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.

Simulation study on the trembling shear behavior of eletrorheological fluid.

The trembling shear behavior of electrorheological (ER) fluids has been investigated by using a computer simulation method, and a shear-slide boundary model is proposed to understand this phenomenon. A thiourea-doped Ba-Ti-O ER fluid which shows a trembling shear behavior was first prepared and then systematically studied by both theoretical and experimental methods. The shear curves of ER fluids in the dynamic state were simulated with shear rates from 0.1 to 1000 s(-1) under different electric fields. The simulation results of the flow curves match the experimental results very well. The trembling shear curves are divided into four regions and each region can be explained by the proposed model.

Boundary effect in electrorheological fluids.

The effect of the boundary friction coefficient on the rheological properties of the electrorheological (ER) fluids in quasistatic and dynamic states is investigated by computer simulation. The relation between the shear stress and the boundary friction coefficient in quasistatic and dynamic states is discussed qualitatively and quantitatively, and the trend matches the previously reported experimental results well. The flow curves of ER fluids, under different friction coefficients, are calculated, and it is found that the friction coefficient affects the flow curves. In two dimensions, the transitions in structure corresponding to the shear stress variations are presented to understand the mechanism of ER fluids.