Acetylcholinesterase and Butyrylcholinesterase Enzyme Inhibitory Activities of Ethanol Extract of Costus afer, Sida acuta and Irvingia gabonensis

Abstract

Background: Scientific research in support of the use of various African plant species for the management of neurodegenerative diseases, including Alzheimer's disease (AD) is currently ongoing. Most of the approved drugs for the treatment of Alzheimer's disease have adverse effects. Therefore, there is urgent need to develop new drugs with minimal side effects. The most remarkable biochemical change in AD patients is a reduction of acetylcholine levels in the hippocampus and neocortex of the brain. Therefore, inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), the enzymes responsible for hydrolysis of acetylcholine is currently the most established approach to treating Alzheimer's disease. Costus afer, Irvingia gabonensis and Sida acuta are medicinal plants commonly utilized in traditional medicine practice for the treatment of neurological disorders. Aims: This study investigated the in vitro acetylcholinesterase and butyrylcholinesterase enzyme inhibitory activities of ethanol leaf extracts of Costus afer, Irvingia gabonensis and Sida acuta. Materials and Methods: Fresh leaves of Costus afer, Irvingia gabonensis and Sida acuta were collected from a farm at Egbu in Owerri North LGA of Imo state. They were washed and spread to air dry at room temperature and ground into fine powder. The acetylcholinesterase and butyrylcholinesterase enzyme inhibitory activity assay was carried out using Ellman’s spectrophotometric method and the percentage inhibition was calculated. Results: The result of the enzyme inhibition assay showed that the plant extracts exhibited concentration-dependent anti-AChE and BChE activity. The extract of Irvingia gabonensis possessed the highest anti-AChE activity with IC50 value (concentration at which there was 50% inhibition of enzyme catalyzed reaction) of 74.63 µg/ml than Costus afer and Sida acuta extracts. Similarly, the extract of Irvingia gabonensis also possessed the highest anti- BChE activity with IC50 value of 153.29 µg/ml than Costus afer and Sida acuta extracts. Conclusion: The findings of this study revealed that the ethanol leaf extracts of Costus afer, Irvingia gabonensis and Sida acuta had moderate AChE and BChE inhibitory activities, therefore supporting the traditional use of the plants in the management of Alzheimer’s disease.