Descoberta de inibidores enzimáticos de plasmodium falciparum a partir do estudo químico de dalbergia miscolobium benth. (fabaceae)

Abstract

Malaria is a worldwide prevalence parasitosis caused by parasites of the genus Plasmodium spp. Despite the existence of treatments for this disease, the emergence of parasite resistance highlights the importance of discovering new candidates with antimalarial activity. In this context, enolase (Pfeno) and pyruvate kinase II (PfPKII) enzymes from P. falciparum are promising targets in the development of antimalarial chemotherapeutics. Pfeno is extremely important for the production of energy in parasites such as Plasmodium spp. and also performs non-glycolytic functions, called "moonlighting" functions. PfPKII is associated with an organelle of the parasite called apicoplast, being essential for the production of nucleoside triphosphate (NTP) derivatives, which is used in several metabolic pathways. In the search for new Pfeno and PfPKII inhibitors, the investigation of natural products is relevant, where several secondary metabolites are well known as antimalarial drugs. Dalbergia miscolobium Benth. (Fabaceae), is an endemic plant of the cerrado popularly known as "jacarandá-docerrado". Species of this genus have antiplasmodial and antioxidant activity, with isoflavones and neoflavones as secondary metabolites. The ethanolic extract of D. miscolobium (DmCcE) showed inhibitory potential against the 3D7 strain (IC50307 9.0 µg/mL) obtained by the SYBR green I assay. This promising result led to the selection of this species for the chemical study guided by in vitro tests on P. falciparum and investigation of fractions and compounds isolated against Pfeno and PfPKII enzymes, in search of new enzymatic inhibitors as potential antiplasmodial agents. The chemical prospection of this crude extract through the CLUE-MS/MS experiment allowed the dereplication of six compounds from the class of flavonoids, terpenoids and phenolic derivatives. Through the GC-MS experiment of the active hexane fraction (DmCcH, IC50307 1.7 µg/mL), three substances of the ester class were identified. The phytochemical study of the active ethyl acetate fraction guided by antiplasmodial activity (DmCCA, IC50307 = 8.4 µg/mL), led to the obtainment of active subfractions. From them, four compounds were isolated through chromatographic techniques, epicatechin (I), compound II (epitaxifolin and cis-dihydroquercetagetin, IC50307 = 24.0 µg/mL), lupenone (III, IC50307 26.6 µM) and lupeol (IV, IC50307 = 33.3 µM), identified by 1D/2D NMR. Furthermore, subfractions A19, A20 (epitaxifolin and = cis-dihydroquercetagetin, compound II) and A21 were promising against PfPKII, with inhibitions above 90% (200 µg/mL).