Withania somnifera

Withania somnifera, known commonly as ashwagandha is an evergreen shrub in the Solanaceae or nightshade family that grows in India, the Middle East, and parts of Africa. Several other species in the genus Withania are morphologically similar.

The plant, particularly its root powder, has been used for centuries in traditional Indian medicine. Ashwagandha supplements, typically containing root or leaf powder or extracts, are commonly sold. Its use in herbal medicine and dietary supplements notwithstanding, there is insufficient scientific evidence that W. somnifera is safe or effective for treating any health condition or disease.

Description

This species is a short 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 (3.9–4.7 in) long. The flowers are small, green and bell-shaped. The ripe fruit is orange-red.

Etymology

The Latin species name somnifera means 'sleep-inducing'. 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

W. somnifera is cultivated in many of the drier regions of India. It is also found in Nepal, Sri Lanka, China, and Yemen. It prefers dry stony soil with sun to partial shade. It can be propagated from seeds 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. Leaf spot disease reduces the concentration of its secondary metabolites. The leaves are also prone to Alternaria dianthicola in India.

A treehopper (Oxyrachis tarandus) feeds on the apical portions of the stem, making them rough and woody in appearance and brown in colour.

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 of W. somnifera are withanolides, a group of triterpene lactones that include withaferin A, alkaloids, steroidal lactones, tropine, and cuscohygrine. Forty withanolides, twelve alkaloids, and various sitoindosides have been isolated from this plant species. Because these withanolides are structurally similar to the ginsenosides of Panax ginseng, W. somnifera is commonly referred to as "Indian ginseng".

Research

Limited, low-quality clinical studies have found that supplementation with various ashwagandha extracts may decrease perceived stress and anxiety, and improve sleep. Because the studies used different extract preparations, durations of use, doses, and types of subjects, it remains undetermined how ashwagandha may have effects in people, as of 2023.

Adverse effects

W. somnifera may cause adverse effects if taken alone or together with prescription drugs. A review of 30 clinical trials found that use of W. somnifera may cause problems with sleep, blurred vision, stomach pain, dry mouth, vertigo, among others. The most common side effects include diarrhea, headache, sedation, or nausea, and the product should not be used during pregnancy or breastfeeding. Ashwagandha may increase testosterone levels which could adversely interact with cancer medications.

Gallery

References

External links

• Media related to Withania somnifera at Wikimedia Commons