Withania somnifera, Ashwagandha
- Ashwagandha is a popular and widely used herbaltonic in the Indian Ayurvedic system of medicine.
- Ashwagandha is a safe and effective treatment fora variety of stress-related and neurological disordersin animal models, cell lines, and humans[1, 2, 7].
- Ashwagandha is believed to have antioxidant, anti-inflammatory, and modulating effects on the brainand related systems which leads to its popular useas an anti-anxiety agent[1, 2].
Withania somnifera, otherwise known as Ashwagandhaor Indian ginseng, is an annual shrub in the Solanaceaeor nightshade family which grows in India, the Mid-dle East, and parts of Africa. Ashwagandha is an ex-tremely revered herb within the Indian Ayurvedic systemof medicine, and is used for various kinds of diseases as anervine tonic for over 3000 years especially for usein a variety of musculoskeletal conditions and to increaseenergy and improve overall health and longevity, in-cluding immunostimulation. More recent research hasalso shown that Ashwagandha may be useful in adap-togenic applications[6, 1], promotion of male fertility,neuroprotective applications, and other protective ap-plications in regards to inflammation and mitochondrialfunction.
Traditionally, the roots of Ashwagandha have beenused as a tonic, aphrodisiac, narcotic, diuretic, andstimulant. It is formed into a paste by crushing theroots with water and applying to joints, ulcers, andpainful swellings in order to reduce inflammation. Itsflowers and seeds have also been historically used asan aphrodisiac, and for treating anxiety and memoryloss. Ashwagandha has a rich history of cultural use,even being mentioned in the Indian Pharmacopoeia andbeing used for all age groups, both sexes, and duringpregnancy to promote “youthful vigor”.
The chemistry of Ashwagandha has been exten-sively studied, and over 50 unique constituents have been identified, including alkaloids, steroidal lactones,saponins containing an additional acyl group, andwithanolides, the structure of which are shown in Fig-ure 2. Ashwagandha is also very rich in iron. Phar-macological studies have confirmed that the plant prepa-ration of Ashwagandha has anti-inflammatory, antioxi-dant, anticancer, anxiolytic, and immunomodulatory ef-fects – as well as influencing neurological, endocrine, andcardiovascular activity. Lastly, several studies have re-ported the safety and efficacy of Ashwagandha extractsfor all age groups and genders, including during preg-nancy – throughout different dosages and lengths of con-sumption in animal and limited human models.
Mode of Action
Due to the extremely complex and varied pharmacolog-ical constituents present in Ashwagandha, and the vari-ous ways in which it can be administered, this scientificreview will focus only on a few mechanisms of action inwhich Ashwagandha is believed to work.
First, the anxiolytic effects of Ashwagandha may beattributed to several mechanisms. The first anxiolyticmechanism could be due to an attenuating effect onthe hypothalamic-pituitary-adrenal (HPA) axis activity,with acute decreases in cortisol and DHEA activity inparticipants taking Ashwagandha. It was also seenthat glycowithanolides obtained from Ashwagandha ex-hibited an anxiolytic effect against pentylene tetrazoleinduced anxiety in rats, and decreased the level of theendocoid marker of clinical anxiety and mitigated ox-idative stress-induced LPO in the frontal cortex of footshock-stressed rats. Another potential mechanism forits anxiolytic effect is through its antioxidant and anti-inflammatory effects – especially in preclinical studieswhich have stated that Ashwagandha can also influ-ence GABAergic and serotonin activity through stim-ulation of the adrenergic and serotonergic systems.Lastly, it has been shown in rat models that Ashwa-gandha protects against neuronal degeneration throughmembrane blebbing, chromatin condensations and frag-mentation, and intracellular spacing. This was in ad-dition to improvements in cerebral neurotransmitter lev-els (adrenaline, dopamine, 5-HTP), as well as reversal ofcorticosterone levels induced by chronic stress and rever-sal of lipid peroxidation.
In regards to neurodegenerative diseases such asParkinson’s, Huntington’s, and Alzheimer’s Disease,there are quite a few studies showing that Ashwagandhaslows, stops, or reverses neuritic atrophy and synapticloss. Additionally, the glycowithanolides withaferin-Aand sitoindosides extracted from the roots were shownto significantly reverse ibotenic acid-induced cognitive defects in an Alzheimer’s Disease model. In a Parkin-son’s Disease model in rats, Ashwaganda extract wasshown to prevent all the changes in antioxidant en-zyme activities, catecholamine content, dopaminergic D2receptor binding and tyrosine hydroxylase expression-induced by 6-OHDA in a dose-dependent manner.There has also been a study which demonstrated thatchronic oral administration of withanoside IV attenuatedthe axonal, dendritic, and synaptic losses and memorydeficits induced by amyloid peptide AΒ(25-35) andthat withanone shows significant inhibition of the amy-loid peptideΒ-42.
Ashwagandha has also been shown to exert significantinhibitory effects on the incorporation of ribosome -35Sinto the granulation tissue, as well as an uncoupling ef-fect on oxidative phosphorylation in the mitochondriaof granulation tissue. Ashwagandha was also foundto influence Mg2+ dependent ATPase activity and toreduce the succinate dehydrogenase enzyme activity ofmitochrondria in granulation tissues in rat models.
In terms of male fertility and its use as an aphrodisiac,Ashwagandha was found to exhibit testicular develop-ment and the spermatogenesis process by lowering thefollicle-stimulating hormone levels, as well as increasingthe interstitial cells stimulating hormone levels. Addi-tionally, Ashwagandha has been shown to affect male fer-tility through both a direct effect (oxidative mechanism)and indirect (non-oxidative) mechanism – this includesan increase of essential metal ion levels in seminal plasmaand germ cells resulting in low sperm cell death andincreased sperm production as well as improved spermparameters. The indirect effect of Ashwagandha is mainly through its decrease of the brain HPA axis andincrease of the HPG axis, which eventually results in anincrease of testosterone levels in the blood.
Both preclinical and clinical research have supportedthe usage of Ashwagandha for the treatment of a va-riety of neurological conditions including cognitive dis-orders, anxiety, depression, Alzheimer’s and Parkin-son’s Disease. The glycowithanolides and sitoindo-sides found within the roots of Ashwagandha have alsobeen shown to significantly reverse ibotenic acid-inducedcognitive defects in Alzheimer’s animal models, and alsoto protect against neuronal injury in Parkinson’s ani-mal models. Additional studies into cell lines haveshown promise for Ashwagandha to potentially be usedfor the treatment of diabetic neuropathy through neu-rites regeneration.
Ashwagandha also has pharmacological effects as ananxiolytic agent, inducing a calming effect comparableto Lorazepam in rat brains through the elevated plus-maze, social interaction, and feeding latency tests – inaddition to exhibiting an antidepressant effect compa-rable to imipramine in forced swim-induced behavioraldespair and learned helplessness tests in rats. In a clin-ical study in human subjects, the root extracts of Ash-wagandha controlled serum cortisol levels devoid of anyside effects. In a randomized, double-blind, placebo-controlled study in healthy adults, a statistically signif-icant reduction in the HAM-A anxiety parameter wasobserved, along with greater reductions in morning cor-tisol and DHEA-S compared to the placebo. Lastly,Ashwagandha was seen in rat models to have similar anx-iolytic effects toPanax ginseng, however, with improvedanabolic activity during swimming tests.
There is also limited evidence from a double-blind,randomized, placebo-controlled pilot study in humansubjects with subclinical hypothyroidism, which showsthat treatment with Ashwagandha root extract effec-tively and significantly normalized the serum thyroid in-dices during an 8-week period with only mild and tem-porary adverse effects.
As described above, Ashwagandha has an extremely var-ied and complex pharmacological profile and mechanismsof action which make it suitable for a large variety ofpotential uses. Besides its potential use as an anti-inflammatory[2, 3, 6, 7] , immunomodulator[2, 6, 8], andmale fertility agent[1, 4], the main uses for Ashwagandhawhich have strong support in literature are mainly as a neuroprotective agent[2, 3, 6, 7] and anxiolytic[1, 2, 3, 6,7].
There is also newer and more limited research showingthat Ashwagandha may extend beyond just an anxiolyticand neuroprotective agent, and may have potential usesin many common brain disorders – including schizophre-nia, dyslexia, ADHD, autism spectrum disorder, depres-sion, bipolar disorder, and addiction[2, 7].
Much of the research into Ashwagandha’s uses hasbeen through animal and cell line models, althoughnewer research has started to examine its effects uti-lizing double-blind, placebo-controlled studies in humanadults. Although most studies confirm that Ashwa-gandha has a very favorable safety and toxicity profile,further research and pharmacological screening is neededin order to determine effective chemical constituents andsafe dosages for long-term use in humans.
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This document was created on July 30, 2021 and last updatedon July 31, 2021.