Molecular interactions between fibrinogen and 6-methoxydihydrosanguinarine and their modulation of anticancer activity in melanoma A375 cells.

Natural benzophenanthridine alkaloids such as sanguinarine, chelerythrine, and 6-methoxydihydrosanguinarine (6-MDS) possess anticancer properties against various cancer cell types. However, the physical interactions of these compounds with blood proteins and the anticancer effects of the resulting complex remain unknown. Therefore, in this study, the interaction between 6-MDS and fibrinogen (Fb) was evaluated through experimental and theoretical studies. The binding analysis revealed that Fb's intrinsic fluorescence is quenched following a moderate interaction with 6-MDS, and a 1:1 complex predominantly forms via hydrogen bonds. Synchronous/ 8-Anilino-1-naphthalenesulfonic acid (ANS) fluorescence and circular dichroism (CD) studies, along with molecular dynamics simulation analysis, indicated that 6-MDS caused a partial rearrangement in the Fb conformation. Differential scanning calorimetry (DSC) measurements showed that upon the addition of 40 μM 6-MDS concentrations, Tm values of Fb slightly decreased, which is consistent with the UV-visible studies. Cellular data revealed IC50 concentrations of 2.85 and 2.65 μM for 6-MDS and the Fb-6-MDS complex against melanoma A375 cells, respectively. These values were significantly lower than those for normal primary human dermal fibroblast (NHDF) cells. It was then observed that the presence of Fb could enhance the anticancer effects of the 6-MDS against melanoma A375 cells via the upregulation of LDH release, ROS production, and caspase-3 activity. Finally, these findings clarify the interaction between Fb and 6-MDS, as well as the anticancer activity of the resulting complex.