The pharmacological actions of Withania somnifera.
|Publication:||Name: Australian Journal of Medical Herbalism Publisher: National Herbalists Association of Australia Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2006 National Herbalists Association of Australia ISSN: 1033-8330|
|Issue:||Date: Winter, 2006 Source Volume: 18 Source Issue: 4|
|Topic:||Event Code: 310 Science & research|
|Geographic:||Geographic Scope: Australia Geographic Code: 8AUST Australia|
Withania somnifera is a valuable herb used in traditional Ayurvedic
medicine and is often taken for its nervous sedative, hypnotic, tonic,
astringent and aphrodisiac properties (Matsuda 2000). The common name of
W. somnifera is ashwagandha or Indian ginseng and it has a long history
of safe usage in all age groups, both sexes and during pregnancy. It is
an official drug mentioned in the Indian Pharmacopoeia of 1985.
W. somnifera has been gaining acceptance and increasing use in western herbal medicine mostly for its role as an adaptogenic herb valuable for combating stress and nervous exhaustion. Eight different studies have been chosen here from the last six years that have attempted to prove the effect of different chemical constituents of the plant. The studies have indicated W. somnifera for a vast array of pathological states, with its actions focused on adaptogenic and tonic activity, anti-inflammatory activity, central nervous system activity, antitumour or chemoprotective activity as well as antimicrobial activity.
The main active constituents in W. somnifeia used for testing purposes are the steroidal lactones or withanolides including withaferin A, sitoindoside IX, X and acylsterol glucosides (including sitoindosides VII and VIII). The plant contains alkaloids including tropine, pseudotropine, isopelletierine and anaferine (Dhuley 1997). W. somnifera is said to be rich in iron (Chuley 1997).
Adaptogenic and tonic activity
A study done on rats showed that W. somnifera increased the swimming time in a physical working capacity test (Dhuley 1999). It was noticed in this study that there was a relative increase in heart weight and in glycogen content in the myocardium. In this study they used 100 mg/kg of body weight of the root extract. They believe that a variety of the withanolides are responsible for this activity and that it works by activating the mitochondrial processes and therefore intracellular energy metabolism.
Another study showed that the root extract of W. somnifera showed anabolic activity in young rats. Weight gain for the W. somnifera treated rats was 227% compared to 157% for the control group. The same rats were observed during pregnancy and the study showed that the body weight of the offspring was 70 g for the W. somnifera treated rats and 45 g for the control group. They believe this was due to the steroidal lactones and their 'steroid-like' activity (Singh 2001).
Central nervous system activity
The sitoindosides VII-X and withaferin were tested to prove their effect on improving short term memory in mice. The test was done using electric shock therapy, treatment with scopolamine (an anticholinergic agent that produces deficits in learning and memory retention) as well as testing mice that had never been on the electric grid before. The mice treated with W. somnifera produced a decrease in the amount of errors while trying to reach the shock free zone after 1hr of training. The effect of W. somnifera on the scopolamine treated mice reversed the deficits in retrieval and acquisition. This study showed an effectiveness of W. somnifera in improving short term memory in both naive and amnesiac mice. The dosage used in this study was important as 50-100 mg/kg did not produce any effect. Dosage of 200 mg/kg of body weight produced significant effect (Dhuley 2002).
The glycowithanolides were extracted in another study to investigate the effects on their anxiolytic and antidepressive actions. The rats were given an anxiogenic agent or were forced to swim to induce 'behavioural despair' and 'learned helplessness'. Control groups were given anxiolitic and antidepressant drugs for this comparative study. The results showed that W. somnifera had the same effects as the drugs in reducing the anxiety markers as well as the same effects in reducing depression (Rege 1999).
Antioxidant, anticancer and chemoprotective activity
A study was done to investigate the antioxidant properties of W. somnifera. The rabbits and mice were given bacteria that caused lipid peroxidation (LPO) due to the effect of the endotoxins from the bacteria which commonly cause free radical damage. The LPO levels were tested. The study concluded that W. somnifera reduced LPO levels by free radical scavenging. This free radical scavenging effect can be evaluated by its effect on the enzymes involved in the metabolism of arachadonic acid and its ability to inhibit the enzymes in the glutathione system (endogenous antioxidant). W. somnifera inhibited LPO through free radical scavenging without modifying the glutathione system. The authors believe this effect is due to the steroidal lactones and withanolides within the plant (Dhuley 1997).
A further study investigated the chemoprotective properties of W. somnifera on induced skin cancers in mice. A dose of 400 mg/kg was given before and during the cancer induction. The mice treated with W. somnifera showed a significant decrease in the incidence and average number of skin lesions. Endogenous antioxidant systems were assessed in the skin cancer control group and it was found that the levels were reduced. After administration of W. somnifera these antioxidant systems were returned to near normal.
They believe these effects are due to the antioxidant effects of the glycowithanolides as well as the anti-inflammatory effects of the withaferin A (Prakash 2002).
Administration of withaferin A to rats with induced arthritis showed that the W. somnifera had a similar structure and function to glucocorticoids suggesting that W. somnifera has a complex influence on inflammation and immune response (Davis 2000).
Withaferin A is believed to cause an antiinflammatory effect on granuloma tissue in rats. It was shown that the action of W. somnifera was comparable to that of hydrocortisone treatment.
This study states that a liver synthesised plasma protein called alpha-2-macroglobulin greatly increases during the inflammatory process. W. somnifera was found more effective at decreasing this protein during inflammation than standard antiinflammatory drugs (Bhattacharya 2000).
Two new withanolides were found in a study done to test the antimicrobial effect of W. somnifera.
These were 4-deoxywithaperuvin (withanolide 1) and 17beta-dihydroxywithanolide (withanolide 2).
They were tested against many different kinds of bacteria, viruses and fungi. They were found to be effective against some bacteria particularly Bacillus cereus, Streptomyces spp. and Pseudomonas flourescens. There was a complete or partially complete inhibitory action on the fungi Aspergillus fumigatus, A. terreus, Penicillum funiculosum and P. waksmani (Ahmad 2002).
There are many good scientific studies to show the actions of the plant W. somnifera. The studies show that this plant is very diverse in its effects and can be used for a wide range of debilities and diseases as well as having a protective effect. Some of the research clearly demonstrated the active constituents that caused the actions, whereas some studies seemed to only give a general idea of which constituents might be causing the action.
More research needs to be done to discover which active constituents are involved with the plant's many actions.
Ahmad M. 2002. New withanolides and other constituents from the fruit of Withania somnifera. Pharmacol Med Chem 6;267-76.
Bhattacharya SK, Bhattacharya A, Sairam K, Ghosal S. 2000. Anxiolytic antidepressant activity of Withania somnifera glycowithanolides: an experimental study. Phytomed 7:6;463-9.
Davis L, Kuttan G. 2000. Immunomodulatory activity of Withania somnifera. J Ethnopharmacol 71:1-2;193-200.
Dhuley J. 1997. Effect of ashwaganda on lipid peroxidation in stress induced animals. J Ethnopharmacol 60; 173-8.
Dhuley J. 1999. Adaptogenic and cardioprotective action of ashwaganda in rats and frogs. J Ethnopharmacol 70;57-63.
Dhuley J. 2002. Nootropic-like effect of ashwaganda (Withania somnifera) in mice. Phytother Res 15:524-528.
Matsuda H, Murakami T, Kishi A, Yoshikawa M. 2000. Structure of withanosides I,II,III,IV,V,VI and VII. New withanolide glycosides from the roots of Indian Withania somnifera Dunal. BioOrganic & Med Chem 9;1499-1507.
Prakash J, Gupta S, Dinda A. 2002. Withania somnifera root extract prevents DMBA- induced squamous cell carcinoma of skin in Swiss albino mice. Nut & Cancer 42:1;91-7.
Rege NN, Tharteum M, Pahanukar SA. 1999. Adaptogenic properties of six rasayana herbs used in Ayurvedic medicine. Phytother Res 13:4;275-91.
Singh B, Saxena A, Chandon BK, Gupla DK, Bhutanikk K, Anand KK. 2001. Adaptogenic activity of a novel withanolide free aqueous fraction from the roots of Withania somnifera. Phytother Res 15:4;311-8.
Andrea is in her final year of studies at Nature Care College in Sydney and is nearing completion of her Bachelor of Health Science. Andrea is originally from Canada and has recently become a citizen of Australia.
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