Scientific Basis for the Therapeutic Use of Withania somnifera : A Review - Ashwagandha

Alternative Medicine Review, August, 2000 by Lakshmi-Chandra Mishra, Betsy B. Singh, Simon Dagenais

Abstract

OBJECTIVE: The objective of this paper is to review the literature regarding Withania somnifera (ashwagandha, WS) a commonly used herb in Ayurvedic medicine. Specifically, the literature was reviewed for articles pertaining to chemical properties, therapeutic benefits, and toxicity. DESIGN: This review is in a narrative format and consists of all publications relevant to ashwagandha that were identified by the authors through a systematic search of major computerized medical databases; no statistical pooling of results or evaluation of the quality of the studies was performed due to the widely different methods employed by each study. RESULTS: Studies indicate ashwagandha possesses anti-inflammatory, antitumor, antistress, antioxidant, immunomodulatory, hemopoetic, and rejuvenating properties. It also appears to exert a positive influence on the endocrine, cardiopulmonary, and central nervous systems. The mechanisms of action for these properties are not fully understood. Toxicity studies reveal that ashwagandha appears to be a safe compound. CONCLUSION: Preliminary studies have found various constituents of ashwagandha exhibit a variety of therapeutic effects with little or no associated toxicity. These results are very encouraging and indicate this herb should be studied more extensively to confirm these results and reveal other potential therapeutic effects. Clinical trials using ashwagandha for a variety of conditions should also be conducted.

(Altern Med Rev 2000;5(4) 334-346)

Introduction

Withania somnifera Dunal (ashwagandha, WS) is widely used in Ayurvedic medicine, the traditional medical system of India. It is an ingredient in many formulations prescribed for a variety of musculoskeletal conditions (e.g., arthritis, rheumatism), and as a general tonic to increase energy, improve overall health and longevity, and prevent disease in athletes, the elderly, and during pregnancy.[1,2] Many pharmacological studies have been conducted to investigate the properties of ashwagandha in an attempt to authenticate its use as a multi-purpose medicinal agent. For example, anti-inflammatory properties have been investigated to validate its use in inflammatory arthritis,[3-6] and animal stress studies have been performed to investigate its use as an antistress agent.[7-10] Several studies have examined the antitumor and radiosensitizing effect of WS.[11-15] The purpose of this paper is to review the literature regarding WS and report on clinically relevant studies, in an attempt to establish a scientific basis for the therapeutic use of WS. Results of studies investigating the chemistry and toxicity of WS will also be

discussed.

Methods

This literature review was limited to published articles and books in the English language. Four computerized medical databases (MEDLINE, CINAHL, EMBASE, Mantis) were searched for the entire duration of each database as available on the OVID computer search service. The following keywords were used for the search: ashwagandha and common misspellings (ashwaganda, aswaganda, aswagandha), withania, somnifera, dunal, withaferin, sitoindoside, solanaceae, Indian ginseng, and winter cherry. Results of these searches were reviewed to identify relevant articles.

Results

A total of 58 articles were found using the search method described above. Research reveals ashwagandha possesses anti-inflammatory, antitumor, antistress, antioxidant, immunomodulatory, hemopoetic, and rejuvenating properties. Ashwagandha also appears to benefit the endocrine, cardiopulmonary, and central nervous systems. Few articles were discovered on the mechanism of action for these effects. Several preliminary studies have been conducted on animals. A summary of the findings of these studies is presented below.

Chemistry

Since many of ashwagandha's uses have not been scientifically validated, skepticism can naturally be expected when presented with an herb purportedly useful in so many ailments. In Ayurvedic medicine there is a class of herbs, including WS, known as adaptogens or vitalizers. Adaptogens cause adaptive reactions to disease, are useful in many unrelated illnesses, and appear to produce a state of nonspecific increased resistance (SNIR)[10,16] to adverse effects of physical, chemical, and biological agents. They are relatively innocuous, have no known specific mechanism of action, normalize pathological effects, and are usually glycosides or alkaloids of a plant.[17,18]

The chemistry of WS has been extensively studied and over 35 chemical constituents have been identified, extracted, and isolated.[19] The biologically active chemical constituents are alkaloids (isopelletierine, anaferine), steroidal lactones (withanolides, withaferins), saponins containing an additional acyl group (sitoindoside VII and VIII), and withanolides with a glucose at carbon 27 (sitoindoside IX and X). WS is also rich in iron. See Figure 1 for the chemical structure of withaferin A, and Figure 2 for sitoindosides IX and X.

[Figures 1-2 ILLUSTRATION OMITTED]