Design, Synthesis, and Neuroprotective Activity of Phenoxyindole Derivatives on Antiamyloid Beta (Aβ) Aggregation, Antiacetylcholinesterase, and Antioxidant Activities

In this investigation, a number of phenoxyindole derivatives were designed, synthesized, and tested for their neuroprotective ability on SK-N-SH cells against Aβ₄₂-induced cell death and biologically specific activities involved in anti-Aβ aggregation, anti-AChE, and antioxidant effects. The proposed compounds, except compounds 9 and 10, could protect SK-N-SH cells at the IC₅₀ of anti-Aβ aggregation with cell viability values ranging from 63.05% ± 2.70% to 87.90% ± 3.26%. Compounds 3, 5, and 8 demonstrated striking relationships between the %viability of SK-N-SH cells and IC₅₀ values of anti-Aβ aggregation and antioxidants. No significant potency of all synthesized compounds against AChE was found. Among them, compound 5 showed the strongest anti-Aβ and antioxidant properties with IC₅₀ values of 3.18 ± 0.87 and 28.18 ± 1.40 μM, respectively. The docking data on the monomeric Aβ peptide of compound 5 demonstrated good binding at regions involved in the aggregation process, and the structural feature made it possible to be a superior radical scavenger. The most effective neuroprotectant belonged to compound 8, with a cell viability value of 87.90% ± 3.26%. Its unique mechanisms for enhancing the protective impact may serve additional purposes since it demonstrated mild biological-specific effects. In silico prediction of CNS penetration shows strong passive penetration ability across the blood–brain barrier from blood vessels to the CNS for compound 8. In light of our findings, compounds 5 and 8 appeared as potentially intriguing lead compounds for new therapeutic approaches to Alzheimer’s disease. More in vivo testing will be revealed in due course.