Radiation is an emission or propagation of energy in the form of electromagnetic

waves or streams of particles . Living things are exposed to radiation

from the start of life on earth. But knowingly or without one's knowledge, humans are

exposed to the detrimental effects of radiation . The origin of radiation

exposure from the artificial source may well be attributed to medical diagnostic and

therapeutic procedures. However, the term 'radiation'continues to be a permanent

mystery to society.

The threats associated on exposure to ionizing radiation were identified subsequent

the invention of X-rays in 1895 by Roentgen. About 23 cases of skin lesions were

reported at the start of 1897 due to the overexposure to X-rays . Initial

studies on radiation- induced cancer appeared in 1902 in the workers of X-ray

generators resulting in acute skin reactions in the ulcerated areas of skin, followed by

leukemia in five radiation workers in 1911. Certainly, after the death of Marie Curie,

and her daughter Irene which was believed to be due to radiation- induced leukemia;

studies confirmed the aftereffects of radiation in tissues of many species.

Gamma radiation induces oxidative damage in the cells by the transfer of radiation

energy to the biological material inducing the production of reactive oxygen species

and therefore referred to as an effective carcinogen . Radiation causes the breaking of bonds and ionizes the biological macromolecules like DNA, membrane lipids, and proteins. Damage to the oxidative base in DNA is induced by

the radiation . Further, ionizing radiation leads to highly complex processes such as single and double-strand breaks in DNA,

crosslink's between DNA and protein, including abasic sites in DNA ultimately

resulting in chromosomal aberrations.

Worldwide analysis on screening for the radioprotective compounds of chemical and

biological origin begun over the past seven decades . The discovery of radioprotective effects of sulfhydryl compound cysteine by Patt et al on the animals exposed to the ionizing radiation paved the way for radiation protection

studies . Consequently, the study on the synthesis of sulfhydryl

compounds like aminothiols and phosphorothioates began. Out of 4000 compounds

screened by a drug developmental program by a US department of defense (Walter

Reed Army Research Institute), WR-2721(S2 (3 aminopropylamino) ethyldihydrophosphothioate)

commonly referred to as Amifostine or Gammafos was the first

compound to act as a promising radio-protectant. The compound was known to

possess a dose modifying factor (DMF) of 2.7 and was able to offer the protection

only if administered before the radiation exposure .