Ginseng, with its active chemical constituents, is a promising nootropic which positively affects behavior and cognition and is gaining more attention from behavioral neuroscientists.
In this article, we will review recent findings and experiments which have established ginseng’s neuroprotective and nootropic properties using animal models and behavioral assessments. First, let’s begin with some facts and an overview of the ginseng plant.
What is Ginseng?
Ginseng is an important part of traditional Chinese medicine and is being re-discovered as a potent nootropic. It is termed an “adaptogen” because of its alleged ability to help restore balance to the body and protect the body from physiologic stress. Since stress is known to affect cognition, ginseng, with its nootropic and protective properties, is bound to be beneficial.
There are two main types of ginseng: Asian (Chinese or Korean) ginseng, known as Panax ginseng or Panax notoginseng, and American ginseng, known as Panax Quinquefolius. Ginseng is available in the market as an extracted herb or as a dry ground root and researchers usually order their supply from reputable companies and reliable pharmaceutical suppliers.
For the ginseng root to be usable, it must grow for a minimum of three years for the American variety or five years for the Asian. The quality and concentrations of the ginsenosides can vary significantly because of the long and hard cultivation process.
Ginseng’s Active Constituents
Both Asian and American ginseng have a common mixture of active ingredients called ginsenosides, a type of plant saponin. Ginsenosides are chemically active ingredients which are likely to be responsible for most of the activities of ginseng, including vasorelaxation, antioxidation, anti-inflammation, and anti-cancer properties.
Thus far, approximately 40 different ginsenoside compounds have been identified, and each of them may have different effects on cells and behavior due to their varying chemical structures. The ginseng root contains 2–3% ginsenosides, of which the most commonly studied are Rg1, Rc, Rd, Re, Rb1, Rb2, and Rb0.
Ginsenosides can affect neurons. Numerous studies have established that ginseng can prevent neuronal loss in spinal cord injury models of cerebral ischemia and amyotrophic lateral sclerosis. In addition to these protective effects, ginsenosides have nootropic effects which are beneficial even in the context of disease models. Therefore, ginseng should be a subject of interest for behavioral studies focused on further examining its therapeutic properties.
Ginseng Improves Memory in Alzheimer’s Disease Rats
Alzheimer’s disease is a condition that is estimated to affect as many as 24 million people worldwide, with 5.5 million being in the United States and is expected to double every 20 years until 2040. Given that there is no cure for Alzheimer’s disease yet, these rates are a cause for concern. Pharmacological interventions do exist, aiming to slow down the disease’s progression, but are often accompanied by side effects such as vomiting, nausea, or body aches. Therefore, more treatment options need to be developed and made available to patients.
In light of this, a group of researchers set out to examine whether Panax ginseng would affect memory in rats which were induced with Alzheimer’s disease via scopolamine injections. The researchers used several experimental groups in order to test how various conditions would affect memory.
The control group in this experiment was composed of rats with memory impairments which received a placebo (salt) while the experimental groups received either ginseng root extract or memantine (a drug approved by the Food & Drug Administration for Alzheimer’s disease). The ginseng group received either 100 mg/kg or 200 mg/kg per day while the memantine group received 20 mg/kg per day. This supplementation schedule lasted for 14 days and was administered once per day via an oral gavage.
In order to assess the rats’ neurocognitive abilities, a Morris Water Maze was used. This maze is essentially a basin filled with water from which the rodents will try to escape. The pool also contains a platform that is slightly visible above the water surface or submerged just below the surface. The platform is meshed or grooved to allow an easy grip, and it acts as a shelter for animals allowing them to escape the water and stand on the platform thus avoiding the stress of having to swim.
Prior to inducing the memory impairments, the rats were trained in this maze, in order to establish memories. Then, after scopolamine-induction and after the supplementation schedule (which spanned for 14 days), the rats were subjected to the Morris Water Maze test again, in order to determine how well they remembered the location of the hidden platform which they had previously learned.
Test results show that the animals which were treated with scopolamine, in order to induce memory impairments, performed much worse than the rats which were given memantine or ginseng. In fact, the rats which were given ginseng at a 200 mg/kg dose had the highest significant effect and outperformed the rats given memantine, based on decreased escape latencies and an increase in the number of crossings.
This experimental design demonstrates the efficacy and worthwhileness of studying ginseng’s impacts on cognition and behavior, especially given the fact that it was able to induce stronger effects than pharmaceutical drugs in certain conditions.
Memory Improvement in Aged Mice
Just as Alzheimer’s disease is a concern to health, so is aging and the natural consequences which it brings to mental functions such as cognition and memory. Ginseng may, however, be on the road to becoming a more commonly used supplement for ameliorating these memory-related impairments.
One study examined whether young and normally aging male C57BL/6 mice, aged 4 and 21 months old, respectively, would be impacted by red ginseng (ginseng prepared at high-temperature levels). The mice were given diet pellets containing 0.12% red ginseng extract (about 200 mg/kg/day) for the course of 3 months. The ginseng supplement had a composition containing 70 mg/g of total crude saponins and 20 mg/g of total ginsenosides. (The control groups were comprised of equally aged mice which did not receive treatment.) At the end of the supplementation period, memory-related behavioral tests began to be administered at 2-day intervals, in order to not tire out the experimental mice. In the next section, we will review this experiment in-depth while focusing on the behavioral tests which were utilized to assess memory.
Memory-Based Behavioral Tests
Firstly, the Y-Maze was used for the first behavioral assessment, testing the spontaneous spatial recognition as a hippocampus-dependent memory test. The Y-Maze is a horizontal maze consisting of three arms (40 cm × 3 cm × 12 cm) which are symmetrically disposed at a 120° angle. In this maze, spontaneous alternation is the goal behavior, wherein the mouse chooses to enter one of the maze’s arms which it has not entered before.
To determine if red ginseng has the potential to modulate memory function in the Y-Maze, older mice which previously demonstrated spatial memory function impairment were tested. When compared with the aged controls, the treated mice displayed higher spontaneous alteration in the novel arm of the maze. This indicated that red ginseng was able to enhance the performance of aged mice in a memory-based test.
Two days after that, the mice were subjected to the Novel Object Recognition task. In this task, an arena with a cage bottom and dark walls were used. On Day 1, mice were allowed to explore the open area in 8-minute sessions and acclimate to the space. Six hours later, two identical objects were deposited in each corner, and each animal was allocated another 8 min to examine the objects. On Day 2, one of the objects was replaced with a new one in a counterbalanced fashion and each mouse was once again given 8 minutes to examine the objects.
During the initial training sessions in the Novel Object Recognition Task, as desired, all mice spent an equal amount of time investigating the objects presented, indicating that all the mice were equally motivated. However, during the recall stage, after some time passed, the red ginseng mice spent a significantly greater amount of time with the novel object than with the familiar one (which was presented during the initial training session). This is a significant finding because their performance was similar to the young controls, indicating that the treated mice had memories intact enabling them to remember the familiar object and that ginseng was, in a way, able to reverse the effect of aging. By contrast, the aged controls did not display such discrimination and spent an equal amount of time interacting with the familiar and unfamiliar objects.
Red ginseng’s effect on learning and spatial memory was also tested in the Morris Water Maze. The escape latency time for all of the conditions was the highest during the training sessions since the mice were still learning how to orient in the water maze. The gradual decrease in the latency indicated that some form of learning was taking place. By Day 4 of the maze protocol, significant differences began to appear between the aged controls and the aged treated mice. At this point, the experimental group began to outperform the controls as demonstrated by their escape latency. The researchers interpreted this decrease in escape latency to suggest that ginseng’s nootropic abilities can extend to improve long-term memory in the aged mice.
Together, the results from the Y-Maze, Novel Object Recognition Task and Morris Water Maze indicate that ginseng can improve memory functions across a variety of different scenarios.
Another study extended this findings to be applicable to female mice. The researchers wanted to establish ginseng’s effect, especially in female mice, since the majority of behavioral research is conducted on male mice, due to the female mice’s estrous cycle which can affect behavioral testing. The female mice were subjected to the step-down test (also referred to as the >Active/Passive Avoidance Test) which is used for studying the conditional memory. Only the 0.028% ginsenoside dose increased the female aged mice’s latency time to be equivalent to the young control’s and only the 0.056% concentration reduced the female aged mice’s total number of errors to be comparable to the young control’s in the Active/Passive Avoidance Test.
Red Ginseng’s Anti-Inflammatory Responses and Anti-Oxidative Effect
In addition to demonstrating nootropic effects, red ginseng exerted an anti-inflammatory effect in aged mice. The elevated levels of nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), TNF-α, and interleukin (IL)-1β, all of which are proinflammatory cytokines typically expressed during aging, were suppressed in the hippocampus of the brain after the administration of red ginseng.
Red ginseng also demonstrated an antioxidative effect in older mice. After 3 months of being administered with red ginseng extract, the expression levels of the nuclear factor E2-related factor 2 (Nrf2) and hemeoxygenase (HO-1) increased in the brain’s hippocampus; these are two very important enzymes involved in antioxidative processes.
Ginseng Anti-Oxidative Properties in the Hippocampus
Flowing from the same experiment described above, ginseng is associated with an increase in glutathione peroxidase (GSH-Px) and total superoxide dismutase (T-SOD) levels in rodents’ serum, two very important antioxidant enzymes implicated in controlling the stress-causing reactive oxygen species (ROS).
Excessive ROS is linked to cellular damage which in turn affects behavior and cognition and can be identified by researchers based on thiobarbituric acid reactive substances (TBARS) levels. Ginseng can also decrease TBARS levels found in the hippocampus, one of the brain’s most important areas contributing to learning and memory.
Ginseng Reduces Anxiety and Depression
Ginseng may be a promising agent for reducing mood-related conditions such as anxiety and depression. In this section, we will cover how behavioral studies have uncovered ginseng’s effect on these affective domains.
Ginseng Lowers Anxiety
Anxiety is a debilitating problem in which worrying, fear, apprehension, and nervousness are generally involved, and may result in physical symptoms such as a pounding heart. In the last few years anxiety has become a serious burden on the population. From 1990 to 2013, the number of people suffering from anxiety/and or depression has increased by roughly 200 million.
In general clinical practice, benzodiazepines are the most commonly used short-term anxiety treatment, but they come with their fair share of side effects, along with the risk of causing dependency. Because of this, new treatments are needed, in order to broaden the ways that anxiety can be reduced in patients seeking help.
One group of researchers systematically examined whether ginseng can be anxiolytic, as it has been traditionally used in Oriental countries such as Japan, Korea, and China, as a medicinal herb for psychiatric conditions such as depression or anxiety.
To test ginseng’s anxiolytic-like effects were tested on male ICR mice which were to be separated into various experimental conditions. Each group received a different quantity and type of ginseng while the control received saline. Also, a positive control group was created in which the rats received 2 mg/kg of diazepam, a controlled benzodiazepine which is used to treat anxiety and produces a calming effect.
The researchers used either red ginseng or sun ginseng for supplementation. Red ginseng is prepared by steaming raw ginseng for 2-3 hours at 98-100 °C. Sun ginseng is steamed at higher temperatures, in order to procure higher amounts of Rg3, Rk1, and Rg5.
The mice were given either total extract or a butanol fraction extract. The mice which were in the red ginseng condition received either 100 mg/kg of total extract or 25, 50, or 100 mg/kg of butanol fraction extract. Similarly, the mice which belonged to the sun ginseng condition received either 25 or 50 mg/kg of total extract or 25 or 50 mg/kg of the butanol fraction extract for sun ginseng.
Ginsenosides Affect Behavior and Reduce Anxiety
In order to determine whether the chemical constituents (described above) of the red and sun ginseng conditions would reduce anxiety-related behavior, the researchers also outlined the exact saponin mix of ginsenosides per condition. The red ginseng butanol fraction extract which they used contained: 12.6% of Rb1, 6.2% of Rb2, 6.9% of Rc, 3.4% of Rd, 6.6% of Re, 2.1% of Rf, 15.8% of Rg, 1.4% of Rg3. The total saponins in the red ginseng butanol amounted to 56.3%. On the other hand, sun ginseng butanol fraction extract was reported to have: 4.5% of Rb1, 4.8% of Rb2, 4.9% of Rc, 23.8% of Rg3, 12.3% of Rk1, and 13.1% of Rg5. The total saponins in sun ginseng is equal to 63.8%.
All of the ginseng-based supplements were given 60 minutes prior to behavioral assessment and diazepam was administered 30 minutes before testing.
In order to measure anxiety levels, an Elevated-Plus Maze was used; an apparatus which has two closed arms and two open arms which share a central platform. The maze is elevated above the ground and the mice must choose between an open and a closed arm to go to. Activity is measured based on how much time the mouse spends in the open or closed arms and the number of entries that it makes. In order for an action to count, four paws must enter the arm or two paws must exit the arm. This maze is well-validated for measuring anxiety-like behaviors.
The researchers found that the conditions which were associated with spending a significantly higher percentage of time in the maze’s open arms were the diazepam group, the red ginseng butanol fraction extract at 100 mg/kg, and the sun ginseng butanol extract at 25 and 50 mg/kg, as well as the sun ginseng total extract at 50 mg/kg. In terms of the percentage of open arms entries, the groups which were significantly better than the control group were the diazepam, the red ginseng butanol fraction extract at 100 mg/kg, the sun ginseng butanol fraction extract at 25 and 50 mg/kg, and the sun ginseng total extract at 50 mg/kg.
When compared to diazepam, diazepam was more significant than that of ginseng-based supplements (P<0.01 vs. P<0.05) when it came to the percentage of time spent in the open arm. However, the significant levels were roughly equivalent (P<0.005) between diazepam, sun ginseng total extract (50 mg/kg), and butanol extract (the 50 mg/kg condition) when assessing the percentage of open arm entries performed. These findings indicate that ginseng can produce the same level of results as diazepam in some situations.
Diazepam and the different types of ginseng were able to exert anxiolytic effects on the subjects. Given these results, this experiment doubly demonstrates ginseng’s ability to ameliorate anxiety-related symptoms and its complexity. The variability of active compounds found in the different types of ginseng (i.e., red vs. sun ginseng, total extract vs. butanol) was responsible for the ginseng-treated mice to perform at the level of the diazepam-treated mice, in some instances. Future research should continue investigating ginseng’s anxiolytic effects while accounting for the fact that, depending on the processing methods, ginseng’s chemical profile may vary.
Antidepressant Effects of Ginseng’s Metabolite S111
A group of researchers set out to demonstrate that 20(S)-protopanaxadiol (referred to as S111), a post metabolic compound which metabolizes in the intestine after ginseng is ingested, may be responsible for the antidepressant effects associated with ginseng.
Using male Swiss mice to induce the olfactory bulbectomy depression model, S111 compounds were administered and the behavioral profiles were compared with control rodents which received fluoxetine, a commonly prescribed selective serotonin reuptake inhibitor (SSRI) used for treating major depressive disorder. To induce this model, a bilateral olfactory bulbectomy was performed while the animals were under chloral hydrate anesthesia and were given 6 days to recover prior to beginning behavioral testing and drug administration. The controls were sham-operated and simply underwent the procedure but without receiving the olfactory bulbectomy.
Then, the rodents were divided into various conditions, receiving either acute (one-time) or chronic (10 doses) supplementation of ginseng. Then, depending on the group, S111 doses were given at either 3.75, 7.5 or 15.0 mg/kg. Fluoxetine conditions followed the same schedule but at a dosage level of 18 mg/kg.
The two standard behavioral assessments were used for measuring depressive-like behaviors, the Tail Suspension Test and the Forced Swimming Test. In both tests, the variable of interest is immobility time, that is how much time the rodent spends without making any motions (except for those necessary for breathing). Immobility in mice is commonly interpreted as being the behavioral equivalent of despair-related emotions which exist in humans.
In the Tail Suspension Test, mice were hung upside down by their tails and the total amount of immobility time was counted across conditions. A single dose of fluoxetine was able to reduce the immobility time compared to non-treated controls. Similarly, a single dose of S111 of 15 mg/kg was also able to reduce the mice’s immobility time when compared with controls, with an average immobility time of roughly 85 seconds compared to the non-treated controls’ of 104 seconds. In the chronic, repeated dose schedule, all three dosage levels of S111 were able to reduce the immobility time. Mice which received 10 doses of 15 mg/kg ginseng S111 performed at the level of mice treated with a single dose of 18 mg/kg of fluoxetine. These findings demonstrate that ginseng’s post metabolic compounds have antidepressant properties.
Similar results were observed in the Forced Swimming Test. Here, the mice were placed in a cylinder filled with water from which they were incapable of escaping. Immobility time was counted in terms of how long the mice spent floating without proactively trying to escape. In this test, too, significant findings were established across all S111-treated conditions, significantly outperforming the non-treated controls. A single dose of fluoxetine of 18 mg/kg was comparable to a single dose of 15 mg/kg of S111, suggesting an equivalency between the two conditions in some regard. The remaining dosage levels, across acute and chronic schedules, were all equally significant in lowering immobility time when compared to non treated controls.
Interestingly, S111, an active metabolite forming after ginseng ingestion, was associated with reduced brain oxidative stress and lower corticosterone concentration levels in the serum levels in the bulbectomy animals, a finding that was not present in the fluoxetine condition.
These findings, given the significant difference between the antioxidant properties of S111 and fluoxetine, show that ginseng metabolites are a promising avenue of pursuit for researchers interested in investigating future therapeutic developments and novel interventions using antidepressants.
Parkinson’s Locomotion Improved in Mice by Ginseng
Ginseng, in addition to its nootropic capabilities of enhancing cognitive processes, may be able to impact motor-related disorders such as Parkinson’s disease. Current research trends are exploring the possibility that ginseng may be beneficial for the human motor system, given the fact that conditions such as Parkinson’s do not have a definite, immediate cure.
One experiment used the Cylinder Test to assess how ginseng would improve the motor capabilities of mice that were modeled to have Parkinson’s disease. This study made use of two experimental rodent models of Parkinson’s disease, in order to assess exactly what effect G115, a ginseng extract, would have on the rodents which were used in the experiment.
The two animal disease models of Parkinson’s which were used in the study were induced with the parkinsonism neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in C57B16 mice or in rats using the MPTP metabolite 1-methyl-4-phenylpyridinium (MPP+). The rodents, prior to being induced with Parkinson’s, were treated for 10 days with the ginseng extract. G115 was added to the rodents’ drinking water with varying dosages and durations, depending on which disease model of Parkinson’s was being used.
The MPTP mice were assigned either 25, 75, 200 or 500 mg/kg/day of G115 to take. The MPP+ rats had only one condition of 100 mg/kg/day of G115. The respective controls for each mouse were rodents from the same disease-induced group which did not receive any ginseng nootropic supplementation.
In order to assess motor skills and behavioral capabilities, the rodents were subjected to behavioral testing using the Cylinder Test. In the Cylinder Test, a mice or rat will be placed within a cylinder and its spontaneous behavior within that enclosed environment will be observed. In this experiment, prior to starting the Cylinder Test assessment, the rodents were injected with apomorphine (APO), a commonly used procedure for inducing motor behavior by targeting the substantia nigra and striatum.
In the behavioral results reports, only the MPP+ infused rats demonstrated significant behavioral differences according to assigned conditions. When placed in the cylinder apparatus, the G115-treated rats receiving 100 mg/kg/day demonstrated significantly less contralateral rotations induced by APO than the non-treated controls. The researchers interpreted these findings to indicate that ginseng prevented less damage to occur as a result from MPP+, thus leading to less functional asymmetry.
Ginseng Prevents Parkinson’s-Related Cell Loss
The ginseng-treated MPTP mice (mentioned above) displayed significant differences in their cellular composition. Mice modeling Parkinson’s disease given the 75 mg/kg/day dose of ginseng G115 had the highest significant preservation of striatal tyrosine hydroxylase interneurons (THI), a type of neuron with distinct electrophysiological properties which is found in the striatum. The mice given this dose suffered only 28% of striatal THI loss compared to non-treated MPTP mice’s 41% loss. Since cells and physiology impact behavioral outcomes, it is still important that the mouse Parkinson’s disease model showed improvement in response to ginseng supplementation. Future research should thoroughly investigate the ways in which ginseng and its extracts can affect motor skills across disease levels.
Ginseng Improves Limb Impairment in Parkinson’s Mice
In a different experiment, panaxatriol saponins from Panax notoginseng were administered to an MPTP-induced Parkinson’s disease model in male Kunming mice (twice per day for 7 days before induction and post-induction) at a dose of 100 mg/kg. The control group received saline.
To measure limb impairment, the Traction Test was used. The mice are hung by their tail upside down, in near vicinity to a horizontal wire. In this predicament, the mice’s natural instinct is to grab at the horizontal wire, in order to regain traction and balance. In this test the mouse can receive one of three scores; it is rated as a ‘3’ for gripping the metal wire with both paws, ‘2’ if it only used one paw, and ‘1’ for failing to grip the wire with either paw.
The researchers established that ginseng supplementation had an effect on the level of limb impairment in mice. The MPTP-induced mice averaged a score of 1 while the healthy controls averaged almost a score of 3. By comparison, the experimental MPTP mice treated with panaxatriol saponins averaged a score of 2.
These findings indicate that ginseng extract is not limited to being a nootropic and can be beneficial also for motor functioning.
Ginseng is a complex, rich nootropic compound with effects that range from memory to motor improvements. Many different forms and types of ginseng can be studied by scientists, offering a wide range of active constituents, in order to assess the various effects which may occur on behavior and cognition.
Disease models are commonly used for studying ginseng’s therapeutic properties, in order to establish possible ways that it can benefit people. Given its antioxidant properties, ginseng may be potent in ways that pharmaceutical drugs aren’t.
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