Prestonia is a genus of plants in the dogbane family Apocynaceae. First described as a genus in 1810, it currently includes 63 species of lianas. They are native to Mexico, Central America, South America, and the West Indies. Their flowers are tube or funnel shaped and have 5 petals, often with noticeable coronas. Prestonia amazonica, which is often named as a hallucinogenic plant, belongs to this genus.
Prestonia is a genus of lianas, a type of woody vine. Their leaves lack glands and have colleters that are arranged oppositely along the stem. As with many in Apocynaceae, their stems contain a latex that ranges from watery to milky. Their flowers occur in cymes that are usually axillary (occurring between the stem and the leaf) but are sometimes terminal (occurring at the ends of branches). They range from tube-shaped to funnel-shaped with usually 5 free coronal lobes and a characteristic annular corona. A single colleter is located at the inner base of their 5 sepals. Their petals range in color from cream to yellow-green, sometimes with red or purple inclusions. They have nectaries located annularly alongside their , gynoecium. The fruit is a follicle that is usually smooth but is winged in some species. The seeds have tufts of hair and are in shape.
Species in Prestonia can be found in the neotropics of Mexico, Central America, South America, and the West Indies. They extend as far north as northeast Mexico and as far south as northern Argentina. Colombia and Brazil have the most species with 25 and 23 known species respectively. They can be found at elevations ranging from sea level to as high as 2800m.
The genus was first described in 1810 by botanist Robert Brown who named the genus after Dr. Charles Preston. It was not until the 1930's that it got significant attention from Robert E. Woodson, who is known to have treated the most species in the genus. It is closely related to Artia and Parsonsia.
Limited evidence has shown bees to be possible pollinators of the genus.
In the montane rainforests of Ecuador, some members of Lepidoptera in Ithomiinae and Arctiinae have been found to engage in on Prestonia amabilis. They do so in order to obtain pyrrolizidine alkaloids that can be used as a chemical defense against predators and as precursor chemicals to male pheremones.
The fresh roots, stems, and leaves of Prestonia mollis are known to be used by people in southern Ecuador (Loja and Zamora-Chinchipe provinces) to disinfect, to treat wounds, and to treat cancer.
Prestonia amazonica is often named as a hallucinogenic plant however the evidence for this is contested. In the mid 1850's botanist Richard Spruce noted the species to be a possible admixture while he was studying caapi, a psychedelic drink more commonly known as ayahuasca. It was the opinion of the ethnobotanist, Richard E. Schultes, that the designation of Prestonia amazonica as a hallucinogenic plant has little evidence behind it beyond Spruce's observations. Thus far, only one chemical analysis has ever been performed on the species in the 1950's. While it found evidence of DMT, a hallucinogenic compound, the validity of the source of the sample analyzed has been called into question. No further chemical analyses have been published.
63 species are accepted.