1 ultraviolet and its influence on human body
1. 1 UV
Sunlight consists of many wavelengths of the electromagnetic spectrum. When sunlight penetrates the earth's atmosphere, some wavelengths of light are filtered out, and the rest of the radiation reaches the earth's surface. This kind of light is called ultraviolet and infrared. Ultraviolet rays interact with skin cells, causing extensive damage. See table 1.
1.2 ultraviolet damage to skin
UVR is an immunosuppressive factor, and the damage to immune function may lead to skin tumors. Toewa et al. first observed that ultraviolet radiation changed the function of antigen presenting cell (APC)- Langerhans cell (Lc). In normal skin tissue, Lc forms a reticular structure in epidermis, and one of its functions is to absorb foreign antigens, migrate to local lymph nodes, and present antigens to T cells. Ultraviolet radiation changes the morphology of epidermal Lc, destroys the reticular structure, reduces the number of Lc and changes its function. The increase of inflammatory cells leads to immune tolerance. In addition, uridylic acid is the product of histidine deamination, which is abundant in the upper epidermis. After ultraviolet irradiation, the trans structure changes into cis structure, thus inhibiting the function of T cells. Many laboratories have confirmed that uridylic acid has immunosuppressive effect.
The influence of ultraviolet rays on the skin is also manifested in the photoaging of the skin. People who are overexposed to the sun will look very old, and all kinds of vegetation will grow on the photoaged skin. There are deep wrinkles, loose skin and many pigment spots. These phenomena reflect the changes of skin structure, but they are completely different from the changes of physiological aging. UVB can cause skin erythema, DNA damage and skin tumor. Sams et al.' s research results show that UVB can damage connective tissue. They irradiated the hairy mice with 30-50 times the minimum UVB of erythema vomiting, resulting in moderate elastic fiber hyperplasia. After long-term chronic irradiation, the decomposition rate of collagen is faster than the cell synthesis ability. Results Dermal thinning and atrophy led to visible skin photoaging. Exposure to uVA radiation can cause erythema reaction and blood vessel damage. Although the density of elastic fiber deposition is lower than UVB, the denaturation of elastic fiber can extend to the deep dermis, which is very harmful to human skin.
1.3 ultraviolet damage to hair
Ultraviolet rays not only affect the skin, but also cause damage to the hair. When hair is exposed to large doses of ultraviolet rays. Hair will change color and brown hair will fade easily. Blonde and red hair turn yellow. This is due to photooxidative bleaching and photodegradation of amino acids (cystine, tyrosine and tryptophan). Photodegradation of amino acids can also lead to the decrease of hair tension. In order to protect skin and hair from ultraviolet rays, the most direct way is to cover them with clothes, hats or umbrellas. In addition, scientists have discovered various substances that absorb or block ultraviolet radiation through research.
2 Sunscreen in the field of cosmetic crystals
2. 1 sunscreen
At present, sunscreen agents widely used in the world can be generally divided into two categories according to their different action mechanisms, namely, ultraviolet absorbers and ultraviolet scatterers. Ultraviolet scattering desk mainly uses the scattering or reflection of some inorganic substances to reduce the harm of ultraviolet rays to the skin, such as kaolin, zinc oxide, talcum powder, titanium oxide, new organic powder and so on. They mainly form a barrier on the skin surface to prevent ultraviolet rays from directly irradiating the skin, but this substance has the disadvantages of large dosage and poor sunscreen effect. Excessive use is easy to block pores and lead to new skin diseases and other adverse consequences. At present, sunscreen refers to an ultraviolet absorber that can absorb ultraviolet rays. The light energy absorbed by their molecules from ultraviolet rays is equal to the energy required to cause "photochemical excitation" of molecules, which can be converted into heat energy or harmless visible light for radiation, thus effectively preventing ultraviolet rays from tanning and sunburning the skin. Sunscreen can be divided into the following categories:
2. 1. 1 PABA derivatives
P-aminobenzoic acid derivatives can effectively absorb 280―300 nm ultraviolet rays and are the earliest ultraviolet absorbers. As UVB absorbents, they are irritating to the skin. Later, after improvement, its homologue-p-dimethylaminobenzoic acid appeared. It is mainly used as an ultraviolet absorber in sunscreen cosmetics for preventing ultraviolet erythema and dermatitis. Important foreign products are: p-aminobenzoic acid, glyceride of p-aminobenzoic acid, ethoxyethyl p-aminobenzoate and amyl p-dimethylaminobenzoate. Commonly used products of this kind of ultraviolet absorber in China are: 4- aminobenzoic acid, monoglyceride of aminobenzoic acid, menthyl benzoate, isobutyl p-aminobenzoate, octyl p-aminobenzoate, 2- ethyl ethyl ethyl ester, etc. Among them, amyl p-dimethylaminobenzoate and glyceryl p-aminobenzoate are both good UVB absorbers.
However, according to the report of the American Skin Cancer Foundation, the analysis of cosmetics made of this ultraviolet absorber found that it may contain carcinogens. This substance may be the decomposition product of ultraviolet absorber. Therefore, its use has been limited.
2. 1.2 o-aminobenzoate derivatives
O-aminobenzoate derivatives can block 290-380 nm ultraviolet rays and have the ability to block UVA and UVB rays, so they are effective ultraviolet absorbers. Its price is low, but its absorption rate is low, and it is also irritating to the skin. This kind of ultraviolet absorber products produced abroad mainly include menthol o-aminobenzoate and high menthol o-aminobenzoate. In addition, octyl, N- dimethyl p-aminobenzoate as UVB absorber can effectively prevent photochemical carcinogenesis.
2. 1.3 cinnamate
Cinnamate is widely used because it can block 280-3 10 nm ultraviolet rays and has high absorption rate. P-ParsoMCX (octyl methoxycinnamate vinegar) is the most common sunscreen cream in the world. It has excellent ultraviolet absorption curve, good safety and good solubility in oily raw materials. It is almost an ideal sunscreen.
At present, the most widely used sunscreen or ultraviolet absorber in sunscreen cosmetics is undoubtedly ocMMethoxveinnamate, hereinafter referred to as OMC, and the COLPA sunscreen series number of the European Union is $28, hereinafter referred to as Colipa$28, but its light resistance or light resistance is not too high. Usually, about 70% of the effective components are degraded by light after being irradiated by 10MED sunlight. Therefore, it is usually necessary to add a higher dose to the formula to make it work effectively. At the same time, in order to reduce the over-stimulation reaction of users with sensitive skin under the stimulation of sunlight after applying sunscreen cosmetics. It is necessary to add excessive irritating ingredients to minimize irritating complaints about products.
In the past few years. Some media in northern Europe reported that some ultraviolet absorbers used in cosmetics, such as OMC, benzophenone, 3 and 4, methyl benzylidene camphor, etc., may have estrogenic activity and are not suitable for children's cosmetic crystals, which caused some panic among European consumers. After careful study, the EU Cosmetics and Non-food Science Committee, which is in charge of cosmetics safety, believes that the above three suspected ultraviolet absorbers have only weak aphrodisiac effect, which is similar to many other commonly used cosmetic raw materials and some drugs, and their use in cosmetics will not affect consumers' health.
2. 1.4 salicylate
Salicylate is the earliest ultraviolet absorber, which can form oxygen bonds in molecules. Low ultraviolet absorption capacity, extremely narrow absorption wavelength range (less than 340 Iiin), and can prevent ultraviolet rays of 280-330 nm. However, after absorbing a certain amount of energy, due to molecular rearrangement, benzophenone structure with strong ultraviolet resistance is formed, resulting in strong photostability. As shown in the figure below.
The compound with the above structural formula is also called pioneer ultraviolet absorber. Their sunscreen effect is not very high, but they are low in price, simple in preparation process and low in toxicity. Can be used with other sunscreens.
At present, only 3.3.5, trimethyl cyclohexanol salicylate vinegar and isooctyl salicylate (C15H2O3) are allowed in the European Union, but the previously allowed p-isopropyl benzyl salicylate has been discontinued due to toxicological problems. FDA has relaxed the restrictions on salicylic acid compounds: 3,3,5,3-cyclohexanol salicylate, isooctyl salicylate and triethanolamine salicylate are allowed.
Generally speaking, the absorption efficiency of salicylic acid compounds to short-wave ultraviolet UVB is quite low, which will inevitably lead the formulator to increase the dose in order to achieve a certain SPF value. However, the photostability of these compounds is very low. Its photodegradation products will cause great problems to the skin.
2. 1.5 benzophenone compound
Benzophenone methyl ketone sunscreen has a strong absorption effect on almost the whole ultraviolet region, because there are intramolecular hydrogen bonds in its structure, and a complete ring is formed between hydroxyl hydrogen on benzene ring and adjacent carbonyl oxygen. When ultraviolet energy is absorbed, molecules are thermally vibrated, hydrogen bonds are broken, and integral rings are opened, so that harmful ultraviolet light is converted into harmless heat energy and released. In addition, after benzophenone absorbs ultraviolet light, not only the hydrogen bond is destroyed, but also the carbonyl group is excited, resulting in tautomerism and enol structure, which also consumes some energy. For example:
The strength of intramolecular hydrogen bond is related to its photostability effect. The stronger the hydrogen bond, the more energy is needed to destroy it, and the more ultraviolet energy is absorbed, the better the effect is. Or vice versa, this sunscreen from Dallas to the auditorium has high thermal stability and light stability. But it is unstable to oxidation, so when preparing colored cosmetics, antioxidants must be added to the formula. This sunscreen cream has good affinity for skin and sticky abdomen, no photosensitive reaction and low toxicity. For example, 2,4-hydroxy-methoxybenzophenone is an effective substance for broad-spectrum ultraviolet absorption. Widely used abroad. 2.2 '- dihydroxy, 4. 4', dimethoxybenzophenone has the same sunscreen effect in ultraviolet A area and ultraviolet B area. It has high thermal stability and light stability. Tetrahydroxyphenyl ketone is a broad-spectrum ultraviolet absorber, which is characterized by its highest efficacy in tanning field and the greatest thermal stability and light stability among similar products. This sunscreen has ortho and para positions. The ortho position shows the absorption peak of UVA. Para-position shows the absorption peak of UVB, so it absorbs ultraviolet rays more widely than other sunscreens, and its safety is better, and only a few people will have temporary allergic reactions. Therefore, it is a widely used ultraviolet absorber.
2. 1.6 camphor derivatives
3- phenyldecyl camphor can effectively absorb the ultraviolet rays in the sunburn range, but it can completely pass the ultraviolet rays in the tanning range. For example, 3-(4- methylbenzylidene) camphor can be used in various tanning agents and sunscreens, and it is stable, non-irritating, non-photosensitive and unchangeable during storage, and has low toxicity, but it is not easily absorbed by the skin. Among them, benzylidene camphor is determined to be a better frame structure of light-stable ultraviolet absorber. The biggest advantage of this structure is that the photosensitive isomerization process will occur under ultraviolet irradiation. That is, it can absorb ultraviolet energy. Simply adopt the method of rotating the double bond connecting benzene ring and norbornane bicyclic ring to release ultraviolet rays with imperceptible heat. This anti-isomerism pendulum can be reversed, which can not only ensure the stability of light, but also ensure the safety of use.
2. 1.7 methane derivatives
It is an efficient UVA ultraviolet absorber and can be made into SPF sunscreen. In foreign countries, these products are mainly 4- isopropyl benzoyl methane and 4- tert-butyl 4- methylaminobenzoyl methane. In recent years, the product developed by Givandan Company in Germany has the trade name Parsol 1789. The name of DTFA is butyl methoxydibenzylmethane, which is called 4- butyl -4- methoxybenzoyl methane, and its molecular formula is C20H22O3. Pale yellow and slightly fragrant, its important function is sun protection, Kmax is 357 nm, and the ultraviolet absorption band is 332. At 385 nm, the SPF value of SPF increased with its dosage, and the SPF value could reach 9- 10. Previously, Pars0 1 1789 was the most effective UVA absorber.
Some plants, such as aloe, burdock, coix seed and houttuynia cordata, walnut and rice bran oil, also have high sunscreen effect and good skin safety because they contain chemical components that can absorb ultraviolet rays. Will not cause adverse reactions to the skin. In addition, vitamin A can prevent the atrophy of connective tissue, make up for the damage caused by ultraviolet rays, improve the composition of skin, prevent the fracture of connective tissue and promote the synthesis of glycosaminoglycan. Vitamin E is an ideal antioxidant and anti-aging agent, which can inhibit the oxidation of unsaturated lipids and resist the damage of ultraviolet rays to the skin.
2. 1.8 inorganic sunscreen preparation
Cb and andler M, R&D managers of negative personal care products of Unlqema Company, said: "The latest research achievements to maintain our company's product commitment include transparent inorganic TIO2. Suspension can be used as a humectant, a repair solution, and seaside debris. " He specifically mentioned that Solaveil CT- 100 is the latest TiO2 dispersion with excellent transparency in the formula.
The innovative achievements of Unlqema company also include the Arise vorsaex emulsion stabilizer technology for sunscreen spray, which can make Ar]acel P 135 exert the maximum active effect and have water resistance. Arlace2 12 1 liquid crystal stabilizer can make onions get a particularly attractive differentiated skin feeling.
Thomson stressed, "A recently completed study shows that the sunscreen formula of Taiwan Province micro-ZnO has a lasting anti-UVA and UVB effect, which is because micro-ZnO is completely resistant to light in the sun and can provide important lasting protection functions for products."
Thomson also said that in addition to inorganic fine ZnO, BASF also developed a new organic UVA filter, which is also completely light-resistant in the sun, and was launched under the trade name Uvinul A Plus at the international cosmetics exhibition. This new patented technology has many advantages over the traditional organic filter Avobe nzono. Uvinul A Plus is completely light-resistant, does not need stabilizers, and is compatible with OMC and ZnO. Through practical patents, it can be used with other common ultraviolet filters, and has broad application prospects.
2.2 Sunscreen products
Using different kinds of sunscreen (or using compound sunscreen) in the formula has become an important content in the development of crystal formula technology of sunscreen cosmetics. Including the combined use of UVB and UVA sunscreen, UVB and UVA sunscreen, absorbent and scattering agent, etc. In order to better play the synergistic effect between sunscreen monomers. At the same time, the use of ultra-fine scattering agent of ultraviolet absorbent and aloe extract and other natural sunscreen ingredients has become a new trend. In order to reduce the skin problems that may be caused by some chemical absorbents, some formulators also add some anti-inflammatory agents to the products, such as A, bisabolol and DP300.
In addition, different types of sunscreen should be selected for different formulations of cosmetics. When preparing sunscreen emulsion and gel, water-soluble and alcohol-soluble ultraviolet absorbers must be used; Oil-soluble ultraviolet absorber must be used when preparing sunscreen oil. Buy some beauty cosmetics. Ultraviolet scattering agents can be used; It is best to use a compound ultraviolet absorber which is both oil-soluble and water-soluble, so as to ensure that the effective ingredients can be evenly distributed on the skin.
The higher the sun protection coefficient (SPP value is the ratio of the minimum energy required to produce erythema on the skin protected by sun protection products to the maximum energy required to produce erythema of the same degree on unprotected skin), the better the shielding effect on solar ultraviolet rays; However, the higher the concentration of added organic ultraviolet absorber, the greater the possibility of skin allergy and the more negative effects it brings. Dermatologists believe that sunscreen products with SPF of 15 are generally enough. Do not exceed 30 at the highest.
Tu et al. of Northwest Institute of Nuclear Technology screened and extracted dozens of plants with ultraviolet absorption, such as Arnebia euchroma, Sophora japonica and Cinnamomum cassia. The extracted natural flavonoids have a good absorption effect on ultraviolet rays, and also have the functions of inhibiting lipid oxidation, anti-inflammation and anti-metamorphosis.
Recently, Swiss Ciba Specialty Chemicals Co., Ltd. introduced a new UVA ultraviolet absorber, Teana Poetry M. Teana Poetry M has dual physical sunscreen function, and its high light stability gives it high safety in practical application.
In addition, when choosing a sunscreen, you should also choose and prepare a suitable substrate. A good substrate will give full play to the sunscreen effect of sunscreen. For absorbing sunscreen, it is very important to choose a good sunscreen carrier. A carrier that is easy to apply, has good affinity with skin and strong water resistance will undoubtedly be more suitable for sun protection. The addition of some special polymers can improve the actual sunscreen ability of products. For scattering sunscreen, it is equally important to choose a suitable substrate. The refractive index of inorganic powder is closely related to light scattering. The greater the ratio of the refractive index of the powder to the refractive index of the matrix, the greater the amount of ultraviolet rays reflected on the surface of the powder. Therefore, people began to pay attention to the use of inorganic sunscreens such as titanium dioxide and zinc oxide, and at the same time try to choose matrix raw materials with low refractive index in the formula.
3 outlook
With the deepening of people's dialectical understanding of the harm and benefits of ultraviolet rays; Judging from the development of new technologies and raw materials for sun protection, many promising researches are being carried out all over the world. They are: (1) research on the efficiency of ultra-fine inorganic particles scattering and absorbing ultraviolet rays and its application; Amino acid UVA absorbent and marine organisms rich in amino acids and high concentration of tyrosine are used in sunscreen cosmetics; Melanin with good sunscreen properties (including natural, biological and synthetic) is used in the research of sunscreen products. The application of ultraviolet absorber in sunscreen cosmetics will be further expanded, and the new ultraviolet absorber with good light stability, low skin permeability and high absorption in all bands will bring innovation and progress in formula technology. We used an ultraviolet energy analyzer to measure the energy change of ultraviolet rays when they reached the ground in an intolerant environment. The results show that even on cloudy days or cloudy days, strong ultraviolet rays can still reach the ground, and the ultraviolet energy reaching the ground in spring is not much lower than that in summer. Ultraviolet rays can penetrate clothes, glass and water and reach human skin. Not only the hot summer needs sun protection, but also the skin needs sun protection. Around the development of modern cosmetic technology and market, sun protection will be a long-term topic.