**3. Ascorbic acid (Vitamin C)**

L-Ascorbic acid (AA), commonly known as vitamin C, is considered one of the organism's most powerful antioxidant agents due to its capacity to donate two electrons from its double link, that of positions two and three; thus, it interacts with the FR, blocking their harmful effect. The human body is not capable of obtaining vitamin C exogenously through foods; it is found concentrated in certain organs such as eye, liver, spleen, suprarenal glands, and thyroids. It is an essential vitamin, in that it participates in reactions such as the synthesis of molecules such as carnitine or thrysine acid, which are fundamental for good bodily function; it participates in iron absorption and presents immunological and antiinflammatory actions such as the synthesis of neurotransmitters and hormones, playing an important role in collagen synthesis (Morales-González, 2009; Mathews-Van Holde 1998).

AA (C6H8O6) is an essential vitamin that is chemically synthesized from glucose by a series of enzyme-catalyzed actions, the last enzyme involved in its synthesis being L-gulonogamma-lactone oxidase (GLO); it is hydrosoluble and possesses acidic and strongly reductive properties. These properties are due to its enediol structure and to the possibility of ionizing the hydroxyl situated on carbon 3, forming an anion that remains stabilized by resonance. Eventually, it can dissociate the carbon-2 hydroxyl, forming a dianion, although it does not acquire the same stability as that of carbon 3. In nature, two isomers are found with nutritive properties (Figure 1): the L- isomer (L-ascorbic acid), and the D-isomer (Ldehydroascorbic acid). The functions of vitamin C apparently reflect its redox capacity. Thus, it participates in some hydroxylation reactions in which it maintains optimal enzymatic activity by means of electron donation. Vitamin C also increases the absorption of no-heme iron and serves as an important mechanism for inactivating highly reactive radicals in tissue cells. Similarly, it delays the formation in the body of nitrosamines , which are possible carcinogens. The accumulated evidence links ascorbic acid with many elements of the immunitary system (Morales-González, 2009).

#### **3.1 Absorption**

102 Liver Regeneration

Vitamin A is a natural antioxidant that prevents cellular aging, eliminates FR, and protects the DNA in its mutagenic action. β-carotene is also a powerful antioxidant. We must clarify that this antioxidant function is only obtained in foods that were submitted to cooking for at least 5 minutes. Some studies have demonstrated that β-carotene supplemented in the diet

On the other hand, in the case of its participation in the regeneration of hepatic cells in alcohol-induced damage, a positive result is obtained, because vitamin A has shown a lesser protector effect against the formation of FR in the reversion of the hepatic regeneration inhibition caused by ethanol consumption, due to that retinol is the principal component of vitamin A, that it is an alcohol, and that retinol as well as ethanol utilize the same enzymatic pathways; thus, storage of vitamin A and of ethanol in hepatic cells is altered. Therefore, an excess of vitamin A and its interaction with the alcohol increase the capacity to produce fibrous tissue that, in the long term, can cause a cirrhosis (Ramírez-Farías et al., 2008). Thus, it is considered that vitamin A can generate, instead of a benefit, a hepatotoxicity with subsequent inflammation, necrosis, and the increase of some serum enzymes (Morales-

L-Ascorbic acid (AA), commonly known as vitamin C, is considered one of the organism's most powerful antioxidant agents due to its capacity to donate two electrons from its double link, that of positions two and three; thus, it interacts with the FR, blocking their harmful effect. The human body is not capable of obtaining vitamin C exogenously through foods; it is found concentrated in certain organs such as eye, liver, spleen, suprarenal glands, and thyroids. It is an essential vitamin, in that it participates in reactions such as the synthesis of molecules such as carnitine or thrysine acid, which are fundamental for good bodily function; it participates in iron absorption and presents immunological and antiinflammatory actions such as the synthesis of neurotransmitters and hormones, playing an important role in collagen synthesis (Morales-González, 2009; Mathews-Van Holde 1998).

AA (C6H8O6) is an essential vitamin that is chemically synthesized from glucose by a series of enzyme-catalyzed actions, the last enzyme involved in its synthesis being L-gulonogamma-lactone oxidase (GLO); it is hydrosoluble and possesses acidic and strongly reductive properties. These properties are due to its enediol structure and to the possibility of ionizing the hydroxyl situated on carbon 3, forming an anion that remains stabilized by resonance. Eventually, it can dissociate the carbon-2 hydroxyl, forming a dianion, although it does not acquire the same stability as that of carbon 3. In nature, two isomers are found with nutritive properties (Figure 1): the L- isomer (L-ascorbic acid), and the D-isomer (Ldehydroascorbic acid). The functions of vitamin C apparently reflect its redox capacity. Thus, it participates in some hydroxylation reactions in which it maintains optimal enzymatic activity by means of electron donation. Vitamin C also increases the absorption of no-heme iron and serves as an important mechanism for inactivating highly reactive radicals in tissue cells. Similarly, it delays the formation in the body of nitrosamines , which are possible carcinogens. The accumulated evidence links ascorbic acid with many elements

has shown some evidence of antitumor action (Allende-Martínez 1997).

**2.3 Antioxidant action** 

González, 2009).

**3. Ascorbic acid (Vitamin C)** 

of the immunitary system (Morales-González, 2009).

Vitamin C absorption is carried out in the small intestine by sodium-dependent active transport (faster and more efficient), or by passive transfusion through a glucose transporter (insulin). L-dehydroascorbic acid is more easily absorbed than L-ascorbic acid. This characteristic is attributed to that the oxidized form of the vitamin remains with ionization to the physiological pH and to that the molecule is slightly hydrophobic, which permits it to penetrate into the membranes, Once inside, it is reduced to ascorbate; in this manner, it circulates mainly in plasma and in suprarenal glands and hypophysis. The effectiveness of the absorption depends on the dose administered, because it has been observed that on increasing the dose, the effectiveness of the absorption diminishes (Morales-González, 2009).

Fig. 2. The chemical structure of vitamin C corresponds to that of a lactone; L-ascorbic acid presents a double connection link between the 2 and 3 carbon; this characteristic allows the molecule to donate electrons from this double link, forming L-dehydroascorbic acid, or in a reversible reaction.

#### **3.2 Antioxidant action**

Similar to vitamin A, vitamin C is a natural antioxidant characterized by the capacity to donate two electrons from its double link at positions two and three, in such as way that it interacts with FR, blocking their harmful effect; consequently, it is oxidized. In addition to exerting an effect on FR, it also acts by regenerating oxidized antioxidants such as αtocopherol and β-carotene. In a study published by Ramírez-Farías et al., in 2008, the author concluded that administration of vitamins C and E provided a protector effect against liver damage; they attenuate lipid peroxidation, and both vitamins present a significantly greater effect than vitamin A against ethanol-mediated toxic effects during hepatic regeneration.
