Alessandra Machado

Sínteses química e enzimática de peptídeos: princípios básicos e aplicações

This review begins with a brief discussion of the biological importance and chemical features of peptides. A description of the existing synthetic methods follows with emphasis on the basic aspects of the chemical and enzymatic syntheses. Techniques used to purify and characterize the synthesized peptides are also discussed. Finally, a few applications of the final products in chemistry, biochemistry, immunology and medicine are presented, such as identification and quantification of naturally occurring peptides, inspection of structure-activity relationships, therapeutics, development and/or improvement of analytical techniques and search for new vaccines.

Evaluation of tissue reaction to Aroeira (Myracrodruon urundeuva) extracts: a histologic and edemogenic study

Objectives This study evaluated subcutaneous tissue response to Aroeira (Myracrodruon urundeuva) extract employing edemogenic and histological analyses. Material and methods Test groups consisted of aqueous and ethanolic Aroeira extracts and saline (control). For edema quantification, 18 rats received an intravenous injection of Evans Blue. After 30 min, the extracts and saline were injected on the dorsum of the rats, which were then sacrificed after 3 and 6 h. Readings were performed in a spectrophotometer. For subcutaneous implantation, 30 rats received a polyethylene tube containing the extracts on their dorsum and then they were killed after 7 and 28 days. The samples were processed for histological analysis and evaluated with a light microscope. The inflammatory infiltrate was quantified. Results There were no statistically significant differences between aqueous extract and saline groups in relation to edema quantification in the different periods (p>0.05). Ethanolic solution resulted in more edema independently of the experimental period (p<0.05). Histological analysis showed similar results on the 7-day period for the 3 groups. There was a notable reduction on inflammatory cell number for saline and aqueous extract groups at 28 days. Conclusion The aqueous extract showed biocompatible properties similar to those of saline.

Reaction of α-chloro-α-phenylselenoesters with silyl enol ethers. Synthesis of α-phenylseleno-γ-keto esters and γ-butyrolactones

Silyl enol ethers of ketones are alkylated with ethyl α-chloro-α-phenylseleno acetate 1a or with ethyl α-chloro-α-phenylseleno propionate 1b, mediated by zinc bromide to give the corresponding α-phenylseleno-γ-keto esters 3 in moderate to good yields.

Interactions of di-imine copper(II) complexes with albumin: competitive equilibria, promoted oxidative damage and DFT studies

Interactions of some diimine copper(II) complexes with bovine serum albumin (BSA) were investigated by spectroscopic techniques in order to compare the stability of the complexes and their capability of causing oxidative damage to the protein. The tri- and tetradentate imine ligands employed in this work contain pyridine, pyrazine or imidazole moieties, which are ubiquitous in biological systems. The relative thermodynamic stabilities of the copper(II) complexes were estimated by circular dichroism (CD) using BSA as the competitive ligand. The apparent stability constants determined for the complexes are very similar to one another and to that of the Cu(BSA) complex itself, for which log KCu(BSA) = 12.9 has already been described in the literature, indicating that the complexes are quite stable under physiological conditions. Two different copper binding sites were evidenced on BSA by spectroscopic measurements (CD, UV-Vis and EPR), depending on the ligand and on the [CuL]:[protein] stoichiometric ratio. Metal binding to any of the sites gives rise to significant protein oxidative damage, especially in the presence of hydrogen peroxide, indicating an oxidative process based on reactive oxygen species (ROS). A small amidated peptide, Asp-Thr-His-NH2, corresponding to the N-terminal region of BSA was synthesized, and its interaction with all the diimine-copper(II) complexes was also investigated in order to clarify the copper imine complex-albumin interactions. Electronic structure calculations at the density functional theory (DFT) level were made to compare the copper-ligand binding energies for each complex with that of the metal coordinated at the N-terminal site of the protein.

Synthesis and properties of cyclic gomesin and analogues

Gomesin (Gm) was the first antimicrobial peptide (AMP) isolated from the hemocytes of a spider, the Brazilian mygalomorph Acanthoscurria gomesiana. We have been studying the properties of this interesting AMP, which also displays anticancer, antimalarial, anticryptococcal and anti‐Leishmania activities. In the present study, the total syntheses of backbone‐cyclized analogues of Gm (two disulfide bonds), [Cys(Acm)2,15]‐Gm (one disulfide bond) and [Thr2,6,11,15,d‐Pro9]‐Gm (no disulfide bonds) were accomplished, and the impact of cyclization on their properties was examined. The consequence of simultaneous deletion of pGlu1 and Arg16‐Glu‐Arg18‐NH2 on Gm antimicrobial activity and structure was also analyzed. The results obtained showed that the synthetic route that includes peptide backbone cyclization on resin was advantageous and that a combination of 20% DMSO/NMP, EDC/HOBt, 60 °C and conventional heating appears to be particularly suitable for backbone cyclization of bioactive peptides. The biological properties of the Gm analogues clearly revealed that the N‐terminal amino acid pGlu1 and the amidated C‐terminal tripeptide Arg16‐Glu‐Arg18‐NH2 play a major role in the interaction of Gm with the target membranes. Moreover, backbone cyclization practically did not affect the stability of the peptides in human serum; it also did not affect or enhanced hemolytic activity, but induced selectivity and, in some cases, discrete enhancements of antimicrobial activity and salt tolerance. Because of its high therapeutic index, easy synthesis and lower cost, the [Thr2,6,11,15,d‐Pro9]‐Gm analogue remains the best active Gm‐derived AMP developed so far; nevertheless, its elevated instability in human serum may limit its therapeutic potential. Copyright

“Aroeira” (Myracrodruon urundeuva) methanol extract: the relationship between chemical compounds and cellular effects

Abstract Context: “Aroeira” [Myracrodruon urundeuva Allemão (Anacardiaceae)] is a tree whose leaves have been studied for therapeutic purposes in medicine and dentistry. Objective: The study chemically identifies the leaf extract of aroeira and determines its effect on human gingival fibroblasts. Materials and methods: An 80% methanol leave extract was obtained by maceration and chemically identified through flow-injection analysis–electrospray ionization–ion trap–tandem mass spectrometry (FIA–ESI–IT–MSn). Cytotoxicity of the aroeira’s methanol extract was evaluated in lineage of fibroblasts. Adherent cells were treated with different concentrations of aroeira’s methanol extract in the medium: 0.1, 1, 10, 100 and 1000 μg/mL. Control cells were cultivated in the medium only. Analyses were done at 24, 48, 72 and 96 h of culture by neutral red assay; and at 24, 48 and 96 h by crystal violet assay. Results: FIA–ESI–IT–MS analysis determined the presence of compounds, for the first time in the species: quercetin-O-glucuronide and quercetin-O-deoxyhexose-O-glucose in the extract. On one hand, neutral red and crystal violet assay showed a reduction (to 50% up until 100%) of cellular viability of groups of 100 and 1000 μg/mL compared with control at 96 h (p < 0.05). On the other hand, lower concentrations (0.1; 1 and 10 μg/mL) of the extract were similar to that of the control at 96 h (p < 0.05), in general. Conclusions: In view of the results, we can conclude that the extract of aroeira presents tannins and flavonoids. Furthermore, the extract is capable of modulating the viability of human gingival fibroblasts according to its concentration.

Atividade anti-inflamatória de produtos naturais em Odontologia: uma revisão sistemática

O objetivo deste estudo foi selecionar artigos de dois produtos naturais propolis e Aroeira ( Myracrodruon urundeuva ), que apresentassem acao anti-inflamatoria na odontologia. Acessou-se a base de dados PubMed, entre os meses de Abril a Agosto de 2015. Os descritores utilizados nas buscas foram “Anti-Inflammatory AND Propolis” AND “Anti-Inflammatory AND M. urundeuva ”, nao sendo estabelecidos limites quanto ao idioma, tipo ou ano de publicacao dos artigos, porem foram selecionados apenas os estudos com aplicacao de produtos naturais pesquisados com atividade anti-inflamatoria na Odontologia. Foram obtidos 207 artigos, e apos analise minuciosa realizada por dois avaliadores, 193 foram excluidos, 154 nao estavam adequados ao tema, 35 correspondentes a revisoes e 4 nao foram encontrados na versao completa. Ao final, foram incluidos 14 artigos, da Propolis (n=12) e da M urundeuva (n=02). Tanto a propolis quanto aroeira apresentou atividade anti-inflamatoria eficaz na Odontologia. A propolis atuou sobre micro-organismos ligados a carie, nas infeccoes endodonticas prevenindo edemas, aliviando complicacoes relacionadas as proteses, como mucosite. A propolis apresenta efeito benefico contra carie dental, tratamento endodontico e mucosite. Ja a aroeira do sertao atua prevenindo a progressao da periodontite. Futuros estudos deverao ser conduzidos, envolvendo seus compostos e mecanismos de acao na inflamacao.