Strychnine, C21H22N2O2, is a poisonous alkaloid drug named for a genus of tropical trees and shrubs of the order Loganiacae. The most notable species is Strychnos nux-vomica, so called from the name nux vomica, given to its seeds, the source of strychnine. The seeds contain 2–5% strychnine plus some brucine. From various species of Strychnos are obtained the clearing nut, the curari, and Ignatius beans; while one kind of upas poison (Upas tieute) is made from a species of Strychnos.
Strychnine occurs in crystals, has an intensely bitter taste, is colorless and odorless, and is virtually insoluble in water, but easily soluble in ethanol, ether, and chloroform. In concentrated sulfuric acid it forms a colorless solution, which, on the addition of potassium dichromate, turns first violet in color before quickly changing through red to yellow. In nitric acid it turns, if pure, to form a colorless solution; however, if brucine is also present, it turns reddish.
Strychnine and brucine occur not only in S. nux-vomica, but in the seeds of S. amara (Ignatius beans) and in the seeds and other parts of several plants of the genus Strychnos. Nux vomica and its alkaloids are very poisonous to all kinds of animals.