Acetylcysteine (AC) is an aminothiol and synthetic precursor of intracellular cysteine and GSH and is thus considered an important antioxidant . AC has been widely used as a research tool in the field of apoptosis research for investigating the role of Reactive oxygen species ROS in induction of apoptosis.

It is generally assumed that the action of AC results from its antioxidative or free radical scavenging property as an antioxidant through increasing intracellular GSH levels; however, AC also possesses a reducing property through its thiol-disulfide exchange activity. For example, AC has been shown to induce cell cycle arrest in hepatic stellate cells by modulating the mitogen-activating protein (MAPK) pathway.

Vitamin B12 is an essential vitamin that’s crucial for many vital metabolic and hormonal functions — including the production of digestive enzymes and carrying important nutrients into and out of cells. Due to how it helps convert and synthesize many other compounds within the body, it’s needed for well over 100 daily functions. Some of the roles that are attributed to vitamin B12 include: red blood cell production, DNA/RNA synthesis, methylation and producing the coating of the nerves.

Glutathione (GSH) is a small protein molecule composed of 3 amino acids: cysteine, glutamate, and glycine called GSH precursors or building blocks. GSH is produced out of these three precursors in every cell of the human body and performs many important roles, such as:

1. Regulation of cell growth and division - For cells to grow and divide they go through several very complex stages. Glutathione reduces the oxides, such as hydrogen peroxide, inside the cell that would otherwise prevent cell division and growth.

2. DNA synthesis and repair synthesis - Glutathione protects the DNA from oxidative stress during cell division which allows for DNA synthesis (division). When the DNA is mutated by a free radical stealing an electron from the DNA, glutathione repairs the mutated DNA by giving up an electron to the DNA (replacing the DNA’s missing electron).

3. Protein synthesis - Glutathione maintains our proteins in their proper form. Its sulfur atom reacts with unnatural sulfur. Sulfur bonds in proteins, breaking them and allowing the proper pairings to form. Amino acid transport (movement into, out of, within a cell, or between cells, by means of some agent such as a transporter). Glutathione is predominately located in the cell, whereas a major fraction of the cellular y-glutamyl transpeptidase (glutathione enzyme) is on the external surface of cell membranes. This means intracellular glutathione is translocated out of many cells – glutathione moves substances, such as amino acids, in and out of the cell.

4. Enzyme catalysis - Glutathione provides the mechanism by which many enzymes are changed (reduced, transformed or changed from one state to another state). Glutathione is the bridge (catalysis) in the chemical reaction between some enzymes.

5. Enzyme activation - The highly reactive sulfide bond in glutathione wakes up or activates enzymes so that they carry out their function or are moved from one phase to the next.

6. Metabolism of toxins (metabolism or biotransformation – breaking down, activating or transforming) - In the liver, the enzyme glutathione S-transferase takes the sulfur from glutathione and attaches it to toxic molecules, this makes the toxin more water soluble (it is diluted in water easily). Once a toxin is water soluble, it is transported to the body's elimination systems and is excreted from the body.

7. Metabolism of carcinogens - Glutathione enzymes transform carcinogens, through chemical reaction, to unreactive and non-genotoxic compounds that can be eliminated without causing damage to the cell or DNA.

8. Metabolism of xenobiotics (xenobiotics - chemical components (drugs and poisons) foreign to the body) - Glutathione interacts with foreign chemicals (primarily, it is a scavenger of harmful xenobiotics that have been oxidized) compounds to neutralize and break them down, then eliminate them from the body.

9. Conjugation to heavy metals (conjugation – joining with and transforming by becoming part of) Glutathione joins with heavy metals to neutralize them and eliminate them from the body.

10. Conjugation to xenobiotics - In some instances, depending on the state of the xenobiotic, Glutathione joins with it instead of metabolizing it.

11. Enhancement of systemic immune function - The immune system works best if the lymphoid cells have properly balanced glutathione. The cloning of T-cells consumes large quantities of cysteine. Macrophages (type of white blood cells), which are only present in sufficient quintiles when there is sufficient Glutathione, provide the cysteine for the T-cell cloning. Glutathione regulates the binding, internalization, degradation and T-cell proliferation by increasing, as much as two times, the number of binding cellular receptors. More receptors equates to more T-cells being produced simultaneously (multiple T-cell cloning). Cellular GSH also affects the growth and replication of T-cells through growth stimulating cytokines.

12. Enhancement of humoral immune function - The role of glutathione in the humoral response is that it protects the cells taking part in the humoral response all along this complex process.

A quick synapsis of the humoral immune response: “humoral” means circulating in the bloodstream. This is an immune response (chiefly against bacterial invasion) that is mediated by B cells and involves the transformation of B cells into plasma cells that produce and secrete antibodies to a specific antigen.

The process in a nutshell is that macrophages engulf and digest the invading pathogen. The digested pieces activate helper T cells which in turn activate the proliferation of B cells that are programed for the specific invading pathogen.

1. Resistance to UV radiation - Glutathione detoxifies reactive oxygen radicals created by radiation which reduces the damage to the cell. Glutathione also interacts covalently and noncovalently (neutralizes the reactivity in several ways) with parts of the cell that keep the cell from triggering apoptosis (cell death).

2. Decreases radiation damage - The action of glutathione in decreasing the damage from radiation is the same as in resistance to UV radiation above.

3. Decreases free radical damage - The crucial cysteine molecule is the key to the protection afforded by glutathione. Its sulfur atom scavenges destructive molecules (peroxides and free radicals) converting them to harmless compounds, such as water.

4. Decreases oxyradical damage - Glutathione detoxifies reactive oxygen radicals by giving them an electron which effectively neutralizes them, or glutathione joins with the oxyradical which again neutralizes it.

Superoxide dismutases (SODs) are a group of metalloenzymes that are found in all kingdoms of life. SODs form the front line of defense against reactive oxygen species (ROS)-mediated injury. These proteins catalyze the dismutation of superoxide anion free radical (O2-) into molecular oxygen and hydrogen peroxide (H2O2) and decrease O2- level which damages the cells at excessive concentration. This reaction is accompanied by alternate oxidation-reduction of metal ions present in the active site of SODs. Based on the metal cofactors present in the active sites, SODs can be classified into four distinct groups, one of which is Copper-Zinc-SOD (Cu, Zn-SOD).

SODs constitute a very important antioxidant defense against oxidative stress in the body. Several studies have been performed that reveal the therapeutic potential and physiological importance of SOD. The enzyme can serve as an anti-inflammatory agent and can also prevent precancerous cell changes. Natural SOD levels in the body drop as the body ages and hence as one age, one becomes more prone to oxidative stress-related diseases.

Superoxide dismutase participates in a dismutation reaction in order to convert superoxide into the less toxic substances of hydrogen peroxide and dioxygen. A dismutation reaction is a reaction in which one substance is oxidized and the other is reduced simultaneously. There are two redox reactions that occur in the copper zinc superoxide dismutase system, and copper catalyzes these reactions. In one reaction Cu2+ is reduced to Cu1+, while the superoxide molecule, O2-, is oxidized to O2. In the second step Cu1+ is oxidized to Cu2+, while a second superoxide molecule is reduced to hydrogen peroxide, H2O2.

Vitamin C is a potent reducing agent, meaning that it readily donates electrons to recipient molecules. Related to this oxidation-reduction (redox) potential, two major functions of vitamin C are as an antioxidant and as an enzyme cofactor.

Vitamin C is the primary water-soluble, non-enzymatic antioxidant in plasma and tissues. Even in small amounts vitamin C can protect indispensable molecules in the body, such as proteins, lipids (fats), carbohydrates, and nucleic acids (DNA and RNA), from damage by free radicals and reactive oxygen species (ROS) that are generated during normal metabolism, by active immune cells, and through exposure to toxins and pollutants (e.g., certain chemotherapy drugs and cigarette smoke). Vitamin C also participates in redox recycling of other important antioxidants; for example, vitamin C is known to regenerate vitamin E from its oxidized form.

Vitamin C’s role as a cofactor is also related to its redox potential. By maintaining enzyme-bound metals in their reduced forms, vitamin C assists mixed-function oxidases in the synthesis of several critical biomolecules. Symptoms of vitamin C deficiency, such as poor wound healing and lethargy, result from impairment of these enzymatic reactions and insufficient collagen, carnitine, and catecholamine synthesis

Vitamin C affects several components of the human immune system; for example, vitamin C has been shown to stimulate both the production and function of leukocytes (white blood cells), especially neutrophils, lymphocytes, and phagocytes. Specific measures of functions stimulated by vitamin C include cellular motility, chemotaxis, and phagocytosis. Neutrophils, mononuclear phagocytes, and lymphocytes accumulate vitamin C to high concentrations, which can protect these cell types from oxidative damage. In response to invading microorganisms, phagocytic leukocytes release non-specific toxins, such as superoxide radicals, hypochlorous acid ("bleach"), and peroxynitrite; these reactive oxygen species kill pathogens and, in the process, can damage the leukocytes themselves. Vitamin C, through its antioxidant functions, has been shown to protect leukocytes from self-inflicted oxidative damage. Phagocytic leukocytes also produce and release cytokines, including interferons, which have antiviral activity. Vitamin C has been shown to increase interferon levels in vitro.