Alcino Palermo de Aguiar

CHEMICAL MODIFICATION OF CROSS-LINKED RESIN BASED ON ACRYLONITRILE FOR ANCHORING METAL IONS

Abstract Network resin based on acrylonitrile has been chemically modified through different reactions to obtain different chelating groups. The beads of resin were synthesized by aqueous suspension copolymerization of acrylonitrile (AN) and divinylbenzene (DVB). The chemical modifications of these beads’ cyano groups were carried out by reaction with hydroxylamine, hydrazine and ethanolamine producing amidoxime, amidrazone and oxazoline groups, respectively. The copolymer and modified resins were characterized by apparent density, surface area, average pore diameter, elemental analysis (CHN), FTIR and optical and electronic microscopies. Qualitative experiments of adsorption were conducted to evaluate the resins (modified and unmodified) on fixing Hg(II), Cd(II), Cu(II), Zn(II), Cd(II), Co(II), Ni(II) and Pb(II) from aqueous solution using batch extractions. Based on the results obtained, it was concluded that it is possible to modify chemically a resin containing cyano groups by different routes and to use these resins as a very low cost effective sorbent for metal ions.

Design, synthesis, and evaluation of hydroxamic acid derivatives as promising agents for the management of Chagas disease.

Today, there are approximately 8 million cases of Chagas disease in the southern cone of South America alone, and about 100 million people are living with the risk of becoming infected. The present pharmacotherapy is sometimes ineffective and has serious side effects. Here, we report a series of 4,5-dihydroisoxazoles incorporating hydroxamate moieties, which act as effective inhibitors of the carbonic anhydrase (CA) from Trypanosoma cruzi (TcCA). One compound (5g) was evaluated in detail and shows promising features as an antitrypanosomal agent. Excellent values for the inhibition of growth for all three developmental forms of the parasite were observed at low concentrations of 5g (IC50 values from 7.0 to <1 μM). The compound has a selectivity index (SI) of 6.7 and no cytotoxicity to macrophage cells. Preliminary in vivo data showed that 5g reduces bloodstream parasites and that all treated mice survived; it was also more effective than the standard drug benznidazole.

Synthesis of crosslinked resin based on methacrylamide, styrene and divinylbenzene obtained from polymerization in aqueous suspension

Abstract A series of porous copolymer beads based on methacrylamide (MA), styrene and divinylbenzene (DVB) was prepared by aqueous suspension polymerization in the presence of diluents to act as precipitants. As MA is totally soluble into aqueous phase, the use of two types of phase transfer agent was investigated, namely: TritonX-100TM [polyoxyethylene-(10)-isooctylphenyl-ether] and tetrabutylammonium perchlorate. The effect of the diluents on the surface appearance and the porous structure of copolymer beads was studied. Suitable particle stabilisation was achieved by using a combination of two suspension agents, namely: gelatin and 2-hydroxy-ethyl-cellulose. The network resins were characterized by optical and scanning electron microscopy, IR spectroscopy, elemental analysis (CHN), apparent density, swelling in different solvents and specific area by BET method. It was observed that the MA incorporation was more effective when TritonTM was employed as phase transfer agent.

Modification of porous copolymers network based on acrylonitrile

SummaryThe preparation of a chelating ion-exchange network based on acrylonitrile was carried out by chemical modification with hydroxylamine. The beads of resin were synthesized by aqueous suspension copolymerization of acrylonitrile (AN), styrene (STY) and divinylbenzene (DVB). The influence of diluent used in the suspension polymerization on the structure of the resulting copolymers was evaluated. The diluents employed were heptane (HEP), toluene (TOL) and anisole (ANI). It was found that the AN incorporation into copolymer structure was dependent on the diluent used. Conversion of nitrile groups into the amidoxime was conducted by treatment with hydroxylamine under alkaline solution. The resins were characterized by apparent density, surface area, average pore diameter, elemental analysis (CHN), FTIR and optical microscopy. Based on the results obtained, it was possible to control the porosity by diluent employed in the synthesis and to modify chemically a resin containing nitrile groups by hydroxylamine reaction.

Microscopic analysis of porosity of 2-vinylpyridine copolymer networks. 1. Influence of diluent

The porous structure of copolymer networks based on 2-vinylpyridine, styrene and divinylbenzene at varied proportions prepared by suspension polymerization was varied by using different kinds of porogen agent, namely toluene, n-heptane, ethyl acetate. The materials were characterized by determination of surface area, average pore diameter and pore volume by BET/BJH, apparent density, elemental analysis (CHN) and swelling degree. Their morphologic characteristics were evaluated by microscopic analyses and correlations among porous structures and reaction parameters were found. It was noted that all synthesized resins have presented narrow particle size distributions; their porosities and visual appearances were dependent on the type and dilution of solvent employed in their syntheses.

Hydroxamic acid derivatives: a promising scaffold for rational compound optimization in Chagas disease.

Abstract This work describes the antitrypanocidal activity of two hydroxamic acid derivatives containing o-ethoxy (HAD1) and p-ethoxy (HAD2) as substituent in the aromatic ring linked to the isoxazoline ring. HAD1 and HAD2 induced a significant reduction in the number of intracellular parasites and consequently showed activity on the multiplication of the parasite. Treatment of cardiomyocytes and macrophages with the compounds revealed no significant loss in cell viability. Ultrastructural alterations after treatment of cardiomyocytes or macrophages infected by Trypanosoma cruzi with the IC50 value of HAD1 revealed alterations to amastigotes, showing initial damage seen as swelling of the kinetoplast. This gave a good indication of the ability of the drug to permeate through the host cell membrane as well as its selectivity to the parasite target. Both compounds HAD1 and 2 were able to reduce the cysteine peptidases and decrease the activity of metallopeptidases

A SIMPLE AND EFFICIENT METHOD FOR THE SYNTHESIS OF NITRILE OXIDE FROM ALDOXIME USING TRICHLOROISOCYANURIC ACID

Treatment of the aldoxime derived from vanilin with trichloroisocyanuric acid in the presence of olefins as dipolarophiles caused the formation of nitrile oxides and subsequent 1,3-dipolar cycloaddition forming the corresponding isoxazoline derivatives in good yields.

Quaternization reaction of 2-vinylpyridine and 4-vinylpyridine network copolymers for 4-nitrophenol adsorption

Este artigo avalia o emprego de copolimeros porosos (a base de estireno-STY e vinilpiridina-VP, reticulados com divinilbenzeno-DVB) como adsorventes de 4-nitrofenol de solucoes aquosas. Os copolimeros foram sintetizados atraves de polimerizacao em suspensao aquosa via radical livre na presenca de heptano (HEP) e tolueno (TOL) em diferentes proporcoes como agentes porogenicos. As unidades de VP nos copolimeros foram modificadas quimicamente pela adicao eletrofilica de monomeros vinilicos funcionalizados (acrilonitrila). Os copolimeros quaternizados foram caracterizados por espectrofotometria na regiao do infravermelho (FTIR), analise elementar (CHN), microscopia otica (OM) e microscopia eletronica de varredura (SEM). This article aims to evaluate porous copolymers (based on styrene-STY and vinylpyridineVP, cross-linked with divinylbenzene-DVB) as adsorbents for 4-nitrophenol from aqueous solution. These copolymers were synthesized by suspension polymerizations in the presence of heptane (HEP) and toluene (TOL) in different proportions as porogenic agents. The VP units of the copolymers were chemically modified by the addition of the electrophilic ethylenic compound (acrylonitrile). The quaternized copolymers were characterized by infrared spectrometry (FTIR), elemental analysis (CHN), optical microscopy (OM) and scanning electron microscopy (SEM).

Peptidase Inhibitors as a Possible Therapeutic Strategy for Chagas Disease

Chagas disease, caused by Trypanosoma cruzi, is one of the neglected parasitic tropical diseases affecting thir- teen million people annually. At present, there are only two compounds used in the clinical treatment to this disease and they were introduced in the 1960s and 1970s. Nifurtimox and Benznidazole have limited effectiveness and serious side ef- fects. New strategies and targets for an effective chemotherapy for American trypanosomiasis need to be developed. Within this framework, the peptidases have aroused great interest as a chemotherapeutic target against Chagas disease. This is because some T. cruzi peptidases have been implicated, among other processes, in host-parasite interactions and parasitic survival in their hosts like cruzipain (cysteine peptidase) and prolyl oligopeptidase (serine peptidase). Besides, some of these peptidases are expressed in all life cycle stages of the parasite and it is essential for replication of the intra- cellular forms. The inhibition of these enzymes has shown high anti-T. cruzi activity in vitro and in vivo. In this review, we describe some peptidase inhibitors that have potential in the fight against T. cruzi. Emphasis is given to cruzipain in- hibitors and the inhibition mechanism proposed for some them. Among these inhibitors are peptidyl irreversible (halo- methyl ketone, diazomethane ketones and vinyl sulfones derivatives) and reversible (aryl ureas and oxadiazoles deriva- tives) inhibitors, besides non-peptidyl inhibitors (thiosemicarbazones, triazole, triazine nitriles and vinyl sulfones deriva- tives). Some serine peptidase inhibitors are also described (tic-based peptides, prolylprolylisoxazoles and prolylprolyli- soxazolines). Other peptidases, including the metallo-, aspartic and threonine (proteosome) peptidases are discussed and along with blocking cruzipain are targets for future therapeutic strategies.

Microscopic characterization of porosity and chemical modification of acrylonitrile copolymer networks

The effects of different kinds of diluents (porogen agents), namely, toluene (TOL), n-heptane (HEP), anisole (ANI) and mixtures of them, on the porous structure of copolymer networks based on acrylonitrile (AN) and divinylbenzene (DVB) prepared by suspension polymerization were analyzed by microscopic analyses [both optical (OM) and scanning electron microscopies (SEM)]. It was noted that all synthesized resins have presented dispersed particles size, and that their porosities were dependent on the type of diluent employed in their syntheses. The amidoximation of cyano groups of AN-DVB copolymers employing two kinds of treatment with hydroxylamine under alkaline solution was also studied.