Antioxidants are important for the body's immune system and to protect the body against free radical attacks. Consistent sex differences were found only for current smoking and CRP, which showed a stronger association with high oxidative stress levels (defined by d-ROMs levels) in men than in women (Additional file 1 : Table S7) and for high age (70-85 years), which was more strongly associated with high oxidative stress levels (defined by TTL) in women than in men (Additional file 1 : Table S8).
Therefore, to match the proportion of individuals with high oxidative stress obtained by the definition based on d-ROMs levels, urinalysis reader the bottom cohort specific TTL quartile (25 %) was used to classify subjects to a high oxidative stress category based on TTL.

Researchers also have shown that a class of experimental medications made from steroid hormones can quench the explosive release of free radicals that often follows head or spinal cord injury and some types of stroke, a reaction that can destroy large amounts of otherwise healthy tissue and turn a minor accident into a case of paralysis.
The assay measures the oxidative degradation of the fluorescent molecule (either beta-phycoerythrin or fluorescein ) after being mixed with free radical generators such as azo-initiator compounds Azo-initiators are considered to produce the peroxyl radical by heating, which damages the fluorescent molecule, resulting in the loss of fluorescence.
In normal conditions (when an individual is in good health and resides in a relatively clean environment) the lung represents a unique tissue for oxidative stress, continually exposed to relatively-high O2 tension, pollutants and the metabolic products derived from them.

Oxidative stress is a strong candidate mechanism of aging ( Finkel & Holbrook, 2000 ). Since oxidative damage from several sources accumulates with age, the free radical theory of aging postulates that aging results from increasing accumulation of damage generated by reactive oxygen species (ROS) (reviewed in Beckman & Ames, 1998 ) that goes unchecked by antioxidant defenses and cellular repair mechanisms with age.
Polyphenols are bioactive compounds broadly spread in plants and they are also significant constituents of the human diet 2. Plants are considered as the main sources of antioxidants, which constitute a rich diversity of compounds such as flavonoids (anthocyanins, flavonols, flavones) and several classes of nonflavonoids (phenolic acids, lignins, stilbenes, terpenoids, etc.). These compounds differ in structure, the number of phenolic hydroxyl groups and their location, leading to variation in their antioxidative and biological potential 8. Some culinary herbs and spices have been proved to be more effective antioxidants than common food additives (butylated hydroxyanisole, butylated hydroxytoluene and propyl gallate) and vitamins (ascorbic acid, α-tocopherol and β-carotene) 9. Therefore herbs and spices rich in antioxidants and other phyto-compounds are able to prevent oxidative stress and its related disorders such as chronic diseases 10,11.

Free radicals have been found to play a role in the development of many diseases including cancer (free radicals are thought to promote cell transformation into a cancer cell), arthritis and inflammatory diseases (increased oxidative stress in rheumatoid arthritis patients suggests antioxidants could have an important role), cardiovascular disease (antioxidants have been found to improve cardiac health), and Alzheimer's disease (antioxidants have a role in removing deleterious free radicals from the brain).
Scientists do not completely understand the mixed results from the trials or the exact mechanism that makes antioxidants effective or ineffective against free radicals, but according to Wright, the study results suggest that it is more effective and potentially safer to get antioxidants through whole foods rather than supplements.
Superoxide anion radical scavenging effect: Superoxides are produced from molecular oxygen due to oxidative enzymes (Sainani et al., 1997) of body as well as via non-enzymatic reaction such as autoxidation by catecholamines (Hemmani and Parihar, 1998).

Testing from the National Measurement Institute (NMI) has revealed that many Australian sunscreen and cosmetic products still contain anatase titanium dioxide, despite years of warnings of its extreme potential to generate free radicals which could damage DNA and protein.
However, d-ROMs levels and TTL had additive predictive values for CVD mortality (Table 4 ). Subjects with high oxidative stress by both definitions had the highest RR for CVD mortality (RR, 2.47; 95 % CI, 1.58-3.98) with about twice the excess risk of subjects with high oxidative stress defined by only d-ROMs levels (147 % excess risk compared to 72 % excess risk).