The Anticholinesterase Properties of Plants from the Northeast of Brazil Selected by an Ethnopharmacological Study for Disorders Relating to the Nervous System

BACKGROUND: Various factors may trigger Alzheimer's disease and the cholinergic hypothesis, which is one of the most widely accepted, argues damage to the brain nuclei, may reduce the production of the choline acetyltransferase enzyme, and cause a decline in the synthesis of acetylcholine (ACh). Studies have thus focused on discovering molecules that are capable of inhibiting the action of cholinesterase enzymes that degrade ACh, thereby preventing the evolution of the disease. OBJECTIVE: The aim of the present study is to assess the anticholinesterase properties of extracts of medicinal plants in a semi-arid region of Northeast of Brazil. MATERIALS AND METHODS: The species were selected by way of an ethnobotanical study and were collected if there were some indications that they are related to the nervous system. The plant samples were extracted using hexane, ethyl acetate, and methanol. Anticholinesterase activity in vitro was assessed by way of bioautography in thin layer chromatography and microassays in 96-well plates. RESULTS: Twenty-three species of plant were collected, and 75 extracts were analyzed. The bioautography revealed that 26.7% of the samples showed inhibitory activity against the acetylcholinesterase (AChE) enzyme. After the test for false positives, 8% of the samples were found to inhibit AChE. Thirty samples were analyzed by microassay (500 μg/mL), on which 86.7% showed moderate to powerful anticholinesterase activity. CONCLUSION: Of the extracts tested, Citrus limonum, Ricinus communis, and Senna occidentalis stand out as was the most promising in terms of anticholinesterase activity and may serve as a guide for the discovery and development of new substances for the treatment of AD. SUMMARY: The bioautography revealed that 26.7% of the samples showed inhibitory activity against the acetylcholinesterase enzyme. Samples were analyzed by microassay (500 μg/mL), upon which 86.7% showed moderate to powerful anticholinesterase activity. Citrus limonum, Ricinus communis, and Senna occidentalis stand out as being the most promising in terms of anticholinesterase activity. C. limonum, R. communis, and S. occidentalis may serve as a guide for the discovery and development of new substances for the treatment of Alzheimer's disease. Abbreviations used: AChE: Acetilcolinesterase