Terpenes, Phenylpropanoids, Sulfur and Other Essential Oil Constituents as Inhibitors of Cholinesterases.

Essential oils constituents are a diverse family of low molecular weight organic compounds with comprehensive biological activity. According to their chemical structure these active compounds can be divided into four major groups: terpenes, terpenoids, phenylpropenes, and "others". In addition, they may contain diverse functional groups according to which they can be classified as hydrocarbons (monoterpenes, sesquiterpenes, and aliphatic hydrocarbons); oxygenated compounds (monoterpene and sesquiterpene alcohols, aldehydes, ketones, esters, and other oxygenated compounds); and sulfur and/or nitrogen sulfur-containing compounds (thioesters, sulfides, isothiocyantes, nitriles, and others). Compounds that act as cholinesterase inhibitors still represent the only pharmacological treatment of Alzheimer´s disease. Numerous in vitro studies showed that some compounds, found in essential oils, have a promising cholinesterase inhibitory activity, such as α-pinene, δ-3-carene, 1,8-cineole, carvacrol, thymohydroquinone, α- and β-asarone, anethole, etc. This review summarizes the most relevant research published to date on essential oil constituents and their acetylcholinesterase/butyrylcholinesterase inhibitory potential as well as their structure related activity, synergistic and antagonistic effects.