Flavonoids, Phenolics and Acetylcholinesterase Inhibitory Potential of Different Solvent Extracts of some Medicinal Plants used as Brain Tonics: A Comparative Study

Alzheimer’s disease (AD) is a common old-age ailment characterized by the loss of memory and impairment of cognitive abilities and associated with an overexpression of cholinesterase enzymes. Quest for effective, safe and affordable inhibitors of these enzymes is thus required. The present project was designed to explore natural bioactive compounds with the ability to act as acetylcholinesterase (AChE) inhibitors. AChE inhibitory activity of methanolic (ME), ethyl acetate (EAE), acetonic (AE) and hydroethanolic (HEE) extracts of common medicinal plants used in brain tonics were estimated. Total phenolic and flavonoid contents of the extracts have also been determined. The plants studied included Borago officinalis L., Salvia haematodes Scop., Matthiola incana (L.) R.Br., Moringa oleifera Lam., Lallemantia royleana (Benth.) Benth., Lavandula stoechas L., Centaurea behen DC. and Coriandrum sativum L. The MEs of all the selected plants showed the highest activity except M. oleifera and S. haematodes whose activity was slightly less than EAE of M. oleifera and AE of S. haematodes. EAEs of B. officinalis, M. oleifera and S. haematodes and AEs of B. officinalis and S. haematodes were also notable. A moderate correlation was found between TPC and AChE inhibitory activity of MEs and a moderately high correlation was found between TPC and AChE inhibitory activity of AEs of the selected plants. The acetylcholinesterase inhibition might play a role in the brain tonic effect of the selected plants. The activity may at least partly be rendered by the phenolic compounds present in the plants.