Design, synthesis, and biological evaluation of naphthalimide derivatives as dual monoamine oxidase-B and amyloid-β aggregation inhibitors for Alzheimer's disease

Alzheimer's disease (AD) is a chronic and progressive neurodegenerative disorder with multifactorial pathogenesis. Amyloid beta (Aβ) and monoamine oxidase (MAO) are among the key therapeutic targets for its treatment. In this investigation, a series of 18 new naphthalimide-based derivatives were synthesized and assessed for multitarget activity against hAChE, esBuChE, MAO-A, MAO-B, Aβ, and paired helical fragment 6 (PHF6) aggregation. The screened compounds predominantly exhibited dual inhibition of MAO-B and Aβ aggregation to counteract oxidative stress and plaque formation. Among the tested compounds, P12 and P17 were found to have remarkable inhibition against Aβ, with 83% and 91% inhibition, respectively, compared to the reference compound quercetin (75% inhibition). The compound P10 was the most effective MAO-B inhibitor, with an IC50 value of 3.09 ± 0.10 µM. Cytotoxicity studies in SH-SY5Y cells confirmed that compounds were non-toxic up to 25 µM. Additionally, the neuroprotection assays revealed that P10 was capable of reducing oxidative stress effectively against H2O2-induced toxicity, while P12 showed superior protection against Aβ-induced neurotoxicity in SH-SY5Y cells. Furthermore, in silico investigations provided structural insights into the predicted ligand-target interaction modes and dynamic behavior of the selected compounds with MAO-B and monomeric Aβ1-42. Consequently, all these findings underscore that naphthalimide derivatives are promising dual inhibitors of amyloid-β aggregation and MAO-B and have potential for further development as MTDLs for AD.