Antioxidant Parameters

There are some important antioxidant parameters that are estimated in various type of pharmacological studies. The details are mentioned below:-

Catalase

Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals). It catalyses the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting the cell from oxidative damage by reactive oxygen species (ROS).

In the food industry, it is used in combination with other enzymes in the preservation of foodstuffs and in the manufacture of beverages and certain food items. Commercial catalases also are used to break down hydrogen peroxide in wastewater.

Hydrogen peroxide (H₂O₂) is widely regarded as a cytotoxic agent whose levels must be minimized by the action of antioxidant defence enzymes. In fact, H₂O₂ is poorly reactive in the absence of transition metal ions. Levels of H₂O₂ in the human body maybe controlled not only by catabolism but also by excretion, and H₂O₂ could play a role in the regulation of renal function and as an antibacterial agent in the urine. Multiple papers have described high (usually ≥50 μM) levels of H₂O₂ as being cytotoxic to a wide range of animal, plant and bacterial cells in culture, although LD50 values and the mode of cell death induced (apoptosis or necrosis) depend on the cell type used, its physiological state, length of exposure to H₂O₂, the H₂O₂ concentration used, and the cell culture media employed.

2.    Superoxide dismutase (SOD)

Superoxide dismutase is an enzyme found in all living cells. An enzyme is a substance that speeds up certain chemical reactions in the body. Superoxide dismutase (SOD) is an enzyme that alternately catalyses the dismutation (or partitioning) of the superoxide (O2−) radical into ordinary molecular oxygen (O2) and hydrogen peroxide (H2O2). Superoxide is produced as a by-product of oxygen metabolism and, if not regulated, causes many types of cell damage. Hydrogen peroxide is also damaging and is degraded by other enzymes such as catalase.

Three forms of superoxide dismutase are present in humans, SOD1 is located in the cytoplasm, SOD2 in the mitochondria, and SOD3 is extracellular. Superoxide dismutase is given as a shot for treating pain and swelling (inflammation) caused by osteoarthritis and rheumatoid arthritis (RA). SOD has powerful anti-inflammatory activity. For example, SOD is a highly effective experimental treatment of chronic inflammation in colitis. Treatment with SOD decreases reactive oxygen species generation and oxidative stress and, thus, inhibits endothelial activation. Therefore, such antioxidants may be important new therapies for the treatment of inflammatory bowel disease.

3.      Thiobarbituric acid reactive substances (TBARS) or Malondialdehyde (MDA)

Thiobarbituric acid reactive substances (TBARS) are formed as a by-product of lipid peroxidation (i.e. as degradation products of fats) which can be detected by the TBARS assay using thiobarbituric acid as a reagent. Malondialdehyde (MDA) is one of the final products of polyunsaturated fatty acids peroxidation in the cells. An increase in free radicals causes overproduction of MDA. Malondialdehyde level is commonly known as a marker of oxidative stress MDA is one of several low-molecular-weight end products formed via the decomposition of certain primary and secondary lipid peroxidation products. Because reactive oxygen species (ROS) have extremely short half-lives, they are difficult to measure directly. Instead, what can be measured are several products of the damage produced by oxidative stress, such as TBARS.

4.      Glutathione (GSH)

Glutathione (GSH) is an antioxidant in plants, animals, fungi, and some bacteria and archaea. Glutathione is capable of preventing damage to important cellular components caused by reactive oxygen species such as free radicals, peroxides, lipid peroxides, and heavy metals. Glutathione exists in reduced (GSH) and oxidized (GSSG) states. The ratio of reduced glutathione to oxidized glutathione within cells is a measure of cellular oxidative stress where increased GSSG-to-GSH ratio is indicative of greater oxidative stress.

Glutathione (GSH) is often referred to as the body's master antioxidant. Composed of three amino acids - cysteine, glycine, and glutamate - glutathione can be found in virtually every cell of the human body. The highest concentration of glutathione is in the liver, making it critical in the body's detoxification process.

5.      Glutathione Peroxidase (GPx)

Glutathione Peroxidase (GPx) is a cytosolic enzyme that catalyzes the reduction of hydrogen peroxide to water and oxygen as well as catalyzing the reduction of peroxide radicals to alcohols and oxygen. The biochemical function of glutathione peroxidase is to reduce lipid hydroperoxides to their corresponding alcohols and to reduce free hydrogen peroxide to water.

“Glutathione, which is involved in the transport of amino acids acts as a coenzyme for enzymes and it protects against oxygen radicals and toxic compounds. GSH peroxidase is capable of utilizing hydrogen peroxide (H2O2) and a variety of organic hydroperoxides as substrates.”