What Are the Functions of Glutathione and Its Applications?

Glutathione is an important active substance in the body, which has many physiological functions such as scavenging free radicals, detoxification, promoting iron absorption, maintaining the integrity of the red blood cell membrane, maintaining DNA biosynthesis, normal cell growth and cellular immunity, etc. [1].

The chemical name of glutathione is N-(N-L-Y-Glutamyl-L-cysteninyl) glycine, i.e. N-(N-L-Y-Glutamyl-L-cysteinyl) glycine. Glutathione is present in all living cells [1], but is more abundant in animal tissues and less abundant in plant tissues. In this paper, the applications and main physiological functions of glutathione are introduced.

1.Biological Functions of Glutathione

1.1 Involvement in Amino Acid Uptake and Transport

In addition to the specific protein carrier system in the plasma membrane, glutathione is also involved in the uptake of amino acids in the small intestine and their transport from the extracellular compartment to the intracellular compartment, the so-called r-glutamyl cycle [2].

The general process of this cycle is as follows: r-glutamyl in the plasma membrane catalyzes the formation of r-glutamic acid and cysteinylglycine from glutathione and the absorbed amino acids, which are then transported to the cell and broken down into amino acids and glutathione inside the cell, thus completing the process of amino acid transport and uptake. The reaction is energized by the ATP cycle.

1 . 2Maintaining the Integrity of the Erythrocyte Membrane and Removing Free Radicals from the Body

Erythrocytes often produce a small amount of H2 02 during metabolism, which can inactivate the sulfhydryl groups of the cell membrane if not removed in time. H2 02 also causes the oxidation of unsaturated fatty acids in the phospholipid molecules of the cell membrane, resulting in the production of lipid peroxides, which are further decomposed to form colloidal agents.

These collagens rapidly cause damage to the red cell membrane and hemolysis occurs. The enzyme glutathione peroxidase, which uses glutathione as a substrate, catalyzes the formation of H2 0 from H2 02 and the formation of alcohols from lipid peroxides, thus avoiding damage to the erythrocyte membrane.

Glutathione scavenges free radicals in the body by binding to them through its sulfhydryl groups, thus preventing the oxidation of sulfhydryl groups and the denaturation of proteins. Glutathione effectively scavenges free radicals, prevents skin aging and pigmentation, and enhances skin luster. At the same time, it can reduce the attack of free radicals on DNA, effectively reducing DNA damage and mutation. Glutathione is also a kind of radiation protection agent, which can effectively scavenge various kinds of highly active free radicals generated in organisms through direct or indirect effects of radiation [1, 3].

1 . 3 Participation in Hemoglobin Reduction

Normal human hemoglobin molecules contain divalent iron (Fe2+ ), which binds to oxygen and becomes oxyhemoglobin. If the divalent iron in hemoglobin is oxidized to Fe3+, it becomes methemoglobin (MHb) and loses its oxygen transport function. However, under normal conditions, glutathione and other reducing substances (such as ascorbic acid, NADH, NADPH) in erythrocytes together form the reduction system of MHb, which can effectively prevent the oxidation of divalent iron [2].

2.How Glutathione Is Applied in the Food Field?

2.1 Application in the Processing of Pasta and Dairy Products

The addition of glutathione in the processing of pasta products can effectively improve the rheological properties of dough, reduce the strength of dough, control the viscosity of dough in a wide range, and effectively shorten the drying time of pasta products [4]. It has been reported [5] that glutathione can directly or indirectly cut the disulfide bonds between gluten protein molecules in bread baking, thus affecting the three-dimensional mesh structure of proteins and the rheological properties of doughs, thus enhancing the quality and flavor of bread.

The addition of glutathione and other additives to dairy products improves the taste and maximizes the quality of dairy products. Glutathione can prevent enzymatic and non-enzymatic browning of pasta and dairy products due to its reducing and antioxidant properties.

2.2 Application in Meat and Seafood Products and Other Food Industries

Since glutathione has excellent reducing properties, adding glutathione to meat and seafood products can not only greatly extend their freshness period, but also strengthen the favorite taste. In addition, glutathione has a strong meat flavor when the L-glutamate nucleic acid system is flavored or coexisted with its mixture [6].

Glutathione also prevents unpleasant discoloration of frozen fish fillets and browning of fish meat. The addition of glutathione to fruits and vegetables is beneficial for maintaining the original nutrition and attractive color and flavor and preventing browning. To enhance the medical effects of anticancer beverages, patents have been filed and granted for the brewing of anticancer beers with high glutathione content [7].

3.How Glutathioneis Is Applied in Medicine?

3.1 Applications in Tumor Therapy

Glutathione is a protective substance against endogenous radioactivity, and it can effectively treat the damage caused by radiation therapy of tumors [8]. Researchers have found that in the case of high glutathione content, the effect of radiation therapy on tumors is poor, while the decrease of intracellular glutathione content, although the effect of radiation therapy is improved, the damage of cells in the body will be greatly increased. Therefore, how to maintain the appropriate level of glutathione in cells to effectively improve the radiotherapy effect of tumors during tumor treatment will be an important issue in future clinical medical oncology treatment.

3 . 2 As a Detoxifying Agent

Glutathione can directly bind to certain poisons and effectively relieve the toxicity of exogenous toxic substances (including drugs) and is generally used in the treatment of poisoning by acrylonitrile, fluoride, carbon monoxide, heavy metals, etc. [1]. At the same time, glutathione can correct the imbalance of acetylcholine and cholinesterase, and play the role of anti-overbalance. Glutathione can also promote the metabolism of amino acids and fatty acids, promote the inactivation of estrogen, and reduce hypoalbuminemia [6].

3 . 3 Other Clinical Applications

Recently, it has been reported [8] that glutathione can inhibit HIV and improve sexual function. In addition, glutathione is effective in the treatment of corneal diseases. Glutathione can also provide glycine and taurine to the liver, ensure the synthesis of glycine and taurine-conjugated choline, and promote the absorption of fat-soluble vitamins (A, D, E, and K) in the digestive tract, thus promoting the liver to synthesize vitamin K-dependent coagulant factor production and reducing bleeding tendency [2]. It has been reported that lower than normal levels of glutathione in the body can lead to a range of conditions such as diabetes, alcoholic liver toxicity, cataracts, cancer, Parkinson's syndrome, and Alzheimer's disease [9].

3 . 4 Application in the Field of Sports [10].

Salminen and Vihko in the United States reported on the application of glutathione in sports. Three weeks of endurance training can increase the glutathione content in mice. Following exercise, muscle glutathione levels increased by 50 percent, and increased hemoglobin levels and antioxidant capacity in the body.

The researchers also found that hemoglobin levels were above 15 percent when athletes performed at their best and that hemoglobin levels are the most important indicator for athletes, especially in endurance events such as middle-distance running and marathons. Glutathione also protects red blood cells from destruction. Therefore, glutathione is a very important topic for research in the field of sports, whether it is sports anemia, prevention of overtraining, or sports nutritional supplementation.

4.Methods for the Determination of Glutathione

At present, there are several methods for the determination of glutathione, among which the modified Tietze reductase method, Griffith method, calorimetry, chromatography, spectrophotometry, capillary electrophoresis, fluorescence photometry [11], etc., and following are some of the more commonly used methods.

4 . 1 High Performance Liquid Chromatography (HPLC) Method

Asensi et al. [12] used methanol-water as the mobile phase and a UV/Vis detector to detect glutathione in soybeans, with a detection limit of 1 nmol/L and an RSD of 1.5%. The limit of detection was 1 nmol/L with an RSD of 1.5%. Cheng Jingjun et al. [13] used KCl solution-HCl solution-methanol-EDTA as the mobile phase and an electrochemical detector (glassy carbon electrode, Ag/AgCl reference electrode, 0.9 V) for the determination of glutathione in rat brain micro cellulose. The content of glutathione in the microdialysis fluid of the mouse brain was determined by an electrochemical detector (the working electrode was Ag/AgCl, the reference electrode was Ag/AgCl, and the working voltage was 0.9 V). The recoveries were 87.3% and the RSD was 1.8%. The recovery was 87.3% with an RSD of 1.8%.

Brent et al. [14] used methanol and sodium acetate solution (PH 7) as mobile phases, and complexed OrthoPhthalaldehyde (OPA) and glutathione to produce a highly fluorescent ternary cyclic derivative with a fluorescence detector, and the detection limit was 0.1 Pmol. 1 Pmol, linear range 0.1 ~ 200 Pmol. The linear range was 0.1~200 Pmol, and the recovery of glutathione was 99.2% with an RSD of 1.2%. The recovery of glutathione was 99.2% with an RSD of 1.2%. 2%. The linear range was 0.1~200 Pmol, and the recoveries of glutathione were 99.2% with an RSD of 1.2%. The method is suitable for the determination of glutathione in mixed components with a wide linear range and high stability.

4.2 High Performance Capillary Electrophoresis (HPCE)

HPCE has a very good separation effect, Frassanito et al. [15] used HPCE to determine the content of glutathione in biological test material, and the detection limit of UV/Vis detector was 0.2 μg/ml, and the linear range was 0.2 μg/ml, and the detection limit was 0.5 μg/ml. The detection limit of the UV/Vis detector was 0.2 μg/ml, and the linear range was 0.2~100 μg/ml. The linear range was 0.2-100 μg/ml with an RSD of 1%.

In 1987, the electrochemical detection technique in HPCE was improved to overcome the problem of the short optical range of the UV-visible absorption detector, and in 1993, Thomas et al. [16] used Hg-modified Au electrodes in the HPCE system for the determination of glutathione in murine brain tissues at a concentration of 10 mmol/L 2 mL at a pH of 5.5. 5, 10 mmol/L 2-(N-morpholine)-ethanesulfonic acid was used as a buffer at 0.5 V (Vs Ag/Au). At a potential of 0.15 V (Vs Ag/AgCl), the detection limit was 0.53 fmol, and the RSD was 0.5 fmol. The limit of detection was 0.53 fmol at 0.15 V (Vs Ag/AgCl) with an RSD of 2.1%. 1 %.

In food, glutathione can improve the flavor and quality of food; in biomedicine, glutathione can protect cells in the body, maintain protein structure and function, remove peroxides and free radicals in the body, detoxify the body, promote the absorption of iron, and participate in the transport and absorption of amino acids. With the development of science and technology, scientists will explore more biological functions as well as applications of glutathione.

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