Medicinal plants have been used for many years and are the source of new active substances and new drugs of pharmaceutical interest. The popular knowledge contained in the open-air markets is studied through urban ethnobotany, and is a good source of information for ethnobotanical research. In this context, we surveyed the literature on works concerning open-air markets in the State of Rio de Janeiro to gather knowledge of the commercialized plants therein. A literature search resulted in ten studies with 376 listed species, distributed in 94 families and 273 genera. Asteraceae family had the greater representation, followed by Lamiaceae and Fabaceae. Solanum was the most frequent genus. Two hundred and twenty four species could be considered potentially toxic or potentially interact with other drugs/medicines. Eighteen species are referred as "not for use during pregnancy", and 3 "not for use while nursing". These results are a source of concern since in Brazil, as it is worldwide, there is the notion that plants can never be harmful. The results for the Sørensen Coefficient showed greater similarity between works performed in very close study areas. Other studies presented low similarity, mainly because of the difficulty in plant identification or a very specific focus in methodology.

O principal objetivo desse trabalho foi estudar as plantas úteis comercializadas em feiras livres em Petrópolis e Nova Friburgo, Rio de Janeiro, Brasil. Os dados foram coletados utilizando as técnicas de observação participante, entrevistas semi-estruturadas e listagem livre com quatro comerciantes de plantas medicinais. A partir dessas entrevistas, 115 espécies (pertencentes a 49 famílias) foram relacionadas: 94 com uso medicinal, 12 com uso religioso e 9 com uso ornamental. Trinta por cento das espécies são nativas e 72% possuem hábito herbáceo. As famílias mais representativas foram Asteraceae (26 espécies) e Lamiaceae (10 espécies). As espécies medicinais indicadas para o tratamento de doenças do sistema respiratório foram mais freqüentes durante o outono e inverno. A espécie denominada como Espinheira-santa (Clarisia cf. ilicifolia) obteve o valor mais alto de Importância Relativa (1,8) e a mais alta colocação em todas as estações do ano utilizando o cálculo Preference Ranking, embora seus níveis de eficiência e toxidez não tenham sido ainda estabelecidos. O estudo se mostrou relevante, pois visa reunir o conhecimento dos informantes sobre as espécies que comercializam em feiras livres e mercados populares no estado do Rio de Janeiro, que representa uma valiosa fonte para a bioprospecção.

The main goal of this paper was the study of the useful plants sold in the open-air fairs of Petrópolis and Nova Friburgo, Rio de Janeiro, Brazil. Data collection was obtained through participant observation, semi structured interviews and free listing with four herbalist informants. From the interviews, 115 species (belonging to 49 families) were recorded: 94 for medicinal purposes, 12 with religious application, and 9 for ornamental purposes. Thirty percent of the species were native, and 72% herbaceous. The most representative families were Asteraceae (26 species) and Lamiaceae (10 species). The medicinal species related to diseases of the respiratory system were more common during the winter and autumn. "Espinheira-santa" (Clarisia cf. ilicifolia) had the highest Relative Importance (1.8) and collocation in all seasons using the Preference Ranking, although its effectiveness or toxicity levels have not been established. The importance of the study is to gather knowledge from local herbalists about commercialized species in open-air fairs and popular markets in the Rio de Janeiro State, which represent valuable resources for bioprospection.