In recent years, with the destruction of the ozone layer, ultraviolet radiation reaching the ground the increasing intensity of UV damage on the human body has become increasingly serious. UV is the wavelength of 200 nlTI ~ 4O0 Bill's rays, according to different wavelengths, can be divided into UVC (200 Bill ~ 280 Bill), UVB (280 Bill ~ 320 nm), UVA (320 Ilm ~ 4OO Ilm) 3 districts segment, which UVc almost entirely blocked the atmosphere, the human body without causing harm. Real barrier through the atmospheric ozone and ultraviolet radiation reaching the earth's surface in the UVB accounts for 1%; UVA accounts for 99%. UVB causes sunburn erythema is a major factor, and UVA penetration is strong, it can penetrate the skin surface directly to the dermis, can cause severe tissue damage and even cause skin cancer. Therefore, as public awareness of sun protection, sunscreen and a variety of skin care products demand has also increased rapidly.
Used in cosmetics, sunscreen can be divided into two categories: one is the UV absorbers, for the organic compounds that can reduce or completely absorb UV radiation, but most is irritating and easy photosensitive material, UV protection for UVA segment not complete enough to join the higher the concentration of the possibility of skin irritation caused by the greater, and the resulting negative effects the more; other is UV screening agent for nanoscale Ti02, ZnO, astaxanthin in all Regional reflection and scattering UV light, because their photocatalytic activity and irritation, combined with easy to plug the holes too large, use the paint coating on the skin like the feeling of the potential problem does not disappear because of heavy use. So from a wide range of plant sources in a broad spectrum sunscreen filters and safe, and efficient development of active ingredients and make use of the cosmetics industry will be the 21st century on the main issue.
UV absorbers are often opaque material can absorb UV light, the amount of UV protection is based on the photophysical effect, that the incidence of these UV absorbers into the ultraviolet absorption and thermal vibration of molecules, and because of intramolecular excitation transferred between state level, can produce phosphorescence and fluorescence. Thus by UV absorption spectra of plant extracts of the test, biotin according to its UV absorption wavelength and absorbance values ​​can predict the effect of sunscreen.
Natural plant extracts in the UV region of the absorption of certain properties, but the absorption intensity varies. And compared to other types of plant extracts, flower extracts like most in the UV region has good absorption properties. Among them, rose, peony, hollyhock and hibiscus flower extract, 5 kinds of 250 nin ~ 320 nin in the strong absorption, rose the most (absorbance 7.62), but after the absorbance at 320 nn3 decreased, so these extract only has the role of anti-UVB ultraviolet rays. Azalea, pomegranate, hibiscus, carnations, osmanthus, honeysuckle and nasturtium extracts such as absorption in the UV region has the following characteristics: the 280 nin ~ 360 r. m absorption strong, 360 nin decreased significantly after the absorbance at 400 r. absorbance less than 0.3 m, indicating that such extracts in the short-wave UVA and UVB absorption region is better, not only for UVB absorbers UVA absorbers can also be made, but the UVA protection is incomplete. In the ultraviolet region (280 nin ~ 400 nm) has good absorption are: yellow hollyhock, Sophora japonica, Saussurea superba, so these three flower extract has broad-spectrum sun protection properties. Source:http://www.cosprm.com