Indole-N-acylhydrazones derivatives as multitarget-directed ligands: potential of privileged scaffolds for Alzheimer’s disease treatment.

Privileged scaffolds such as indole and N-acylhydrazone are used on development of multitarget-directed ligands (MTDL). The use of MTDL for the treatment of multifactorial diseases like Alzhemier's disease (AD) may be promising. They could act in targets like enzymes acetylcholinesterase (AChE), myeloperoxidase (MPO) and monoamine oxidase B (MAO-B), and chelator of metals redox as Cu²⁺, all involved on DA pathophysiology - oxidative stress, neuroinflammation, and degeneration (Curr. Neuropharmacol. (2014) 12:239; Acta Neuropathol. Commun. (2022) 10:38). The profile of six indole-N-acylhydrazone derivatives was evaluated as MTDL for AD treatment. AChE and butyrylcholinesterase (BChE) inhibition were evaluated via Ellman's method. MPO inhibition was determined by producing HOCl and other physiological substrates using TNB bleaching as indicator. The inhibition of MAO-A/B was evaluated by peroxidase-coupled assay using HRP and tyrosine. Chelation test of biometals was done in methanol using UV spectrum changing for detection. AChE was inhibited by S1-S6 at 300µM in 65.1±3.5%, 44±4.8%, 62.3±5.6%, 57.9±4%, 42.5±1.5%, and 64.6±2.9%, respectively. On the other hand, BChE was inhibited only by S1, S2, and S4 in 48.8±7%, 68.4±6%, and 45.7±3.7%, respectively. In MPO chlorination assay S1, S3, S5, and S6 were the most active derivatives and presented IC₅₀ values of 37.9±8.4µM, 4.8±1.3µM, 9.5±1.3µM, and 13.7±0.8µM, respectively. MPO peroxidase cycle was inhibited by S2, S3, and S4 with IC₅₀ values of 33.1±1.8µM, 31.3±4.7µM, and 0.9±0.2µM, respectively. Against MAO, the derivatives S1, S4, and S6 presented MAO-B IC₅₀ values of 6.2±0.8µM, 0.35±0.1µM, and 3.7±0.4µM, respectively. While for MAO-A S4 and S6 presented IC₅₀ values of 1.8±0.2µM and 13.8±3.9µM, respectively. They all formed complexes (L+M/2:1) with biometal Cu²⁺ and S4 also complexed with Fe²⁺, Mg²⁺ and Zn²⁺. All derivatives acted as MTDL and S6 was the best candidate inhibiting all enzymes and acts as copper chelator.