Nontoxic and Neuroprotective β‑Naphthotacrines for Alzheimer's Disease

The synthesis, toxicity, neuroprotection, and human acetylcholinesterase (hAChE)/ human butyrylcholinesterase (hBuChE) inhibition properties of β-naphthotacrines1–14 as new drugs for Alzheimer’s disease (AD) potential treatment, are reported. β-Naphthotacrines1–14 showed lower toxicity than tacrine; moreover, at the highest concentration assayed (300 μM) compounds 7, 10 and 11 displayed 2.25–2.01-fold higher cell viability than tacrine in HepG2 cells. A neuroprotective effect was observed for compounds 10 and 11 in a neuronal cortical culture exposed to a combination of oligomycin A/rotenone. An efficient and selective inhibition of hAChE, was only observed for the β-naphthotacrines bearing electron-donating substituents at the aromatic ring, β-naphthotacrine10 being the most potent (hAChE: IC50 = 0.083 ± 0.024 μM). Kinetic inhibition analysis clearly demonstrated that β-naphthotacrine10 behaves as a mixed-type inhibitor (Ki2= 0.72 ± 0.06 μM) at high substrate concentrations (0.5–10 μM), while at low conc...