Harmala alkaloids are several alkaloids that act as monoamine oxidase inhibitors (MAOIs). These alkaloids are found in the seeds of Peganum harmala, as well as Banisteriopsis Caapi (Ayahuasca), leaves of tobacco and coffee beans. The alkaloids include harmine, harmaline, harmalol, and their derivatives, which have similar chemical structures, hence the name "harmala alkaloids". These alkaloids are of interest for their use in Amazonian shamanism, where they are derived from other plants. Harmine, once known as telepathine and banisterine, is a naturally occurring beta-carboline alkaloid that is structurally related to harmaline, and also found in the vine Banisteriopsis caapi. Tetrahydroharmine is also found in B. caapi and P. harmala. Dr. Alexander Shulgin has suggested that harmine may be a breakdown product of harmaline. Harmine and harmaline are reversible inhibitors of monoamine oxidase A (RIMAs). They can stimulate the central nervous system by inhibiting the metabolism of monoamine compounds such as serotonin and norepinephrine.

Nicotiana rustica, commonly known as Aztec tobacco or strong tobacco, is a rainforest plant in the family Solanaceae native to South America. It is a very potent variety of tobacco, containing up to nine times more nicotine than common species of Nicotiana such as Nicotiana tabacum. More specifically, N. rustica leaves have a nicotine content as high as 9%, whereas N. tabacum leaves contain about 1 to 3%. The high concentration of nicotine in its leaves makes it useful for producing pesticides, and it has a wide variety of uses specific to cultures around the world. However, N. rustica is no longer cultivated in North America, as N. tabacum has replaced it.