(-)-5-Demethoxygrandisin B a New Lignan from Virola surinamensis (Rol.) Warb. Leaves: Evaluation of the Leishmanicidal Activity by In Vitro and In Silico Approaches.

Leishmaniasis is a complex disease caused by infection with different Leishmania parasites. The number of medications used for its treatment is still limited and the discovery of new drugs is a valuable approach. In this context, here we describe the in vitro leishmanicidal activity and the in silico interaction between trypanothione reductase (TryR) and (-)-5-demethoxygrandisin B from the leaves of Virola surinamensis (Rol.) Warb. The compound (-)-5-demethoxygrandisin B was isolated from V. surinamensis leaves, a plant found in the Brazilian Amazon, and it was characterized as (7R,8S,7'R,8'S)-3,4,5,3',4'-pentamethoxy-7,7'-epoxylignan. In vitro antileishmanial activity was examined against Leishmania amazonensis, covering both promastigote and intracellular amastigote phases. Cytotoxicity and nitrite production were gauged using BALB/c peritoneal macrophages. Moreover, transmission electron microscopy was applied to probe ultrastructural alterations, and flow cytometry assessed the shifts in the mitochondrial membrane potential. In silico methods such as molecular docking and molecular dynamics assessed the interaction between the most stable configuration of (-)-5-demethoxygrandisin B and TryR from L. infantum (PDB ID 2JK6). As a result, the (-)-5-demethoxygrandisin B was active against promastigote (IC50 7.0 µM) and intracellular amastigote (IC50 26.04 µM) forms of L. amazonensis, with acceptable selectivity indexes. (-)-5-demethoxygrandisin B caused ultrastructural changes in promastigotes, including mitochondrial swelling, altered kDNA patterns, vacuoles, vesicular structures, autophagosomes, and enlarged flagellar pockets. It reduced the mitochondria membrane potential and formed bonds with important residues in the TryR enzyme. The molecular dynamics simulations showed stability and favorable interaction with TryR. The compound targets L. amazonensis mitochondria via TryR enzyme inhibition.

Adsorption of Vi Capsular Antigen of Salmonella Typhi in Chitosan-Poly (Methacrylic Acid) Nanoparticles.

The development of a nanoparticulate system for the carrier antigen is now an important tool in the vaccination process, since a smaller number of doses is necessary for effective immunization. Thus, in this work a nanoparticulate system using polymers of chitosan and poly (methacrylic acid) (CS-PMAA) to adsorb the Vi antigen of Salmonella Typhi was developed. CS-PMAA nanoparticles with different proportions of chitosan and poly (methacrylic acid) were obtained and reached sizes from 123.9 ± 2.48 to 234.9 ± 2.66 nm, and spherical shapes were seen in transmission microscopy. At pH 7.2, the nanoparticles had a cationic surface charge that contributed to the adsorption of the Vi antigen. Qualitative analyses of the isolated Vi antigen were performed using Fourier-transform infrared spectroscopy, which indicated the presence of all the characteristic bands of the capsular polysaccharide, and nuclear magnetic resonance, which showed signals for the five hydrogens and the N-acetyl and O-acetyl groups which are characteristic of the Vi antigen structure. In the adsorption kinetics study, the Vi capsular antigen, contained in a phosphate buffer solution of pH 7.2, experienced 55% adsorption on the 1-1% (CS-PMAA) nanoparticles. The adsorption kinetics results showed the ability of the nanoparticulate system to adsorb the Vi antigen.

In vitro acaricidal activity of Crescentia cujete L. fruit pulp against Rhipicephalus microplus.

Cattle tick (Rhipicephalus microplus) is an important constraint on livestock production, particularly in tropical and subtropical areas. Synthetic acaricides are the primary method of control this thick. Resistance of R. microplus to synthetic acaricides has given rise to the need of new scientific investigations on alternative ways to control it. The objective of this work was to conduct a chemical investigation of Crescentia cujete L. fruit pulp and to evaluate the acaricide effect on R. microplus larvae of extracts, fractions, and isolated substances from this species. Crescentia cujete is a Bignoniaceae and it is characteristic of tropical climates. Its most distinctive feature is its fruit, which is spherical and gourd-like, with a hard woody shell and gelatinous pulp. The fruit pulp of C. cujete was extracted with ethanol by maceration yielding an extract and a residue. The extract was partitioned giving an ethyl acetate phase (EAF) that was fractionated by chromatographic procedures yielding cinnamic acid and benzoic acid. The remained botanic material from the ethanol extraction was further and successively extracted with ethyl ether and methanol under reflux. The acaricide effect of all extracts and fractions was evaluated against R. microplus using the larval packet test. The best result was observed for the EAF that caused 100% of mortality when a 10% solution was used and with LC50 of 5.9%. Cinnamic acid was also tested showing 63.0% of mortality with LC50 of 6.6% at the same concentrations and time of the experiment. The data obtained in this study provides information related to the chemical nature and the acaricide activity of the C. cujete epicarp that has not been previously reported. This study shows that the ethyl acetate phase of the ethanol extract of C. cujete fruit pulp is a potential alternative control for R. microplus and its activity is in part associated to cinnamic acid, its major compound.

Chemical investigation of Cyperus distans L. and inhibitory activity of scabequinone in seed germination and seedling growth bioassays.

Chemical investigation of the rhizomes of Cyperus distans (Cyperaceae) led to the identification of α-ciperone, cyperotundone and scabequinone, besides other common constituents. Complete assignment of the (13)C NMR data of scabequinone is being published for the first time. The inhibitory effects of C. distans extracts and scabequinone on the seed germination and seedling growth of Mimosa pudica, Senna obtusifolia and Pueraria phaseoloides were evaluated. Seed germination inhibition bioassay revealed that S. obtusifolia (52-53%) was more sensitive to the hexane and the methanol extracts at 1% than M. pudica (0-10%). Scabequinone at 250 mg L⁻¹ displayed seed germination inhibitions more than 50% and radicle growth reduction of more than 35% of the test species S. obtusifolia and P. phaseoloides, while the hypocotyl growth of M. pudica was significantly affected (>50%) by the quinone at the same concentration. These results demonstrate that scabequinone contributes to the overall inhibitory activities of C. distans.

Chemical constituents and allelopathic and antioxidant activities of Alchorneopsis floribunda Müll. Arg. (Euphorbiaceae).

Chemical investigation of extracts from the stems and leaves of Alchorneopsis floribunda Müll. Arg., collected in the Amazon region, was performed. The main isolated compounds were triterpenes (α-amyrin, ß-amyrin, lupeol, betulin, betulinic acid, uvaol, erythrodiol and oleanolic acid) and phenolic acid derivatives from 4-hydroxybenzoic acid (gallic and protocatechuic acids and isocorilagin). In the germination assays, high inhibitory allelopathic effects of the extracts and isocorilagin were observed and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity of isocorilagin was higher than those of the standards used (Trolox and butylated hydroxyanisole). This is the first chemical study of the genus Alchorneopsis (Euphorbiaceae).

Ricinine and other constituents of Aparisthmium cordatum (Euphorbiaceae).

The chemical study of Aparisthmium cordatum (Euphorbiaceae) led to the isolation of tannins, together with the alkaloid ricinine and other common compounds. The composition of A. cordatum is similar to most of the Alchornea species, from the same subtribe, except for the occurrence of ricinine. This study rectifies the first investigations published for A. cordatum that were conducted with Croton palanostigma.

Gastric antiulcer and anti-inflammatory activities of the essential oil from Casearia sylvestris Sw.

To investigate the antiulcer and antiinflammatory activities of the essential oil from Casearia sylvestris leaves (EOCS) the following tests were used: rat paw edema, granulomatous tissue test, vascular permeability, writhing test, gastric ulcer stress-induced and evaluation of gastric secretion (pylorus ligation test). The total yield of EOCS was 2.5% with LD50 of 1100 mg/kg in mouse. The major compounds identified using gas chromatography were caryophyllene, thujopsene, alfa-humulene, beta-acoradiene, germacrene-d, bicyclogermacrene, calamenene, germacrene B, spathulenol and globulol. The EOCS orally administered to the rats at 125 mg/kg resulted 36% of inhibition in carrageenan-induced edema in the rat paw assay (p<0.05, Student's t-test). However, both rat paw edema dextran-induced and vascular permeability assay using histamine showed no significant inhibition. Mice submitted to the writhing test using acetic acid presented 58% and 56% of inhibition in writhes with EOCS and indomethacin, respectively. Furthermore, EOCS inhibited 90% of stress-induced gastric ulcer, while cimetidine inhibited 70% (p<0.05, Student's t-test). The volume of gastric secretion in the group treated with EOCS was greater than the group treated with cimetidine. The EOCS also showed no changes related to H+ levels in the gastric secretion. With the overall results obtained in this study the authors suggest an anti-inflammatory activity for the EOCS of Casearia sylvestris beyond its anti-ulcer activity.