L-Carnosine is a dipeptide that occurs naturally in various tissues of the human body and is composed of β-alanine and histidine. It plays a variety of biological roles in the human body, including antioxidant, anti-glycation and protection from cell damage. Below we will describe in detail the uses of L-carnosine and a common synthesis method.

　　Use of L-carnosine

　　L-carnosine has a wide range of applications in biology and medicine:

　　1. Anti-oxidation and anti-aging

　　L-carnosine can remove free radicals and reduce the damage caused by oxidative stress on cells, thus playing a role in delaying aging. It also stabilizes cell membranes, reduces lipid peroxidation, and prevents the development of neurodegenerative diseases.

　　2. Anti-saccharification

　　L-carnosine inhibits the glycation reaction, preventing sugar molecules from forming harmful glycation end products (AGEs) with proteins, which are associated with a variety of diseases, including diabetes complications and cardiovascular disease.

　　3. Cushioning

　　As an effective cell-solute buffer, L-carnosine can maintain the stability of the cellular environment and help cells resist the effects of acid-base changes.

　　4. Other functions

　　L-carnosine also has certain neuroprotective effects, is able to regulate enzyme activity, and can chelate certain heavy metal ions, reducing their toxic effects on the human body.

　　Synthesis method

　　L-carnosine can be synthesized in a variety of ways, a typical synthesis method is described below:

　　A) Prepare hydrazine hydrolysis reaction solution

　　In a 1000 ml four-mouth reaction bottle, 50 grams (0.14 moles) of phthalyl-L-carnosine intermediate, 200 ml of water, and 10.8 grams (0.17 moles) of hydrazine hydrate (80% mass percentage concentration) were added.

　　Heat until reflux reaction for 1 hour, and then add appropriate acetic acid to adjust the pH value of the material to 5.5.

　　The by-products were removed by filtration and hydrazolysis reaction solution was obtained.

　　B) Preparation of L-carnosine

　　Add 100 ml of dichloromethane and 9.6 g (0.09 moles) of benzaldehyde to the hydrazine hydrolysis reaction solution obtained in step A.

　　Stir at room temperature for 12 hours, then let the ingredients stand and layer.

　　The dichloromethane layer is separated and the water layer is washed twice with 50 ml of dichloromethane.

　　Add 3 grams of activated carbon and 25 ml of 18% ammonia and decolorize at 60°C for 0.5 hours.

　　The activated carbon is removed by filtration, and the decolorizing solution is concentrated in vacuum until solid precipitates.

　　Add 300 ml methanol, stir for 2 hours and strain.

　　After the cake was dried at 100°C for 6 hours, 28.6 grams of L-carnosine product was obtained, and no hydrazine residue was detected in the product.

　　L-carnosine, as a multifunctional bioactive peptide, has many biological functions such as anti-oxidation, anti-glycation and cell protection. The synthesis method involves several steps, including hydrazine hydrolysis reaction and subsequent purification process. With the deepening of scientific research, the application prospect of L-carnosine will be more extensive.