**10. Natural anti-oxidant in human body**

As we know that free radicals attack on DNA and interferes with normal physiology of cell and to protect DNA from these attacks a series of defense mechanism is developed by body. Anti-oxidant act at different levels and by different mechanism in the defense system such as preventive mechanism, radical scavenging and repair and adaptation (**Table 2**).


## **10.1 First line of defense**

Preventive oxidants are the first line of defense and they act by suppressing the formation of free radicals. Catalase (CAT), glutathione peroxide (GPx) and superoxide dismutase (SOD) are the examples of enzymatic oxidants.
