Withania somnifera (Ashwagandha)




Withania somnifera, known commonly as ashwagandha, Indian ginseng, poison gooseberry, or winter cherry, is a plant in the Solanaceae or nightshade family. Several other species in the genus Withania is morphologically similar. Although thought to be useful as a medicinal herb in Ayurveda and sold in many countries as a dietary supplement, it is insufficient scientific evidence that it is safe or effective for treating any disease.

Description

This species is a short, tender perennial shrub growing 35–75 cm (14–30 in) tall. Tomentose branches extend radially from a central stem. Leaves are dull green, elliptic, usually up to 10–12 cm (4 to 5 in) long. The flowers are small, green, and bell-shaped. The ripe fruit is orange-red.

Etymology

The species name somnifera means "sleep-inducing" in Latin. The name, ashwagandha, is a combination of the Sanskrit words ashva, meaning horse, and gandha, meaning smell, reflecting that the root has a strong horse-like odor.


Cultivation

Withania somnifera is cultivated in many of the drier regions of India. It is also found in Nepal, China, and Yemen. It prefers dry stony soil with the sun to partial shade. To propagate it can be grown from seed in the early spring, or from greenwood cuttings in the later spring.

Diseases and pests

Withania somnifera is prone to several pests and diseases. Leaf spot disease caused by Alternaria alternata is the most prevalent disease, which occurs in a severe form in Punjab, Haryana, and Himachal Pradesh. A decline in the concentration of its secondary metabolites occurs by leaf spot disease. A treehopper feeds on the apical portions of the stem, making them rough and woody in appearance and brown in color.

The carmine-red spider mite (Tetranychus urticae) is the most prevalent pest of the plant in India. In recent years, this plant has been serving as a new reservoir host for an invasive mealybug species Phenacoccus Solenopsis.



Phytochemistry

The main phytochemical constituents are withanolides – which are triterpene lactones – withanolides, withaferin Alkaloids, steroidal lactones, tropine, and cuscohygrine. Some 40 withanolides, 12 alkaloids, and numerous sitoindosides have been isolated. Withanolides are structurally similar to the ginsenosides of Panax ginseng, leading to a common name for W. somnifera, "Indian ginseng".

Traditional medicine

The plant, particularly its root powder, has been used for centuries in traditional Indian medicine. Mainly due to the poor quality of the clinical research, there is no high-quality evidence that it provides any medicinal benefit as a therapy or dietary supplement, and may cause adverse effects if taken together with prescription drugs.