Fermented tea leave extract against oxidative stress and ageing of skin in vitro and in vivo

Abstract Objective The objective is to develop a natural and stable anti‐oxidative stress and anti‐ageing ingredient. In this study, we evaluated the changes in white tea leaves fermented with Eurotium cristatum PLT‐PE and Saccharomyces boulardii PLT‐HZ and their efficacy against skin oxidative stress. Methods We employed untargeted metabolomics technology to analyse the differential metabolites between tea extract (TE) and fermented tea extract (FTE). In vitro, using H 2 O 2 ‐induced HaCaT cells, we evaluated cell vitality, ROS, and inflammatory factors (TNF‐α, IL‐1β, and IL‐6). Additionally, we verified the effects on the extracellular matrix and nuclear DNA using fibroblasts or reconstructed skin models. We measured skin hydration, elasticity, wrinkle area, wrinkle area ratio, erythema area, and erythema area ratio in volunteers after using an emulsion containing 3% FTE for 28 and 56 days. Results Targeted metabolomics analysis of white tea leaves yielded more than 20 differential metabolites with antioxidant and anti‐inflammatory activities, including amino acids, polypeptides, quercetin, and liquiritin post‐fermentation. FTE, compared to TE, can significantly reduce reactive oxygen species (ROS) and protect against oxidative stress‐induced skin damage in H 2 O 2 ‐induced HaCaT cells. FTE can inhibit H 2 O 2 ‐induced collagen degradation by suppressing the MAPK/c‐Jun signalling pathway and can also mitigate the reactive oxygen species damage to nuclear DNA. Clinical studies showed that the volunteers' stratum corneum water content, skin elasticity, wrinkle area, wrinkle area ratio, erythema area, and erythema area ratio significantly improved from the baseline after 28 and 56 days of FTE use. Conclusion This study contributes to the growing body of literature supporting the protective effects against skin oxidative stress and ageing from fermented plant extracts. Moreover, our findings might inspire multidisciplinary efforts to investigate new fermentation techniques that could produce even more potent anti‐ageing solutions.