Prospecção química de plantas do cerrado e sua influência na atividade leishmanicida

Abstract

The search for arginase inhibitors, a metalloenzyme from Leishmania sp. has been an alternative to interfere in the metabolic pathways involving this essential enzyme for the development of the leishmaniasis protozoan, which is a serious public health problem worldwide. Leishmania amazonensis arginase inhibitors (LaARG) from Natural Products (NPs) have been found, such as plant metabolites. However, several classes of plant secondary metabolites have not yet been investigated against LaARG. Given these factors, an in vitro screening of plant extracts against LaARG and the Leishmania protozoan was performed. The ethanolic extracts that showed significant inhibitory activity above 70%, evaluated at 25 μg/mL, were from the plants Drimys brasiliensis, Tabebuia ochracea, Erythroxylum suberosum and Qualea grandiflora. For the species Q. grandiflora, in addition to the arginase inhibitory activity, the metabolomic variation of the stem bark of specimens collected in different localities, from Cerrado de Goiás (Catalão-GO) and Cerrado paulista (São Carlos-SP) and on the influence of abiotic stress, burned. Among the ethanol extracts evaluated, only T. ochracea leaves had effective inhibition of the promastigote forms of Leishmania infantum with 87.41% inhibition (concentration of 100 μg/mL). Chemical prospection of active extracts from stem bark and leaves of D. brasiliensis and ethyl acetate fractions from flowers and stem bark of Q. grandiflora was performed by High Performance Liquid Chromatography (for Q. grandiflora), Chromatography Ultra Efficiency Liquid coupled to High Resolution Mass Spectrometry and by Nuclear Magnetic Resonance experiments for both species. Through the analysis of mass spectra using databases from different libraries and using molecular networking (GNPS), 12 compounds of the species D. brasiliensis belonging to the classes of flavonoids, hydroxycinnamic acids, aldehyde and dihydroxybenzoic acid were identified. The molecular modeling study was also carried out with some compounds previously identified in D. brasiliensis and E. suberosum and with the 12 compounds identified in D. brasiliensis in this work. In Q. grandiflora from Goiás (QgCcEcA-GO) 9 compounds were found and after the influence of fires (QgCcEqA) 12 compounds, among them, ellagic acid, gallic acid, gallotannins, ellagitannins and flavonoids. From the flowers, 19 compounds belonging to the class of flavonoids, gallotannins, ellagic acid derivatives, carboxylic acids and hydroxycinnamic acids were characterized. Molecular docking revealed that the affinity of these natural compounds was lower when compared to the inhibitor (R)-2-amino-6-borono-2-[1-(3,4- dichlorobenzyl)piperidin-4-yl]hexanoic acid (score -32.95 kJ/mol), a compound with an analogous structure to the natural substrate (L-arginine) of arginase, and none of the evaluated natural products showed interactions with the Mn2+ ion in the catalytic site of the enzyme. The compounds with the best affinities observed by the scores were the alkaloid (110) from E. suberosum with similar interactions to the competitive inhibitor ABHDP (-16.91 kJ/mol) and the dihydroxybenzoic acid (5C) from D. brasiliensis (-13 .64 KJ/mol).