Antioxidant Activity of a Combined Extract of Leonurus japonicus and Trichosanthes kirilowii root and Its Anti-wrinkle Effects on UV-Induced Photoaging Models

Objectives: This study aimed to investigate the inhibitory effects of Leonurus japonicus (LS), Trichosanthes kirilowii root (TKR), and their combination (LS+TKR) on skin photoaging induced by ultraviolet (UV) radiation, through molecular mechanistic analysis and in vivo validation. Methods: The antioxidant potential was evaluated using the DPPH radical scavenging assay. Human dermal fibroblasts (HDFn) were used to assess cell viability (MTT assay), collagen synthesis (PIP assay), and MMP-1 inhibition (ELISA) under UVA irradiation. For in vivo validation, HR-1 hairless mice were exposed to UVB for 9 weeks. Skin changes were analyzed through digital microscopy and histological observations using Hematoxylin & Eosin (H&E) and Masson’s Trichrome (M&T) staining. Results: LS+TKR demonstrated excellent cell viability at concentrations below 100 mg/ml and exhibited potent antioxidant activity with a 98.7% DPPH radical scavenging rate. In HDFn cells, the LS+TKR combination significantly enhanced collagen synthesis by 46.4% and inhibited MMP-1 expression by 52.3% compared to the control, showing superior efficacy over single extracts. This suggests a synergistic effect between Leonurine from LS and Triterpenoids from TKR in blocking collagen degradation pathways and promoting procollagen synthesis. In the hairless mice model, topical application of LS+TKR markedly suppressed UVB-induced wrinkle formation. Histological analysis further confirmed the normalization of epidermal thickness and the restoration of dermal collagen density, along with reduced inflammatory cell infiltration. Conclusion: These findings demonstrate that the combination of Leonurus japonicus and Trichosanthes kirilowii root extracts effectively inhibits skin photoaging through multifaceted mechanisms involving antioxidant defense, collagen synthesis promotion, and dermal matrix preservation. This study provides a scientific foundation for the development of high-functional cosmeceutical ingredients. Future research on the optimization of blending ratios and transdermal delivery systems will further enhance its global competitiveness in the K-beauty industry.