Tiossemicarbazonas: métodos de obtenção, aplicações sintéticas e importância biológica

Thiosemicarbazones are a class of compounds known by their chemical and biological properties, such as antitumor, antibacterial, antiviral and antiprotozoal activity. Their ability to form chelates with metals has great importance in their biological activities. Their synthesis is very simple, versatile and clean, usually giving high yields. They are largely employed as intermediates, in the synthesis of others compounds. This article is a survey of some of these characteristics showing their great importance to organic and medicinal chemistry.

Estudo dos efeitos do silício e do fósforo na redução da disponibilidade de metais pesados em área de mineração

This study was developed with a soil contaminated by heavy metals, with the purpose of evaluating the action of silicon and phosphorus as protection agents through simple extractions by DTPA. The collected samples were prepared and incubated with five doses of silicon and five doses of phosphorus, with four replicates, amounting to 100 experimental units. After 30 and 60 days, samples of each treatment were collected, submitted to pH analyses and simple extraction by DTPA. The amounts of DTPA-extracted metals depended on the doses of silicon and phosphorus and on the pH. Treatments with silicon and phosphorus was efficient in decreasing the availability of heavy metals in soil.

Análise estatística e optimização de perfis de redução termoprogramada (TPR)

The effect of operational variables and their interaction in TPR profiles was studied using a fractional factorial experimental design. The heating rate and the reducing agent concentration were found to be the most important variables determining the resolution and sensitivity of the technique. They showed opposite effects. Therefore, they should be manipulated preferentially in order to obtain optimized TPR profiles. The effect of sample particle size was also investigated. The tests were carried out within a Cu/Zn/Al2O3 catalyst used for the water-gas shift reaction that presented two distinct species of Cu2+ in TPR profiles.

Redução catalítica seletiva de óxidos de nitrogênio sobre hematita contendo cobre

The activity of copper-doped hematite in the SCR with propane, in the presence of oxygen, was evaluated in this work. It was found that copper sulfate led to the production of solids with different specific surface areas depending on the amount of copper. The sulfur and copper species were mainly located on the surface. The copper-containing catalysts were more active in the reduction of nitrogen oxides and less active in the propane oxidation as compared to pure hematite. This behavior was assigned to an association of both sulfur and copper species to produce new sites active for NO reduction.

Ocorrência e atividade biológica de quassinóides da última década

Quassinoids, the bitter principles of the Simaroubaceae family, are a group of structurally complex and highly oxygenated degraded triterpenes. They are divided into five groups according to their basic skeleton, C-18, C-19, C-20, C-22 and C-25. In recent years, attention has been focused on quassinoids because several of them have shown promising biological activities. This paper features a review of some characteristics of these compounds, updating known information with discoveries from the last decade and covering chemical structures, basic skeletons, occurrence in genus and species, besides detailed studies of biological activities such as antitumor, antimalarial, phytotoxic, antifeedant, insecticidal, anti-inflammatory and antiulcer.

Redução de vitamina C em suco de caju (Anacardium occidentale L.) industrializado e cajuína

Vitamin C degradation was evaluated in industrialized cashew juice of high pulp content and in cajuina by the method of Tillmans during eleven days of storage after the opening of the flask. For recently opened juices, vitamin C was found in the concentration range of 112 to 170 mg for 100 g of juice. The degradation of vitamin C in industrialized cashew juices changes when different additives are used. All of the cajuinas presented a vitamin C content below that specified on the label.

Cinética de redução do catalisador CuO/ZnO/Al2O3

The reduction kinetics of a CuO/ZnO/Al2O3 catalyst by hydrogen was investigated isothermally and by temperature programmed reduction (TPR). Two reducible Cu2+ species were detected; the first one was identified as CuO bulk and the other as Cu2+ strongly interacting with alumina, possibly in the form of copper aluminate. The activation energies for the reduction of these two species were 60 and 90 kJ mol-1, respectively, and the reaction order with respect to hydrogen was one. The isothermal reduction data showed that the isotropic growth model is the most appropriate to describe the reaction rate data for both Cu2+ species.

Composição química e atividade biológica das folhas e frutos de Triphasia trifolia

The chemical composition of the essential oils from leaves and fruits of Triphasia trifolia was analyzed by GC-FID and GC-MS. The major constituents of oil obtained from leaves were sabinene (35.4%) and myrcene (34.1%), while the prevalent compounds in oil from fruits were sabinene (37.2%), beta-pinene (23.95) and gamma-terpinene (16.3%). Both oils showed moderate antimicrobial activity. The fruit decoction was also investigated leading to the isolation of the coumarins isopimpinelin, (R)-byakangelicin and (S)-mexoticin. From leaves were isolated the coumarins (R)-byakangelicin, aurapten, (S)-mexoticin, isosibiricin, isomerazin and coumurrayin and the flavonoid vitexin. All coumarins showed cholinesterase inhibition on TLC tests.

Síntese, avaliação biológica e modelagem molecular de arilfuranos como inibidores da enzima tripanotiona redutase

Trypanosoma cruzi is a protozoan parasite that causes a severe disease (Chagas'disease) in Central and South America. The currently available chemotherapeutic agents against this disease are still inadequate. The enzyme trypanothione reductase (TR) is considered a validated molecular target for the development of new drugs against this parasite. In this regard, a series of arylfurans based on 2,5-bis-(4-acetamidophenyl)furan was synthesized and tested for their in vitro inhibitory activity against TR. Molecular modeling studies of putative enzyme-inhibitor complexes revealed a possible mechanism of interaction. From synthesized compounds, a benzylaminofuran derivative was found to be more active than the lead compound.

Métodos de obtenção, reatividade e importância biológica de 4-tiazolidinonas

Molecules containing the 4-thiazolidinone ring are known to possess a wide range of biological properties including antimicrobial and anti-inflammatory activities among others. These compounds can be synthesized by cyclization reactions involving alpha-haloacetic acid or alpha-mercaptoacetic acid and employed in several chemoselective reactions. Comprehensive reviews have been written on 4-thiazolidinones in 1961 by Brown and in 1980 by Singh et al. In the recent literature, some new synthesis methods for 4-thiazolidinone derivatives and several reactions have been reported. These advances warrant to review the chemical and biological properties of compounds with this important heterocycle employed in synthetic organic chemistry and medicinal chemistry.

Reatividade de ciclopropenonas frente a nucleófilos e sua correlação com potenciais de redução em meio aprótico

In this work we studied the reactivity of isopropylphenylcyclopropenone towards some nitrogen nucleophiles whose reactions with methylphenylcyclopropenone and diphenylcyclopropenone were previously studied. The electrochemical behavior of these cyclopropenones was evaluated for the first time, and a correlation between electrochemical parameters and reactivity of this class of compounds was done.

Diastereosseletividade na redução de enonas bicíclicas com hidretos volumosos

Reduction of five substituted octalones employing lithium tri-sec-butylborohydride (L-selectride®) in THF and ethyl ether led to allylic alcohols with moderate diastereoselectivity. The stereoselectivity of addition of bulky hydrides showed to be different from most examples in the literature and was strongly influenced by substitution on the octalone ring.

Atividade biológica do lapachol e de alguns derivados sobre o desenvolvimento fúngico e em germinação de sementes

The natural quinones lapachol, α-lapachone and β-lapachone, and the synthetic derivative β-lapachone-3-sulfonic-acid were assayed for inhibition of fungal growth (Fusarium oxysporum) and germination of lettuce seeds (Lactuca sativa L.). β-Lapachone has the strongest activity as a germination inhibitor and lapachol shows no effect. β-Lapachone, followed by lapachol, are the most active in reducing fungal growth.

Composição química e atividade biológica de extrato oleoso de própolis: uma alternativa ao extrato etanólico

Propolis is mostly used as hydroalcoholic extract. Recently there has been a growing number of patents dealing with new solvents for preparing propolis extracts. This study aimed to prepare edible oil propolis extracts and compare their chemical composition and biological activity with ethanolic propolis extracts. ESI-MS and spectrophotometric methods were used for qualitative and quantitative analyses, respectively. Antibacterial activity was evaluated by diffusion in agar. Cytotoxicity was tested by MTT assay using tumor cell lines. The oil is able to extract bioactive compounds from propolis. Further studies are needed to improve extraction efficiency and to characterize the active components.

Óxidos do tipo perovskita para reação de redução de no com CO

In this work, the perovskite-type oxides LaNiO3, LaMnO3, La0,7Sr0,3NiO3 and La0,7Sr0,3MnO3 were prepared by co-precipitation and tested in the NO reduction with CO at 400 and 500 ºC for 10 h. The catalysts were characterized by X-ray diffraction, temperature programmed reduction with hydrogen, nitrogen adsorption and chemical analysis. The nonstoichiometric oxygen was quantified by temperature programmed reduction, and the catalytic tests showed that the La0,7Sr0,3MnO3 catalyst presented the higher performance for the reduction reaction of NO with CO. The partial substitution of lanthanum by strontium increased the NO conversion and the N2 yield.