Application of tannic acid, how much do you know?

Tannic acid has a strong inhibitory effect on streptococci, and 0.25 g/L of tannic acid can achieve a 100% inhibitory rate. At the same time, tannic acid can also inhibit the activity of gingival hyaluronidase and collagenase, so adding tannic acid in toothpaste can prevent gum disease and periodontitis, and has the function of anti-caries. Tannic acid has strong ultraviolet absorption characteristics, especially in the far ultraviolet region with high energy and great destructive power (λmax =263 nm, ε=8350).

In addition, tannic acid has a strong inhibitory effect on the Maillard reaction that easily causes skin aging, so tannic acid can be used as an active ingredient in sunscreen and anti-aging in cosmetics. Cosmetics prepared by using the astringent properties of tannic acid are non-irritating to the skin, have a moderate astringent effect, and have good moisturizing properties. For example, mix 50 g of SiO2 with 45 g of 10% elastin aqueous solution, then mix with 5 g of 50% tannic acid aqueous solution at 40 °C, dry in vacuum, grind into powder and then dry, the obtained porous The elastin-tannin complex can be used as a cosmetic skin care component.

In addition, tannic acid used in cosmetics can also improve skin color, strengthen blood circulation and promote hair growth. Under the action, it can maintain a delicate, white and tender complexion. The germanium-containing tannin and water-soluble iron salt can be used to make black hair dye. The self-oxidizing hair dye prepared by acid, tannin and diamine derivatives is safe to use, with high color fastness and natural hair after treatment.

The pharmacological activity of tannic acid is a comprehensive reflection of its interaction with biological proteins, enzymes, polysaccharides, nucleic acids, etc., as well as its anti-oxidation and complexation with metal ions.

In traditional prescriptions, catechin cream mainly containing tannic acid and catechin tannins are often used as hemostatic agents for wounds and burns because of their astringent properties, and because they have a certain antibacterial effect, they can protect wounds. Department, to prevent wound infection and inflammation. Tannic acid can also be used as an antidote when alkaloids and some heavy metal ions are poisoned, because it can be chelated with it to form a precipitate, reducing the absorption of the body, and the complexation of tannic acid with calcium ions outside cells or tissues, It can resist the contraction induced by smooth muscle calcium and lower blood pressure. For example, glycerin (5-10 parts), sunflower oil (5-10 parts), and tannic acid (1-5 parts) can be formulated into quick-acting antihypertensive drugs .

The antimutagenic, antitumor and anticancer properties of tannic acid have aroused great interest of pharmacists. Studies have shown that tannic acid and tea tannins have a good inhibitory effect on chemically induced skin, lung, and forestomach tumors. For example, pretreatment of mouse skin with tannic acid can inhibit the early activity of (±)-7β,8α-dihydroxy-9α,10β-epoxy-7,8,9,10-tetrahydrophenylpyrene-induced skin tumors , also inhibited the growth of chemically induced SENCAR mouse skin tumors in the early and middle stages. Gali in the United States studied the anticancer effect of tannic acid extracted from sumac leaves, five seeds and tara fruit pods in mice. These tannic acids can hinder the induction of ornithine decarboxylase and the production of peroxides to varying degrees, and improve the anti-oxidation and anti-cancer effects in mice. Anti-AIDS research on tannins is of great interest due to their higher activity and lower toxicity compared to synthetic anti-AIDS virus (AIDS) drugs.

Edible tannins can be used as clarifiers and stabilizers for beverages and wines, and can also be combined with plant fibers to form solidified tannins, which can be used as filter adsorbents for wines, iron removal and decolorization of soybean soy sauce.

The Sichuan Academy of Forestry has developed a solidified tannin with plant cellulose as the carrier and penta tannic acid as the ligand, which is used for iron removal in the production of fruit wine and liquor, and the iron removal efficiency can reach more than 90%. Adding Wuzi tannin 6 g/100 L to wort and beer can reduce high molecular nitrogen in wort by 5 mg/100 mL, reduce the formation of diacetyl, and improve the colloidal stability and taste stability of beer. Tannic acid has a good function of trapping free radicals due to its phenolic hydroxyl group, and can be used as a food antioxidant.

For example, food-grade tannic acid is used instead of SO2 as wine antioxidant, and the aroma components are analyzed by gas chromatography, which proves that tannic acid is a good wine preservative. However, due to the strong hydrophilicity of tannic acid, although it has strong oxidation resistance in the water phase, it cannot reflect its superiority in the oil phase due to the barrier of solubility.

Before the 1970s, Tara tannic acid was mainly used as a leather tanning agent. Tanned leather with Tara tannin, the finished leather is light, soft, elastic, and has a good color, which is comparable to lacquer leaf. Experiments have shown that the tanning effect of tara tannin is similar to that of excellent wattle extract. Leather products tanned with tara tannin have the characteristics of light color, non-fading, hard texture and smoothness. Due to the good tanning properties of tara tannin, it is recommended as lacquer extract, catechu extract, The substitute of wattle extract is a promising tanning material. Moreover, the tanned leather with tara tannin is only obtained from the fruit, fruit pods or leaves, and there is no need to cut down trees, and its resources can be used sustainably.

Tannic acid can be used as an effective inhibitor of calcium and magnesium minerals in ore flotation process. Tannic acid interacts with the mineral surface through chemical adsorption, hydrogen bond force and electric double layer electrostatic force, etc., and has a strong competitive adsorption with the collector on the mineral surface, or the collector is decomposed from the mineral surface. Tannic acid molecules adsorbed on the mineral surface contain a large amount of -OH and -COOH, which can make the mineral surface hydrophilic. Using dodecylamine as a collector and tannic acid as a regulator can effectively separate wollastonite and diopside. Using Auger electron spectroscopy, it was found that the binding energy of Ca2p on the surface of diopside is higher than that of limestone. -OH in nic acid and -COO- obtained by hydrolysis are more likely to combine with Ca2 + on the surface of diopside. Fang Xihui et al. used single minerals to study the effects of tannic acid, calcium hypochlorite and their combined agents on the flotation behavior of pyrite and chalcopyrite. The results showed that at about pH 9.5, tannic acid and The combined agent of calcium hypochlorite is technically feasible and can realize the separation of copper and sulfur under low alkali conditions. In addition, tannic acid is also the best precipitating agent in the wet germanium extraction process, and the germanium precipitation rate can reach more than 90%.

According to the property of tannic acid to chelate many metal ions, tannic acid can be used as a descaling agent for boilers and heat exchangers. Tannic acid complexes with Ca2+ and Mg2+ in the water, thereby reducing the hardness of the water and softening the water in the boiler. The complexes can further form large-sized mud deposits and be discharged with the sewage. In addition, tannic acid can also form a dense film with the metal pipe wall to passivate it, which plays a protective role and prevents the corrosion of pipes and boilers. In water treatment, tannin can also be used to purify waste water containing protein and surfactant, so that flocs can be precipitated and then removed, so as to reduce COD and avoid the foul smell of protein organic matter in water. Tannin can also recover ultrafine precious metal powder in aqueous solution. For example, sewage containing 3 g/L silver powder is treated with 10 g/L gelatin and 10 g/L tannic acid, stirred, left standing and filtered, and the filter cake is dried and heated to 900 Decomposition at ℃ can obtain silver with a purity of 90%.

Tannic acid, gallic acid, etc. can be used as anti-rust and anti-corrosion agents for ferrous metals (iron, steel) used in industry, construction, watercraft and seaport equipment. The ortho phenolic hydroxyl group in the tannic acid molecule can react with Fe3+ in the rust to form a black stable and dense chelate-iron tannin, which firmly covers the steel surface, thereby preventing the development of rust, and the tannin The ability to absorb oxygen also plays a role in preventing the oxidation of the steel surface, and can also inhibit the reproduction of iron-phagic bacteria. Wang Jikui et al. treated the surface of A3 steel with tannic acid solution, and obtained a uniform blue film with obvious corrosion resistance. The suitable process conditions were concentration 4 g/L, temperature 20, pH 3.5, and treatment time 60 seconds. It is found by scanning electron microscope that tannic acid and Fe3 + form an amorphous complex film with a network structure. The film layer is uniform and the color is bright, which has a good application prospect.