeutic efficacy of PDT, which consequently expands the range of clinical applications. If successful, these efforts will provide PDT therapy for infectious, cancer and other diseases with minimal risk to healthy tissue.