2.1.1 Cardiovascular disease

In the last four decades, especially in the developed countries of Europe and America, scientists have shown increasing interest in plant research. It is estimated that today about 60% of the total world population in treatment relies on herbs and natural products that are thus recognized as an important source of drugs [1]. Phytochemistry studies a huge variety of organic substances that have been discovered and which accumulate in plants. Furthermore, phytochemistry is also defining the structure of these compounds, their biosynthesis, metabolism, natural distribution, and biological activities [2]. An important place among them is occupied by aromatic plants, whose aroma is associated with the presence of essential oils and complex mixtures of volatile compounds, dominated by mono- and sesquiterpenes. In addition to essential oils, aromatic plants are characterized by the presence of plant phenolic compounds, primarily coumarins and phenylpropanoids, that have been shown to possess multiple pharmacological activities. Investigations of these secondary biomolecules intensified when some commercial synthetic antioxidants were found to exhibit toxic, mutagenic, and carcinogenic effects [3]. It was also found that excessive production of oxygen radicals in the body initiates the oxidation and degradation of polyunsaturated fatty acids. It is known that free radicals attack the highly unsaturated fatty acid membrane systems and induce lipid peroxidation, which is a key process in many pathological conditions and one of the reactions that cause oxidative stress. Particularly, the biological membrane lipids in the spinal cord and brain are vulnerable, because they contain high levels of polyunsaturated fatty acids. Moreover, the brain contains significant amounts of transitional prooxidant metals and consumes a lot of oxygen. These features facilitate the formation of oxygen radicals involved in the processes of aging, Alzheimer's and Parkinson's disease, ischemic heart damage, arthritis, myocardial infarction, arteriosclerosis, and cancer. Phenolic antioxidants "stop" free oxygen radicals and free radicals formed from the substrate by donating hydrogen atoms or electrons. Many plant species and aromatic plants have been tested because of their antioxidant and

The aim of this chapter was to show the antioxidant role of phenolic acids and flavonoids presented in aromatic plants and to assess their potential capacity as

Atmospheric oxygen (O2) is present as a biradical with two unpaired electrons, which have the same spin quantum number and are located opposite the orbited orbits. This electronic structure of molecular oxygen determines its chemical reactivity and allows the absorption of individual electrons, with the formation of numerous intermediate, partially reduced oxygen species that are commonly referred to as reactive oxygen species (ROS) [5, 6]. These reactive oxygen species are able to react with basic cellular structures and biomolecules [7] and are respon-

The normal concentration of free radicals in the body is very low. However, the effects are very disruptive, as the chain reaction allows one free radical to cause changes in thousands of molecules and damage DNA, RNA, and enzymes in cell membranes and leads to the formation of lipoxygenation products before being inactivated. Which part of the cell (proteins, nucleic acids, membrane lipids, cytosolic molecules) or the extracellular component (hyaluronic acid, collagen) will react with free radicals depends on the nature of the radical and the site of its formation (e.g., cytosolic membranes, mitochondria, endoplasmic reticulum, peroxisome, cell membranes). Due to the presence of molecular oxygen in aerobic

sible for the emergence of many diseases and degenerative damage [8].

antiradical activities [4].

Antioxidants

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scavengers of different free radicals.

2. Oxygen as a toxic molecule

ROS, RNOS, and LP are considered to be the major contributors to the etiology of atherosclerosis and various chronic disorders such as coronary disease, stroke, and ischemic dementia [9]. Antioxidants introduced through food can reduce the occurrence of cardiovascular diseases by inhibiting the production of free radicals and oxidative stress, protecting LDL from oxidation and aggregation, and inhibiting the synthesis of proinflammatory cytokines [10].

## 2.1.2 Neurodegenerative diseases

Oxidative stress often occurs in the brain, because although it represents only 2% of the body weight, the brain uses up to 20% of oxygen added. Also, the brain contains large amounts of polyunsaturated fatty acids subject to lipid peroxidation under conditions of high oxygen concentration [11, 12].

## 2.1.3 Carcinogenesis

Although there are insufficient facts to confirm that the presence of free radicals is necessary in the process of carcinogenesis, it is clear that they can lead to mutations, transformations, and cancers [13]. Regarding the development of cancer, the most important target for ROS is DNA. Carcinogenesis is the result of successive mutations in DNA molecules leading to uncontrolled growth and cell phenotypic modification. One of the first steps in this process is the direct interaction of electrophiles or free radicals with cellular DNA in which promutagen lesions develop. If no repair is performed, these lesions result in mutations in the next generation of cells [14]. An increased intake of antioxidants through diet or dietary supplements is associated with a reduction in the onset of cancer.

#### 2.1.4 Aging

A reduced amount of free radicals or a reduction in the speed of their production postpones the aging process and a whole series of diseases related to the aging process [15]. A certain maximum life potential characterizes each animal species. There is a reciprocal correlation between the speed of oxygen consumption (and therefore the production of free radicals) and the maximum life potential. Some studies have shown that the aging process can be slowed by increased food intake

that increases antioxidant capacity (e.g., fruit and vegetables) or by supplemental intake of vitamins E, C, and β-carotene [16].

encompasses a wide range of plant substances that form one of the most numerous classes of secondary biomolecules that have a common characteristic of an aromatic ring carrying one or more hydroxyl groups as substituents, including functional derivatives (esters, glycosides, etc.). However, this broad definition also includes some non-phenolic substances. For this reason, it is recommended to combine a definition that includes a chemical description and a biogenetic origin. In nature, there are two general biosynthetic pathways for the synthesis of plant phenols: (1) a polyacetate route and (2) a phenylpropanoid route with scrub acid as an intermediate. Some phenols are formed by a combination of these two times [17]. The efficiency of phenolic compounds in protection against oxidative stress depends on their reactivity in relation to toxic oxygen species and the reactivity of phenoxy radicals relative to critical biomolecules. Chemical or enzymatic oxidation of phenolic components of plant tissue results in a dark color which is of particular importance in food technology. Their susceptibility to oxidation allows their use in

Phenolic compounds also increase the activity of antioxidant enzymes, thus indirectly affecting the concentration of harmful oxygen radicals in the living cell. In high concentrations, radical reactions such as DNA damage, superoxide anion

The term "phenolic acid" includes hydroxy and other functional derivatives of benzoic acid (C6▬C1) and cinnamic acid (C6▬C3) [19, 20]. Figures 1 and 2 give

the protection of fats and oils.

3.1.1 Phenolic acids

Figure 1.

Figure 2.

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Chemical compounds of basic benzoic acid derivatives.

Chemical formulas of basic derivatives of cinnamic acid.

production, etc. can also be act as a prooxidant [18].

Flavonoids and Phenolic Acids as Potential Natural Antioxidants

DOI: http://dx.doi.org/10.5772/intechopen.83731

the structures of the basic representatives of these acids.
