Background: Huperzia phlegmaria has been used for the treatment of the neurological
disorder. Alkaloids are the 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 that were induced cognitive deficits by scopolamine.
Methods: AChE inhibitory activity and kinetic inhibition mechanism were investigated by Ellman's
assay. Mice were administrated orally HpAE (30 mg/kg and 60 mg/kg) for fourteen days, injected
scopolamine at a dose of 3 mg/kg one day for Y- maze test and 1 mg/kg four days for Morris
water maze test intraperitoneally to induce cognitive impairment. The Y-maze and the Morris water
maze were used for evaluating 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 a 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 HpAE 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 the 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 doses
(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 doses (30 mg/kg and 60 mg/kg) may be
used for prevention and treatment of Alzheimer’s disease.