Design, Synthesis, and Acetylcholinesterase Inhibitory Activity of Novel Oxytocin Analogs as Potential Therapeutics for Alzheimer’s Disease

Oxytocin (OXT) has demonstrated potential therapeutic effects in Alzheimer’s disease (AD) through mechanisms such as reducing amyloid-β (Aβ) accumulation and tau deposition, as well as exerting antioxidant and anti-inflammatory properties. A recent study further revealed that OXT can decrease acetylcholinesterase (AChE) activity in liver and kidney tissues, suggesting that its effects on Aβ and tau pathology may be mediated, at least in part, through AChE inhibition. Based on this rationale, a series of OXT derivatives were designed, synthesized, and evaluated using protein-protein interaction analysis, molecular docking, in vitro AChE inhibition assays, enzyme kinetics, and antioxidant assays. Docking and protein-protein interaction studies showed that OXT and its analogues fit well within the 20 Å gorge of the AChE active site, engaging both the catalytic active site (CAS) and the peripheral anionic site (PAS). In vitro AChE inhibition assays revealed promising activity, with OXT (Cmpd.16) and analogue 7 (Cmpd.7) exhibiting IC₅₀ values of 8.5 µM and 3.6 µM, respectively. Kinetic analysis determined inhibition constants (Kᵢ) of 45 µM for Cmpd.16 and 6 µM for Cmpd.7, with both compounds following a mixed-type inhibition mechanism. Furthermore, antioxidant evaluations indicated potential neuroprotective properties. In conclusion, OXT analogues act as dual-binding site AChE inhibitors, as supported by docking, protein-protein interaction, and kinetic analyses, and display greater inhibitory activity than OXT itself. These findings suggest that OXT analogues represent promising candidates for further development as AChE inhibitors for AD therapy.