Oxidative stress has received a considerable scientific attention as a mediator in the etiology of many human diseases. Oxidative stress is the result of an imbalance between free radicals and antioxidants. Cells can be damaged by free radicals that are considered to play a main role in the aging process and diseases development. Antioxidants are the first line of defense against the detrimental effects of free radical damage, and it is essential to maintain optimal health via different mechanisms of action. Types of antioxidants range from those generated endogenously by the body cells, to exogenous agents such as dietary supplements. Antioxidant insufficiency can be developed as a result of decreased antioxidant intake, synthesis of endogenous enzymes, or increased antioxidant utilization. To maintain optimal body function, antioxidant supplementation has become an increasingly popular practice through improving free radical protection. In this chapter, we first elucidate the oxidative stress, and then define the antioxidant and its categories. Finally, introduce the antioxidants mode of actions for cell protection from free radicals.

Background:The major components of petroleum are hydrocarbons which are toxic and have been implicated in a number of human diseases. Petroleum hawkers are exposed to these hydrocarbons continuously by inhalation. This study aimed to determine the effects of petroleum exposure on malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD) and reduced glutathione (GSSH) among petroleum hawkers in Bauchi metropolis. This was a descriptive cross-sectional study carried out among 120 consenting petroleum hawkers in Bauchi metropolis.Method: Venous blood samples were collected from the subjects and analyzed using spectrophotometric technique, data was also collected using structured interviewer-administered questionnaire and analyzed using SPSS version 23 software. Analysis employed descriptive and inferential statistics. Level of significance was set at 0.05. Result:The result showed statistically significant mean difference in superoxide dismutase (SOD) in exposed group as compared to unexposed group (p<0.001). There were also differences in mean of malondialdehyde (MDA), catalase (CAT) and reduced glutathione (GSSH) though this differences were not statistically significant with p-values 0.100, 0.127 and 0.057 respectively. In addition, petroleum hawkers who were exposed to petroleum products for greater than 8hrs had higher malondialdehyde (MDA) levels compared to those exposed for less than 8hrs and this difference was statistically significant ( p-value=0.003). Conclusion:The results of this study showed that petroleum hawkers are at risk of adverse effects on human health especially diseases of liver and kidney.