Browsing by Author "Eaton, Peter"
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- Acetylated cashew gum-based nanoparticles for the incorporation of alkaloid epiisopiloturinePublication . Rodrigues, Jessica do Amaral; Araújo, Alyne Rodrigues de; Pitombeira, Nadia Aline; Plácido, Alexandra; Almeida, Miguel Peixoto de; Veras, Leiz Maria Costa; Delerue-Matos, Cristina; Lima, Filipe Camargo Dalmatti Alves; Neto, Augusto Batagin; Paula, Regina Célia Monteiro de; Feitosa, Judith Pessoa Andrade; Eaton, Peter; Leite, José Roberto Souza A.; Silva, Durcilene Alves daThe natural alkaloid epiisopiloturine has recently become the focus of study for various medicinal properties, particularly for its anti-inflammatory and antischistosomal effect. The incorporation of active molecules in natural polymeric matrices has garnered increasing interest during recent decades. A new derivative of cashew gum successfully obtained by gum acetylation has shown great potential as a carrier in controlled drug release systems. In this work, epiisopiloturine was encapsulated in acetylated cashew gum nanoparticles in order to increase solubility and allow slow release, whereas the morphology results were supported by computer simulations. The particles were produced under a variety of conditions, and thoroughly characterized using light scattering and microscopic techniques. The particles were spherical and highly stable in solution, and showed drug incorporation at high levels, up to 55% efficiency. Using a dialysis-based in vitro assay, these particles were shown to release the drug via a Fickian diffusion mechanism, leading to gradual drug release over approximately 6 h. These nanoparticles show potential for the use as drug delivery system, while studies on their potential anti-inflammatory action, as well as toxicity and efficacy assays would need to be performed in the future to confirm their suitability as drug delivery candidates.
- Anthelmintic, Antibacterial and Cytotoxicity Activity of Imidazole Alkaloids fromPilocarpus microphyllusLeavesPublication . Rocha, Jefferson A.; Andrade, Ivanilza M.; Véras, Leiz M.C.; Quelemes, Patrick V.; Lima, David F.; Soares, Maria J.S.; Pinto, Pedro L.S.; Mayo, Simon J.; Ivanova, Galya; Rangel, Maria; Correia, Manuela; Mafud, Ana Carolina; Mascarenhas, Yvonne P.; Delerue-Matos, Cristina; Moraes, Josué de; Eaton, Peter; Leite, José R.S.A.Pilocarpus microphyllus Stapf ex Wardlew (Rutaceae), popularly known as jaborandi, is a plant native to the northern and northeastern macroregions of Brazil. Several alkaloids from this species have been isolated. There are few reports of antibacterial and anthelmintic activities for these compounds. In this work, we report the antibacterial and anthelmintic activity of five alkaloids found in P. microphyllus leaves, namely, pilosine, epiisopilosine, isopilosine, epiisopiloturine and macaubine. Of these, only anthelmintic activity of one of the compounds has been previously reported. Nuclear magnetic resonance, HPLC and mass spectrometry were combined and used to identify and confirm the structure of the five compounds. As regards the anthelmintic activity, the alkaloids were studied using in vitro assays to evaluate survival time and damaged teguments for Schistosoma mansoni adult worms. We found epiisopilosine to have anthelmintic activity at very low concentrations (3.125 μg mL-1 ); at this concentration, it prevented mating, oviposition, reducing motor activity and altered the tegument of these worms. In contrast, none of the alkaloids showed antibacterial activity. Additionally, alkaloids displayed no cytotoxic effect on vero cells. The potent anthelmintic activity of epiisopilosine indicates the potential of this natural compound as an antiparasitic agent. Copyright © 2017 John Wiley & Sons, Ltd.
- Characterization and Biological Activities of Ocellatin Peptides from the Skin Secretion of the Frog Leptodactylus pustulatusPublication . Marani, Mariela Mirta; Dourado, Flávio Santos; Quelemes, Patrick Veras; Araujo, Alyne Rodrigues de; Perfeito, Márcia Luana Gomes; Barbosa, Eder Alves; Véras, Leiz Maria Costa; Coelho, Andreia Luísa Rodrigues; Andrade, Etielle Barroso; Eaton, Peter; Longo, João Paulo Figueiró; Azevedo, Ricardo Bentes; Delerue-Matos, Cristina; Leite, José Roberto S. A.Eight new peptides were isolated from the skin secretion of the frog Leptodactylus pustulatus and their amino acid sequences determined by de novo sequencing and by cDNA cloning. Structural similarities between them and other antimicrobial peptides from the skin secretion of Leptodactylus genus frogs were found. Ocellatins-PT1 to -PT5 (25 amino acid residues) are amidated at the C-terminus, while ocellatins-PT6 to -PT8 (32 amino acid residues) have free carboxylates. Antimicrobial activity, hemolytic tests, and cytotoxicity against a murine fibroblast cell line were investigated. All peptides, except for ocellatin-PT2, have antimicrobial activity against at least one Gram negative strain. Ocellatin-PT8 inhibited the growth of Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Salmonella choleraesuis strains with MICs in the 60−240 μM range. No significant effect was observed in human erythrocytes and in a murine fibroblast cell line after exposure to the peptides at MICs. A comparison between sequences obtained by both direct HPLC-MS de novo sequencing and cDNA cloning demonstrates the secretion of mature peptides derived from a pre-pro-peptide structure.
- Chitosan-based silver nanoparticles: A study of the antibacterial, antileishmanial and cytotoxic effectsPublication . Lima, Douglas dos Santos; Gullon, Beatriz; Cardelle-Cobas, Alejandra; Brito, Lucas M; Rodrigues, Klinger AF; Quelemes, Patrick V; Ramos-Jesus, Joilson; Arcanjo, Daniel DR; Plácido, Alexandra; Batziou, Krystallenia; Quaresma, Pedro; Eaton, Peter; Delerue-Matos, Cristina; Carvalho, Fernando Aecio A; Silva, Durcilene Alves da; Pintado, Manuela; Leite, Jose Roberto de SáSilver nanoparticles have been studied as an alternative for treatment of microbial infections and leishmaniasis, without promoting induction of microbial or parasite resistance. In this study, chitosan-based silver nanoparticles were synthesized from silver nitrate (AgNO3), sodium borohydride as a reducing agent, and the biopolymer chitosan as a capping agent. The chitosan-based silver nanoparticles were characterized by ultraviolet–visible, Fourier transform infrared, dynamic light scattering, zeta potential, atomic force microscopy, and transmission electron microscope. The antibacterial assay was performed by determination of the minimum inhibitory concentration. The antileishmanial and the cytotoxic effects induced by AgNO3, chitosan, and chitosan-based silver nanoparticles were analyzed by resazurin and MTT colorimetric assays, respectively. AgNO3, chitosan, and chitosan-based silver nanoparticles induced a marked activity against all bacterial strains and promastigote forms of Leishmania amazonensis at minimum inhibitory concentrations ranging from 1.69 to 3.38 µg Ag/mL. Interestingly, the chitosan-based silver nanoparticles presented less cytotoxicity than the AgNO3 alone and were more active against L. amazonensis than solely chitosan. Furthermore, the cytotoxic concentrations (CC50) of both chitosan and chitosan-based silver nanoparticles against macrophages were significantly higher than the IC50 against promastigotes. Thus, the chitosan-based silver nanoparticles represent a promising alternative for the treatment of microbial infections and leishmaniasis.
- Copper nanoparticles stabilized with cashew gum: Antimicrobial activity and cytotoxicity against 4T1 mouse mammary tumor cell linePublication . Amorim, Adriany; Mafud, Ana Carolina; Nogueira, Silvania; Ramos-Jesus, Joilson; Araújo, Alyne Rodrigues de; Plácido, Alexandra; Neta, Maria Brito; Alves, Michel Muálem Moraes; Carvalho, Fernando Aécio Amorim; Rufino Arcanjo, Daniel Dias; Braun, Sacha; López, Marta Sánchez-Paniagua; López-Ruiz, Beatriz; Delerue-Matos, Cristina; Mascarenhas, Yvonne; Silva, Durcilene; Eaton, Peter; Leite, José Roberto Souza AlmeidaCopper nanoparticles stabilized with cashew (CG-CuNPs) were synthesized by reduction reaction using ascorbic acid and sodium borohydride, using the cashew gum (CG) as a natural polymer stabilizer. Dynamic light scattering, atomic force microscopy, Fourier-transform infrared spectroscopy, UV-Vis spectrophotometry, and x-ray diffraction were used to characterize the nanoparticles (CG-CuNPs), and copper was quantified by electrochemical measurement. The UV-vis spectra of the CG-CuNPs confirmed the formation of nanoparticles by appearance of a surface plasmon band at 580 nm after 24 h of reaction. The Fourier-transform infrared spectrum of CG-CuNPs showed the peak at 1704 cm−1 from cashew gum, confirming the presence of the gum in the nanoparticles. The average size of CG-CuNPs by dynamic light scattering and atomic force microscopy was around 10 nm, indicating small, approximately spherical particles. Antimicrobial assays showed that CG-CuNPs had activity against Staphylococcus aureus ATCC 29213 with a minimal inhibitory concentration of 0.64 mM. The cytotoxicity assay on BALB/c murine macrophages showed lower cytotoxic effects for CG-CuNPs than CuSO4·5H2O. Viability cell assays for CG-CuNPs at (0.250 mM) inhibited by 70% the growth of 4T1 LUC (4T1 mouse mammary tumor cell line) and NIH 3T3 cells (murine fibroblast cells) over a 24-h period. Therefore, CG-CuNPs can be used as an antimicrobial agent with lower cytotoxic effects than the CuSO4·5H2O precursor.
- Identification of Eschweilenol C in derivative of Terminalia fagifolia Mart. and green synthesis of bioactive and biocompatible silver nanoparticlesPublication . Araujo, Alyne Rodrigues de; Ramos-Jesus, Joilson; Oliveira, Taiane Maria de; Carvalho, Andressa Maria A. de; Nunes, Paulo Humberto M.; Daboit, Tatiane Caroline; Carvalho, Ana P.; Barroso, M. Fátima; Almeida, Miguel Peixoto de; Plácido, Alexandra; Rodrigues, Artur; Portugal, Camila C.; Socodato, Renato; Relvas, João B.; Delerue-Matos, Cristina; Silva, Durcilene Alves da; Eaton, Peter; Leite, José Roberto de Souza de A.A green synthetic route was developed to prepare silver nanoparticles (AgNPs) in aqueous solution for biological applications. Eschweilenol C, a compound derivative ellagic acid was identified as the main constituent of the aqueous fraction of the ethanolic extract of Terminalia fagifolia Mart. by NMR analysis. In the green synthesis, the ethanolic extract of T. fagifolia and its aqueous fraction were used to promote silver reduction and nanoparticle stabilization. The synthesized AgNPs presented a spherical or polygonal morphology shape by TEM analysis and AgNPs showed high levels of antioxidant and considerable antibacterial and antifungal activities. Synthesized nanoparticles presented significant antioxidant activity by sequestration of DPPH and ABTS radicals, in addition to iron reduction (FRAP assay) and measurement of antioxidant capacity in ORAC units, in addition, AgNP synthesized with the aqueous fraction also demonstrated antioxidant potential in microglial cells. Gram-positive and Gram-negative bacteria were susceptible to growth inhibition by the nanoparticles, among which the AgNPs formed by the ethanolic extract was the most effective. The data obtained by AFM images suggested that AgNPs could lead to the lysis of bacteria and subsequent death. The antifungal assays showed high efficiency against yeasts and dermatophytes. This work represents the first description of antifungal activity by AgNPs against Fonsecaea pedrosoi, the etiologic agent of chromoblastomycosis. In relation to biocompatibility, the AgNPs induced lower haemolysis than AgNO3.
- In Situ Synthesis of Silver Nanoparticles in a Hydrogel of Carboxymethyl Cellulose with Phthalated-Cashew Gum as a Promising Antibacterial and Healing AgentPublication . Lustosa, Ana; Oliveira, Antônia de Jesus; Quelemes, Patrick; Plácido, Alexandra; Silva, Francilene da; Oliveira, Irisdalva; Almeida, Miguel de; Amorim, Adriany; Delerue-Matos, Cristina; Oliveira, Rita de; Silva, Durcilene da; Eaton, Peter; Leite, José de AlmeidaSilver nanoparticles have been shown to possess considerable antibacterial activity, but in vivo applications have been limited due to the inherent, but low, toxicity of silver. On the other hand, silver nanoparticles could provide cutaneous protection against infection, due to their ability to liberate silver ions via a slow release mechanism, and their broad-spectrum antimicrobial action. Thus, in this work, we describe the development of a carboxymethyl cellulose-based hydrogel containing silver nanoparticles. The nanoparticles were prepared in the hydrogel in situ, utilizing two variants of cashew gum as a capping agent, and sodium borohydride as the reducing agent. This gum is non-toxic and comes from a renewable natural source. The particles and gel were thoroughly characterized through using rheological measurements, UV-vis spectroscopy, nanoparticles tracking analysis, and transmission electron microscopy analysis (TEM). Antibacterial tests were carried out, confirming antimicrobial action of the silver nanoparticle-loaded gels. Furthermore, rat wound-healing models were used and demonstrated that the gels exhibited improved wound healing when compared to the base hydrogel as a control. Thus, these gels are proposed as excellent candidates for use as wound-healing treatments.
- Ocellatin-PT antimicrobial peptides: High-resolution microscopy studies in antileishmania models and interactions with mimetic membrane systemsPublication . Oliveira, Mayara; Gomes-Alves, Ana Georgina; Sousa, Carla; Marani, Mariela Mirta; Plácido, Alexandra; Vale, Nuno; Delerue-Matos, Cristina; Gameiro, Paula; Kuckelhaus, Selma A. S.; Tomás, Ana M.; Leite, José Roberto S. A.; Eaton, PeterAlthough the mechanism of action of antimicrobial peptides (AMPs) is not clear, they can interact electrostatically with the cell membranes of microorganisms. New ocellatin-PT peptides were recently isolated from the skin secretion of Leptodactylus pustulatus. The secondary structure of these AMPs and their effect on Leishmania infantum cells, and on different lipid surface models was characterized in this work. The results showed that all ocellatin-PT peptides have an a-helix structure and five of them (PT3, PT4, PT6 to PT8) have leishmanicidal activity; PT1 and PT2 affected the cellular morphology of the parasites and showed greater affinity for leishmania and bacteria-mimicking lipid membranes than for those of mammals. The results show selectivity of ocellatin-PTs to the membranes of microorganisms and the applicability of biophysical methods to clarify the interaction of AMPs with cell membranes.
- Quaternized cashew gum: An anti-staphylococcal and biocompatible cationic polymer for biotechnological applicationsPublication . Quelemes, Patrick V.; Araújo, Alyne R. de; Plácido, Alexandra; Delerue-Matos, Cristina; Maciel, Jeanny S.; Bessa, Lucinda J.; Ombredane, Alicia S.; Joanitti, Graziella A.; Soares, Maria José dos S.; Eaton, Peter; Silva, Durcilene A. da; Leite, José Roberto S.A.Chemical modifications to cashew gum (CG) structure have been previously reported to obtain new physicochemical characteristics, however until now there were no reports of modifications by introduction of new functional groups to add cationic character. This study presents a quaternization route for CG using a quaternary ammonium reagent. The chemical features of the quaternized cashew gum derivatives (QCG) were analyzed by: FTIR, elemental analysis, degree of substitution, Zeta potential, 1H NMR and 1H-13C correlation (HSQC). QCG were evaluated for their anti-staphylococcal activity by determining minimum inhibitory and bactericidal concentrations against pathogenic Staphylococcus spp. and by imaging using atomic force microscopy. Moreover, the mammalian cell biocompatibility were also assessed through hemolytic and cell toxicity assays. QCG presented promising antimicrobial activity against methicillin-resistant S. aureus and biocompatibility on tested cells. These results show that QCG could be a promising tool in the development of biomaterials with an anti-septic action.
- Quaternized cashew gum: An anti-staphylococcal and biocompatible cationic polymer for biotechnological applicationsPublication . Quelemes, Patrick V.; Araújo, Alyne R. de; Plácido, Alexandra; Delerue-Matos, Cristina; Maciel, Jeanny S.; Bessa, Lucinda J.; Ombredane, Alicia S.; Joanitti, Graziella A.; Soares, Maria José dos S.; Eaton, Peter; Silva, Durcilene A. da; Leite, José Roberto S.A.Chemical modifications to cashew gum (CG) structure have been previously reported to obtain new physicochemical characteristics, however until now there were no reports of modifications by intro-duction of new functional groups to add cationic character. This study presents a quaternization route for CG using a quaternary ammonium reagent. The chemical features of the quaternized cashew gum derivatives (QCG) were analyzed by: FTIR, elemental analysis, degree of substitution, Zeta potential, 1H NMR and 1H-13C correlation (HSQC). QCG were evaluated for their anti-staphylococcal activity by deter-mining minimum inhibitory and bactericidal concentrations against pathogenic Staphylococcus spp. and by imaging using atomic force microscopy. Moreover, the mammalian cell biocompatibility were also assessed through hemolytic and cell toxicity assays. QCG presented promising antimicrobial activity against methicillin-resistant S. aureus and biocompatibility on tested cells. These results show that QCG could be a promising tool in the development of biomaterials with an anti-septic action.