AlkaloidsA very mixed group, alkaloids mostly contain a nitrogen-bearing molecule (-NH2) that makes them particularly pharmacologically active. Some are well-known drugs and have a recognized medical use. Vincristine, for example, derived from Madagascar periwinkle (Vinca rosea, p. 282), is used to treat some types of cancer.Other alkaloids, such as atropine, found in deadly nightshade (Atropa belladonna, p. 69), have a direct effect on the body, reducing spasms, relieving pain and drying up bodily secretions.