*4.2.5.1 Application*

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].

**13**

*Antioxidant Categories and Mode of Action DOI: http://dx.doi.org/10.5772/intechopen.83544*

extreme free radicals and oxidative stress [52].

and neuroprotective pharmacological properties [40, 54].

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

Studies showed that serum uric acid levels are highly predictive of mortality in patients with coronary artery disease, heart failure, or diabetes. In addition, high uric acid level is associated with deleterious effect on vascular function. Recently, it has been found that patients with high serum uric acid level had impaired flow-mediated dilation, which was normalized by therapy for 3 months with the xo inhibitor allopurinol [53].

Lipoic acid is a strong antioxidant, and it reveals a great capability of antioxidant when given natural or as a synthetic drug. Lipoic acid is a short-chain fatty acid, composed of sulfur in their structure that is known for its contribution in the reaction that catalyzes the oxidation decarboxylation of α-keto acids, for example pyruvate and α-ketoglutarate, in the citric acid cycle. Lipoic acid and its reduced form, dihydrolipoic acid (DHLA), are capable of quenching free radicals in both lipid and aqueous domains. Lipoic acid and DHLA have been revealed to have antioxidant, cardiovascular, antiaging, detoxifying, anti-inflammatory, anticancer,

Regarding the pathology of diabetes, there are many potential applications for lipoic acid. In type I diabetes, destruction of pancreatic β-cells leads to loss secretion of insulin, while the major problem in type II diabetes is insulin resistance of peripheral tissues. Lipoic acid has potential preventive or ameliorative effect in both

Flavonoids are low in molecular weight and are the main type of phenolic compounds in plants. They are structured by 15 carbon atoms, organized in a C6-C3-C6 configuration. Due to their high redox potential, flavonoids are, in particular, important antioxidants that allow them to function as reducing agents, hydrogen donors, and singlet oxygen quenchers. In addition, they include a metal chelating potential [55].

Flavonoids are generally found in many fruits and vegetables. When human increasingly consumed it, flavonoids have been linked with a decrease in the incidence of diseases such as prostate [56, 57] or breast cancer [58, 59].

*4.2.6 Uric acid*

*4.2.6.1 Application*

*4.2.7 Lipoic acid*

*4.2.7.1 Application*

*4.2.8 Flavonoids*

*4.2.8.1 Application*

type I and type II diabetes [54].
