Licoricidin, an isoflavonoid isolated from Glycyrrhiza uralensis Fisher, prevents UVA-induced photoaging of human dermal fibroblasts

Objective: Licoricidin is an isoflavonoid isolated from Glycyrrhiza uralensis Fisher. In this study, we investigated the effects of licoricidin on photoaging of UVA-irradiated human dermal fibroblasts (HDFs).

Methods: In vitro Reactive Oxygen Species (ROS) scavenging activity, cellular protective effect and inhibition of Elastase activity was determined by Fe³⁺ -EDTA/H₂ O₂ systems, photohaemolysis and Elastase activity assay, respectively. Anti-oxidative capacity of the compound was evaluated by fluorescent ELISA and 2', 7'-dichlorofluorescin-diacetate (DCF-DA) assay. The expression of protein and phosphorylation was examined using Western blot.

Results: The ROS scavenging activity (OSC₅₀ ) of licoricidin was 2.77 μM. It was 3.1-fold higher than that of L-ascorbic acid. Its protective effects were confirmed in a study of ¹ O₂ -induced cellular damage to human erythrocytes. The τ₅₀ value of 10 μM of licoricidin was 71.0 min; this was markedly higher than that obtained with α-tocopherol (37.0 min). The Elastase inhibitory activity of licoricidin (IC₅₀ of 61.2 μM) was 2.1-fold more potent than that of oleanolic acid. Licoricidin markedly reduced the UVA-induced intracellular ROS in a concentration-dependent manner. Western blot revealed that licoricidin attenuated the UVA-dependent induction of MMP-1 protein. Mechanistically, this appeared to be due to licoricidin-dependent inhibition of mitogen-activated protein kinases (MAPK) phosphorylation, which resulted in decreased c-Jun activation and reduced c-Jun and c-Fos expression.

Conclusion: Licoricidin blocks UVA-induced photoaging via ROS scavenging. This activity converges to limit the activity of MMP-1. These data suggest that licoricidin may be considered as an active ingredient in new topically applied anti-ageing formulations.