The main component of green tea polyphenols is EGCG (i.e., Gallocatechin gallate). EGCG has been shown to have a number of health benefits. Its properties range from antioxidants to anti-inflammatory drugs, and have a variety of benefits, including cardiovascular health, cancer prevention, reducing the risk of cognitive impairment, improving diabetes, and helping to lose weight, etc.
EGCG can prevent skin cancer and reduce UV damage. EGCG has the characteristics of UV protection, may play a preventive role in the development of skin cancer. EGCG treatment is reported to reduce collagen synthesis in mice and the secretion of fibroblast collagenase (processing after 24 hours). Because UV-induced in-cell damage is typically represented by effects on collagen synthesis and collagenase secretion levels. In addition, UVB-induced damage was quantified by measuring UVB-induced guinea pig erythema. EGCG was reported to significantly reduce erythema within 24 hours of exposure. Another study also analyzed the effects of EGCG on epidermos Langehans cells (LCs) and described a decrease in the number of cells exposed to ultraviolet light. Histological tests showed a 58% reduction in skin LCs damage in participants treated with EGCG compared to the control group.
The dose dependence effect of green tea polyphenols was tested at different concentrations (1-10%). At concentrations of 2.5% or higher, appropriate protective effects are shown. These results are consistent with a recent study to detect UV-induced DNA oxidation damage by measuring the depletion of CD1a-plus cells and the production of UV-induced anti-8-hydroxy-2-deoxydocyanide (8-OHdG). 8-OHdG is associated with UV-induced nucleic acid modification. Compared to non-radiant skin, exposed to ultraviolet light treated with green tea, CD1a plus cells were reduced by 35%. Media-treated skin decreased by 57% after irradiation, similar to untreated skin. The levels of 8-OHdG in the skin coated with green tea extract and exposed did not vary significantly compared to those in the undiensed skin.
But media-treated skin shows a higher level of 8-OHdG. In addition, EGCG has been reported to reduce UV-induced der skin and epidermos production of H2O2 and NO, inhibiting the immersion of CD11b plus cells (CD11b plus is a marker of the surface of macrophages and neural granulocytes) and is an indicator of oxidative stress. EGCG also inhibits the production of epidermal lipid peroxide (LPO) and has a positive effect on other antioxidant (GSH) levels.
A similar study, involving the same type of mice, provided additional information about the extent to which EGCG induced apoptosis in tumors and non-tumor areas of UVB radiation. After 20 weeks of UV-B exposure, the mice were treated with EGCG once a day for a total of 18 weeks, 5 days a week. This treatment resulted in an increase in apoptosis of 72% of non-malignant tumors and an increase in apoptosis of 56% of squamous cell carcinomas, but had no effect on hyperpliogenic or non-tumor areas.