belladonna alkaloid
any substance obtained from the shrub Atropa belladonna (commonly known as belladonna or deadly nightshade). Such substances were known to the ancient Hindus and were used in the Middle Ages as poisons (the genus is named for Atropos, eldest of the mythological Fates, who cuts the thread of life). Their pharmacology was unknown until the 1860s, when they were found to affect heart rate, salivary secretion, and other body functions. Atropine and scopolamine are the best known examples.