Research Progress on Allicin in Enhancing Immune Function
Allicin, as a key bioactive component in garlic, has received extensive attention in the field of immunomodulation research in recent years. This article reviews the source and physicochemical properties of allicin, systematically sorts out the research progress in its role of enhancing immunity，including its effects on immune organs, immune cells, and immune-related cytokines，while analyzing the existing problems in current research and prospecting its future application prospects. The aim is to provide references for the in-depth research and practical application of allicin in immunomodulation-related fields.
Keywords: Allicin; Immunity; Immunomodulation; Central Immune Organs
1. Introduction
Immunity refers to the ability of the body to recognize and eliminate foreign invading substances, as well as aging, damaged cells and mutant cells within the body. It serves as a crucial barrier for maintaining human health. When the body's immunity declines, it becomes vulnerable to pathogen invasion, leading to various diseases. Garlic is a common food-medicinal plant with a long history of medicinal and edible use in China. Allicin, the main bioactive component produced when alliin (present in garlic) is catalyzed by alliinase after garlic is crushed, exhibits a variety of biological activities, such as antibacterial, antioxidant, and anti-tumor effects. In recent years, a growing number of studies have shown that allicin plays a positive role in enhancing the body's immunity.
2. Source and Physicochemical Properties of Allicin
2.1 Source
Free allicin does not exist in intact garlic bulbs; instead, it is present in the form of its precursor, alliin. When garlic undergoes mechanical damage (such as cutting or crushing), alliinase is released, which catalyzes the decomposition of alliin to produce allicin. In addition, allicin can also be obtained through artificial synthesis. However, naturally derived allicin is more favored due to its advantages in safety and biocompatibility.
2.2 Physicochemical Properties
Allicin appears as a pale yellow to orange-yellow oily liquid with a strong pungent odor. It is easily soluble in organic solvents such as ethanol and ether but has low solubility in water. Meanwhile, allicin has poor stability and is sensitive to light, heat, oxygen, and other factors. It tends to decompose and lose its activity under high temperature, strong light, or aerobic conditions. Therefore, during the extraction, storage, and application of allicin, corresponding measures such as light protection, low-temperature storage, and oxygen isolation should be adopted to maintain its activity.
3. Effects of Allicin on Immunity
3.1 Effects on Immune Organs
Immune organs are important components of the body's immune system, including central immune organs and peripheral immune organs. They play a key role in the production, differentiation, maturation of immune cells, and immune response. Studies have found that after administering a certain dose of allicin to mice, the thymus index (ratio of thymus weight to body weight) of the mice increased significantly. Pathomorphological observation of thymus tissue showed that the thymic cortex thickened and the number of lymphocytes increased, indicating that allicin can promote thymus development and enhance its function. In addition, allicin can increase the spleen index of mice and the number of immune cells in the spleen. Further studies on spleen tissue have revealed that allicin can promote the proliferation and differentiation of immune cells in the spleen, thereby enhancing the immune function of the spleen. Although there are relatively few direct studies on the effect of allicin on lymph nodes at present, based on its positive effects on other immune organs, it is speculated that allicin may also promote the immune function of lymph nodes by regulating the migration and distribution of immune cells.
3.2 Effects on Immune Cells
Immune cells are the basic units that perform immune functions, including lymphocytes (T cells, B cells, etc.), mononuclear phagocytes (macrophages, monocytes, etc.), and granulocytes. In in vitro experiments, when allicin was added to cultured T lymphocytes, the proliferation rate of T lymphocytes increased significantly, and the expression level of activation markers on their surface also increased remarkably. This indicates that allicin can enhance the activity of T lymphocytes and improve the body's cellular immune response. In addition, the level of antibodies in the serum of mice treated with allicin was significantly higher than that in the control group, suggesting that allicin can enhance the humoral immune function of the body. At the same time, relevant studies have found that after allicin treatment, the killing rate of NK cells in the peripheral blood of mice against target cells increased significantly. This may be related to allicin promoting the expression of killer receptors on the surface of NK cells and enhancing their ability to secrete cytotoxic factors.
3.3 Effects on Immune-Related Cytokines
Cytokines are bioactive small-molecule proteins secreted by immune cells and some non-immune cells. They play an important role in signal transmission during immunomodulation and can regulate the proliferation, differentiation, and function of immune cells. Allicin can affect the body's immune function by regulating the secretion levels of various immune-related cytokines. Studies have shown that allicin can stimulate immune cells such as macrophages to secrete tumor necrosis factor-α (TNF-α), enhancing their killing effect on pathogens and tumor cells. Meanwhile, TNF-α can cooperate with other cytokines to jointly regulate the body's immune balance.
4. Application Status of Allicin in Enhancing Immunity
4.1 Application in the Food Field
Due to its natural, safe properties and ability to enhance immunity, allicin has certain applications in the food field. At present, there are some garlic-based food products, such as garlic powder, garlic flakes, and garlic essential oil, which retain a certain amount of allicin during processing. These products are considered to have certain health-care functions and are popular among consumers. In addition, some studies have used allicin as a food additive in meat products, condiments, and other foods. This not only extends the shelf life of food but also endows food with certain immunomodulatory functions.
4.2 Application in the Pharmaceutical Field
In the pharmaceutical field, research on the application of allicin in enhancing immunity has also made certain progress. Some drugs or health products with allicin as the main component have been developed for the adjuvant treatment of diseases related to low immunity. For example, in the adjuvant treatment of respiratory tract infections, allicin preparations can improve the body's immunity, enhance the body's resistance to pathogens, thereby shortening the course of the disease and alleviating symptoms. At the same time, in the adjuvant treatment of tumors, allicin has also been tried to improve the immunity of patients and enhance their quality of life.
4.3 Application in the Feed Field
In the feed field, allicin, as a green and safe feed additive, has also been applied to a certain extent. Studies have shown that adding an appropriate amount of allicin to livestock and poultry feed can improve the immunity of livestock and poultry and reduce the occurrence of diseases. For example, adding allicin to chicken feed can improve the disease resistance of chickens and reduce the incidence of respiratory and digestive diseases; adding allicin to pig feed can enhance the immunity of pigs and promote their growth and development.
5. Existing Problems and Prospects
Although current research on allicin in enhancing immunity has achieved certain results, allicin has poor stability and is prone to decomposition under the influence of various factors in practical applications, which limits its wide application in the food, pharmaceutical, and other fields. Secondly, although the mechanism of action of allicin has been studied to a certain extent, some studies still remain at the level of phenomenon observation, and the understanding of its specific action targets and molecular regulatory networks is not deep enough. In addition, there are relatively few clinical trials of allicin in humans, and its safety and efficacy in humans need to be further verified.
6. Conclusion
As a key bioactive component in garlic, allicin shows a significant positive effect in enhancing the body's immunity. According to existing studies, it can promote the development and functional enhancement of immune organs such as the thymus and spleen, effectively regulate the proliferation, activation, and functional exertion of various immune cells, and affect the secretion of immune-related cytokines, thereby improving the body's immune function. This effect is reflected in multiple aspects, including cellular immunity, humoral immunity, and non-specific immunity. In addition, relying on its natural and safe properties, allicin has initially demonstrated application value in the food, pharmaceutical, and feed fields, providing strong theoretical support for the development and application of related products. In general, allicin has good development potential in the field of immunomodulation. With the continuous deepening of relevant research and the effective solution to existing problems, allicin is expected to play a more important role in safeguarding human health, promoting the development of the food industry, and advancing animal husbandry in the future.
References
[1] Wang CJ, Wang C, Han J, et al. Effect of combined treatment with recombinant interleukin-2 and allicin on pancreatic cancer[J]. Mol Biol Rep, 2013, 40(12): 6579-85.
[2] Xu S, Liao Y, Wang Q, et al. Current studies and potential future research directions on biological effects and related mechanisms of allicin[J]. Crit Rev Food Sci Nutr, 2023, 63(25): 7722-7748.
[3] Patil S, Sayed ME, Mugri MH, et al. Allicin May Promote Reversal of T-Cell Dysfunction in Periodontitis via the PD-1 Pathway[J]. Int J Mol Sci, 2021, 22(17): 9162.
[4] Gruhlke MCH, Antelmann H, Bernhardt J, et al. The human allicin-proteome: S-thioallylation of proteins by the garlic defence substance allicin and its biological effects[J]. Free Radic Biol Med, 2019, 131: 144-153.
[5] Deng Y, Ho CT, Lan Y, et al. Bioavailability, Health Benefits, and Delivery Systems of Allicin: A Review[J]. J Agric Food Chem, 2023, 71(49): 19207-19220.
