In-vitro evaluation of acetylcholinesterase inhibition and antioxidant activity of selected Palestinian medicinal plants: Implications for Alzheimer’s disease therapy

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Salam Yousef Jamil Abu Zaitoun
Background: Cholinesterase inhibitory therapy serves as a strategy for the treatment of Alzheimer’s disease (AD), several acetylcholineesterase inhibitors are used for the symptomatic treatment of patients with mild to moderate AD. These compounds have been reported to have adverse effects including gastrointestinal disturbances. Numerous medicinal plants have been used in Traditional Arabic Palestinian Herbal Medicine (TAPHM) for the treatment of several diseases, including improvement of memory, Alzheimer’s disease (AD) and old age related disease. Ethnopharmacological approach and bioassay guided isolation have provided a lead in identifying potential AChE inhibitors from plant sources. This study was therefore aimed at investigating in vitro possible acetylcholinesterase inhibitors (AChEIs) in herbal medicines traditionally used in Palestine for the treatment of memory loss, and to point out the role of these plants as potential sources for development of newly potent and safe natural therapeutic agents of AD.
Methods: The effect on AChE activity of 92 extracts of 47 medicinal plants including ten medicinal plants reported in TAPHM for treatment of age related diseases were evaluated for its anticholinestrase and antioxidant activity.
Results: Thirty eight percent of extracts inhibited AChE by > 50%, only 8 extracts showed irreversible inhibition, Antioxidant activity was demonstrated by 73 extracts of which Majorana syriaca and Rosmarinus officinalis (IC50 0.21 and 0.38 mg/ml) were the most active. Interestingly, differential results have been obtained which indicate the variability of the mode of actions for the selected plants; 27 extracts inhibited the enzyme reversibly while eight extracts showed irreversible inhibition. Additionally, the reversible interaction of Majorana syriaca, Juglans regia, Rosmarinus officinalis, Menthe spicata, and Feoniculum vulgare against AChE make them effective, new and promising agents for treatment of AD in the future, either as total extracts or their single bioactive constituents.
Conclusions: Palestinian flora have shown to be a rich source for, new and promising agents (AChEIs) for the treatment of AD Further studies are needed to isolate and identify the active compounds responsible for AChEI activities.

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