3Biorefining and Advanced Materials Research Center, SRUC, Kings Buildings, West Mains Road, Edinburgh EH9 3JG, UK
Withania somnifera L. Dunal (Ashwagandha), a key medicinal plant native to India, is used globally to manage various ailments. This review focuses on the traditional uses, botany, phytochemistry, and pharmacological advances of its plant-derived constituents. It has been reported that at least 62 crucial and 48 inferior primary and secondary metabolites are present in the W. somnifera leaves, and 29 among these found in its roots and leaves are chiefly steroidal compounds, steroidal lactones, alkaloids, amino acids, etc. In addition, the whole shrub parts possess various medicinal activities such as anti-leukotriene, antineoplastic, analgesic, anti-oxidant, immunostimulatory, and rejuvenating properties, mainly observed by in vitro demonstration. However, the course of its medical use remains unknown. This review provides a comprehensive understanding of W. somnifera, which will be useful for mechanism studies and potential medical applications of W. somnifera, as well as for the development of a rational quality control system for W. somnifera as a therapeutic material in the future.
The World Health Organization (WHO) stated that approximately 30% of drugs contain plant-derived compounds, and approximately more than half of the global population depends upon plant-derived medicines, including those of Ayurveda, the traditional plant-based medicine of India [1,2]. The Botanical Survey of India (BSI) reported that approximately 7500 of the 15,000 plant species in India are used for medicinal purposes [3]. A list of 32 therapeutically important plants of India prioritized by the National Bank for Agriculture and Rural Development (NABARD) includes Withania somnifera, regularly called as ashwagandha. The National Medicinal Plant Board (NMPB), India, has also described Withania species as a valuable therapeutic plant in great demand in domiciliary and global markets [4,5].
W. somnifera, indigenous to the Indian sub-continent, is used as indigenous medicine throughout Southeast Asia. Its roots, seeds, and leaves have been used for over 3000 years for multiple health purposes, and are included in Ayurvedic, Allopathic, Unani, homeopathic, and other medical systems [6]. Due to its superlative therapeutic properties, it is also known as the Queen of Ayurveda or a Rasayana herb. Withania spp. are members of the Solanaceae family (Bentham and Hooker, 1862–1883), also known as the deadly nightshade family. The Solanaceae family embraces 84 genera, comprising 3000 species, distributed all over the globe [6]. The genus Withania contains 26 species, only 2 of which, W. somnifera and W. coagulans (known as Paneer booti, Ashutosh booti or rishyagandha), are economically and medicinally important in many regions [7]. Other potentially important species are W. simonii, W. adunensis, and W. riebeckii.
Two subspecies have also been reported—W. somnifera Dunal and W. somnifera Kaul [8]. Both species of Withania, i.e., W. somnifera and W. coagulans, are cultivated on a large scale in India [9]. In Sri Lanka, two cultivars of W. somnifera are used, but the Indian cultivar is more suitable for drug development due to its starchy nature, whereas the local cultivar has fibrous roots that are difficult to transform into powder [10]. Its common name, ashwagandha, is a combination of two Sanskrit words, ashwa and gandha, and means “horse’s smell”, referring to the sweaty horse-like smell of the roots [9,11]. Other names include winter cherry, poison gooseberry [12,13], or “Indian ginseng”, due to its restorative properties.
However, the mechanism of drug use by W. somnifera has not been elucidated. Accordingly, there are unreasonable points in the current W. somnifera quality management system. In fact, its medicinal value has received less attention, despite its long history of clinical application. In this review, information regarding various aspects of W. somnifera was collected from peer-reviewed journals for the period 2000–2022. PubMed, Shod Ganga, Web of Science, Google Scholar, etc., was used to retrieve electronic information. Based on this information, we performed a full review of W. somnifera aiming to provide information to better understand the pharmacological mechanism and potential medicinal applications of this species, and to develop a reasonable quality control system for W. somnifera as medicinal material in the future.
Ashwagandha (Withania somnifera) is an important medicinal herb that has been used in Ayurvedic medicine for centuries. The roots and leaves of ashwagandha are used to make supplements and remedies that help reduce stress anxiety arthritis, and more. For ashwagandha growers, ensuring proper pollination is crucial to maximize seed and fruit production, and ultimately boost the yield. In this comprehensive guide, we’ll cover everything you need to know about pollinating ashwagandha plants for the best results.
The Importance of Pollination for Ashwagandha
Pollination is the transfer of pollen grains from the male part (anther) of a flower to the female part (stigma) of the same or another flower. It is an essential step in the reproductive process of flowering plants like ashwagandha. Here’s why pollination is so important:
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Pollination enables fertilization and fruit production The fruits contain the valuable ashwagandha seeds that are used for propagation and boosting yields
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It leads to greater genetic diversity, giving rise to plants that can better adapt to changing climatic conditions and disease resistance.
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Pollinated ashwagandha flowers produce more and larger fruits, resulting in a higher seed count. More seeds equal more new plants and higher yields.
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Manual pollination can increase fruit set by up to 65% compared to open pollination.
Natural Pollination in Ashwagandha
In nature, pollination in ashwagandha occurs through insects and other pollinators. The star-shaped, greenish-yellow flowers of ashwagandha attract various pollinators like bees, butterflies, flies, and beetles. However, relying solely on natural pollinators can be risky due to factors like pesticide use, climate change etc. that are decimating pollinator populations. Insufficient natural pollination often leads to lower yield.
Manual Pollination Methods
Performing manual pollination ensures maximum pollination, fruit set and yield. It involves manually transferring pollen from anther to stigma using tools. Here are two simple methods:
Using a Paintbrush
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Identify ashwagandha flowers to be pollinated. Pick male and female flowers that have opened and have visible reproductive parts.
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Use a clean, fine-tipped paintbrush to collect pollen from the anther of a male flower.
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Gently brush the sticky pollen-coated brush on the stigma of the selected female flower to pollinate it.
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Repeat for all flowers.
Using a Cotton Swab
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Take a cotton swab and gently dab it on the anther of a male flower to collect pollen.
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Lightly roll the pollen-covered swab tip over the stigma of a female flower to transfer pollen.
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Repeat the pollen collection and transfer process for all flowers.
Tips for Effective Pollination
Follow these tips to ensure successful pollination and maximum ashwagandha fruit and seed set:
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Conduct pollination early morning when flowers are fresh, and pollen is dry.
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Pollinate every day during peak flowering season for best results.
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Tap flowers gently to dislodge pollen before collecting it.
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Use freshly opened, disease-free flowers. Reject flowers with discoloration or spots.
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Label manually pollinated flowers to track fruit development.
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Gently tie a string around pollinated buds to avoid losing track.
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Maintain proper spacing between plants for easy access to flowers.
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Keep notes on blooming times, pollinated flowers, and fruit set for reference.
Ensuring Optimal Growth Conditions
While pollination is critical, providing optimal growing conditions is equally important to maximize ashwagandha yields:
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Plant in well-draining, sandy loam soil with a pH between 6.0-7.5.
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Ensure the soil is enriched with compost or manure before planting.
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Give plants plenty of sunlight – at least 6 hours of full sun is ideal.
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Practice regular weeding and keep the plants well-spaced for air circulation.
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Water plants thoroughly once a week during growth period. Avoid overwatering.
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Apply organic potassium-rich fertilizer every 4-6 weeks during flowering and fruiting.
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Monitor regularly for pests like spider mites and aphids. Take prompt action if infestation is spotted.
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Inspect leaves frequently and treat any fungal disease like leaf spot using sulphur-based fungicides.
Harvesting and Processing Ashwagandha
With successful pollination and proper care, your ashwagandha plants will produce ripe fruits in about 120-180 days. Here are some tips for harvesting and processing the valuable roots and seeds:
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Identify maturity by the drying and splitting of the fruit skin. Harvest fruits by gently uprooting the entire plant.
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Wash and clean the roots thoroughly. Air dry them under shade for 2-3 weeks before use.
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pluck the fruits and dry them in shade for a few days to extract the seeds easily.
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Place seeds in an airtight container and store in a cool, dry place. They remain viable for 2 years.
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Roots can be pulverized, powdered, or cut into pieces for direct use or formulation into supplements.
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Seeds can be sown directly or grown into seedlings for plantation.
The Takeaway
3. Flowers and Fruits
Flowers are inconspicuous, solitary, green or dull yellow in color, 4–6 mm in diameter, bisexual, pedicellate, highly protogynous, small, and bell-shaped. Cross-pollination is carried out by ants and bees [32]. Inflorescences are axillary umbellate cymes. The calyx is gamosepalous with valvate aestivation. The corolla is greenish-yellow, valvate, campanulate, and has 5–8 mm lobes. Stamens (5) are polyandrous and epipetalous. Anthers are dithecous, basifixed, and introse. The ovary is superior, bilocular, and has axile placentation. Fruit are orange-red berries containing very light seeds, which are small, smooth, lens-shaped, or kidney-shaped, 2–2.5 mm length × 1.5–2 mm width × 0.5 mm height. Its flowers and fruits are having many phytoconstituents which helps in anti-microbial activities as well as works as a milk thickening agents as shown in [33].
| Parts of Plant | Name of Phytoconstituents | Biological Activities | References |
|---|---|---|---|
| Fruits and flowers | Amino acids, aspartic acid, alanine, chamase, condensed tannins, cystine, flavonoids, glutamic acid, glycine, hydroxyproline, isopsoralen, peroxidases, proteolytic enzyme, Psoralen, proline, tyrosine, and valine. | Anti-microbial, milk thickening agent, and treats respiratory problems | [34,35,36] |
W. somnifera has played a role in human society since prehistoric times. Its medicinal nature is specified in Ayurvedic books, such as Astanga Hridaya, Bhava Prakasha Nighantu, Charaka Samhita, and Sushruta Samhita [12,28,37]. Its Ayurvedic properties are Atishukrala, boosts semen quality and quantity; Balya, which provides power; Vajikara (andrology), which enhances sensual problems; Kshayapaha, which helps to treat weakness and provides nutritive conditions; Rasayani (chemotaxis), which rejuvenates the body and removes toxins; Shwitrapaha, which heals white discoloration of the skin; and Shothahara, which treats swelling in tissue and clears impurities (Ama). Some Ayurvedic qualities includes Rasa (taste) Tikta (bitter), Kasaya (astringent), Madhura (sweet), katu (pungent), Guna (characteristics), Snigdha (Softness, unctuous), Laghu (light), Virya (potency), Usna (hot potency), Vipaka-Madhura and Doshakarma-Kapha (natural coolants), Vata, and Samaka (pain management) [38].
5. Anti-Stress and Anti-Anxiety/Psychotropic Activity
Withanolide glycosides show anti-stress properties and having positive effects on boosting memory [69]. They help treat stress-induced conditions such as gastric ulceration, cognitive deficit, irregular glucose homeostasis, sexual dysfunction, changes in plasma corticosterone levels, and immunosuppression [7].
Withania somnifera root and seed extracts show anti-stress activity. An in vivo study was performed in mice to determine the anti-stress activity of the plant. An alcoholic extract of roots and seeds was prepared in normal saline and a single dose (100 mg/kg) was administered intraperitoneally to 20–25 g mice to test their swimming performance in water at 28′–30′ C. The experiment showed a promising result; the swimming rate was almost double that of the control [70].
Research conducted at University of Texas Health Science Center showed that Withania somnifera extract slows down the brain by reducing neuron excitability and inhibiting nerve transmission, closely related to the primary inhibitor Gama-Aminobutyric acid (a neurotransmitter) [71].
Glycowithanolides of Withania somnifera, sitoindoside IX and sitoindoside X at a concentration of 50–200 mg/kg, and glycosides (sitoindosides VII and VIII) at a concentration of 50–200 mg/kg orally, showed significant anti-stress activity in albino mice and rats and resulted in increased memory retention [8].
Double-blind, placebo-controlled studies were performed to determine the anti-stress activity of W. somnifera in human trials. Sixty adults were randomly assigned to take 240 mg of a standardized ashwagandha extract (Shoden) once daily. The results were measured using the Depression, Anxiety, Stress Scale-21 (DASS-21), hormonal changes in cortisol, dehydroepiandrosterone-sulphate (DHEA-S), the Hamilton Anxiety Rating Scale (HAM-A), and testosterone levels. It was found that ashwagandha extract was associated with greater reductions than placebo for mean mHAM-A score, morning cortisol C-reactive protein, pulse rate, and blood pressure, and increased significantly for mean serum DHEAS and hemoglobin [72,73,74].
Studies suggest that the stress-relieving property of ashwagandha is due to modulation of the HPA axis. The HPA axis is an important hormonal response system which controls stress. This axis ensures that the body quickly responds to nerve-racking moments and returns to a normal state.
The alkaloids present in the plant have relaxant and antispasmodic effects against many spasmogens in uterine, intestinal, bronchial, tracheal, and blood vascular muscles. For example, Ashwagandholine exerts relaxant and antispasmodic effects [75].
W. somnifera possesses anti-inflammatory properties in both acute and chronic types of inflammation. Cultures of cartilage from patients with osteoarthritis and rheumatoid arthritis have been used to demonstrate its protective effects on chondroblasts [76]. Related effects on cytokines, transcription factors, and the suppression of nitric oxide (NO) have also been observed [77]. A decoction of root and leaf extracts containing alkaloids and withanolides proved effective against the denaturation of protein in vitro. Additionally, anti-inflammatory properties have been described for constituents such as withaferin A and 3-b-hydroxy-2,3-dihydrowithanolide F [78]. Thus, W. somnifera also exerts anti-arthritis effects and is used to treat osteoarthritis. It may be taken together with other supplements such as Articulin-F. This also works as an analgesic and helps to soothe the nerve system from pain.
W. somnifera has anti-microbial components in leaves and roots [79], which are effective against human pathogenic bacteria, fungi, and viruses [80,81]. The leaves of W. somnifera have anti-bacterial properties, and are effective against bacteria such as Pseudomonas aeruginosa and Staphylococcus aureus. Its antibacterial phytochemicals identified so far include withaferin A and 3-b-hydroxy-2,3-dihydrowithanolide F. The plant contains many alkaloids and other polar compounds with anti-bacterial activities which activate the immune system of the host [82]. Withaferin A inhibits the growth of various bacteria and pathogenic fungi; it is also active against Micrococcus pyogenes, partially active against Bacillus subtilis, and inhibits Ranikhet disease, vaccinia virus, and Entamoeba histolytica [43]. W. somnifera helps to provide protection against systemic Aspergillus infection by activating the macrophage function, which increases phagocytosis and the intracellular killing of peritoneal macrophages [83], while W. somnifera shows anti-fungal activity against Helminthosporium sativum [84]. Some glycoproteins derived from W. Somnifera inhibit the growth of phytopathogenic fungi (Aspergillus flavus and Fusarium verticilloides) by prohibiting their spore formation and the growth of hyphae [79]. Withaferin A has been found to inhibit infectious bursal disease virus [85], herpes simplex virus [86], HIV infection [87], and coronavirus [19].
Phytochemicals from W. somnifera have insecticidal activities and can protect from many insects such as Callosobruchus chinensis, Sitophilus oryzae, Triboliumcastaeneum [88,89], and Spodoptera litura, mosquito vectors such as Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus [90], and termites [91]. They also show herbicidal activity against the noxious weed Parthenium hysterophorus.
W. somnifera acts as an anti-diabetic, reducing blood sugar and cholesterol levels [29]. It decreases streptozocin, which is particularly toxic to insulin-producing beta cells of the pancreas and induces hyperglycemia. The anti-diabetic effect of the plant may arise from pancreatic islet free radical scavenging activity. The hyperglycemic activity of streptozocin results from reduced pancreatic islet cell superoxide dismutase (SOD) activity, which leads to the accumulation of degenerative oxidative free radicals in islet beta cells [92].
Histopathological studies confirm that the alcoholic extract of W. somnifera leaves inhibits CCl4-induced alterations in transaminase activity and pentobarbitone sleeping time, indicating hepatoprotective properties [93]. This also inhibits ochratoxin A, which causes liver inflammation and suppresses macrophage chemotaxis [83].
Various studies have demonstrated the anticarcinogenic effects of W. somnifera secondary metabolites in animals and cell cultures, especially withaferin A and withanone [94]. Due to a broad spectrum of cytotoxic and tumor-sensitizing actions, the plant has potential applications in novel complementary therapies for integrative oncology. Effects against the HL-60 leukemia cell line, myeloid leukemia, and bladder, breast [95], prostate, colon, kidney, gastric, and lung cancer, have been described [96]. The mechanisms of W. somnifera-derived anticarcinogenic activity include antiproliferative effects [97], apoptosis [98], radio-sensitization, mitotic arrest, antiangiogenics, and the enhancement of cell defense mechanisms [99]. Leaf extracts have been used for the selective killing of cancer cells. Withaferin A is more effective than doxorubicin in inhibiting breast and colon cancer cell growth [58]. Due to these functions, W. somnifera bioactive agents have the potential to fight cancer by reducing tumor cells [100,101]. W. somnifera displays activity against urethane-induced lung tumors in mice and radio-sensitizing actions. Withaferin A, 3-hydroxy-2,3-dihydrowithanolide F, and withanolides D and E all showed anti-tumor activity in vitro against human epidermoid nasopharynx carcinoma and in vivo against Ehrlich ascites carcinoma, sarcoma, and mammary adenocarcinoma. They also acted as mitotic poison against human larynx carcinoma cells at the metaphase. The effect of Withaferin A also increased with the help of Methyl-thiodeacetyl colchicine. W. somnifera has many phytochemicals with unsaturated lactones in the side chain attached to the allelic primary alcohol group at C25 and highly oxygenated rings at the other end of the molecule, which may afford them cariostatic properties [43]. This also helps to reverse the harmful effects of urethane on lymphocytes, improve the leukocyte count, increase body weight, and reduce mortality [70]. Fibroid tumors of the uterus are also treated and help to reduce uterine bleeding [102].
Withania somnifera exhibits anticancerous property due to its phytochemicals (Withanolide and withaferin). Withanolide suppresses the inducible and constitutive expression of the “NF-kappa B” signaling pathway involved in extensive cancer development [103]. In addition, Withaferin induces apoptosis in tumor cells and prevents their spreading [104].
W. somnifera helps to purify blood. It is used to treat heart weaknesses and blood disorders [29]. The effects of digoxin (a drug used to treat irregular heartbeat and heart failure) are similar to this plant. W. somnifera helps to reduce blood pressure by blocking the action of autonomic ganglia and exerting myocardial depressant, as well as positive inotropic and chronotropic effects [70]. W. somnifera also exhibits hypercholesteremic, hypolipidemic, and anti-atherogenic activities. It works against atherogenesis and vascular intimal damage. It inhibits lipid peroxidation, platelet aggregation, delays the plasma re-calcification time, and improves the release of the lipoprotein lipase enzyme. It reduces body weight and increases high-density lipoprotein cholesterol levels [105]. The root powder has anti-aging effects, as it increases red blood cells and hair melanin, and decreases serum cholesterol [58,71,78].
If You’re Not Growing Ashwagandha In Your Garden You Need To Watch This!!
FAQ
Is ashwagandha self-pollinating?
Does ashwagandha need cold stratification?
What is the root yield of ashwagandha?
How many days does it take for ashwagandha plant to grow?
How to grow ashwagandha?
This comprehensive guide will provide you with all the information you need to grow ashwagandha successfully. The first stage of ashwagandha growth is germination. This stage begins when the seed is planted and ends when the seedling emerges from the soil. Ashwagandha seeds are small and should be planted about ¼ inch deep in moist soil.
What is the flowering stage of ashwagandha?
The flowering stage begins when the plant starts producing flowers and ends when the flowers start to turn into fruits. Ashwagandha plants produce small green or yellow flowers that are about ¼ inch in size. During this stage, it’s important to continue providing your ashwagandha plant with plenty of light and water.
Do you need ashwagandha seeds before planting?
Before planting, you need to purchase high-quality ashwagandha seeds or seedlings. It’s crucial to buy only from reputable seed companies to ensure maximum germination and healthy seedlings. When buying seedlings, make sure they are at least four to six inches tall, green, healthy, and free of any signs of pests or diseases.
Does ashwagandha need a lot of water?
Ashwagandha does not require excessive water and prefers dry conditions over wet. Water the plants deeply but infrequently, allowing the soil to dry out between watering sessions. This approach encourages deeper root growth, which is beneficial for the plant’s overall health and resilience.