1, hydroquinone (hydroquinone) is a traditional and effective whitening ingredients, it has the effect of coagulation of protein, by coagulation of amino acids in tyrosinase, so that the enzyme freezes and loses catalytic activity. In addition, hydroquinone can cause melanocyte degeneration and death at certain concentrations. The US FDA considers hydroquinone as a safe and effective whitening agent. The amount of use approved by the European Community is 2%. The November 1999 edition of China’s cosmetic hygiene code allows its use in topical skin whitening products with a dosage limit of 2%, and requires the labeling of “contains hydroquinone” on the product’s package insert. 2000 edition of CTFA’s Cosmetic Ingredient Review Summary clearly states that hydroquinone is prohibited for use in residual cosmetics. It is generally believed that 2% of hydroquinone is safe for the skin, while the dosage in blemish removal drugs can be 3% to 5%, and more than 5% may cause the phenomenon of “white spots” and allergy. At present, it is not used much, mainly because of the side effect problem. 2.Tragic acid and its derivatives The application and discovery of tragic acid is from ancient folk medicine. Its whitening mechanism is to inhibit the activity of tyrosinase, while inhibiting the activity of dihydroxyindole acid (DHICA) oxidase and blocking the polymerization of dihydroxyindole (DHI). This is one of the few single whitening agents that can inhibit multiple enzymes at the same time, so it is a class of whitening agents that is worth studying. Long-term use of tric acid has cytotoxic effects and increases the probability of chromosomal interchange and chromosomal aberrations in ovarian cells. Because of its carcinogenicity when taken orally, tric acid has been banned in Japan, and the import and production of topical tric acid has been suspended in the same country. Since tric acid is unstable to light, heat and metal ions and has poor skin absorption, a number of tric acid derivatives have been developed to improve its properties, such as tric acid dipalmitate. Compared with tric acid, dipalmitate is less prone to discoloration, is not affected by acidity or alkalinity, and is less irritating to the skin. The mechanism of action of tric acid derivatives is currently considered to be the same as that of tric acid, and its inhibition of tyrosinase is stronger than that of tric acid. Triglyceride derivatives start from the two hydroxyl groups on triglyceride and generally undergo esterification and alkylation. Esterification can form a monoester of tric acid, but also can form a double ester. 3, arbutin Arbutin (arbutin) is a natural active substance isolated from a variety of plants, its chemical name is 4-hydroxyphenyl β-D-glucopyranoside (β-arbutin). β-arbutin depigmentation mechanism has been reported, it is a tyrosinase inhibitor, mainly blocking the synthesis of dopa and dopaquinone, thereby curbing the growth of melanin, and thus has a skin whitening effect. At present, the amount of β-arbutin added in cosmetics is about 3%, less than this amount has a weak inhibitory effect on the catalytic activity of tyrosinase in the skin, and the whitening effect is not obvious. Alpha-arbutin is a differential isomer of beta-arbutin, and its chemical name is 4-hydroxyphenyl alpha-D-glucopyranoside. Nishmura, a Japanese scholar, found that the strength and safety of α-arbutin inhibition of tyrosinase is much better than that of β-arbutin, which is being widely used now. It is 10 times stronger than β-arbutin inhibition. In 2002, Pentaparm and Shiseido launched a new active skin whitening agent containing α-arbutin. α-arbutin has obvious effect on the scar formed by UV burns, and its chemical properties are more stable than β-arbutin, so it can be more easily added to various skin whitening and brightening cosmetics. 4.Vitamin C and its derivatives Vitamin C is prepared by biological fermentation and is an extremely psychologically acceptable whitening agent. Vitamin C has obvious effect on removing acquired melanin deposits and has anti-oxidant and free radical scavenging effects. Vitamin C and derivatives, which directly reduce melanin, disintegrate melanin by direct destruction, thus rapidly whitening. The whitening mechanism of vitamin C is mainly to reduce melanin and lighten pigmentation, but because the reduced melanin may still be oxidized again, it must be maintained in sufficient concentration for a long time to be effective. In addition, since the process of melanin production is an oxidation process, vitamin C can inhibit the action of peroxidase through its own antioxidant property. Its application is limited because it does not penetrate easily into the skin stratum corneum, and it is easily oxidized and unstable. The development of vitamin C derivatives is mainly in Japan, and the most commonly used ones are: vitamin C magnesium phosphate, vitamin C palmitate, etc. The main phosphate salts of vitamin C are vitamin C magnesium phosphate and vitamin C sodium phosphate. The whitening effect of vitamin C magnesium phosphate is better than vitamin C sodium phosphate, and the price is lower than the latter, which dominates the market of vitamin C-based whitening agents. Another important vitamin C derivative is vitamin C-2-O-α-glucopyranose, which is stable and easy to add to cosmetic formulations, but it is produced by fermentation and is expensive. 5.Endothelin antagonists Endothelin antagonists are important skin lightening agents discovered in the 1990s. It can be extracted from the natural plant chamomile or prepared by biofermentation method. Some foreign people extracted endothelin antagonist from European herb chamomile, and the in vivo and in vitro experiments showed that it has the following three effects: (1) high efficiency: under the effect of chamomile extract, which is an endothelin antagonist, endothelin cannot associate with the receptor point on melanocyte, so there will be no additional melanin formation; (2) fast depigmentation: because tyrosinase exists in the melanin of melanocyte Because the action point of endothelin antagonist is outside the melanocyte membrane, it only needs to pass through two layers to be effective, which is why for the removal of UV-induced pigmentation, the use of endothelin antagonist is four times faster than that of tyrosinase inhibitor. (3) Uniform melanin distribution: the production of extracellular melanin caused by UV irradiation leads to skin discoloration and uneven pigmentation distribution, and this situation will be fundamentally improved by using endothelin antagonists. 6.Placenta Placenta is a biological agent extracted from human, bovine and sheep’s placenta, which is a nutritional and moisturizing agent used in advanced cosmetics to speed up skin metabolism and accelerate skin melanin metabolism. Many whitening products on the market contain this ingredient, and supplemented with active components such as vitamin E, vitamin C derivatives and other whitening components. Since only 20% of people use placenta to whiten effectively, and some consumers are afraid of being infected by mad cow disease when using it, they have doubts, so although placenta has been extracted from pigs, some large international companies producing cosmetics no longer use placenta. 7, plant flavonoids Flavonoids are widely present in the plant world, many of which have a free radical removal in the skin, promote skin metabolism, reduce pigmentation, moisturize the skin and other effects. In China, many plant flavonoid extracts have been developed industrially, such as ginkgo biloba extract, bamboo leaf extract, licorice flavonoids, soy isoflavones, etc., some of which have been used in the cosmetics industry. It has been proved that, in addition to analgesic, cough suppressant, anti-inflammatory, anti-ulcer and anti-metabolic effects, licorice can also strengthen the immune function of the body, prevent viral hepatitis, anti-cancer and anti-AIDS. Licorice flavonoids extracted from licorice have various effects in beauty cosmetics. Studies have shown that licorice flavonoids are a good whitening ingredient, and their whitening effect mainly comes from their inhibition of tyrosinase, dopachrome isomerase (TRP I2) activity, and blocking of 5,6.dihydroxyindole (DHI) polymerization. It is a full-featured botanical whitening ingredient that helps fight UV rays while inhibiting tyrosinase activity, and also improves rough, dehydrated and inflamed skin. In addition, many of our traditional Chinese herbs have good whitening and spot-removing effects, and there are many remedies for facial spots that have been passed down to this day. This green plant ingredient has excellent whitening effect and is the future direction of such cosmetics. Angelica sinensis: blood activation, antibacterial and anti-inflammatory, water removal and whitening, contains a variety of vitamins and active components, and has skin whitening effect. Xinyi: treats facial disorders, acne and itchy skin. The chemical composition is mainly pinene, camphene and glucoside, etc. It has antibacterial, anti-inflammatory and anti-allergic effects. Rhizoma Ligusticum Chuanxiong: Promotes the flow of qi and blood, dispels wind and pain, removes pus from the flesh, and eliminates bruises and blood. It has anti-aging and whitening effects on the skin. Salvia miltiorrhiza: It is used to treat various facial skin diseases, and has the effect of removing silt and creating new blood, invigorating blood and removing annoyance. Its chemical composition mainly includes ketones, alcohols and various amino acids, vitamins and trace elements, etc. It can scavenge free radicals and improve blood circulation, i.e. anti-aging of skin and the effect of beauty and whitening. In addition, there are also white sapodilla, dahurica cocos, fresh peel, white peony, atractylodes, cuscuta, azulene extract (azelaic acid), etc. have certain skin whitening effect.