Exploring the Roots and Stems of Ashwagandha Plant: Anatomy and Function

In recent years, there has been a significant surge in reports on the health-promoting benefits of winter cherry (Withania somnifera), also known as Ashwagandha. Its current research covers many aspects of human health, including neuroprotective, sedative and adaptogenic effects and effects on sleep. There are also reports of anti-inflammatory, antimicrobial, cardioprotective and anti-diabetic properties. Furthermore, there are reports of reproductive outcomes and tarcicidal hormone action. This growing body of research on Ashwagandha highlights its potential as a valuable natural remedy for many health concerns. This narrative review delves into the most recent findings and provides a comprehensive overview of the current understanding of ashwagandha’s potential uses and any known safety concerns and contraindications.

Indian ginseng is also known as Indian winter cherry, Ashwagandha, or the herb Vitania sluggard (Withania somnifera). The raw material used in medicine is the root, and the name “Ashwagandha” is derived from the word “ashwa”, meaning horse. It is believed that after consuming the root, one gains powers similar to that of a horse. The second part of the name “gandha,” means fragrance and refers to the characteristic smell of the fresh root of the plant [1]. Since ancient times, it has been traditionally used in Ayurvedic medicine as a substance that strengthens the nervous system. This is evidenced by its adaptogenic effects and medicinal uses—the so-called “rasayana”. below shows the comprehensive health benefit of Ashwagandha.

The history of its use in traditional Indian medicine dates back nearly 3000 years. Its root has been used as an aphrodisiac, narcotic, tonic, diuretic, anthelmintic and stimulant. It is naturally native to India, but it is also cultivated in other areas such as the Mediterranean countries, the Himalayan areas, Africa, Canary Islands, Cape of Good Hope and Australia [2,3,4].

In recent years, there has been a growing interest in the potential health benefits of Ashwagandha, particularly in the areas of stress management, cognitive function, and physical performance. Several studies have suggested that Ashwagandha supplementation may exhibit neuroprotective activity, be helpful in obsessive-compulsive disorder, and exhibit anti-inflammatory, immunomodulatory and antibacterial properties.

Additionally, there is evidence to suggest that Ashwagandha supplementation may be helpful in infertility, anticancer and antidiabetic treatment. Studies have suggested that Ashwagandha may exhibit cardioprotective properties, be helpful in the treatment of sleep disorders, improve stress resilience, reduce anxiety, be helpful in hypothyroidism, and enhance muscle strength and recovery.

While the potential health benefits of Ashwagandha are promising, further research is needed to fully understand its mechanisms of action and to determine its effectiveness in treating various health conditions. In this context, this paper aims to review the current literature on the activity of Ashwagandha, with a focus on its potential benefits for stress management, cognitive function, and physical performance.

Ashwagandha is characterized by a rich phytochemical composition. Depending on the location of the raw material, it exhibits a diverse composition of chemical compounds. Its active substances that play a crucial role in pharmacological action are witanolides and alkaloids. Witanolides are compounds whose essential structure is that of ergostane, which has a six-membered lactone ring at the C-8 or C-9 position. The group of witanolides includes witanopherin A, witanolides A-Y, witanone, witadomniferin A, and witasomniferols A-C. shows the main active compounds present. Alkaloids include witanin, somniferin, somnin, tropin, somniferinin, pseudowitanin, pseudotropin, choline, kuskohigrin, isopeletierin, and anaferin [5]. Also present in the raw material are flavonoids which include 3-O-rutinoside, 6,8-dihydroxycemferol, quercetin and its glycosidic derivative, 3-O-rutinoside-7-O-glucoside.

Additionally, witanolid glycosides, which have a structure that contains a glucose moiety at position C-27, are also present in the raw material. This group of compounds includes sitoindoside IX and sitoindoside X. Ashwagandha also contains steroidal saponins that contain an acyl group–sitoindoside VII and VIII. Saponins, coumarins (scopoletin), sterols, chlorogenic acid, resins, lipids, carbohydrates and fatty acids have also been identified in the raw material [6].

3. Neuroprotective and Anti-Neurodegenerative Effects

For many years, the phenomenon of aging populations has been observed, which also implies a significant increase in the percentage of people suffering from dementia syndromes. Dementia is a syndrome with a multifactorial aetiology characterized by a range of symptoms caused by a brain disease, typically with a chronic and progressive course. This condition affects higher cortical functions, including memory, thinking abilities, orientation, comprehension, learning abilities, and emotional control.

Neurodegenerative diseases cause the destruction of the central nervous system, resulting in irreversible damage. Over the course of Alzheimer’s disease, an abnormal deposition of β-amyloid protein in the brain is observed. In its fibrillar form, it has a neurotoxic effect because it induces the formation of free radicals and impairs glucose transport in neurons, which leads to cell damage and death. Hyperphosphorylated τ proteins in Alzheimer’s disease form clusters surrounding the core of the senile plaque, consisting of β-amyloid. Physiologically, τ proteins stabilize microtubules, along with other proteins. Accumulating senile plaques are accompanied by microglia (inflammatory response cells), attempting to break down and remove damaged and dead neurons as well as senile plaques. Microglia cells produce toxins, destroying both diseased and healthy cells and enhancing the brain’s inflammatory response [7].

In studies conducted on human nerve cells, Ashwagandha has been shown to neutralize the toxic effects of β-amyloid, an implication in neurocognitive impairment during HIV infection [8]. A study was conducted on rats that were orally administered vitanon—an ingredient isolated from the root of Whitania somnifera. Significant improvements in cognitive function were observed as a result of the inhibition of amyloid β-42, and a reduction in pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and MCP-1, nitric oxide, and lipid peroxidation was also observed. There was also a decrease in the activity of β and γ-secretase, enzymes responsible for the formation of insoluble neurotoxic aggregates of β-amyloid [9]. In addition, withaferin A extracted from Ashwagandha appears to be a promising ingredient in terms of Alzheimer’s disease treatment. It works by reducing β-amyloid aggregation and inhibiting τ protein accumulation. In addition, withaferin A is responsible for inhibiting oxidative and pro-inflammatory chemicals and regulating heat shock proteins (HSPs), the expression of which increases when cells are exposed to stressors. However, more medical studies are needed to assess the safety of withaferin A and to confirm its neuroprotective effects in the treatment of Alzheimer’s disease [10]. In addition, it has been noted that withaferin A from Ashwagandha extract significantly inhibits not only the production of amyloid β, but also the gene expression of neuroinflammatory molecules related to NF-κB [11]. A study was also conducted in transgenic mice that were given a half-purified extract of Whitania somnifera root containing mostly withanolides for 30 days. After this time, it was noted that Ashwagandha offset the negative effects of Alzheimer’s disease by increasing the number of the LDL receptor-related protein LRP1 (low density lipoprotein related protein 1) in the liver [12]. Increasing LRP1 levels reduced amyloid β and reversed the behavioural deficits in Alzheimer’s disease [13]. Studies suggest that LRP1 functionally modulates the steps required to form the β-amyloid precursor protein APP, which is critical for amyloid β production and APP processing [14]. The study also shows that LRP1 is a key regulator of protein proliferation τ [15]. The effect of Withania somnifera derivatives on the formation of β-amyloid 42 deposits in Alzheimer’s disease was studied. It was observed that withanolide A, withanolide B, witanoside IV and witanoside V interact with the hydrophobic core of β-amyloid 1–42 in the form of an oligomer, which prevents further interaction with monomers and reduces aggregation [16,17]. In another study, Withania somnifera extract was bioconverted by the fungus Beauveria bassiana. The resulting cysteine and glutathione derivatives of withaferin A were purified and fully characterized. It was shown that CR-777, a glutathione derivative of withaferin A, has neuroprotective effects and can be a protective agent against many neuronal stressors [18]. It is known that one of the most important components of Ashwagandha–withanolide A combats neurodegenerative processes in Alzheimer’s disease and Parkinson’s disease. However, it was only relatively recent that the ability of withanolide A to penetrate the blood-brain barrier (BBB) was demonstrated. In another study, adult mice were administered three different doses of vitanolide A intranasally: 1 mg/kg, 5 mg/kg, 10 mg/kg. The intranasal administration allowed for the penetration of the test substance into the cortex and cerebellum. After treatment with withanolide A, a significant reduction in cerebral infarction, improvement in blood-brain barrier function, and reduction in cerebral oedema were noted. An improvement in biochemical parameters and a reduction in excessively high levels of neurotransmitters, which had been caused by previous ischemia, were also noted. The highest dose administered (10 mg/kg) significantly reduced morphological damage, apoptosis and necrosis in brain tissues [19].

Neurodegenerative diseases also affect animals, not just humans, but in both cases the course of the disease and its pathomechanism is very similar. Canine Cognitive Dysfunction (CCD) is an age-dependent disease in which pathological changes in the brain are observed, leading to memory loss and impaired motor function. In both dogs and humans, a progression of oxidative damage in the brain is noted with age. In a study conducted on human embryonal neuroblastoma SK-N-SH cells, Ashwagandha extract was shown to have antioxidant properties (significantly reduces free radical generation). It also modulated cholinergic transmission, potentially inhibiting acetylcholinesterase activity, which may have benefits in the treatment of canine cognitive dysfunction and Alzheimer’s disease [20].

Additionally, it has been noted that withaferin A in the form of Ashwagandha extract significantly inhibits not only the production of amyloid β, but also the gene expression of neuroinflammatory molecules related to NF- κB [21].

In Parkinson’s disease, the degeneration of the dopaminergic neurons of the nigrostriatal system is observed. This leads to an imbalance between dopamine’s inhibitory action and acetylcholine and glutamic acid’s excitatory action. Factors that induce the degeneration of nigrostriatal cells include:

• Genetic conditions;
• Endo- and exogenous toxic factors;
• Neuroinfections;
• Oxidative stress;
• Reduced growth factors;
• The sum of the action of several of the above factors.

The disease is slightly more common in men than in women, and although the cause is not known, it is thought that this may be due to the protective role of estrogen [22].

A study was conducted on rats with 6-hydroxydopamine-induced Parkinson’s disease. Prior to an injection of 6-hydroxydopamine into the striatum, the rats were orally administered a Withania somnifera extract at doses of 100, 200, and 300 mg/kg body weight for 3 weeks. It was observed that administration of Ashwagandha significantly reduced lipoperoxidation, increased glutathione concentration, increased glutathione S-transferase, glutathione reductase, glutathione peroxidase, superoxide dismutase and catalase activities, catecholamines, and dopamine D2 receptor binding and enhanced tyrosine hydroxylase expression [23].

Although Withania somnifera significantly improves biochemical parameters in Parkinson’s disease, its effects depend on the dose administered [23,24,25]. In addition, in a study conducted on fruit flies, it was shown that administration of a standardized methanol extract of Ashwagandha root counteracts deficits associated with Parkinson’s disease [26]. In mice with Parkinson’s disease, administration of Ashwagandha extract not only improved biochemical parameters, but also reduced motor impairment compared to the control group [25,27]. It has been observed that oral administration of Withania somnifera extract (100 mg/kg, i.p.) to mice increases the levels of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) and also normalizes the levels of lipoperoxidation markers in the striatum of the mice [25].

Huntington’s Disease is an incurable disease. Current medications only work on the symptoms and slow down the progression of the disease. The disease is inherited in an autosomal dominant manner, which means that statistically, half of the offspring will receive the disease-causing allele. A mutation in the IT15 gene encoding the huntingtin (htt) protein on chromosome 4 leads to a conformational change in huntingtin, into its insoluble form. The N-terminal part of the mutant huntingtin protein, containing expanded polyglutamine repeats, accumulates leading to accelerated neuronal apoptosis. This leads to an imbalance of dopamine, GABA, serotonin, and acetylcholine [28].

The compound 3-Nitropropionic acid (3-NP) is a potent neurotoxin. It induces oxidative and nitrosative stress, inhibits complex II of the mitochondrial electron transport chain (resulting in a deficit of moma energy), and is responsible for biochemical and neurobehavioural changes very similar to those observed in Huntington’s disease. In an animal model, symptoms of Huntington’s Disease were artificially induced by applying 3-NP intraperitoneally. It was observed that the chronic administration of Ashwagandha extract had a beneficial effect on biochemical parameters and motor function due to the antioxidant properties of the plant studied. There was a decrease in lipoperoxidation, a decrease in the levels of lactate and nitrate dehydrogenase, an increase in the levels of superoxide dismutase and catalase, and an unblocking of the mitochondrial complex and thus a restoration of ATP synthesis. The effect was dose-dependent—100 mg/kg and 200 mg/kg [29]. In another study in mice, the beneficial effect of withaferin A, isolated from Ashwagandha, was demonstrated. The inability of cells to maintain proteostasis is a sign of aging and a hallmark of many neurodegenerative diseases, including Huntington’s disease. In this mouse model, withaferin A ameliorates the impaired proteostasis by activating the heat shock response and delaying disease progression. The mice with Huntington’s Disease treated with withaferin A lived significantly longer, and restoration of behavioural and motor deficits was also observed, including a reduction in body weight. Biochemical studies confirmed the activation of heat shock, the reduction of mutant huntingtin aggregates, and the improvement of striatal function in the brain in mice. In addition, withaferin A significantly reduced inflammatory processes, as noted by reduced microglia activity [30,31].

3. Treatment of Obsessive-Compulsive Disorder, Alcohol Withdrawal Syndrome

Obsessive-compulsive disorder (OCD) is a chronic psychiatric disorder that involves patients experiencing symptoms in the form of intrusive thoughts and ry. Patients perceive them as undesirable, unwanted, compulsive, and irrational. Although the severity of the cognitive disturbance can vary considerably from patient to patient, OCD makes daily life significantly more difficult—especially in its severe form, where it can significantly impair psychosocial functioning [32,33,34]. Genetic and psychological factors play a significant role in the aetiology of OCD, but structural and functional abnormalities within the central nervous system are equally important [33,34]. Obsessive-compulsive disorder is thought to be associated with the dysregulation of the serotonergic system [35]. Ashwagandha root extract may be a helpful adjunct to SSRIs in the treatment of patients with obsessive-compulsive disorder [35]. A study was conducted on mice that exhibited behavioural symptoms similar to those observed in OCD. In this animal model, mice were administered a methanolic extract of Withania somnifera (doses: 10, 25, 50, 100 mg/kg) and an aqueous extract of Withania somnifera. It was observed that the administration of the aqueous and methanolic extract of Ashwagandha significantly improved behavioural deficits in the mice, without affecting motor activity. The results obtained were similar to those of the standard treatments: fluoxetine, ritanserin, and para-chlorophenylalanine [36].

The effect of Ashwagandha in Alcohol Withdrawal Syndrome (AWS) in rats was studied. It was observed that the oral administration of Ashwagandha alleviated withdrawal anxiety due to chronic alcohol consumption, indicating a protective effect of the study plant in the management of ethanol-withdrawal reactions [37]. Haque et al., confirmed that Ashwagandha have beneficial effects on controlling behavioural changes, anxiety and seizures in alcohol withdrawal symptoms in rats, and it improves locomotor activity [38].

Due to its properties, Withania somnifera is being studied for the treatment of many diseases associated with inflammation in the body, such as cardiovascular, pulmonary, and autoimmune diseases and diabetes, cancers, and neurodegenerative diseases. Preclinical studies have demonstrated the ability of this plant to regulate mitochondrial function and apoptosis and reduce inflammation by inhibiting inflammatory markers such as cytokines (including IL-6 and TNF-a), nitric oxide, and reactive oxygen species. Meanwhile, in a mouse model with lupus, a potential inhibitory effect of Ashwagandha root powder was demonstrated in conditions such as proteinuria and nephritis [39]. Ashwagandha is also being investigated for its efficacy in rheumatoid diseases. In a study conducted in an animal model, Withania somnifera root powder was administered orally to rats for three days, one hour before inflammation was induced by an injection of CFA (complete Freund’s adjuvant). In the control group (positive control), rats were administered phenylbutazone. Changes in the concentrations of a number of serum proteins, such as α2 glycoprotein, acute phase protein α1 and prealbumin, were demonstrated, along with a significant reduction in inflammation [40]. In a study using the HaCaT human keratinocyte cell line, an aqueous solution from Ashwagandha root was found to inhibit the NF-κB and MAPK (mitogen-activated protein kinase) pathways by decreasing the expression of pro-inflammatory cytokines, including interleukin (IL)-8, IL-6, tumour necrosis factor (TNF-α), IL-1β, and IL-12, and increasing the expression of anti-inflammatory cytokines. Based on these results, it can be concluded that the anti-inflammatory effects of Ashwagandha could potentially be used in the prevention of skin inflammation [41]. In a preclinical study of the anti-neuroinflammatory effects of Ashwagandha water extract (ASH-WEX) against lipopolysaccharide-induced systemic neuroinflammation, animals treated with ASH-WEX showed an inhibition of reactive gliosis; production of inflammatory cytokines such as TNF-α, IL-1β, and IL-6; and expression of nitro-oxidative stress enzymes. The underlying molecular mechanisms for the anti-inflammatory potential of ASH-WEX appear to involve inhibition of lipopolysaccharide (LPS)-activated NFκB, P38 and JNK/SAPK MAPK pathways. The results of this study suggest the potential use of Withania somnifera in suppressing nervous system inflammation associated with various neurological disorders [42]. Evidence presented in a study by Kanjilal et al. [43] showed that Ashwagandha extract applied for a period of 8 to 12 weeks can be useful in managing arthritis symptoms in patients. The immunomodulatory effect was confirmed in a study on the effect of Withania somnifera root powder on the stimulation of immune activity in immunodeficient mice. Administration of Withania somnifera was found to increase the total number of white blood cells and bone marrow cells, as well as to increase the titre of circulating antibodies and antibody-producing cells and to stimulate the production of immune cells and the phagocytosis of macrophages [44]. A randomized, double-blind, placebo-controlled trial with an open-label extension was conducted to evaluate the effect of Ashwagandha extract on the immune system of healthy participants. The results of the study showed that Ashwagandha extract significantly increased natural killer cell activity and cytokine levels, compared to placebo [45].

Drug resistance in micro-organisms is a major and growing threat, although now widely recognized. In recent years, a significant increase in infections caused by drug-resistant strains has become a major problem. It is known that the reckless and often unwarranted use of antibiotics has resulted in the development of drug-resistant strains, and in some situations, these drugs have become completely ineffective. Ashwagandha, therefore, appears to be a valuable addition to pharmacotherapy in the treatment of bacterial infections. Many of the drugs currently used to treat bacterial infections, despite their efficacy, have many dangerous side effects related to their toxicity. Ashwagandha is a safe, non-toxic plant with almost no side effects. In the studies that have been conducted, it has been proven to effectively inhibit the growth of methicillin-resistant Staphylococcus aureus and Enterococcus spp. [46]. Withania somnifera root extract has also been shown to effectively inhibit the growth of the Gram-negative bacteria Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi, Citrobacter freundi, and Klebsiella pneumoniae [47,48,49]. The mechanism of its antimicrobial action is attributed to several of its properties; it has an immunomodulatory effect because it enhances immune reactivity (immunopotentiation), cytotoxic effects, and gene silencing [50].

Animal model studies also show that Withania somnifera is an effective treatment for salmonellosis, as it significantly alleviates the course of infection following infection with this pathogen [51]. Withania somnifera can also be an effective anti-caries agent, depending on the concentrations used. It significantly slows the growth of bacteria present in the oral cavity, such as Streptococcus mutant and Streptococcus sobrinus. It also inhibits bacterial acid production, acid tolerance, and biofilm proliferation [52]. It shows particular efficacy against Salmonella typhi [39]. The witanolides isolated from Ashwagandha induce cell death (acts on promastigotes) in Leishamania donovani by activating the process of apoptosis (ROS release from mitochondria occurs) and disrupting the mitochondrial membrane potential [53]. Studies have shown that Ashwagandha also exhibits valuable antifungal properties against some fungal species; it inhibits Candida albicans. It is important to note that Aspergillus flavus and Aspergillus niger seem to be resistant to the compounds it contains [48]. However, Withania somnifera glycoprotein isolated from its root tubers shows both antifungal properties against Aspergillus flavus, Fusarium oxysporum, Fusarium verticilloides, and antibacterial properties against Clavibacter michiganensis subsp. Michiganensis [54]. Murugan et al. [55] found that W. somnifera extract showed an enhanced antibacterial activity against P. aeruginosa. The study on the mechanism of antibacterial activity by Ashwagandha extract using morphological analysis and membrane stabilization assays showed that it acts by damaging the cell membrane of P. aeruginosa.

Studies in mice also show that Withania somnifera extracts (especially those at higher concentrations) are effective in the treatment of malaria, significantly reducing parasitaemia [56].

Plant Anatomy and Structure