Photoprotective effects of Lithospermum erythrorhizon and Pueraria lobata extracts on UVB‐induced photoaging: A study on skin barrier protection

Aim Lithospermum erythrorhizon and Pueraria lobata exhibit promising potential as cosmetic additives for mitigating skin barrier impairment induced by photoaging. Despite their potential, the precise mechanisms underlying their protective and ameliorative effects remain elusive. This study sought to assess the reparative properties of Lithospermum erythrorhizon and Pueraria lobata extracts (LP) on UVB‐irradiated human skin keratinocytes (HaCaT cells) and explore the therapeutic potential of LP as a skin barrier protection agent. Materials and Methods Antioxidant activities were gauged through 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS), and reactive oxygen species (ROS) assays. The expression levels of skin barrier‐related markers, encompassing metalloproteinases (MMPs) and hyaluronidase (HYAL) were scrutinized using enzyme‐linked immunosorbent assay (ELISA), reverse transcriptase (RT)‐PCR, and Western blotting, with a particular focus on the involvement of the transforming growth factor (TGF)‐β/Smad and nuclear factor‐κB (NF‐κB) signaling pathways. Results The study revealed that LP effectively scavenges free radicals, diminishes ROS production in a dose‐dependent manner, and significantly attenuates UVB‐induced expression of MMP‐1 and MMP‐3 through modulation of the hyaluronan synthase (HAS)2/HYAL1 signaling axis in UVB‐irradiated HaCaT cells. Additionally, LP demonstrated enhanced TGF‐β signaling activation, fostering procollagen type I synthesis, and concurrently exhibited mitogen‐activated protein kinases (MAPK)/NF‐κB signaling inactivation, thereby mitigating pro‐inflammatory cytokine release and alleviating UVB‐induced cellular damage. Conclusion In conclusion, the observed protective effects of LP on skin cellular constituents highlight its substantial biological potential for shielding against UVB‐induced skin photoaging, positioning it as a promising candidate for both pharmaceutical and cosmetic applications.