Objective To investigate the protective effect of Thanaka extract against UVB-induced photoaging damage in skin. Methods HaCaT cells were treated with 0-25 μg/mL Thanaka extract and 30 mJ/cm2UVB. CCK-8 method was used to observe the effect of Thanaka extract and its effect on the viability of HaCaT cells after UVB irradiation. HaCaT cells were treated with low （3 μg/mL）， medium （6 μg/mL） and high （12 μg/mL） concentrations of Thanaka extract and 30 mJ/cm2 UVB. DCFH-DA fluorescent probe was used to detect intracellular reactive oxygen species （ROS） content； JC-1 fluorescent probe was used to detect mitochondrial membrane potential； Superoxide dismutase （SOD） and malondialdehyde （MDA） were used to detect the levels of antioxidant and oxidative damage. Results The treatment of 0-25 μg/mL of Thanaka extract at all concentrations had no significant effect on cell viability. The viability of HaCaT cells was increased after treatment with 12 μg/mL of Thanaka extract compared with that of the UVB group （P<0.05）. Further experiments showed that ROS content decreased （P<0.05）， SOD activity increased （P<0.05） in the medium and high concentration of Thanaka extract groups；MDA level decreased （P<0.05） and mitochondrial membrane potential rebounded in the low， medium， and high concentration of Thanaka extract groups compared with the UVB group. Conclusion Thanaka extract can promote the viability and antioxidant level of HaCaT cells after UVB irradiation， and reduce the oxidative stress damage produced by UVB， and its underlying mechanism may be related to mitochondrial function

Thanaka extract, UVB, Photoaging, Reactive oxygen species, Mitochondria