The Best Supplements to Support Memory and Brain Health As You Age
This blog has not been approved by your local health department and is not intended to provide diagnosis, treatment, or medical advice.
In this article:
- Best Overall: Vitamin B, Omega-3s, or a Quality Multivitamin
- Best Foods: Greens and Blueberries
- Best for Brain Power: PQQ, Acetyl-L-carnitine, Resveratrol, Curcumin
- Best for Fighting the Effects of Aging: Glutathione
- Best for Protecting the Brain: L-Serine
- Best for Memory and Cognitive Function: Lion's Mane and Hup A
- Takeaway: Boosting Brain Function Based on Need
Memory loss and decreased brain power are NOT inevitable as we age.
Brain cells are the most complex, long-living, and nutritionally demanding cells in the body. Scientific studies have shown that intelligence, memory, behavior, and concentration are all influenced by the quality of brain nutrition. Young or old, our nutritional status plays a vital role in determining how well our brain functions.
There are many dietary supplement ingredients that promote improved brain health. This article will focus on those with the most research support. It is also important to point out that there is a very strong link between cardiovascular health and brain health. Not surprisingly, many of the same dietary, lifestyle, and supplement strategies to support heart health have the additional benefit (either directly or indirectly) of supporting brain health as well.
Best Overall: Vitamin B, Omega-3s, or a Quality Multivitamin
Numerous studies have shown that brain function is directly related to nutritional status, especially for key nutrients like vitamins, minerals, and omega-3 fatty acids.1-3
Given the frequency of nutrient deficiency, especially in the elderly population, it is possible that many cases of impaired mental function and memory have a nutritional cause.
B vitamins and omega-3 fatty acids are critically important to brain function and memory are. Not surprisingly, they work best when both are taken.
Let’s take a look first at a study conducted at Oxford’s Department of Clinical Neurosciences that highlights the impact of supplemental B vitamins.4 The study involved 156 elderly patients who had mild cognitive impairment and a high risk of developing severe loss of mental function. The patients were divided into two groups: one group took a daily supplement with 800 micrograms of folic acid, 20 milligrams of vitamin B6, and 500 micrograms of vitamin B12; the other group took a placebo supplement. Those levels of folic acid, B6, and B12 are what you might typically find in a high potency multiple vitamin and mineral formula.
Before the trial and during the testing period, the researchers utilized magnetic resonance imaging (MRI) to measure the patients’ atrophy levels of grey matter in their brains. Atrophying (shrinking) grey matter is a sign of accelerated aging of the brain.
Upon completion of the two-year study, researchers found that those given the B vitamin supplement had about seven times less grey matter shrinkage than the placebo group.
The researchers also found that those whose grey matter shrunk fastest had higher levels of homocysteine, and those with higher homocysteine levels initially received the greatest benefit from the B vitamin supplements. Homocysteine is a metabolite of the amino acid methionine that will be increased if B12, B6, or folic acid levels are low. Homocysteine can lead to increased oxidative damage to the brain and other tissues.
In their conclusion, the Oxford researchers found that B-vitamin supplementation can slow the atrophy of specific brain regions that are associated with cognitive decline.4
Another study conducted at Oxford University found that having higher levels of omega-3 fatty acids in the brain boosted the benefits of B vitamins in improving cognitive function.5
More than 250 people with poor brainpower were given a set of tests to measure their cognition and levels of the omega-3 fatty acids EPA and DHA in their blood. The participants were split into two randomly selected groups, who received either a B-vitamin supplement or a placebo pill over two years. Their cognitive performance was also measured, and the results compared with the baseline results from the start of the study.
What the researchers found was that for people with low levels of EPA+DHA, the B vitamin supplement had little to no effect in preventing the loss of gray matter. But for those with high baseline EPA+DHA levels, the B vitamins were very effective in preventing cognitive decline compared to the placebo. These results are game-changing because they show that B vitamins better slow the rate of brain atrophy in mild cognitive impairment in those with a good level of EPA+DHA.
Of course, a higher intake of these omega-3 fatty acids is associated with better mood and mental function scores on their own. For example, analysis from the famous Framingham Heart Study found that people with higher blood levels of DHA reduced their risk of developing dementia by 47% when compared to people with lower levels of DHA.
The results from this study suggest that simply eating fish rich in omega-3 fatty acids 2-3 times a week or taking a fish oil providing at least 1,000 mg of EPA+DHA daily reduce the risk of developing severe mental decline by nearly 50%.6-8
The bottom line is that taking a high potency multiple vitamin and mineral formula that supplies sufficient B vitamins along with taking 1,000 to 2,000 mg of EPA+DHA from quality fish oil may dramatically reduce the risk of mental decline with aging.
Best Foods: Greens and Blueberries
In addition to fish supplying omega-3 fatty acids, there are many other foods that benefit brain function.
Green Leafy Vegetables
A study from Rush University Medical Center in Chicago looked at 960 participants of the Memory and Aging Project, who completed a food frequency questionnaire and who also had at least 2 cognitive assessments over a nearly five-year period. The conclusion was that consumption of approximately 1 serving per day of green leafy vegetables and foods rich in vitamin K1, lutein, folate, α-tocopherol, nitrate, and kaempferol blocks the cognitive decline associated with aging.
Try adding a greens supplement with super greens such as spirulina, chlorella, wheatgrass juice, barley grass juice, and others to your diet.
Blueberries and other flavonoid-rich food or extracts are another food that is particularly helpful in boosting brainpower. In animal studies, researchers have found that blueberries help protect the brain from oxidative stress and memory loss.10 When older rats were given the human equivalent of 1 cup of blueberries a day, they demonstrated significant improvements in both learning capacity and motor skills, making them mentally equivalent to much younger rats. When the rats' brains were examined, the brain cells of the rats given blueberries were found to communicate more effectively than those of the other older rats that were not given blueberries.
Try eating more blueberries as well as take a flavonoid-rich extract like blueberry, grape seed, or pine bark extract (100 to 300 mg daily).
Best for Brain Power: PQQ, Acetyl-L-carnitine, Resveratrol, Curcumin
Mitochondria are the energy-producing compartments in our cells. There is growing research documenting the role of decreased mitochondrial function in aging, decreased cognitive function, and poor memory. The brain accounts for only about two percent of our body weight, but it consumes more than twenty percent of the body’s energy and oxygen. The brain requires exceptional mitochondrial energy production in order for it to function optimally.
Enhancing mitochondrial function requires the following:
- Provide all essential nutrients by taking a high-potency multiple vitamin and mineral formula
- Utilize mitochondrial antioxidants and enhancers
- Cofactors in energy metabolism (B vitamins are particularly important)
- Pyrroloquinoline quinone (PQQ), Coenzyme Q10, L-Acetyl-Carnitine
- Curcumin, resveratrol, flavonoids, and other phytochemicals
- Boost glutathione and L-serine levels to enhance brain detoxification
- Reduce damaging factors
- Environmental toxins
- Drugs (Rx, OTC, and illicit)
CoQ10 and PQQ
Regarding mitochondrial enhancers, two dietary supplements that have been shown to work together very well in boosting memory and cognition are coenzyme Q10 (CoQ10) and pyrroloquinoline quinone (PQQ).
CoQ10 is very well known, but PQQ is just beginning to get popular. PQQ is a powerful antioxidant that specifically protects against mitochondrial damage. It also promotes the spontaneous generation of new mitochondria within aging cells, a process known as mitochondrial biogenesis. This effect is why PQQ is so exciting as an anti-aging strategy.
While PQQ is effective on its own, when it is combined with coenzyme Q10 even better results have been noted. In one study of 71 middle-aged and elderly people aged between 40-70, supplementation with 20 mg per day of PQQ resulted in improvements on tests of higher cognitive function compared to the placebo group, but in the group receiving 20 mg of PQQ along with 300 mg of CoQ10, the results were even more dramatic.11 PQQ and CoQ10 are both involved in mitochondrial energy production, so these results are not that surprising.11,12
Acetyl-L-carnitine (ALC) is the most important form of carnitine, a compound that our body makes (like CoQ10), but sometimes deficiency occurs.
Carnitine plays a key role in fat, carbohydrate, and protein metabolism and energy production and is critical for mitochondrial metabolism. ALC is considered the preferred form of carnitine to take for promoting brain health.13
ALC protects and enhances the activity of mitochondria in brain cells and reduces oxidative stress. That leads to higher energy production within brain cells and that leads to better brain function.
Clinical studies have shown ALC can improve mental performance and memory. Some of the improvements noted include short-term learning tasks, special learning tasks, timed tasks of attention, and tasks of personal recognition. Sometimes the effects are noted within the first month of use, but long-term use of ALC (e.g., greater than one year of use) is definitely associated with improvements in long-term memory and attention.14 The typical dosage for ALC is 900 to 1,500 mg per day.
Resveratrol is a plant compound found in low levels in the skin of red grapes, red wine, cocoa powder, baking chocolate, dark chocolate, peanuts, and mulberry skin. Resveratrol activates an enzyme known as sirtuin 1 that plays an important role in the regulation of cellular life spans; it also boosts brain function and promotes improved blood sugar control by enhancing insulin action.
Clinical research in humans shows resveratrol lowers markers of brain inflammation associated with aging and poor mental function in older adults.15,16 As a result, resveratrol improved mood, mental cognition, and scores on measures of activities of daily living in older adults.
Most resveratrol supplements use Japanese knotweed (Polygonum cuspidatum) as the source. The typical dosage is 1,000 mg of natural trans-resveratrol daily.
Curcumin is the yellow pigment of turmeric. In addition to exerting a number of antiaging effects, curcumin is showing incredible promise as a brain protector and booster.17
Residents of rural India, who eat large amounts of turmeric, have been shown to have the lowest incidence of age-related brain issues in the world. Of course, turmeric (the main component of curries) can be liberally consumed in the diet but taking a curcumin product provides higher dosage levels to produce better results.
In a study conducted at UCLA, 40 adults between the ages of 50 and 90 years who had impaired cognition and memory were randomly assigned to receive either a placebo or Theracurmin, a highly bioavailable form of curcumin, at a dosage of 90 milligrams of curcumin twice daily for 18 months.18
All 40 subjects received a standardized battery of mental assessments at the start of the study and at six-month intervals and after 18 months. Those who took Theracurmin experienced significant improvements in their memory and attention abilities, while the subjects who received a placebo did not. In memory tests, those taking curcumin improved by 28 percent over the 18 months. Those taking curcumin also had mild improvements in mood, and their brain PET scans showed significantly less damage. Theracurmin and other curcumin products are an important step for people seeking prevention of age-related mental decline.
Best for Fighting the Effects of Aging: Glutathione
One of the most important compounds that every cell in your body produces is glutathione. The cells use this valuable compound to protect themselves from damage as well as aid in detoxifying harmful compounds.
Glutathione is a small protein molecule composed of the amino acids glutamate, cysteine, and glycine. Over the course of 100 years of research, more than 100,000 scientific papers have established maintaining cellular glutathione levels as one of the most important keys in maintaining proper cellular function, immune health, and slowing the aging process. Glutathione is the body's most effective detoxifying agent. Glutathione binds undesirable toxins, pollutants, cancer-causing chemicals, heavy metals, and drug metabolites and excretes them through the urine or the gut.19
Glutathione levels tend to drop as we age, as well as when we are exposed to toxins, drugs, environmental pollution, and any other compound that causes oxidative damage. A drop in brain glutathione is devastating to brain cells.20 A healthy diet can help raise glutathione levels, but only to a limited extent, supplementation is much more effective.
The most popular supplemental approach to boost glutathione levels is taking either glutathione or N-acetylcysteine. Prior to recent studies, there was some controversy with glutathione as a dietary supplement because it was thought that glutathione may not be absorbed when taken orally. There have been several studies that show oral glutathione is absorbed and can improve cellular protection.21
The typical dosage for oral supplementation of reduced glutathione is 250 to 1,000 mg per day. The dosage for N-acetylcysteine (NAC) as a dietary supplement to boost tissue levels of glutathione, including brain levels, is generally 500 to 1,200 mg daily.22
Best for Protecting the Brain: L-Serine
The discovery that may halt, slow down, and even improve degenerative brain diseases came from an ethnobotanist, Paul Cox. Ethnobotany is the study of the way indigenous people use plants in their customs and diet.
In the late 1990s, Cox, who received his Ph.D. from Harvard, became interested in why the Chamorro people of Guam were more than 100 times more likely to develop symptoms often associated with degenerative brain diseases like ALS, Alzheimer’s, and Parkinson’s: slurred speech, facial paralysis, loss of motor skills, immobility and dementia.
His answer came in 2002 when he and Oliver Sacks, the late neurologist published a paper in the journal Neurology that laid out his theory that the diets of these people were extremely high in a toxic compound, β-methylamino-L-alanine (BMAA), that was responsible for the brain degeneration. Other populations around the world, most notably the United States and France, also showed that higher dietary levels of BMAA were also linked to brain degeneration.
BMAA produces its brain-damaging effects by causing an altered shape of brain proteins by replacing the amino acid L-serine. Basically, brain cells mistake BMAA for L-serine and when they replace BMAA for L-serine in the proteins the brain cell manufactures it leads to a protein that is not shaped the way that it should be leading to a degeneration of the protein and toxicity to the brain cells. The proteins are not folded properly. They are either folded in odd ways or not folded at all.
In the brain, BMAA can also lead to the formation of a toxin known as beta-carbonate. This compound can bind to receptors on brain cells for neurotransmitters including one known as N-methyl-D-aspartate (NMDA) receptors. This, in turn, can lead to brain cell death due to a number of reasons that ultimately leave the cell more susceptible to damage.
In preclinical tests, when brain cells exposed to BMAA were also exposed to L-serine it prevented the formation of misfolded or unfolded proteins. Furthermore, L-serine prevents the increase in the formation of an enzyme that causes brain cell death that is induced by BMAA.
Best for Memory and Cognitive Function: Lion's Mane and Hup A
Lion’s Mane Mushroom (Hericium erinaceus)
Lion’s mane mushrooms are large, white, and with numerous long white spines so that it resembles a lion’s mane. These mushrooms most often grow on dead and decaying hardwood in the wild or now cultivated.
Lion's mane is rich in a wide range of bioactive compounds including compounds known as erinacines found in the mycelium (underground fruit body portion of the mushroom) that can pass through the blood-brain barrier to exert some impressive effects in animal models.24,25 These compounds stimulate cells known as oligodendrocytes in the central nervous system (CNS), the brain, and spinal cord.26
Oligodendrocytes are responsible for promoting myelination, the process in which the myelin sheath that surrounds the axon segments of nerve cells is formed. The myelin sheath is an insulating layer that electrical impulses transmit quickly and efficiently along with the nerve and brain cells. In the brain, the integrity and function of the myelin sheath are critical, especially in the aging brain, for memory, movement, and cognition.
In a double-blind, placebo-controlled trial in 50- to 80-year-old Japanese men and women showing impaired memory and cognition, the subjects who took four 250 mg tablets containing lion’s mane mushroom powder three times a day for 16 weeks.27 After termination of the intake, the subjects were observed for the next 4 weeks.
At weeks 8, 12, and 16 of the trial, the lion’s mane group showed significantly increased scores on mental function tests compared with the placebo group.
At four weeks after the supplementation, the scores decreased significantly in the lion’s mane group. These results show the brain-boosting effect of lion’s mane requires continued supplementation.
In another human clinical trial, lion's mane in older adults with mild cognitive impairment showed similar results.28
Huperzine-A (Hup A)
Huperzine-A (Hup A) is a naturally occurring alkaloid compound found in Chinese club moss (Huperzia Serrata). Hup A exerts a multitude of beneficial actions that produce clinically meaningful effects in poor memory and cognition.29,30 Hup A inhibits the breakdown of the neurotransmitter acetylcholine (ACH) by reversibly blocking the enzyme acetylcholinesterase.
A deficiency of ACH is one of the hallmark features of poor memory and concentration. By preventing the breakdown of ACH, Hup A can enhance its activities to improve cognitive function and memory. Hup A also prevents brain cell damage caused by various neurotoxins, enhances the activities of the brain’s antioxidant enzymes, and promotes the formation of new brain cells. The typical dosage of Hup A is 200 mcg twice daily. Be sure to use pure Hup A and not crude Huperzia preparations for both safety and efficacy.
Takeaway: Boosting Brain Function Based on Need
If you are showing signs of decreased brainpower or loss of memory, you must act now and be very aggressive in your diet, lifestyle, and supplement strategy. Remember, blood flow is a big factor in brain function, so too is getting enough sleep and fighting against the effects of stress. So make sure you are doing all you can in that area as well.
Here are the key supplements that I recommend for really making a BIG impact on brain function and protecting the brain against aging. Note, these supplements are listed in order of need:
Normal: Phase 1 Support
No loss of brain function or memory, just want to keep it that way:
- High potency multiple vitamin and mineral formula
- Fish oil supplement: 1,000 to 2,000 mg of EPA+DHA+DPA daily.
- Curcumin: 90 mg per day.
- Choose one of the following:
- Reduced glutathione (GSH): 250 to 500 mg per day.
- N-acetylcysteine (NAC): 500 to 1,200 mg daily.
Mild: Phase 2 Support
Healthy, but feeling a lack of brainpower and loss of short-term memory.
- Take Phase 1 Support
- MemFood, 1 scoop, or one packet daily. Each dosage providing:
- L-Serine: 4.2 g
- Organic Lion's Mane (Hericium erinaceus)(Mycelial biomass and fruit body cultured on organic oats): 2 g
- Blueberry Juice Powder (Vaccinium corymbosum)(fruit): 2 g
- MEM Blend 290 mg
- Acetyl-L-Carnitine (from Acetyl-L-Carnitine HCL), Organic Turmeric Extract (Curcuma longa)(rhizome), trans-resveratrol (from Polygonum cuspidatum Extract)(root), French Maritime Pine Bark Extract (Pinus pinaster), Pyrroloquinoline Quinone Disodium Salt (PQQ)
- Coenzyme Q10: take either 100 mg of the ubiquinol form or 300 mg of the ubiquinone form.
Critical: Phase 3 Support
When there is a critical need to support brain function and memory.
- Take all of the above (Phase 1 and Phase 2 Support), but increase the dosages of the following:
- MemFood – one scoop or packet twice daily.
- Fish oil supplement: 1,000 to 2,000 mg of EPA+DHA+DPA daily.
- Curcumin: 180 mg per day.
- Add the following:
- Huperzine A – 200 mcg twice daily.
- Muscaritoli M. The Impact of Nutrients on Mental Health and Well-Being: Insights From the Literature. Front Nutr. 2021 Mar 8;8:656290.
- Tardy AL, Pouteau E, Marquez D, Yilmaz C, Scholey A. Vitamins and Minerals for Energy, Fatigue and Cognition: A Narrative Review of the Biochemical and Clinical Evidence. Nutrients. 2020 Jan 16;12(1):228.
- Miquel S, Champ C, Day Jet al. Poor cognitive ageing: Vulnerabilities, mechanisms and the impact of nutritional interventions. Ageing Res Rev. 2018 Mar;42:40-55.
- Douaud G, Refsum H, de Jager CA, et al. Preventing Alzheimer’s disease-related gray matter atrophy by B-vitamin treatment. Proc Natl Acad Sci U S A. 2013 Jun 4;110(23):9523-8.
- Oulhaj A, Jernerén F, Refsum H, et al. Omega-3 Fatty Acid Status Enhances the Prevention of Cognitive Decline by B Vitamins in Mild Cognitive Impairment. J Alzheimers Dis. 2016 Jan 6;50(2):547-57.
- Schaefer EJ, Bongard V, Beiser AS, Lamon-Fava S, Robins SJ, Au R, Tucker KL, Kyle DJ, Wilson PW, Wolf PA. Plasma phosphatidylcholine docosahexaenoic acid content and risk of dementia and Alzheimer disease: the Framingham Heart Study. Arch Neurol. 2006 Nov;63(11):1545-50.
- von Schacky C. Importance of EPA and DHA Blood Levels in Brain Structure and Function. Nutrients. 2021 Mar 25;13(4):1074.
- Hosseini M, Poljak A, Braidy N, Crawford J, Sachdev P. Blood fatty acids in Alzheimer's disease and mild cognitive impairment: A meta-analysis and systematic review. Ageing Res Rev. 2020;60:101043.
- Bennett DA, Dawson-Hughes B, Booth SL, et al. Nutrients and bioactives in green leafy vegetables and cognitive decline: Prospective study. Neurology. 2018 Jan 16;90(3):e214-e222.
- Cherniack EP. A berry thought-provoking idea: the potential role of plant polyphenols in the treatment of age-related cognitive disorders. Br J Nutr. 2012 Sep;108(5):794-800.
- Nakano M, Ubukata K, Yamamoto T, Yamaguchi H. Effect of pyrroloquinoline quinone (PQQ) on mental status of middle-aged and elderly persons. FOOD Style. 2009;21:13(7):50-3.
- Yang X, Zhang Y, Xu H, et al. Neuroprotection of Coenzyme Q10 in Neurodegenerative Diseases. Curr Top Med Chem. 2016;16(8):858-866.
- Malaguarnera M. Carnitine derivatives: clinical usefulness. Curr Opin Gastroenterol. 2012 Mar;28(2):166-76.
- Thal LJ, Calvani M, Amato A, Carta A. A 1-year controlled trial of acetyl-l-carnitine in early-onset AD. Neurology. 2000 Sep 26;55(6):805-10.
- Koushki M, Dashatan NA, Meshkani R. Effect of Resveratrol Supplementation on Inflammatory Markers: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Clin Ther. 2018 Jul;40(7):1180-1192.e5.
- Marx W, Kelly JT, Marshall S, et al. Effect of resveratrol supplementation on cognitive performance and mood in adults: a systematic literature review and meta-analysis of randomized controlled trials. Nutr Rev. 2018 Jun 1;76(6):432-443.
- Bhat A, Mahalakshmi AM, Ray B, et al. Benefits of curcumin in brain disorders. Biofactors. 2019;45(5):666-689.
- Small GW, Siddarth P, Li Z, et al. Memory and Brain Amyloid and Tau Effects of a Bioavailable Form of Curcumin in Non-Demented Adults: A Double-Blind, Placebo-Controlled 18-Month Trial. Am J Geriatr Psychiatry. 2018;26(3):266-277.
- Forman HJ, Zhang H, Rinna A. Glutathione: overview of its protective roles, measurement, and biosynthesis. Mol. Aspects Med. 2009;30, 1−12.
- Dwivedi D, Megha K, Mishra R, Mandal PK. Glutathione in Brain: Overview of Its Conformations, Functions, Biochemical Characteristics, Quantitation and Potential Therapeutic Role in Brain Disorders. Neurochem Res. 2020;45(7):1461-1480.
- Park EY, Shimura N, Konishi T, et al. Increase in the protein-bound form of glutathione in human blood after the oral administration of glutathione. J Agric Food Chem. 2014;62(26):6183-6189.
- Tardiolo G, Bramanti P, Mazzon E. Overview on the Effects of N-Acetylcysteine in Neurodegenerative Diseases. Molecules. 2018;23(12):3305.
- Dunlop RA, Carney JM. Mechanisms of L-Serine-Mediated Neuroprotection Include Selective Activation of Lysosomal Cathepsins B and L. Neurotox Res. 2020;10.1007/s12640-020.
- Ghosh S, Nandi S, Banerjee A, Sarkar S, Chakraborty N, Acharya K. Prospecting medicinal properties of Lion's mane mushroom. J Food Biochem. 2021 Jun 24:e13833.
- Ryu SH, Hong SM, Khan Z, Lee SK, Vishwanath M, Turk A, Yeon SW, Jo YH, Lee DH, Lee JK, Hwang BY, Jung JK, Kim SY, Lee MK. Neurotrophic isoindolinones from the fruiting bodies of Hericium erinaceus. Bioorg Med Chem Lett. 2021 Jan 1;31:127714.
- Huang HT, Ho CH, Sung HY, Lee LY, Chen WP, Chen YW, Chen CC, Yang CS, Tzeng SF. Hericium erinaceus mycelium and its small bioactive compounds promote oligodendrocyte maturation with an increase in myelin basic protein. Sci Rep. 2021 Mar 22;11(1):6551.
- Mori K, Inatomi S, Ouchi K, et al. Improving effects of the mushroom Yamabushitake (Hericium erinaceus) on mild cognitive impairment: a double-blind placebo-controlled clinical trial. Phytother Res. 2009 Mar;23(3):367-72.
- Saitsu Y, Nishide A, Kikushima K, et al. Improvement of cognitive functions by oral intake of Hericium erinaceus. Biomed Res. 2019;40(4):125-131.
- Wang R, Yan H, Tang XC. Progress in studies of huperzine A, a natural cholinesterase inhibitor from Chinese herbal medicine. Acta Pharmacol Sin. 2006 Jan; 27(1):1-26.
- Tun MK, Herzon SB. The pharmacology and therapeutic potential of (-)-huperzine A. J Exp Pharmacol. 2012 Sep 5;4:113-23.