Using two ways of functionalizing
amiridine-acylation with
chloroacetic acid chloride and reaction with
thiophosgene-we have synthesized new homobivalent bis-amiridines joined by two different spacers-bis-N-acyl-alkylene (3) and bis-N-
thiourea-alkylene (5) -as potential multifunctional agents for the treatment of
Alzheimer's disease (AD). All compounds exhibited high inhibitory activity against
acetylcholinesterase (AChE) and
butyrylcholinesterase (BChE) with selectivity for BChE. These new agents displayed negligible
carboxylesterase inhibition, suggesting a probable lack of untoward
drug-drug interactions arising from hydrolytic biotransformation. Compounds 3 with bis-N-acyl-alkylene spacers were more potent inhibitors of both
cholinesterases compared to compounds 5 and the parent
amiridine. The lead compounds 3a-c exhibited an IC50(AChE) = 2.9-1.4 µM, IC50(BChE) = 0.13-0.067 µM, and 14-18%
propidium displacement at 20 μM. Kinetic studies of compounds 3a and 5d indicated mixed-type reversible inhibition. Molecular docking revealed favorable poses in both catalytic and peripheral AChE sites.
Propidium displacement from the peripheral site by the hybrids suggests their potential to hinder AChE-assisted Aβ42 aggregation. Conjugates 3 had no effect on Aβ42 self-aggregation, whereas compounds 5c-e (m = 4, 5, 6) showed mild (13-17%) inhibition. The greatest difference between conjugates 3 and 5 was their
antioxidant activity. Bis-amiridines 3 with N-acylalkylene spacers were nearly inactive in
ABTS and FRAP tests, whereas compounds 5 with
thiourea in the spacers demonstrated high
antioxidant activity, especially in the
ABTS test (TEAC = 1.2-2.1), in agreement with their significantly lower HOMO-LUMO gap values. Calculated ADMET parameters for all conjugates predicted favorable blood-brain barrier permeability and intestinal absorption, as well as a low propensity for
cardiac toxicity. Thus, it was possible to obtain
amiridine derivatives whose potencies against AChE and BChE equaled (5) or exceeded (3) that of the parent compound,
amiridine. Overall, based on their expanded and balanced pharmacological profiles, conjugates 5c-e appear promising for future optimization and development as multitarget anti-AD agents.