Erythroxylum bezerrae Plowman: isolamento, caracterização e avaliação da atividade farmacológica de seus metabólitos secundários

Abstract

This work describes the chemical study of the bark of wood of the stem of Erythroxylum bezerrae, a plant endemic to the Northeast Region, aiming at the isolation and structural elucidation of new bioactive compounds. The chemical investigation carried out with E. bezerrae resulted in the isolation of 19 substances. From the ethanolic extract of the stem bark of eight compounds belonging to the class of tropane alkaloids, six of which were unpublished, called: 3α-(4-hydroxy-3,5-dimethoxybenzoiloxy)-6β-(benzoiloxy)-7β-hydroxy-tropane (EB-1), 3α-(3,4,5-trimethoxybenzoiloxy)-6β-(benzoiloxy)-7β-hydroxy-tropane (EB-2), 3α-(3,4,5-trimethoxycinnamoiloxy)-6β-(3,4,5-trimethoxybenzoiloxy)-tropane (EB-3), 6β-(benzoiloxy)-7β-(3,4,5-trimethoxybenzoiloxy)-3α-hydroxy-tropane (EB-4), 6β-(benzoiloxy)-7β-(4-hydroxy-3,5-dimethoxybenzoiloxy)-3α-hydroxy-tropane (EB-5) and 3α-(3,4,5-trimethoxycinamoiloxy)-6β-(4-hydroxy-3,5-dimethoxibenzoiloxy)-7β-hydroxy-tropane (EB-6). In addition to these, two known alkaloids were isolated: 3α-(3,4,5-trimethoxycinnamoiloxy)-6β-(3,4,5-trimethoxybenzoiloxy)-7β-hydroxy-tropane (EB-7) e 3α-(3,4,5-trimethoxycinnamoiloxy)-6β-(benzoiloxy)-7β-hydroxy-tropane (EB-8). From the hexane extract of the wood of the stem, 11 diterpenes were isolated, of which ten are kauranes and one labdane. Chromatographic techniques were used to isolate the substances, including column chromatography on silica gel, solid phase extraction (SPE-C18) and high-performance liquid chromatography (HPLC). The structural determination of the isolated compounds was performed using spectroscopic techniques such as hydrogen and carbon nuclear magnetic resonance (1H and 13C NMR), one- and two-dimensional, mass spectrometry (MS), single crystal X-ray diffraction analysis and, still, comparison with data recorded in the literature. The isolated alkaloids were submitted to cytotoxic activity tests against the strains L929 (Murine Fibroblast), PC-3 (Prostate), HCT-116 (colon carcinoma), SNB-19 (Nervous System) and NCIH-460 (Lung), however, only compounds EB-5 and EB-6 were considered active, with IC50 values ranging from 10.55-13.89 µM and 3.38-15.02 µM, respectively. Additionally, a test was performed for anti-inflammatory activity of diterpene compounds and cytotoxicity on RAW 264.7 murine macrophage cells. The evaluation of cell viability showed IC50 values for EB9-EB19 ranging from 70.57-346.3, with EB-9, EB-10 and EB-16 being the samples with the lowest cytotoxicity and with the greatest ability to inhibit the production of nitric oxide (NO), 3.21 ± 0.23, 3.76 ± 0.21 and 3.56 ± 0.32 µM, respectively.