Neurotoxic Components in Aromatic Plant Essential Oils Literature-Based Review

Abstract

Essential oils are natural secondary metabolites obtained from plants and are rich in monoterpenes, sesquiterpenes, and aromatic compounds. They have been widely used throughout history for medicinal, cosmetic, and aromatherapeutic purposes (Ceylan, 1987; Chávez-González et al., 2016). With the increasing interest in natural products, the use of essential oils has expanded considerably; however, toxic effects associated with improper and uncontrolled use have become an important health concern (Posadzki et al., 2012). Certain lipophilic monoterpenes are capable of crossing the blood–brain barrier, thereby causing neurotoxic effects on the central nervous system (Güneş, 2022).

In this thesis, the chemical structures, mechanisms of action, toxicological profiles, and clinical risks of neurotoxic constituents found in essential oils were evaluated based on the literature. Particular emphasis was placed on monoterpene compounds with neurotoxic potential such as thujone, camphor, α-terpinene, and 1,8-cineole (Pelkonen et al., 2013; Santos et al., 2015). Essential oils obtained from plants including Salvia officinalis, Artemisia absinthium, Tanacetum vulgare, and Thuja occidentalis were reported to cause severe toxic effects such as convulsions, epileptiform seizures, and hepatotoxicity due to their high thujone content (Lachenmeier et al., 2006; Abass et al., 2011). Similarly, essential oils containing camphor and α-terpinene were shown to induce neurological disorders, memory impairment, and neuromuscular hyperactivity at high doses (Baldissera et al., 2016; Liebelt et al., 1993).

In conclusion, although essential oils possess significant therapeutic properties, they may also present serious neurotoxic risks. Therefore, standardization, accurate dosing, controlled duration of use, and pharmacist supervision are considered essential for their safe use.