L-theanine（Theanine, CAS No.: 3081-61-6） is a unique amino acid of tea. It was first isolated from green tea in 1950. It is not only the characteristic amino acid of tea, but also one of the flavor substances of tea. It has a strong positive correlation with the quality of green tea, and the correlation coefficient is 0.787 ~ 0.876. There are more than 20 kinds of amino acids in tea, theanine accounts for about 50% ~ 60% of the total amino acids in tea; It is found that trace amounts have been detected in tea plum, mushroom, Camellia oleifera and other plants, but have not been found in other plants.

As early as 1985, the U.S. Food and Drug Administration (FDA) recognized theanine and confirmed that synthetic theanine is a generally recognized safe substance (GRAS), and there is no limit regulation in the process of use. The safety test showed that the acute toxicity of Theanine in rats was more than 5g / kg; In the subacute experiment of theanine taken continuously for 28 days (2G / kg per day), no toxic reaction was found in rats; No mutagenic effect of theanine was found in the mutagenic experiment; The bacterial recovery mutation experiment also proved that it did not lead to gene mutation. With good safety and stability, theanine has been widely used in foods such as beverages, baked snacks, frozen snacks and so on; In addition, theanine also plays an important role in food because of its special properties and biological activity.

Blood pressure regulation is mainly achieved through the increase or decrease of catecholamine and serotonin in the central and peripheral nervous system. Yokogoshi et al. Proved through experiments that theanine can reduce the content of serotonin, reduce the synthesis of serotonin in the brain and increase its decomposition in the brain. When different doses of theanine were injected into spontaneously hypertensive rats (SHR), the blood pressure decreased, and the degree of decline showed a dose-response relationship. The blood pressure decreased significantly in the high-dose group; However, even the highest dose of theanine did not change the blood pressure of normal rats; Similar to theanine, glutamate did not reduce blood pressure.

Recent studies have shown that theanine itself has no antitumor activity, but it can improve the efficacy of a variety of antitumor drugs. Adriamycin (adriamycin cm) can inhibit some tumors. Theanine can protect the concentration of adriamycin in tumor tissues and reduce the exudation of adriamycin from Ehrlich ascites tumor cells. Therefore, when theanine is used with adriamycin, the inhibition of tumor growth in vivo can be increased by 2.1 times and the concentration of adriamycin in tumor tissues can be increased by 2.9 times. In addition, injection of the anticancer drug idarubicin can reduce the number of leukocytes and bone marrow cells, but when combined with theanine, it can alleviate the toxicity of idarubicin and promote the antitumor effect of idarubicin, indicating that theanine has a selective regulatory effect on the toxicity caused by idarubicin. Doxorubicin combined with theanine can inhibit the metastasis of M5076 ovarian sarcoma to the liver. Recently, SA dzuka et al. Further studied the pathway of theanine improving the anticancer activity of doxorubicin, pointing out that theanine increases the concentration of doxorubicin in tumor cells by inhibiting glutamate transmission in tumor cells, so as to improve its anticancer efficacy. Theanine is very beneficial to the clinical chemotherapy of cancer patients. It not only promotes the effect of some antitumor drugs, but also improves the quality of life of cancer patients.

Generally speaking, animals and people always produce very weak pulse impulses on the surface of the brain, called brain waves. Under different mental conditions, the brain will produce brain waves with different current frequencies. Brain waves are divided according to frequency α、β、δ and θ Wave, δ When Bo was sleeping, θ When the wave is in the ton state, α When the wave is quiet (relaxed state), β Waves appear separately in the excited state. Some people conducted human experiments to verify the effect of theanine on spirit, let the experimenters drink water and theanine aqueous solution, and measure EEG after 60min; Results EEG changes were found at the end of drinking water, but significant changes were observed after drinking theanine α Therefore, theanine can promote the generation of second wave, so as to cause a comfortable and pleasant feeling. And theanine did not cause sleep θ The number of waves increases, so theanine can not only stabilize people's mood, but also make people pay more attention.

Glutamate is an excitatory neurotransmitter, and its content in nerve cells is maintained at 1mmol-10mmol / L. During cerebral ischemia, due to the interruption of O2 supply, the intracellular energy substance adenosine triphosphate (ATP) production is reduced and gradually depleted. The nerve cell membrane is separated, too much glutamate is released outside the cell, and acts on the receptor to continuously increase the intracellular calcium concentration, stimulate the activities of various decomposition enzymes, and finally act on the cell to destroy and die. Theanine has a competitive protective effect on glutamate receptor, so theanine has a protective effect on brain tissue and can avoid brain nerve cell death caused by cerebral ischemia.

Menstrual syndrome (PMS) is a symptom of mental and physical discomfort in women 3 to 10 days before menstruation. Juneja et al. Investigated the effect of theanine on PMS and asked 24 women to take theanine 200mg every day. Two months later, PMS symptoms were significantly improved, such as headache, low back pain, chest pain, weakness, fatigue, inability to concentrate, irritability and so on. Its mechanism needs further study, which may be related to the sedative effect of theanine.

After fed with 0.028% theanine for 16 weeks, the weight of mice decreased significantly compared with the control group, and the abdominal fat decreased to 58% of the control group. At the same time, the contents of neutral fat and cholesterol in blood decreased by 32% and 15% respectively, and the cholesterol in liver decreased by 28%. Therefore, the weight loss effect of tea is the result of the joint action of various components in tea, including theanine. Theanine is especially effective in reducing cholesterol in the body.