*4.2.6 Uric acid*

*Antioxidants*

*4.2.3 Vitamin C*

*4.2.3.1 Application*

*4.2.4 Carotenoids*

[42, 45].

attack [49].

cancer [42].

*4.2.5 Vitamin A*

*4.2.5.1 Application*

prohibit cell lipid peroxidation [9].

*4.2.4.1 Application*

In extracellular fluids, vitamin C, a water-soluble vitamin, is the most important antioxidant and can protect biomembranes against lipid peroxidation injury through eliminating peroxyl radicals in the aqueous phase before peroxidation initiation. Vitamin C is an effective antioxidant located in the aqueous phase of cells; it simply loses electrons to give stability to reactive species such as ROS [45]. In addition to vitamin C's biological functions as a superoxide and hydroxyl radicals'

Vitamin C plays an essential function in the defense against oxidative damage particularly in leukocytes, as well as the possible effect it may have on the treatment of chronic degenerative diseases, autoimmune diseases, and cancer

Carotenoids are structurally and functionally different natural pigments found in many fruits and vegetables. A combination of carotenoids and tocopherols antioxidants in the lipid phase of biological membranes may enhance better antioxidant protection than tocopherols alone. Antioxidant characteristics of carotenoids include scavenging single oxygen and peroxyl radicals, thiyl, sulfonyl, sulfur, and NO2 radicals and giving protection to lipids from superoxide and hydroxyl radical

Carotenoids and some of their metabolites are proposed to play a protective function in several ROS-mediated disorders, include cardiovascular, cancer, and myocardial infarction among smokers. Carotenoid-rich food and supplementation decrease morbidity in nonsmokers and reduce the risk of prostate

Vitamin A, a lipid soluble vitamin, is important for human health and has free radicals scavenging features that aid it to act as a physiological antioxidant in protecting a number of chronic diseases such as cardiovascular disease and cancer. All transretinol, the parent compound, are the most abundant dietary form of vitamin A that occurs naturally in the form of fatty acid esters such as retinyl palmitate, while retinal and retinoic acid are the minor natural dietary components of vitamin A [45]. Vitamin A was first labeled as an inhibitor of the effect of linoleic acid on the oxidation processes. At present, vitamin A and carotenoids are known for their antioxidant actions depending on their capability to interact with radicals and

Vitamin A is important for life in mammals; it cannot be synthesized in body and has to be supplied by food. Due to its role as antioxidant, vitamin A has a new role in preventive nutrition against neurodegenerative diseases. Recently, vitamin A

has increased the interest in supplementation via food [50].

scavenger, it also functions as an enzyme cofactor [42].

**12**

Uric acid, hyperuricemia, is a potent free radical scavenger and estimated ~60% of free radical scavenging capacity in plasma [51]. Uric acid is a physiological antioxidant and an effective preventer of the production of ROS species during the action of xanthine oxidase (XO) in catalysis reaction of xanthine and hypoxanthine [42]. A study illustrated the urate ability to scavenge oxygen radicals and protect the erythrocyte membrane from lipid oxidation, characterized further by Ames et al. through the effect of uric acid in protection of cells from oxidants, which related to a variety of physiological situation [51]. Nevertheless, it is probable that the increase in serum level of uric acid is a response to protect against the detrimental effects of extreme free radicals and oxidative stress [52].
