Rosemary (Rosmarinus officinalis)
Rosemary is rich in terpenoids like rosmarinic acid, carnosic acid, and ursolic acid, which are biosynthesized via the mevalonate and methylerythritol phosphate pathways in the plant. Also, some compounds in rosemary, such as rosmarinic acid and 1,8-cineole, act as acetylcholinesterase inhibitors, thereby increasing the levels of acetylcholine in synapses.
Literature Review
Clinical studies indicate that the oral intake of 500 mg of rosemary twice daily for a month led to a roughly 14% improvement in memory compared to a placebo.[i] Early clinical trials involving healthy adults between the ages of 65 and 90 suggest that a single dose of 750 mg of powdered rosemary leaf mixed with tomato juice may speed up memory. However, single doses ranging from 1500-6000 mg seemed to negatively impact memory speed. No definitive benefits in attention and memory were observed across the dosage range of 750-6000 mg.[ii]
Preliminary research in healthy adults aged 62 or younger indicates that taking a combination product with equal parts of rosemary, lemon balm, and sage twice daily for two weeks can modestly improve word recall compared to a placebo. This effect was not observed in adults aged 63 and above. It remains uncertain whether the benefits were due to rosemary alone, the other ingredients, or the combination of all.[iii]
Mechanism of Action
General: The leaves of rosemary are the part of the plant most commonly used for medicinal or therapeutic purposes. The essential oil from the leaf is considered the active component. The dried leaves contain an essential oil concentration ranging from 0.6% to 2.5%. This oil mainly consists of 1,8-cineole, borneol, camphor, carvacrol, and alpha-pinene. Additional constituents include phenolic diterpenes, flavones, rosmarinic acid (a derivative of caffeic acid), the triterpene ursolic acid, other terpenes like verbenone, and carnosic acid.[iv]
Antiobesity effects: Studies in animals suggest that rosemary leaf extract can counteract weight and fat mass gains in mice fed a high-fat diet. This is thought to be due to the inhibition of pancreatic lipase activity. Further, research in cell cultures indicates that specific components in rosemary—carnosic acid and carnosol—can inhibit the conversion of pre-fat cells into fat cells.[v]
Neurological effects: In human studies, taking rosemary for a period of 10 days was shown to elevate the levels of brain-derived neurotrophic factor (BDNF), which is believed to play a role in managing depression-related neuroimmune responses.[vi] Early data also hint that rosemary could inhibit cholinesterases and protect dopaminergic neurons.[vii],[viii]
Additionally, rosemary may have antidepressant effects through the monoaminergic system, as well as antinociceptive effects mediated by the endogenous opioid system. These antinociceptive effects are inhibited by naloxone.[ix] Research on cell cultures indicates that rosemary extract might also boost the production of nerve growth factor in certain brain cells, potentially aiding in the growth and function of nerve tissue. Rosemary is also believed to offer some protection to neurons from oxidative stress.[x],[xi]
References
[i]Nematolahi P, Mehrabani M, Karami-Mohajeri S, Dabaghzadeh F. Effects of Rosmarinus officinalis L. on memory performance, anxiety, depression, and sleep quality in university students: A randomized clinical trial. Complement Ther Clin Pract. 2018;30:24-28.
[ii]Pengelly A, Snow J, Mills SY, et al. Short-term study on the effects of rosemary on cognitive function in an elderly population. J Med Food 2012;15:10.
[iii]Perry NSL, Menzies R, Hodgson F, et al. A randomized double-blind placebo-controlled trial of a combined extract of sage, rosemary and Melissa, traditional herbal medicines, on the enhancement of memory in normal healthy subjects, including influence of age. Phytomedicine. 2018 Jan 15;39:42-48.
[iv]Pengelly A, Snow J, Mills SY, et al. Short-term study on the effects of rosemary on cognitive function in an elderly population. J Med Food 2012;15:10.
[v]Harach, T., Aprikian, O., Monnard, I., Moulin, J., Membrez, M., Beolor, J. C., Raab, T., Mace, K., and Darimont, C. Rosemary (Rosmarinus officinalis L.) Leaf Extract Limits Weight Gain and Liver Steatosis in Mice Fed a High-Fat Diet. Planta Med 11-16-2009
[vi]Achour M, Ben Salem I, Ferdousi F, et al. Rosemary tea consumption alters peripheral anxiety and depression biomarkers: A pilot study in limited healthy volunteers. J Am Coll Nutr. 2021:1-10.
[vii]Adsersen, A., Gauguin, B., Gudiksen, L., and Jager, A. K. Screening of plants used in Danish folk medicine to treat memory dysfunction for acetylcholinesterase inhibitory activity. J Ethnopharmacol 4-6-2006;104(3):418-422.
[viii]Park, J. A., Kim, S., Lee, S. Y., Kim, C. S., Kim, do K., Kim, S. J., and Chun, H. S. Beneficial effects of carnosic acid on dieldrin-induced dopaminergic neuronal cell death. Neuroreport 8-27-2008;19(13):1301-1304.
[ix]Machado, D. G., Bettio, L. E., Cunha, M. P., Capra, J. C., Dalmarco, J. B., Pizzolatti, M. G., and Rodrigues, A. L. Antidepressant-like effect of the extract of Rosmarinus officinalis in mice: involvement of the monoaminergic system. Prog.Neuropsychopharmacol.Biol.Psychiatry 6-15-2009;33(4):642-650.
[x]Satoh, T., Kosaka, K., Itoh, K., Kobayashi, A., Yamamoto, M., Shimojo, Y., Kitajima, C., Cui, J., Kamins, J., Okamoto, S., Izumi, M., Shirasawa, T., and Lipton, S. A. Carnosic acid, a catechol-type electrophilic compound, protects neurons both in vitro and in vivo through activation of the Keap1/Nrf2 pathway via S-alkylation of targeted cysteines on Keap1. J Neurochem. 2008;104(4):1116-1131.
[xi]Tamaki, Y., Tabuchi, T., Takahashi, T., Kosaka, K., and Satoh, T. Activated Glutathione Metabolism Participates in Protective Effects of Carnosic Acid against Oxidative Stress in Neuronal HT22 cells. Planta Med 11-25-2009
