Isolamento, caracterização química e avaliação do potencial anti-leishmania das flores de Arrabidaea brachypoda (DC) Bureau

Abstract

Leishmaniasis is characterized as a protozoal infection transmitted through the blood meal of a sandfly. The drugs used in the treatment have a series of side effects, high cost, high toxicity and difficulty in administration. Natural products then appear as an alternative to conventional treatment. Among them, there is Arrabidaea brachypoda, which is a shrub native to the cerrado and commonly used by the Brazilian population for the treatment of various diseases. Previous studies performed on hydroethanolic extract showed that the roots of the plant are rich in dimeric flavonoids, which act as possible therapeutic agents. The objective of this work was to study the antileishmanial activity of the extract and fractions of the flowers of Arrabidaea brachypoda, as well as the isolation and chemical characterization of active compounds. The extract was obtained by the percolation method with ethanol/water (7:3) and partitioned with dichloromethane (DCM) and ethyl acetate (AcOEt). To investigate the chemical diversity of the extract and fractions of Arrabidaea brachypoda, the GNPS (Global Natural Products Molecular Networking) platform was used, making it possible to record 19 compounds from the classes of flavones, flavonols, flavanones, isoflavones, simple coumarin and cinnamic acid and their derivatives through the analysis of correspondences with the spectral libraries. The in vitro assay against promastigotes of Leishmania amazonensis indicated high activity for the dichloromethane fraction (IC50 = 21.50 µg/mL), showing inhibition values similar to the tested standard (Amphotericin B). The metabolites present in the DCM fraction were then separated using chromatographic techniques: open column packed with silica and high performance liquid chromatography on a semi-preparative scale. Six substances were isolated, 4 of them from the classes of flavones: apigenin, 5- methoxy-chrysin, chrysin and acacetin and two dimeric flavonoids: brachydins A and C, identified by UV, NMR and UPLC-QTOF-HRMS. Among the isolates, 5-methoxy chrysin and brachydin-C showed the best cytotoxicity values against the promastigotes of Leishmania amazonensis, with IC50 values of 18.90 and 14.17 µg/mL, respectively.These chemical characterization steps contributed to the discussion of the genus and species of the studied plant, since most of the published studies refer to the roots of Arrabidaea brachypoda. Finally, the results obtained from this study show the potential biological effect of Arrabidaea brachypoda flowers as a possible pharmacological agent.