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The major environmental factor responsible for skin cancer is ultraviolet (UV) radiation, present in sunlight. UV radiation is directly linked to the production of reactive oxygen species (ROS), which accumulate in exposed cells and cause serious damage. The antioxidant systems present in cells cannot always sufficiently neutralize the ROS. Therefore, supplementation with exogenous antioxidants has been proposed. The antioxidant properties of some isoflavones, such as genistein, have already been well-proven. Genistein has limited bioavailability. However, its derivatives, with increased lipophilicity, could facilitate its transfer into cells, where they can expose its antioxidative potential. This study aims to investigate three genistein derivatives, with greater lipophilicity than the native compound, regarding their cytotoxicity, antioxidative properties, and effect on the cell cycle in normal human dermal fibroblasts (NHDF) and a melanoma cancer cell line (Me45). Results showed that lipophilic modification of the genistein molecule changes the biological response of NHDF and Me45 cell lines to UV-C radiation, but the lipophilicity cannot be directly linked with the activity of the compounds. A comparison of the effects of the genistein derivatives on healthy and cancerous cells suggests that their mode of action strongly depends on the type of cell involved.

In this study two genistein derivatives (G1 and G2) are reported as inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), and differences in the inhibition of AChE are described. Although they differ in structure by a single methyl group, the inhibitory effect of G1 (IC50=264 nmol/L) on AChE was 80 times stronger than that of G2 (IC50=21,210 nmol/L). Enzyme-kinetic analysis, molecular docking and molecular dynamics (MD) simulations were conducted to better understand the molecular basis for this difference. The results obtained by kinetic analysis demonstrated that G1 can interact with both the catalytic active site and peripheral anionic site of AChE. The predicted binding free energies of two complexes calculated by the molecular mechanics/generalized born surface area (MM/GBSA) method were consistent with the experimental data. The analysis of the individual energy terms suggested that a difference between the net electrostatic contributions (ΔEele+ΔGGB) was responsible for the binding affinities of these two inhibitors. Additionally, analysis of the molecular mechanics and MM/GBSA free energy decomposition revealed that the difference between G1 and G2 originated from interactions with Tyr124, Glu292, Val294 and Phe338 of AChE. In conclusion, the results reveal significant differences at the molecular level in the mechanism of inhibition of AChE by these structurally related compounds.