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Abstract. Plant-derived compounds are important sources of effective anti-cancer agents. Pterodon pubescens is a native Brazilian plant popularly known for its anti-inflammatory and anti-arthritic effects. The ethanolic extract of its seeds (EEPp) is a viscous, brown and fragrant oil containing geranylgeraniol, farnesol, naphthalene, dimethyldodecatrienol and vouacapan diterpene derivatives, in addition to other compounds. This study investigated the in vitro anti-leukemic properties of EEPp using the resistant human leukemia cell line K562. The EEPp anti-proliferative effect was demonstrated by the inhibition of DNA synthesis and cell growth, and the induction of cell cycle arrest in the G 1 phase. Furthermore, cyclin E2 mRNA levels were down-regulated, while those of cyclin D1 were up-regulated. An EEPp anti-leukemic effect may have also triggered apoptosis, as it increased the number of shrunken cells and phosphatidylserine cell membrane exposure. These observations suggest that EEPp deregulates cyclin D1 and E2 expression, inducing cell cycle arrest and apoptosis of leukemic cells.

BackgroundPlant derived compounds have been shown to be important sources of several anti-cancer agents. As cell cycle deregulation and tumor growth are intimately linked, the discovery of new substances targeting events in this biochemical pathway would be of great value. The anti-leukemic effect of an ethanolic extract of Pterodon pubescens seeds (EEPp) has been previously demonstrated and now we show that a terpenic subfraction (SF5) of EEPp containing farnesol, geranylgeraniol and vouacapan derivatives induces apoptosis in the human chronic myelogenous leukemia cell line K562. This work addresses SF5’s antiproliferative mechanisms in these cells since they are still unclear.MethodsDNA synthesis in K562 cells was assessed by [3H]-methyl-thymidine incorporation and cell cycle status by flow cytometry. The expression of cyclins D1 and E2, of the cell cycle inhibitor p21 and of the proto-oncogene c-myc was evaluated by semi-quantitative RT-PCR. Extracellular-signal-regulated kinases (ERK) 1/2 and nuclear factor kappa B (NF-κB) activation was evaluated by western blotting.ResultsIn K562 cells, SF5 treatment induced a higher inhibition of DNA synthesis and cell growth than the original EEPp hexanic fraction from which SF5 originated, and also arrested the cell cycle in G1. Exposure of these cells to SF5 led to a decrease in cyclin E2 and c-myc expression while p21 mRNA levels were increased. Furthermore, SF5 inhibited the activation of mitogen-activated protein kinase (MAPK) ERK 1/2 and NF-κB.ConclusionsThis work suggests that the anti-leukemic action of SF5 is linked to the inhibition of ERKs, NF-κB and c-myc signaling pathways resulting in reduced cyclin E2 mRNA expression and cell cycle arrest in the G1 phase.

Malaria is one of the most important tropical diseases; the use of amodiaquine as a current chemotherapy in the treatment of malaria has shown some problems such as hepatotoxicity and agranulocytosis. In this work we present the rational design, synthesis, and biological evaluation (antimalarial activity, cytotoxicity and genotoxicity) of four new fluoroamodiaquine analogues. The results showed significant correlation between MolDock score and IC 50 values. The molecules 7b and c were the most active of the planned compounds, with lower IC 50 against Plasmodium falciparum W2 strain (0.9 and 0.8 µM, respectively) and an excellent cytotoxicity profile. The present study revealed no mutagenicity or genotoxicity for the analogues. Confirming our docking results, the molecular dynamics showed that compound 7b remains stably bound to the heme group by means of π-stacking interactions between quinoline and the porphyrin ring. Based on these findings, this study may prove to be an efficient approach for the rational design of hemozoin inhibiting compounds to treat malaria.Key words docking; molecular dynamics; molecular modeling; antimalarial Malaria is one of the most important tropical diseases, affecting 97 countries. It is an infectious disease caused by five species of Plasmodium genus protozoa, from which the P. falciparum is the most lethal in humans. There were approximately 198 million cases of malaria reported in 2013, and an estimated number of 584000 deaths, mainly in African subSaharan countries.1)The chemotherapy combination of artesunate and amodiaquine (ASAQ) is currently the treatment recommended by WHO. However, recent reports show that P. falciparum has become resistant to these chemotherapeutic agents. In addition, the use of amodiaquine (AQ) (Fig. 1) has shown some problems such as hepatotoxicity and agranulocytosis.2-4) This is a result of the biotransformation that occurs in the liver by CYP450 enzymes, which generates a reative quinoneimine metabolite, the amodiaquine quinone imine (AQQI) 5) (Fig. 1). This metabolite binds irreversibly to cellular macromolecules, leading to cell death by oxidation and, probably, to direct toxicity as well as immune-mediated hypersensitivity reactions.6,7) The mechanism of action of AQ and other 4-aminoquinolines is based on the inhibition of the parasite's mechanism of detoxification of heme, namely, the inclusion of free heme into hemozoin. By doing so, AQ increases the concentration of free heme inside the host cell acidic digestive vacuole, killing the parasite by oxidative stress. [8][9][10][11][12][13] The design of new amodiaquine derivatives with reduced toxicity and increased activity is a current matter of study.14-17) It's already well established in the literature that the fluorine insertion in this series is favorable to reduce the hepatotoxicity, by forming new compounds that are more resistant to oxidation and hence less likely to form toxic quinone imine metabolites in vivo. 2,3,17,18) O'Neill et al. demonstrated that the 4′-hydroxyl group could b...