"Various chemicals in essential oils help prove cognitive function in healthy individuals in three ways: by increasing the binding of acetylcholine to its receptors, by inhibiting acetylcholinesterase activity (as already noted), and by lowering acetylcholinesterase levels (by inhibiting phospholipase C gamma activity). Phospholipase C gamma (and beta) activity lead to the formation of amyloid plaques and peroxynitrites -the toxin held responsible for short-term memory loss in Alzheimer’s disease. Chemicals in various essential oils (including rosemary and sage) such as methoxyphenols (eugenol, thymol, and carvacrol) and if present rosmarinic acid and ursolic acid scavenge peroxynitrites (convert them into a less dangerous form). These compounds also reverse much of the damage that peroxynitrites do to transport systems, enzymes, tau proteins, and receptors involved in short-term memory (muscarinic acetylcholine), sleep (melatonin), mood (serotonin and opioid), social recognition (oxytocin), alertness (dopamine), and smell (olfactory). They also inhibit the influx of calcium thus limiting the death of neurons and the release of glutamate thus limiting the death of surrounding cells (see the following articles: Alkam, et al. “A natural scavenger of peroxynitrites, rosmarinic acid, protects against impairment of memory induced AB 25-35″ and Irie, “Effects of eugenol on the Central Nervous System: Its possible application to treatment of Alzheimer’s disease, depression, and Parkinson’s disease.”
Alzheimer’s disease can likely be effectively treated with aromatherapy using various essential oils.