Introduction
It is ironic that oxygen an element indispensable for life can under certain situations have severely deleterious effects on the human body. Most of the potentially harmful effects of oxygen are due to the formation and activity of a number of chemical compounds know as reactive oxygen species which have a tendency to donate oxygen to other substances. Many such reactive species are free radicals and have a surplus of one or more free-floating electrons rather than having matched pairs and are therefore unstable and highly reactive. Types of free radicals include the hydroxyl radical the superoxide radical the nitric oxide radical and the jipid peroxyl radical.