Essential oils derived from different plant species have revealed encouraging clinical and preclinical results to reverse cognitive and memory impairments in Alzheimer’s disease, a review study has found.
The study, “Essential Oils as Treatment Strategy for Alzheimerʼs Disease: Current and Future Perspectives,” was published in the journal Planta Medica.
Few compounds exist for the management of Alzheimer’s disease, and available treatments only provide symptom relief.
Essential oils are composed of a blend of complex, volatile, and naturally derived compounds obtained from plants. These are commonly found in leaves, seeds, flowers, bark, and rhizomes and are extracted through cold-pressing, hydro-distillation methods.
Studies have shown essential oils have important therapeutic and pharmaceutical benefits related to cardiovascular disease and cancer, as well as having anti-diabetic, antimicrobial, neuroprotective and anti-aging effects.
In fact, aromatherapy for Alzheimer’s, which has been used for a long time, has been found to be effective.
Researchers in this study reviewed relevant in vitro (laboratory experiments), in vivo (animal experiments), and clinical studies to determine the potential use of essential oils in the treatment of Alzheimer’s disease.
Scientific databases were explored to gather studies that evaluated the use of various essential oils in different models of Alzheimer’s disease from April 1998 to June 2018.
Among the 55 essential oils previously identified as potentially beneficial for Alzheimer’s treatment, 28 were included in the review based on the quality of the studies.
“The literature review displayed promising evidence that supports the use of EOs for reversing cognitive and memory impairment of AD [Alzheimer’s disease],” the researchers wrote.
They found that most of the clinical and animal studies prefer inhalation as the main route of administration of essential oils for Alzheimer’s therapy.
When inhaled, these oils enter the bloodstream through the lung mucosa, nasal passage, or even diffused directly into the olfactory nerve and reach the brain’s limbic system — a complex network in the brain that controls basic emotions (fear, pleasure, anger).
Essential oils obtained from numerous medicinal plants were reported to possess anti-Alzheimer’s potential, and specifically the effects of S. officinalis, S. officinalis ssp. lavandulifolia (vahl), M. officinalis, L. angustifolia, and R. officinalis have been proven in clinical studies.
Essential oils were found to be mostly nontoxic at the recommended doses. Most of these oils possess an anticholinesterase property, which means they can stop the action of the cholinesterase enzyme (responsible for breaking down acetylcholine), resulting in higher levels of acetylcholine.
Acetylcholine is a brain signaling molecule heavily involved in regulating memory and cognition and cholinesterase inhibitors can prevent degradation of acetylcholine and maintain its concentration in the synapse — the junction between two nerve cells that allow them to communicate.
Oxidative stress — cellular damage as a consequence of high levels of oxidant molecules — also plays a major role in the mechanisms that lead to Alzheimer’s disease. Essential oils can work to relieve oxidative stress, protecting the brain from neuronal damage.
Importantly, essential oils also have the ability to cross the blood-brain barrier, a semipermeable membrane that protects the brain from the outside environment, allowing them to exert their activity directly in the brain.
“Our literary survey revealed encouraging results regarding the various essential oils being studied in preclinical and clinical studies of Alzheimerʼs disease with significant effects in modulating the pathology through anti-amyloid, antioxidants, anticholinesterase, and memory-enhancement activity,” the researchers wrote.
“However, it is important to initiate further studies on pharmacokinetics [how the body affects a medicine] and toxicities of EOs [essential oils] and their bioactive markers responsible for anti-Alzheimer’s action. More cell culture and in vivo studies are essential,” they added.