Barbellatanic acid, a new antitrypanosomal pseudo-disesquiterpenoid isolated from Nectandra barbellata, displayed interaction with protozoan cell membrane.

As part of our ongoing studies involving the discovery of new natural prototypes with antiprotozoal activity against Trypanosoma cruzi from Brazilian plant species, the chromatographic fractionation of hexane extract from leaves of Nectandra barbellata afforded one new pseudo-disesquiterpenoid, barbellatanic acid. The structure of this compound was elucidated by NMR and HR-ESIMS data analysis. Barbellatanic acid displayed a trypanocidal effect with IC50 of 13.2 µM to trypomastigotes and no toxicity against NCTC cells (CC50 > 200 µM), resulting in an SI value higher than 15.1. The investigation of the lethal mechanism of barbellatanic acid in trypomastigotes, using both fluorescence microscopy and spectrofluorimetric analysis, revealed a time-dependent permeation of the plasma membrane. Based on these results, this compound was incorporated in cellular membrane models built with lipid Langmuir monolayers. The interaction of barbellatanic acid with the models was inferred by tensiometric, rheological, spectroscopical, and morphological techniques, which showed that this compound altered the thermodynamic, viscoelastic, structural, and morphological properties of the film. Taking together, these results could be employed when this prodrug interacts with lipidic interfaces, such as protozoa membranes or liposomes for drug delivery systems.

Essential Oils of Aromatic Plant Species from the Atlantic Rainforest Exhibit Extensive Chemical Diversity and Antimicrobial Activity.

Microbial resistance, caused by the overuse or inadequate application of antibiotics, is a worldwide crisis, increasing the risk of treatment failure and healthcare costs. Plant essential oils (EOs) consist of hydrophobic metabolites with antimicrobial activity. The antimicrobial potential of the chemical diversity of plants from the Atlantic Rainforest remains scarcely characterized. In the current work, we determined the metabolite profile of the EOs from aromatic plants from nine locations and accessed their antimicrobial and biocidal activity by agar diffusion assays, minimum inhibitory concentration, time-kill and cell-component leakage assays. The pharmacokinetic properties of the EO compounds were investigated by in silico tools. More than a hundred metabolites were identified, mainly consisting of sesqui and monoterpenes. Individual plants and botanical families exhibited extensive chemical variations in their EO composition. Probabilistic models demonstrated that qualitative and quantitative differences contribute to chemical diversity, depending on the botanical family. The EOs exhibited antimicrobial biocidal activity against pathogenic bacteria, fungi and multiple predicted pharmacological targets. Our results demonstrate the antimicrobial potential of EOs from rainforest plants, indicate novel macromolecular targets, and contribute to highlighting the chemical diversity of native species.

Antitrypanosomal Lactones from Nectandra barbellata.

Twigs of Nectandra barbellata were extracted using a solution of the ionic liquid 1-butyl-3-methylimidazolium bromide (BMImBr) in H2O, assisted by microwave (MAE). After successive chromatographic steps, one sesquiterpene, costic acid, and three new related lactones, (R)-3(7)-Z-3-hexadec-21-enylidene-5-(hydroxymethyl)tetrahydrofuran-2-one (1), (R)-3(7)-Z-3-hexadecylidene-5-(hydroxymethyl)tetrahydrofuran-2-one (2), and (R)-3(7)-Z-3-docosylidene-5-(hydroxymethyl)tetrahydrofuran-2-one (3), were isolated. After structural elucidation using IR, UV, HRESIMS, NMR, ECD, and VCD, compounds 1-3 were tested against trypomastigote forms of Trypanosoma cruzi. The mechanism of action of bioactive isolated compounds was studied using different fluorescent-based approaches to investigate alterations of the plasma membrane, permeability/electric potential (ΔΨp), reactive oxygen species levels, mitochondria (electric membrane potential, ΔΨm/ATP levels), Ca2+ levels, and pH of the acidocalcisomes. In addition, in silico studies predicted no resemblance to pan assay interference compounds (PAINS).

Anti-Trypanosoma cruzi activity of costic acid isolated from Nectandra barbellata (Lauraceae) is associated with alterations in plasma membrane electric and mitochondrial membrane potentials.

As part of our continuous studies on prospecting metabolites from Brazilian plant species with pharmacologic activity against Trypanosoma cruzi, the n-hexane extract from twigs of Nectandra barbellata (Lauraceae) was subjected to a bioactivity-guided fractionation to afford the sesquiterpene costic acid. As results, costic acid induced a trypanocidal effect with IC50 of 37.8 and 7.9 µM to trypomastigotes and intracellular amastigotes, respectively. When tested in L929 cells, no cytotoxicity was detected in the highest tested concentration (CC50 > 200 µM), resulting in SI values >5 and >25 to trypomastigotes and amastigotes, respectively. Based on these promising results against T. cruzi, a mechanistic study of the parasite death was investigated. The flow cytometry analysis of costic acid-treated parasites showed depolarization of the plasma membrane electric potential. Spectrofluorimetrical analysis and transmission electron microscopy showed no evidence of plasma membrane permeability alteration of trypomastigotes, but strong ultrastructural damage, evidenced by large vacuoles. Although Ca2+ and reactive oxygen species (ROS) levels were unaltered after short time incubation with costic acid, it rapidly affected the mitochondria, leading to a depolarized potential of the membrane, reducing the ATP levels. In silico studies of costic acid showed good predictions for drug-likeness, with adherence to Lipinskís rules of five (RO5), good ADMET properties and no alerts for Pan-Assay Interference Compounds (PAINS). Therefore, costic acid demonstrated promising activity against T. cruzi parasites, with high selectivity to intracellular amastigotes. Considering the lethal action of costic acid in affecting a vital and unique organelle as the mitochondria, it could be considered a new hit compound for future drug design studies for Chagas disease.