Withania somnifera: From Traditional Use to Evidence Based Medicinal Prominence

Withania somnifera is wonder shrub used traditionally as a folk medicine for several remedies in the Indian subcontinent. During last few decades numerous scientific studies have shown the potential therapeutic prospects of this herb and of its various constituents in different disease models. Several classes of compounds including withanolides, sitoindosides and other useful alkaloids have been isolated from this plant with promising medicinal value. It has been demonstrated that different parts of plant including roots, leaves and fruits exhibit unique biological activities that actually are manifested to the presence and the abundance of specific constituent/s in the respective parts of the plant. It was also established that same plant grown at different locations under varied environmental conditions influences the synthesis of the individual constituents in different parts of the plant, hence their biological activities. Studies conducted in cellular and murine models have shown that extracts made of roots bear immune activating properties, whereas leaf extracts showed anticancer activities. It has been observed that root and leaf extracts of plant characterised with about a dozen markers displayed that root extracts demonstrated Th1 specific immunomodulatory and anti-inflamatory activities, whereas leaf extracts showed anticancer properties, respectively. It was further explored that anti-cancer potential of leaf extracts was mainly due to Withaferin A, a potent cytotoxic withanoloid, existing in abundance and a major constituent in the leaves of the plant. Similarly, anti-inflammatory and Th1 immune skewing properties of the root extract was conferred to the higher amount of Withanolide A, present in the roots of the plant along with other constituents. Meanwhile several studies have deciphered the role of individual constituents in various biological activities with extensive mechanism of action discussed in this review. This review while summarises the potential medicinal benefits of the W.somnifera, it also emphasizes that marketed product of the plant extracts for human consumption should scientifically validated for bioactive constitutents.