A series of novel tacrine derivatives and tacrine-coumarin heterodimers were designed, synthesized, and biologically evaluated for their potential inhibitory effect on both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Of these compounds, tacrine-coumarin heterodimer 7c and tacrine derivative 6b were found to be the most potent inhibitors of human AChE (hAChE), demonstrating IC50 values of 0.0154 and 0.0263 μM. Ligands 6b, 6c, and 7c exhibited the highest levels of inhibitory activity against human BuChE (hBuChE), demonstrating IC50 values that range from 0.228 to 0.328 μM. Docking studies were performed in order to predict the binding modes of compounds 6b and 7c with hAChE/hBuChE.

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We have screened a library of structurally distinct acridine derivatives (19 compounds) for their ability to inhibit lysozyme amyloid aggregation in vitro. Studied acridines were divided into three structurally different groups depending on the molecule planarity and type of the side chain-planar acridines, spiroacridines and tetrahydroacridines. Thioflavine T fluorescence assay and transmission electron microscopy were used for monitoring the inhibiting activity of acridines. We have found that both the structure of the acridine side chains and molecule planarity influence their antiamyloidogenic activity. The planar acridines inhibited lysozyme aggregation effectively. Spiroacridines and tetrahydroacridines had no significant effect on the prevention of lysozyme fibrillization, probably resulting from the presence of the heterocyclic 5-membered ring and non-planarity of molecule. Moreover, in the presence of some tetrahydroacridines the enhanced extent of aggregation was detected. We identified the most active acridine derivates from studied compound library characterized by low micromolar IC50 values, which indicate their possible application for therapeutic purpose.

While amyloid-related diseases are at the center of intense research efforts, no feasible cure is currently available for these diseases. The experimental and computational techniques were used to study the ability of glyco-acridines to prevent lysozyme amyloid fibrillization in vitro. Fluorescence spectroscopy and atomic force microscopy have shown that glyco-acridines inhibit amyloid aggregation of lysozyme; the inhibition efficiency characterized by the half-maximal inhibition concentration IC50 was affected by the structure and concentration of the derivative. We next investigated relationship between the binding affinity and the inhibitory activity of the compounds. The semiempirical quantum PM6-DH+ method provided a good correlation pointing to the importance of quantum effects on the binding of glyco-acridine derivatives to lysozyme. The contribution of linkers may be explained by the valence bond theory. Our data provide a basis for the development of new small molecule inhibitors effective in therapy of amyloid-related diseases.