DMT is produced in many species of plants often in conjunction with its close chemical relatives 5-methoxy-"N","N"-dimethyltryptamine (5-MeO-DMT) and bufotenin (5-OH-DMT). DMT-containing plants are commonly used in indigenous Amazonian shamanic practices. It is usually one of the main active constituents of the drink ayahuasca; however, ayahuasca is sometimes brewed with plants that do not produce DMT. It occurs as the primary psychoactive alkaloid in several plants including "Mimosa tenuiflora", "Diplopterys cabrerana", and "Psychotria viridis". DMT is found as a minor alkaloid in snuff made from Virola bark resin in which 5-MeO-DMT is the main active alkaloid. DMT is also found as a minor alkaloid in bark, pods, and beans of "Anadenanthera peregrina" and "Anadenanthera colubrina" used to make Yopo and Vilca snuff, in which bufotenin is the main active alkaloid. Psilocin and its precursor psilocybin, an active chemical in many psilocybin mushrooms, are structurally similar to DMT.