Maria Fernanda Alves do Nascimento

Triterpenes from Minquartia guianensis (Olacaceae) and in vitro antimalarial activity

Minquartia guianensis, popularly known as acariquara, was phytochemically investigated. The following triterpenes were isolated from the dichloromethane extract of leaves: lupen-3-one (1), taraxer-3-one (2) and oleanolic acid (3). The dichloromethane extract of branches yielded the triterpene 3β-methoxy-lup-20(29)-ene (4). The chemical structures were characterized by NMR data. Plant extracts, substance 3, squalene (5) and taraxerol (6), (5 and 6 previously isolated), were evaluated by in vitro assay against chloroquine resistant Plasmodium falciparum. The dichloromethane extract of leaves and the three triterpenes assayed have shown partial activity. Thus, these results demonstrated that new potential antimalarial natural products can be found even in partially active extracts.

Synthesis, in vitro Antimalarial Activity and in silico Studies of Hybrid Kauranoid 1,2,3-Triazoles Derived from Naturally Occurring Diterpenes

We herein report the synthesis of hybrid kauranoid molecules of type 1,2,3-triazole-1,4-disubstituted aiming to improve the antimalarial activity of kaurenoic and xylopic acids. The CuI-catalyzed cycloaddition of azides and kauranoid terminal alkynes was explored as a hybridization strategy. Kauranoid terminal alkynes were prepared from kaurenoic and xylopic acids that were isolated from Wedelia paludosa D. C. (Asteraceae) and Xylopia frutescens Aubl. (Annonaceae). A total of 15 kauranoid derivatives, including nine new triazoles, were obtained and five out of these were more active than the original diterpenes. Interestingly, an increased activity was observed for a kauranoid propargyl ether. Interaction between ent-kaurane diterpene derivatives and Ca2+-ATPase (PfATP6) was investigated. Synthesis of diterpene derivatives emerges as a possible route to be explored in the quest of potentially new inhibitors of PfATP6.

Phytochemical Investigation of Anti-plasmodial Metabolites from Brazilian Native Piper Species

Abstract The World Health Organization estimates there are 300 and 500 million new cases of malaria worldwide, every year, mostly in Africa, Asia, South Pacific Islands and South America. New efforts to search for novel drugs for treating malaria remain important in countries like Brazil, where many endemic areas still exist. The Amazonia region is responsible for more than 97 % of the malaria cases in the country. Two Piper species were chemically investigated in order to identify new anti-plasmodial plant secondary metabolites. The crude extract and sub-fractions from leaves of Piper lucaeanum were previously assayed against a resistant strain of Plasmodium falciparum. Hydrodistillation of the leaf essential oils (EO) from Piper lucaeanum and Piper claussenianum were analyzed by GC-MS. The main constituents found from P. lucaeanum leaf oil were α-pinene (30.0 %), α-zingiberene (30.4 %), β-sesquiphelandrene (11.1 %), β-bisabolene (8.9 %), while from P. claussenianum inflorescences oil nerolidol (23.7 %) and linalool (56.5 %) were the major volatile components. The oils exhibited relevant biological activity against the resistant strain of P. falciparum. P. lucaeanum leaf EO was the most promising active sample (IC50 = 2.6 µg/mL), followed by P. claussenianum EO (IC50 = 7.9 µg/mL), the pure nerolidol (IC50= 11.1 µg/mL) and the linalool (IC50= 35.0 µg/mL). These results highlight the potential of Piper oils as a source of active metabolites in the research of new anti-maliarial compounds.

Spleen cell proliferation during and after skin myiasis by human bot fly Dermatobia hominis

Spleen cells from mice were examined at 5, 10, 15, 20 and 25 days post-infection (dpi) with Dermatobia hominis larva and at 5, 10, 15, 30 and 60 days post-larval emergence (dple). Cell proliferation in vitro assays were carried out with RPMI-1640 medium and larval secretory product (LSP) of D. hominis at 5, 10, 15, 20 and 25 days. When each group of mice was tested against each medium, significance was only seen for 25 dpi, with increasing order: LSP-10 d, -25 d, -5 d, -20 d, -15 d and RPMI. Significant results were also observed when each medium was tested against mice at each dpi or dple. Each dple group vs. each medium produced significant results only for 10 dple, with increasing order: LSP-5 d, -20 d, -25 d, -10 d, -15 d and RPMI. Comparative tests were also carried out between groups to refine certain observations. The LSPs were also analyzed using SDS-PAGE. The results prove that myiasis caused depletion of spleen cells, particularly under the effect of the LSP-10 and -15, but the cells tended to increase up to 60 dple. This in vitro assay may represent the real systemic immune response in the relationship LSP-D. hominis-host.

Synthesis by Click Reactions and Antiplasmodial Activity of Lupeol 1,2,3-Triazole Derivatives

Lupeol, a triterpene frequently found in Asteraceae plant species, showed moderate to low activity in different strains of Plasmodium falciparum, the most virulent malaria etiological agents. In this work, lupeol was isolated from Parahancornia fasciculata, a plant that is used to treat malaria in the Amazonia region. In the search of more activity lupeol derivatives, five new 1,2,3-triazole hybrid molecules were synthetized by copper-catalyzed azide-alkyne cycloaddition. The antiplasmodial activity of the semi-synthetic compounds were evaluated by the lactate dehydrogenase assay; the lupeol propargyl ether was the only one to disclosing increased activity (half maximal inhibitory concentration-IC50-62.0 ± 1.92 μmol L) in relation to lupeol (IC50 117.00 μmol L). Therefore, this work revealed a new class of interesting lupeol derivatives that can be obtained by linking electron donors to the hydroxy group at C-3.

In vitro antiplasmodial activity and identification, using tandem LC-MS, of alkaloids from Aspidosperma excelsum, a plant used to treat malaria in Amazonia

ETHNOPHARMACOLOGICAL RELEVANCE Aspidosperma excelsum Benth. (Apocynaceae), a native tree in the Brazilian Amazonia, is traditionally used to treat various diseases, including malaria. AIM OF STUDY To investigate the chemical constitution, antiplasmodial activity and cytotoxicity of samples obtained from A. excelsum trunk bark by different procedures aiming to evaluate their potential as an antimalarial phytomedicine. MATERIALS AND METHODS A hydroethanolic extract and alkaloid extracts were prepared and assayed for antiplasmodial activity and cytotoxicity against chloroquine-resistant Plasmodium falciparum (W2 strain) and HepG2 cells, respectively. Taking into account the known occurrence and antimalarial activity of Aspidosperma monoterpene indole alkaloids (MIA), acid-base extractions were carried out and the fractions were assayed for antiplasmodial activity and cytotoxicity. All the samples were analysed by hyphenated chromatographic techniques, such as UPLC-DAD-ESI-MS/MS and HRMS (HPLC-MS MicroTOF), comparing their chemical composition to the literature data. RESULTS The hydroethanolic extract disclosed a moderate in vitro activity against chloroquine-resistant Plasmodium falciparum (W2 strain) with IC50 23.68 ± 3.08 µg/mL), low cytotoxicity to HepG2 cells (> 250 µg/mL) and good SI (> 10.56). A total of 20 known monoterpene indole alkaloids were identified, seven of which are here firstly described for A. excelsum. Known highly active alkaloids, namely demethylaspidospermine, aspidocarpine, and ochrolifuanine are present in active alkaloid fractions and might contribute to their observed antiplasmodial effect. An alkaloid fraction (Ae-Alk2), obtained directly from trunk bark by extraction with dil. aqueous HCl, pointed out for its activity (IC50 8.75±2.26 µg/mL, CC50 185.14±1.97 µg/mL, SI 21.16) and should be highlighted as the most promising out of the assayed samples. CONCLUSION The present results represent a preliminary support to the alleged antimalarial use of A. excelsum trunk bark and allowed to highlight alkaloid fractions as promising phytomedicines.

Antiplasmodial activity and cytotoxicity, isolation of active alkaloids, and dereplication of Xylopia sericea leaves ethanol extract by UPLC-DAD-ESI-MS/MS

To assess the antiplasmodial activity of the ethanol extract of Xylopia sericea leaves, Annonaceae, often associated with antimalarial use and to perform a bioguided isolation of active compounds.

Leaves from the Tree Poincianella pluviosa as a Renewable Source of Antiplasmodial Compounds against Chloroquine-Resistant Plasmodium falciparum

Poincianella pluviosa. For conditions, see Experimental section. (A) gallic acid (tR = 8.35 min); (C) galloyl tannin (tR = 15.32 min); (E) galloyl tannin (tR = 20.01 min); (G) brevifolin carboxylic acid (tR = 21.96 min); (H) corilagin (tR = 22.54 min); (I) valoneic acid dilactone (tR = 23.35 min); (J) unidentified galloyl tannin (tR = 25.18 min); (K) ellagic acid derivate (tR = 25.57 min); (L) brevifolin derivate (tR = 26.07 min); (M) quercetin-3-O-(6-O-galloyl) β-D-glucopyranoside (tR = 28.79 min); (O) isovitexin (tR = 29.51 min); (P) isoquercitrin (tR = 30.34 min); (Q) ellagic acid (tR = 30.81 min). Labels on x (mAu: milli absorption units) and y (min: minutes).

Synthesis, SAR, and Docking Studies Disclose 2-Arylfuran-1,4-naphthoquinones as In Vitro Antiplasmodial Hits

A total of 28 lapachol-related naphthoquinones with four different scaffolds were synthesized and spectroscopically characterized. In vitro antiplasmodial activity was assayed against the chloroquine-resistant Plasmodium falciparum W2 strain by the parasite lactate dehydrogenase (pLDH) method. Cytotoxicity against Hep G2A16 cell was determined by the MTT assay. All compounds disclosed higher in vitro antiplasmodial activity than lapachol. Ortho- and para-naphthoquinones with a furan ring fused to the quinonoid moiety were more potent than 2-hydroxy-3-(1′-alkenyl)-1,4-naphthoquinones, while ortho-furanonaphthoquinones were more cytotoxic. Molecular docking to Plasmodium targets Pfcyt bc1 complex and PfDHOD enzyme showed that five out of the 28 naphthoquinones disclosed favorable binding energies. Furanonaphthoquinones endowed with an aryl moiety linked to the furan ring are highlighted as new in vitro antiplasmodial lead compounds and warrant further investigation.