Prediction of pilocarpine production from soil attributes and the nutritional status of Pilocarpus microphyllus

Abstract

Jaborandi (Pilocarpus microphyllus), an endemic species of the Brazilian flora threatened with extinction, is the only natural source of pilocarpine, an alkaloid widely used in the pharmaceutical industry. This compound is extracted from the leaf tissue and may be affected by edaphic and nutritional variations. The aim of this study was to correlate soil chemical parameters and leaf nutrient contents with pilocarpine production in Pilocarpus microphyllus plants collected from areas of the Carajás National Forest. In samples collected from 83 plants, pilocarpine, leaf nutrients (N, P, K, S, Mg, Ca, B, Zn, Cu, Fe, and Mn), and soil chemical attributes (P, K, S, Mg, Ca, B, Zn, Cu, Fe, Mn, organic matter, pH, and Al) were evaluated. The mean values of pilocarpine varied between 0.4% and 2.2% of the leaf dry matter, which are rare. In general, the soils presented low nutrient availability, marked acidity, and very high Fe and Mn values. In the leaves, low concentrations of N, P, and K and high leaf concentrations of Fe (2239.13 mg kg−1) and Mn (2095.46 mg kg−1) were observed, which suggested that P. microphyllus is a metal accumulator species. Through multivariate analysis, the model that best predicted pilocarpine production was composed of leaf N, leaf Mg, soil Fe (positive predictors), soil S, and leaf P (negative predictors). The nutritional management for large-scale cultivation of P. microphyllus should be focused mainly on the amounts of N, Fe, and Mg.