Relationships between Plant Folklore and Antitumor Activity: an Historical Review1

The National Cancer Institute’s (NCI) record of plants that have shown significant inhibitory effect in experimental tumor systems (active plants), 1960–1974, was compared with species and genera in references on medicinal folklore, including poisonous plants, to determine whether their percentages of active plants were significantly greater than those screened at random (10.4%). The percent active species in medicinal and/or poisonous references in general were found to be 1.4 to 2.6 times greater, while the number and different kinds of medicinal uses appear related to geographical data of species that also indicate medicinal plants were screened more thoroughly because of their widespread occurrence. The best correlation is seen with poisonous plants, including medicinal plants that suggest a moderate to strong therapeutic effect; their percentages of active species were nearly three (29.3%, anthelmintics) to four times (45.7%, arrow and homicidal poisons) greater than plants screened at random. Selection of plants based strictly on use in folk medicine would probably benefit new (start-up) screening programs, whereas in the long-term, it appears more cost effective to systematically screen the broadest diversity of plants readily available since the common medicinal species would be collected irregardless. A systematic collection strategy could give emphasis to genera that have not been exhaustively studied, especially to species with medicinal uses that indicate toxicity or are considered poisonous.