Gallic acid (GA) is a component of hydrolyzable tannins, also known as gallic acid, and its chemical name is 3,4,5-trihydroxybenzoic acid. The content of gallic acid in Yunnan Pu'er tea is relatively high, and it has many biological functions such as antibacterial, anti-inflammatory, anti-tumor, antimutagenic, etc.
Gallic acid itself has a significant antioxidant effect. In addition, it has many effects such as anti-tumor, trypanosomicidal, liver protection and anti hepatitis B virus; Recently, it has been pointed out that gallic acid may be one of the effective components of Pu'er tea that inhibit the cholesterol synthesis of HepG2 cell line. On the whole, the content of gallic acid in Pu'er tea (9.01mg/g) is higher than that of other herbal medicines. In this sense, gallic acid is one of the important physiological active ingredients of Pu'er tea.
White or light brown needle shaped crystal or powder. Melting point 235-240 ℃ (decomposition). When heated to 100-120 ℃, crystal water is lost, and when heated to 200 ℃ or above, carbon dioxide is lost to generate pyrogallic acid (pyrogallol). Soluble in hot water, ether, ethanol, acetone and glycerin, insoluble in cold water, insoluble in benzene and chloroform.
Gallic acid has many uses in pharmaceutical, ink, dye, food, light industry and organic synthesis. Gallic acid and ferric ion generate blue black precipitate, which is the raw material of blue black ink; It is also used for tanning in industry; It can also be used as a photographic developer. Propyl gallate is an antioxidant, which can be used in edible oils to prevent odor deterioration. In medicine, gallic acid is a hemostatic astringent and a mild local irritant.
It is mainly used as the coupler of blue black ink. The pharmaceutical industry is used to prepare sulfanilamide synergist TMP and as the coordination agent of sulfanilamide drugs such as SMZ and SD ethyl. The food industry is used to prepare the preservative propyl gallate. The national defense industry is used to prepare explosion-proof agents. In addition, it can also be used in the production of mordant dyes and as developer
Used as depolarizer in electrochemical analysis; Used to reduce phosphomolybdic acid; Used for testing antimony, barium, bismuth, calcium, cerium, copper, etc; Used for determination of phosphorus, nitrite, silver, thorium, titanium, etc
It is made from Chinese nutgall. The main component of Chinese nutgall is tannin, which belongs to hydrolytic tannin. It can dissolve in hot water and has a astringent taste. It is an amorphous complex organic substance. Chinese gallnut tannin is a complex mixture of gallnut acid, diploid acid and glucose in the form of glycosides or esters. Tannic acid is hydrolyzed under pressure to produce gallic acid and glucose Chemicalbook. During hydrolysis, gallic acid ester is first formed, and then di gallic acid ester is hydrolyzed to gallic acid. The hydrolysis temperature is 133-135 ℃, and the pressure is 0.18-0.2MPa. The end point is reached when the pressure rises to 0.18MPa and the reaction lasts for 2h. Compared with normal pressure hydrolysis, sulfuric acid and steam can be saved, and the production capacity can be increased by 25%