Qual a influência do ambiente urbano nas plantas medicinais?

Abstract

The population widely uses medicinal plants to treat various diseases. The susceptibility of plants to specific environmental conditions is variable, raising many questions about medicinal plants' behavior when grown in an urban environment. Most people in the urban environment obtain medicinal plants through their own cultivation. Thus, this work aimed to detect possible changes induced by exposure to the urban environment in medicinal plants grown in two sites in the city of Rio de Janeiro, the forest site, located close to the largest urban forest on the planet and the urban site, located in the central metropolitan area, on the edge of the busiest avenue in the municipality. Three species widely used in folk medicine, Eugenia uniflora L., Lippia alba (Mill.) N.E.Br. ex Britton &P.Wilson and Plectranthus barbatus Andr. had their leaves investigated.This study presents integrated analyzes of environmental conditions, physiology, anatomy, and phytochemistry, in addition to cytotoxicity experiments.The results obtained with the soil analysis showed a similar chemical profile, in which the concentrations of Calcium (Ca), Sulfur (S), and Lead (Pb) were higher in the urban site. Among the chemical elements analyzed in the specimens of E. uniflora, Pb stands out, as it was detected in the leaves of the urban site in the limit concentration allowed by the WHO.E. uniflora leaves from the urban site revealed necrosis and reddish spots, greater stomatal density, smaller stomata, and a greater number of crystals and secretory glands, in addition to evident storage of starch, lipids, and mucilage. Although the chemical difference between the extracts produced from the leaves of E. uniflora, grown in the two study sites, is not expressive, significant differences were observed regarding VERO cells' viability submitted to their extracts. Regarding the external structure of L. alba and P. barbatus, the results revealed differences in the density of stomata, trichomes, and glandular trichomes.Regarding histology, the parameters measured for the leaf blade of P. barbatus showed that the dimension of the palisade parenchyma increased statistically in the urban site. In the leaves of L. alba from the urban site, the chlorophyll parenchymatic tissues were less developed and compacted. The alterations analyzed, such as the increase in frequency and decrease in the size of stomata and the higher frequency of secretory glands, crystals, trichomes, and glandular trichomes, may have contributed to the acclimatization of these species to the urban condition, being characteristics with possible uses for urban biomonitoring. The results highlight variations in the leaf morphoanatomical properties and in the chemical and cytotoxic characteristics of preparations made from medicinal plants developed in an urban environment, which allows us to conclude that the environmental factors of this place are sufficient to promote variations in the structural and metabolic characteristics of the organisms.