Withania somnifera root extracts induce skin darkening in wall lizard melanophores via stimulation of cholinergic receptors.

The effects of the root extract of Withania somnifera and its active ingredient Withaferin A on the isolated melanophores of the wall lizard H. flaviviridis were studied in order to establish the mechanism of skin darkening at the cellular level. Significant skin darkening activity of the extract of W. somnifera and Withaferin A was observed on the isolated melanophores of the wall lizard. The melanin dispersal effects leading to the darkening of the skin were antagonised by atropine and hyoscine, and were also found to be highly potentiated by neostigmine. These findings suggest that the extract of W. somnifera, as well as its active principle, mimic the action of acetylcholine in melanin dispersion, thus leading to skin darkening via stimulation of cholinergic receptors of muscarinic nature within the melanophores of the wall lizard.