Multitarget Biological Profiling of New Naphthoquinone and Anthraquinone-Based Derivatives for the Treatment of Alzheimer's Disease

Two series of naphthoquinone and anthraquinone derivatives decorated with an aromatic/heteroaromatic chain have been synthesized and evaluated as potential promiscuous agents capable of targeting different factors playing a key role in Alzheimer's disease (AD) pathogenesis. On the basis of the biological profiling, most of them exhibited a significant ability to inhibit amyloid aggregation, PHF6 tau sequence aggregation, acetylcholinesterase (AChE), and monoamine oxidase (MAO) B. In particular, naphthoquinone resulted as one of the best performing multitarget-directed ligand (MTDL) experiencing a high potency profile in inhibiting β-amyloid (Aβ) aggregation (IC = 3.2 μM), PHF6 tau fragment (91% at 10 μM), AChE enzyme (IC = 9.2 μM) jointly with a remarkable inhibitory activity against MAO B (IC = 7.7 nM). Molecular modeling studies explained the structure-activity relationship (SAR) around the binding modes of representative compound in complex with hMAO B and hAChE enzymes, revealing inhibitor/protein key contacts and the likely molecular rationale for enzyme selectivity. Compound was also demonstrated to be a strong inhibitor of Aβ aggregation, with potency comparable to quercetin. Accordingly, atomic force microscopy (AFM) revealed that the most promising naphthoquinones and and anthraquinones and were able to impair Aβ fibrillation, deconstructing the morphologies of its fibrillar aggregates. Moreover, the same compounds exerted a moderate neuroprotective effect against Aβ toxicity in primary cultures of cerebellar granule cells. Therefore, our findings demonstrate that these molecules may represent valuable chemotypes toward the development of promising candidates for AD therapy.