Estudos da interação de Maytenus ilicifolia (Celastraceae) e Xanthomonas albilineans envolvidos na formação de triterpenos quinonametídeos

Quinonemethide triterpenes (QMTs), maytenin (1) and pristimerin (2) (Figure 1) show accumulation in the root bark of Maytenus ilicifolia (Celastraceae)1. These compounds show biological potential, including antimicrobial (unpublished data), antitumor and anti-inflammatory activities2. The evaluation of these metabolites against Xanthomonas albilineans, a bacterium present in the soil that infests sugarcane plantations, showed to be potentially active, being 1 (IC50 0.46 mM) twice more active than 2 (IC50 1.0 mM) and the positive control tetracycline (IC50 1.0 mM). Due to the restricted accumulation of such triterpenes in the root bark of M. ilicifolia, combined with its previous proteomic studies, which demonstrated a large number of proteins (99) involved in the response to metabolic stress, the hypothesis that QMTs 1 and 2 may have their biosynthetic pathway regulated by plant-microorganism interactions was raised. Thus, some studies of M. ilicifolia seedlings inoculated with X. albilineans were carried out to study such hypothesis. The concentrations of 1 and 2 were evaluated by high-performance liquid chromatography diode array detection (HPLC-DAD) before the infection. The concentrations of 1 and 2 in the root barks of M. ilicifolia seedlings showed variation on QMT production among three individuals. That data will set a baseline in QMT capability of production of the analyzed individuals for comparison after their inoculation with the bacteria. Expression level of genes involved in QMT production (coding for friedelin synthase and cytochrome P450) will also be analyzed before and after inoculation to evaluate the possible plant response to X. albilineans.