Antiplasmodial activity of coumarins isolated from Polygala boliviensis: in vitro and in silico studies.

Polygala boliviensis is found in the Brazilian semiarid region. This specie is little chemically and biologically studied. Polygala spp. have different metabolites, especially coumarins. Studies indicate that coumarins have antimalarial potential, denoting the importance of researching new active compounds from plants, since the resistance of Plasmodium strains to conventional therapy has increased. The present study aimed to evaluate the antiplasmodial activity of auraptene and poligalen against a chloroquine-resistant strain of Plasmodium falciparum. Coumarins were isolated from P. boliviensis by open column chromatography and identified by Nuclear Magnetic Resonance Spectroscopy. A cytotoxicity assay was carried out using MTT test, and the in vitro antiplasmodial activity was evaluated using the W2 strain. The antiplasmodial activity results found were IC50=0.171 ± 0.016 for auraptene and 0.164 ± 0.012 for poligalen; the selectivity indexes were 78.71 and 609.76, respectively. Inverse virtual screening in the BRAMMT database by OCTOPUS 1.2 was applied to coumarins to find potential P. falciparum targets and showed higher affinity energy of auraptene for purine nucleoside phosphorylase (PfPNP) and of poligalen for dihydroorotate dehydrogenase (PfDHODH). Molecular Dynamics studies (MD and MM-GBSA) approach were applied to calculate binding energies against selected P. falciparum targets and showed that all coumarins were stable at the binding site during simulations. Furthermore, energies were favorable for complexation. This is the first report of auraptene in P. boliviensis species and of in vitro antiplasmodial activity of auraptene and poligalen. In silico studies indicated that the mechanism of action of coumarins is the inhibition of PfPNP and PfDHODH.Communicated by Ramaswamy H. Sarma.

Asemeia ovata (Polygalaceae): Quantitative determination and evaluation in silico of identified substances by HPLC-DAD.

BACKGROUND: In Brazil, the Asemeia genus has 19 species (12 endemic) and 2 varieties (both endemic) and some of them are found in semi-arid Bahia. OBJECTIVE: The objective of this study was to quantitatively determine identified substances by HPLC-DAD in Asemeia ovata extracts and to predict their biological activities in silico. METHOD: The quantification method by HPLC-DAD has been validated according to the guidelines of the International Conference of Harmonization. The prediction in silico activities was made by Target Fishing methods (TF), followed by docking by the program DOCK 6.7 and assessment of interaction profiles for Protein-Ligand Interaction Profiler server. RESULTS: It was possible to identify and quantify using HPLC-DAD substances: rutin, luteolin-7-O-glucoside, caffeic acid, p-coumaric acid and trans-ferulic acid. The ChemProt 2.0 server was selected for TF method, which has shown potential activity of compounds on molecular targets such as Carbonic anhydrase 12, epidermal growth factor receptor and sodium-glucose cotransporter 2. CONCLUSION: This work provides new results for the species both from a biological and chemical point of view, and has interesting potential to be discovered with the prospect of further studies.