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This project is partly funded by UKRI Grant No. EP/X029174/1. We would like to thank Prof. Ming-Hsu Li for meaningful supports on this work.

Abstract:A new series of benzylaminochalcone derivatives with different substituents on ring B were synthesized and evaluated as inhibitors of acetylcholinesterase. The study is aimed at identification of novel benzylaminochalcones capable of blocking acetylcholinesterase activity for further development of an approach to Alzheimer's disease treatment. These compounds were produced in moderate to good yields via Claisen-Schmidt condensation and subjected to an in vitro acetylcholinesterase inhibition assay, using Ellman's method. The in silico docking procedure was also employed to identify molecular interactions between the chalcone compounds and the enzyme. Compounds with ring B bearing pyridin-4-yl, 4-nitrophenyl, 4-chlorophenyl and 3,4-dimethoxyphenyl moieties were discovered to exhibit significant inhibitory activities against acetylcholinesterase, with IC 50 values ranging from 23 to 39 µM. The molecular modeling studies are consistent with the hypothesis that benzylaminochalcones could exert their effects as dual-binding-site acetylcholinesterase inhibitors, which might simultaneously enhance cholinergic neurotransmission and inhibit β-amyloid aggregation through binding to both catalytic and peripheral sites of the enzyme. These derivatives could be further developed to provide novel leads for the discovery of new anti-Alzheimer drugs in the future.

Background: Huperzia phlegmaria has been used for the treatment of neurological disorder. Alkaloids are main bioactive compounds found in Huperzia phlegmaria. We aimed to investigate the acetylcholinesterase (AChE) inhibitory activity in vitro of Huperzia phlegmaria alkaloid extract (HpAE) and protective effects on mice which were induced cognitive deficits by scopolamine. Methods: AChE inhibitory activity and kinetic inhibition mechanism was investigated by Ellman's assay. Mice were administrated orally HpAE (30 mg/kg and 60 mg/kg) for fourteen days, and injected scopolamine at a dose of 1 mg/kg intraperitoneally for four days to induce cognitive impairment. The Y-maze and the Morris water maze were used for evaluating the memory behaviors. Acetylcholine (ACh) levels and AChE activity were measured in brain tissue. Glutathione peroxidase (GPx), superoxide dismutase (SOD) activities, and malondialdehyde (MDA) groups were also evaluated in the mouse brain tissues. Results: Our data showed that HpAE had the strong AChE inhibitory activity with an IC50 value of 5.12 ± 0.48 μg/mL in a concentration-dependent manner. Kinetic inhibition analysis demonstrated that HpPAE inhibited AChE followed the mixed inhibition type with Ki (representing the affinity of the enzyme and inhibitor) was 4.37 ± 0.35 µg/mL. Scopolamine induced the cognitive impairment in Morris Water Maze and Y-maze test along with reduced brain levels of ACh and antioxidant enzyme and increased AChE activity in mouse brain tissues. Treatment with HpAE at both dose (30 mg/kg and 60 mg/kg) decreased the SCP-induced cognitive impairment in both behavioral tests along with decreased acetylcholinesterase activity and MDA level, and increased ACh level and antioxidant enzyme in mouse brain tissues. Conclusion: Our results suggested that the HpAE at both dose (30 mg/kg and 60 mg/kg) may be used for prevent and treatment of Alzheimer’s disease.

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