Synthesis and in vitro evaluation of vanillin derivatives as multi-target therapeutics for the treatment of Alzheimer's disease.

A number of novel naphthalimido and phthalimido vanillin derivatives were synthesised, and evaluated as antioxidants and cholinesterase inhibitors in vitro. Antioxidant activity was assessed using DPPH, FRAP, and ORAC assays. All compounds demonstrated enhanced activity compared to the parent compound, vanillin. They also exhibited BuChE selectivity in Ellman's assay. A lead compound, 2a (2-(3-(bis(4-hydroxy-3-methoxybenzyl)amino)propyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione), was identified and displayed strong antioxidant activity (IC of 16.67 µM in the DPPH assay, a 25-fold increase in activity compared to vanillin in the FRAP assay, and 9.43 TE in the ORAC assay). Furthermore, 2a exhibited potent BuChE selectivity, with an IC of 0.27 µM which was around 53-fold greater than the corresponding AChE inhibitory activity. Molecular modelling studies showed that molecules with bulkier groups, as in 2a, exhibited better BuChE selectivity. This work provides a promising basis for the development of multi-target hybrid compounds based on vanillin as potential AD therapeutics.