Evaluation of anticholinesterase activity of supercritical fluid extracts from olive leaves

Nowadays, valorization of biological wastes from agricultural activity and processing industry has become a challenge. The olive oil industry has a great economic, commercial and industrial relevance in Spain, being olive leaves one of the main by-products and a promising source of bioactive compounds. Several authors have reported the presence and biological activity of different terpenoids in olive leaves; among them, the most abundant triterpenoids in olive leaves (derived from oleanane and ursane) have been described as possessing pharmacological activity against neurodegenerative disorders. Alzheimer’s disease (AD) is the most common neurodegenerative disorder, accounting for approximately two thirds of all cases of dementia and affecting up to 20% of individuals older than 80 years. At present, there is not effective treatment for this disease. Since AD is a multifactorial neurological pathology, a current strategy is to target different factors, being one of them related to the high activity of the enzyme acetylcholinesterase (AChE) in the brain. This work was oriented towards the valorization of olive leaf residues through the systematic and selective supercritical fluid extraction (SFE) of different families of bioactive terpenoids with potential anticholinergic (anti-AChE) activity. Thus, a sequential SFE procedure was applied for the isolation of low, medium and high molecular weight terpenoids (C10-C15, C15-C20, C20-C30), using CO2 as pure solvent and different working pressures (from 80-120 bar) at 40°C. Extracts obtained at different SFE conditions were characterized by GC-MS and its anti-AChE activity evaluated. Good anti-AChE activity was obtained for some of the terpene-rich SFE extracts from olive leaves, demonstrating the interest of this strategy to help to discover promising therapeutic approaches and natural compounds that can delay the detrimental effects of AD.