Study On Protective Role Of Total Flavonoids From Lycium Barbarum Leaves To Skin Photodamage Caused By UVB Radiation

It had been found that the total flavonoids from Lycium barbarum leaves had protective effects against photooxidation, photosensitive and inflammation damage, some of them can remove the free radical of skin, and avoid the damage of skin cells. The UVB was the most main factor of skin damage, which was related with reactive oxygen species(ROS), ROS caused mitochondrial apoptosis and DNA strand breakes, and prompted the release of some inflammatory factors, or led to the erythema and edema of skin. The optical damage of skin is the hot issue of common concern to people, so it is very necessary to study the method of UVB prevention. Development of effective natural antioxidants, so delay skin aging and prevent optical damage of skin caused by UVB radiation has important signif icance. Lycium barbarum leaves have high nutritional and medicinal value, it contains a large number of flavonoids. As a natural source of flavonoids, total flavonoids from Lycium barbarum leaves was studied the influence of topical using it on the skin-photodamage caused by UVB radiation, which has been reported rarely at home and abroad. Objective: 1. To set up the hairless mice acute injury of ultraviolet model. 2. After topical using total flavonoids from Lycium barbarum leaves cream, to investigate the UVB radiation effects on the skin appearance, the minimal erythema dose(MED), the skin structure, the change of antioxidant enzyme activity, and the content of Hyp and MDA of hairless mice after UVB radiation. Methods: 1. To prepare the oil- in-water type Lycium barbarum leaves flavonoids cream. 2. To shave off the dorsal hair with 6%Na2S, UVB radiation after 2 days, with irradiation time and the hairless mice dorsal skin changes as a benchmark, confirm the hairless mice acute injury of ultraviolet model. 3. The hairlessness mice were randomly divided into six groups, in addition to the control group, UVB irradiation 2h/day for two weeks to cause skin irradiation of UVB damage model, UVB direct exposure to UVB model group, before the irradiation, the base grope smear cream base, and the treatment groups were irradiated dorsal skin at the back of the external low, medium and high doses of Lycium barbarum leaves flavonoids cream. 4. Every 2 days prior to irradiation, weighing mice weight. The dorsal skin of mice was observed per day, at 14 th day, rating it based on scoring criteria, and determining minimal erythema dose(MED) before the radiation of the first and 14 th days. 5. On the 14 th day, all of the mice were sacrificed immediately after the end of irradiation, taking the irradiated area of the dorsal skin. With HE staining, changes were observed in mouse skin tissue morphology. And determined the activity of SOD, GSH-Px, CAT and the content of MDA and hydroxyl proline Hyp were investigated in skin tissue by UV spectrophotometry. Results: 1. Changes in weight of mice: after UVB irradiation, the weight of model group mice increased slowly, but the difference was not significant. 2. The mice dorsal skin appearance changing: UVB model group compared with the control group, the mice dorsal skin appearance score was signif icantly higher(P<0.01), compared with the base group, scores did not change significantly( P>0.05). Lycium barbarum leaves flavonoids high-dose group compared with the UVB model group, score signif icantly lower(P<0.01). 3. Mice dorsal skin minimal erythema dose(MED): UVB model group compared with the control group, no significant changes in minimal erythema dose(P>0.05). Compared with the model group, after topical using Lycium barbarum leaves flavonoids cream 14 days, the MED of mice dorsal skin was significantly increased(P<0.01), and the high dose group SPF = 20. 4. Mice skin pathology by HE staining, light microscopy revealed pathology of model group presented photoaging state, inflammation. Compared with the model group, the skin tissue of Lycium barbarum leaves flavonoids high-dose group biopsy visible injury mitigation. 5. Mice skin tissue biochemical parameters: Compared with the control group, MDA content in UVB model mice back skin tissue increased, Hyp content decreased, SOD, GSH-Px and CAT activity decreased signif icantly(P<0.01). With the model group comparing high-dose topical Lycium barbarum leaves flavonoids cream can signif icantly reduce the content of MDA in dorsal skin tissue, increasing Hyp content, and SOD, GSH-Px and CAT activity(P<0.01). Conclusion: Topical using total flavonoids from Lycium barbarum leaves prevent skin damage caused by UVB radiation, possibly by increasing the skin tissue SOD, GSH-Px and CAT activity. Thereby effectively remove free radicals in the skin, so enhance the own ability of skin to resistance to ultraviolet.