Produtos naturais com potencial terapêutico: estudos do efeito no estresse oxidativo, no processo inflamatório e em Leishmania amazonensis

Abstract

Lantana camara L. and Mitracrapus frigidus are species with a broad spectrum of bioactivities and present a wide variety of secondary metabolites. However, there are still few studies regarding the antilesihmanial, antioxidant, anti-inflammatory and cytotoxic activities of these species. Therefore, the objective of this work was to investigate the antileishmanial, cytotoxic, antioxidant and anti-inflammatory activities of different extracts of these species. The extracts of L. camara L were produced by static maceration using solvents with increasing order of polarity. The dichloromethane extract of. M frigidus leaves was obtained by static maceration and the aqueous extract by infusion followed by lyophilization. First the extracts were tested against promastigotes and amastigotes of L. amazonensis, murine peritoneal macrophages, human erythrocytes, DPPH test and had their content of phenolic substances and terpenes measured. The extracts of L. camara L. were more active and selective for antileishmanial activity, presented high contents of terpenes and hemolytic activity. The extracts of M. frigidus showed the best antioxidant activities, absence of hemolytic potential and the highest contents of phenolic substances. Subsequently, the ethanolic extract of L. camara L. leaves (LCE) was selected for fractionation and purification of substances with antileishmanial potential, where it was observed that LCE presents higher biological activity and/or lower toxicity than its fractions. Given the previous result, LCE had its mechanism of action investigated by different assays and was characterized by UFLC-QTOF-MS. LCE induced oxidative stress and caused alterations in mitochondria, lipid metabolism, nucleus and kinetoplast of L. amazonensis promastigotes, leading to cell death mainly by apoptosis-like. In addition, LCE increased NO levels in macrophages infected with amastigote forms. LCE presented in its composition triterpenes, flavonoids, iridoids, and glycosylated terpenes. Regarding anti-inflammatory activity, the aqueous extract of M. frigidus (MFAq) was selected due to its better antioxidant activity. MFAq was chemically characterized by means of UFLC-QTOF-MS and had its antioxidant potential further investigated. The anti-inflammatory pot ential of MFAq was investigated by in vitro, in silico and in vivo tests. In addition, this extract had its cytotoxic potential further investigated in murine peritoneal macrophages and the J774A.1 cells. MFAq showed a promising antioxidant activity in all the tests performed, causing no cytotoxic changes in the macrophages strains tested. The in vitro anti-inflammatory tests demonstrated that MFAq was able to reduce the production of NO, TGF-β, PGE2 and lipid bodies in macrophages stimulated with LPS and IFN-γ. Chemical characterization revealed the presence of flavonoids, alkaloids, disaccharides, phenolic acids and glycosylated quinones. In silico analysis revealed that rutin and chlorogenic acid present in MFAq are promising inhibitors of cyclooxygenase 2 (COX-2) and make hydrogen bonds with residues present in the catalytic site of this enzyme. The results demonstrate that the antileishmanial potential of L. camara L. extracts may be related to the terpene contents found, among them ursolic acid, and that these substances probably act through synergy, since LCE shows a more promising biological activity than its pure fractions/compound. The anti-inflammatory activity of MFAq is also related to the chemicals found and probably correlates with the presence of phenolic substances.