Neuroprotective, neurite enhancing, and cholinesterase inhibitory effects of Lamiaceae family essential oils in Alzheimer's disease model

Introduction: The present study investigates the cholinesterase inhibitory and neuritogenic activities of selected essential oils from the Lamiaceae family, as well as their neuroprotective and antioxidant potential against scopolamine-induced cytotoxicity in SH-SY5Y cells. Methods: The anticholinesterase activity was analysed using a modified Ellman's assay. The neuroprotective potential was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Intracellular reactive oxygen species (ROS) levels were quantified using 2',7’- dichlorofluorescin diacetate assay. A neurite outgrowth assay was employed to evaluate the neuritogenic activity. Results: Oregano leaf (terpineol-type), peppermint leaf, rosemary, and sage essential oils have antibutyrylcholinesterase activity, while oregano leaf (phenol-type) essential oil has both acetylcholinesterase and butyrylcholinesterase inhibitory activities. Pretreatment with lavender flower essential oil (30 µg/mL), linalool, and linalyl acetate for 24 hours protects against scopolamine-induced toxicity. Linalool also displayed a significant decrease in intracellular ROS. The oregano leaf (terpineol-type), peppermint, rosemary, and sage essential oils at 100 µg/mL exhibited neuritogenic activity, with the highest activity being observed with oregano leaf (terpineol-type) essential oil. Discussion/Conclusions: Essential oils from plants of Lamiaceae family displayed anticholinesterase, neuroprotective, antioxidant, and neuritogenic activities. These properties demonstrate their potential as complementary treatments to prevent and/or delay dementia-related diseases such as Alzheimer's disease.