ABSTRACT
Humans are exposed to many carcinogens, but the most significant may be the reactive species derived from metabolism of oxygen and nitrogen. Formation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the human body can cause oxidative damage to biological macromolecules such as DNA, lipids, and proteins (1) that may contribute to the development of cancer, cardiovascular and neurological diseases, cataract, and other oxidative stress-mediated
dysfunctions (2-4). Therefore, the assumption is often made that ROS=RNS are always ‘bad’, but the human body also needs ROS=RNS as, for example, their function in primary immune defence or for relaxation of smoothmuscles in blood vessel-walls.
