Radioprotectors in radiotherapy - advances in the potential application of phytochemicals.

Radiotherapy, in addition to chemotherapy, is currently the primary method of cancer treatment based on destruction of malignant cells by ionizing radiation. Unfortunately, it also affects normal cells, which is associated with negative consequences for a patient. Radioprotectors are compounds used to prevent/protect the non-tumor cells from the harmful effects of radiation. To play their role these compounds should meet several criteria; among others, they should significantly protect normal cells from radiation without changing the tumor cell radiosensitivity. In general, agents used to alter normal tissue toxicity from radiation can be broadly divided into three categories based on timing of delivery in relation to radiation: chemical radioprotectors, mitigators, and treatment. These groups include a diverse range of synthetic compounds in terms of their structure and protective mechanisms. The aminoradiothiol amifostine is the only radioprotectant approved in clinical application. However, its use is limited due to toxicity concerns (it may cause hypotension). Natural compounds, derived from plants, meet all criteria of the ideal radioprotector. They exert their protective actions against adverse effects of ionizing radiation by several mechanisms. Plant compounds that show radioprotective activity include flavonoids and phenolic acids, stilbenes, lycopene, alkaloids, peptides, polysaccharides, and phytohormones. Garlic, green tea, apples, citrus, and ginger are examples of constituents of the human diet that contain radioprotective substances.