oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Electrochemical Properties of Biologically Active Heterocyclic Naphthoquinones
Tonholo, Josealdo;Freitas, Luciano R.;Abreu, Fabiane C. de;Azevedo, Dayse C.;Zani, Carlos L.;Oliveira, Alaíde B. de;Goulart, Marília O. F.;
Journal of the Brazilian Chemical Society , 1998, DOI: 10.1590/S0103-50531998000200008
Abstract: a series of natural and synthetic heterocyclic naphthoquinones, some of them with anti-plasmodial and trypanocidal activities, were studied by cyclic voltammetry in aprotic media (dmf/tbap). in this solvent, the voltammograms of the quinones show two pairs of waves, corresponding to reversible or quasi-reversible one-electron transfer processes to form the semiquinone anion radical (q·) and the dianion (q2-). within the studied series, ortho-quinones undergo reduction easier than isomeric para-quinones. however, para-naphthoquinones fused to an aromatic heterocyclic ring are more easily reduced than the corresponding ortho-naphtoquinones with a non aromatic heterocycle. substituents effects correlated very well with the first reduction potential (epc1) and the half wave potential (e1/2). high yield reductive acetylation was achieved by electrolyses in the presence of acetic anhydride. comparison of electrochemical data with reported antimalarial activities showed no correlation, differently from the already reported trend in relation to trypanocidal activities.
The Trypanocidal Activity of Naphthoquinones: A Review  [PDF]
Ant?nio Ventura Pinto,Solange Lisboa de Castro
Molecules , 2009, DOI: 10.3390/molecules14114570
Abstract: Naphthoquinones are compounds present in several families of higher plants. Their molecular structures confer redox properties, and they are involved in multiple biological oxidative processes. In folk medicine, especially among Indian populations, plants containing naphthoquinones have been employed for the treatment of various diseases. The biological redox cycle of quinones can be initiated by one electron reduction leading to the formation of semiquinones, unstable intermediates that react rapidly with molecular oxygen, generating free radicals. Alternatively, the reduction by two electrons, mediated by DT-diphorase, leads to the formation of hydroquinone. Lapachol, α-lapachone and β-lapachone, which are isolated from the heartwood of trees of the Bignoniaceae family, are examples of bioactive naphthoquinones. In this review, we will discuss studies investigating the activity of these natural products and their derivatives in the context of the search for alternative drugs for Chagas disease, caused by Trypanosoma cruzi, a neglected illness that is endemic in Latin America.
Tabebuia avellanedae naphthoquinones: activity against methicillin-resistant staphylococcal strains, cytotoxic activity and in vivo dermal irritability analysis
Eliezer Pereira, Thelma Machado, Ivana Leal, Desyreé Jesus, Clarissa Damaso, Antonio Pinto, Marcia Giambiagi-deMarval, Ricardo Kuster, Kátia dos Santos
Annals of Clinical Microbiology and Antimicrobials , 2006, DOI: 10.1186/1476-0711-5-5
Abstract: The compounds β-lapachone, 3-hydroxy β N lapachone and α-lapachone were tested to determine the MIC values against methicillin-resistant S. aureus, S. epidermidis and S. haemolyticus strains, being the two last ones hetero-resistant to vancomycin. Experiments of protein synthesis analysis to investigate the naphthoquinones action were assessed. In vitro toxicity to eukaryotic BSC-40 African Green Monkey Kidney cell cultures and in vivo primary dermal irritability in healthy rabbits were also performed.The compounds tested showed antibacterial activity (MICs of 8, 4/8 and 64/128 μg/mL to β-lapachone, 3-hydroxy β N lapachone and α-lapachone, respectively), but no bactericidal activity was observed (MBC > 512 μg/mL for all compounds). Although it has been observed toxic effect in eukaryotic cells, the compounds were shown to be atoxic when applied as topic preparations in healthy rabbits. No inhibition of proteins synthesis was observed.Our results suggest that quinones could be used in topic preparations against wound infections caused by staphylococci, after major investigation of the pharmacological properties of the compounds. Studies about the use of these compounds on tumoral cells could be carried on, due to their effect in eukaryotic cells metabolism.The south-american tree Tabebuia avellanedae (Bignoneaceae) is known in the popular medicine as Ipê-Roxo, Pau D'Arco, Lapacho, among others [1,2]. For many decades, preparations made with this plant were used in South and North America as antineoplasic, antifungal, antiviral, antimicrobial, antiparasitical and anti-inflammatory treatment [1-5]. Pharmacological activities of this species are related to saponins, flavonoids, coumarins, and natural antibiotics [3,6], while the chemical profile presented by most of the studies has shown the quinones as the main active substances [1-4,6].The increasing prevalence of multi-resistant bacteria made the search of new antimicrobial agents an important strategy for the establ
Synthesis of branched naphthoquinones from castor oil
Adriano Olímpio da Silva,Dênis P. de Lima,Rosangela da Silva Lopes,Ricardo Vieira de Lima
Orbital : the Electronic Journal of Chemistry , 2012,
Abstract: The naphthoquinones are cyclic aromatic α,β-dienonas with a basic framework derived from naphthalene. They are also found in many higher plants, algae, fungi and as the product of the metabolism of some bacteria having large biologica activity described in the literature such as antibacterial, anti-inflammatory, antitumor, anticancer and trypanocidal [1-3]. Castor oil is an abundant raw material in Brazil of great versatility and, it is present in biodiesel production, surfactants, cosmetics and others. Considering the importance of naphthoquinones and, the availability of the ricinoleic acid from castor oil, the aim of this study was the preparation of new branched naphthoquinones in order to test their trypanocidal activity. Castor oil was submitted to saponification with sodium hydroxide, ethanol and water under reflux for 6 h. We then carried out an acid hydrolysis with hydrochloric acid and the formed ricinoleic acid was extracted with ethyl acetate. Following, through Kochi-Anderson addition reaction it was performed the alkylation of a naphthoquinone 1 and 2, using ammonium persulfate, silver nitrate, acetonitrile and water, under heating at 70-80 ° C during 3 h, to give the branched naphthoquinones 4 and 5 (scheme 1). The naphthoquinone 3 will be similarly submitted to this procedure. The naphthoquinones 4 and 5 were purified by column chromatography on sílica gel using hexane as the eluent. The compounds were characterized by mass spectrometry and 1H and 13CNMR spectroscopy.
Theoretical and voltammetric studies of 5-Nitro-heterocyclic derivatives with potential trypanocidal activities
Paula, Fávero R.;Trossini, Gustavo H. G.;Ferreira, Elizabeth I.;Serrano, Silvia H. P.;Menezes, Carla M. S.;Tavares, Leoberto C.;
Journal of the Brazilian Chemical Society , 2010, DOI: 10.1590/S0103-50532010000400022
Abstract: stereoelectronic properties of nitro-heterocyclic bioisosteric congeners were investigated using theory-level quantum chemistry and cyclic voltammetry with the goal of determining physico-chemical properties that affect the redox potential of the nitro group. molecular geometry, physicochemical properties and stereoelectronic surfaces, such as molecular electrostatic potential, and homo and lumo orbitalar distributions, were calculated using the am1 semiempirical method. the redox potential of nitro-heterocyclic compounds, which corresponds to the (ar-no2/ar-no2?- ) redox couple, was measured in aprotic media (dmso and 0.1 mol l-1 bu4nh4bf4) using glassy carbon as working electrode, pt wire, ag/agcl, kcl(sat) as counter and reference electrodes, respectively. analysis of minimal energy conformers of all derivatives indicated a break in structural planarity located between the hydrazine nitrogen and benzamide moiety. no statistical correlation was obtained using the pls regression method, taking in account all physicochemical properties and the redox potential, which might result from the lack of coplanarity effect in the molecular structure of the compounds.
Article Synthesis and Trypanocidal Activity of Novel 2,4,5-Triaryl-N-Hydroxylimidazole Derivatives  [PDF]
Ramon Borges da Silva,Vanessa Brand?o Loback,Kelly Salom?o,Solange Lisboa de Castro,James L. Wardell,Solange M. S. V. Wardell,Thadeu Estevam Moreira Maramaldo Costa,Carmen Penido,Maria das Gra?as Muller Oliveira de Henriques,Samir Aquino Carvalho,Edson Ferreira da Silva,Carlos Alberto Manssour Fraga
Molecules , 2013, DOI: 10.3390/molecules18033445
Abstract: Herein, we report the design, synthesis and trypanocidal activity of some novel trisubstituted imidazole derivatives. These heterocyclic derivatives were structurally planned by exploring the concept of molecular hybridisation between two arylhydrazones derived from megazol, which has potent trypanocidal activity. The trypanocidal activity of these triarylimidazole derivatives was evaluated against infective trypomastigote forms of T. cruzi and the derivative 2'-(4-bromophenyl)-1-methyl-5'-phenyl-1 H,3' H-2,4'-biimidazol-3'-ol showed moderate biological activity (IC 50 = 23.9 μM) when compared to benznidazole, a standard trypanocidal drug. These compounds did not present cytotoxic effects at concentrations near the trypanocidal IC 50, being considered a good starting point for the development of new anti-Chagas drug candidates.
In vitro antimalarial activity of fractions and constituents isolated from Tabebuia billbergii
Gómez-Estrada,Harold; Gaitán-Ibarra,Ricardo; Díaz-Castillo,Fredyc; Pérez,Hilda A; Medina,José D;
Revista Cubana de Plantas Medicinales , 2012,
Abstract: introduction: in vitro antimalarial activity of naphthoquinones (1-5), isolated from tabebuia billbergii (bureau & k. schum.) standl., was investigated. tabebuia billbergii, commonly known as guayacán, is a plant traditionally used in the amazon in numerous conditions like bacterial and fungal infections, fever, syphilis, malaria, trypanosomiasis, as well as stomach and bladder disorders, and tumours. objective: to study the dichloromethane extracts of both the trunk and the inner bark of tabebuia billbergii and to demonstrate the antimalarial activity of some of its bioactive components. methods: some bioactive components were evaluated for the antimalarial activity against plasmodium berghei, by using the inhibition of the differentiation cycle of the parasite measure by the 3h-hypoxanthine incorporation and compared to that obtained for chloroquine. results: conventional chromatographic techniques and bioassay-guided fractionation (artemia salina) allowed isolating from the active fractions one naphthoquinone (lapachol) and four naphtho-furan-4,9-diones. these compounds proved to have an important antiplasmodial effect, with very encouraging ic50's, especially when compared to the results shown by chloroquine in the same experiment. in addition, two triterpenes, β-sitosterol and stigmasterol, were obtained from the bark. conclusions: the activity-guided fractionation (a. salina) of dichloromethane extracts of the trunk and the inner bark of tabebuia billbergii led to the isolation and the identification of five quinonoid compounds with antiplasmodial effect. the significant inhibitory activity in vitro against plasmodium berghei observed for compound 2-acetyl-naphtho-[2,3b]-furan-4,9-dione allow us to present them as a potential antimalarial compound.
Biologically Relevant Heterocyclic Compounds  [PDF]
Lucjan Strekowski
Molecules , 2004, DOI: 10.3390/90300039
Abstract: Heterocyclic chemistry is a rapidly growing branch of organic chemistry. [...]
In vitro antimalarial activity of fractions and constituents isolated from Tabebuia billbergii Actividad antimalárica in vitro de fracciones y constituyentes aislados de Tabebuia billbergii
Harold Gómez-Estrada,Ricardo Gaitán-Ibarra,Fredyc Díaz-Castillo,Hilda A Pérez
Revista Cubana de Plantas Medicinales , 2012,
Abstract: Introduction: in vitro antimalarial activity of naphthoquinones (1-5), isolated from Tabebuia billbergii (Bureau & K. Schum.) Standl., was investigated. Tabebuia billbergii, commonly known as guayacán, is a plant traditionally used in the Amazon in numerous conditions like bacterial and fungal infections, fever, syphilis, malaria, trypanosomiasis, as well as stomach and bladder disorders, and tumours. Objective: to study the dichloromethane extracts of both the trunk and the inner bark of Tabebuia billbergii and to demonstrate the antimalarial activity of some of its bioactive components. Methods: some bioactive components were evaluated for the antimalarial activity against Plasmodium berghei, by using the inhibition of the differentiation cycle of the parasite measure by the 3H-hypoxanthine incorporation and compared to that obtained for chloroquine. Results: conventional chromatographic techniques and bioassay-guided fractionation (Artemia salina) allowed isolating from the active fractions one naphthoquinone (lapachol) and four naphtho-furan-4,9-diones. These compounds proved to have an important antiplasmodial effect, with very encouraging IC50's, especially when compared to the results shown by Chloroquine in the same experiment. In addition, two triterpenes, β-sitosterol and stigmasterol, were obtained from the bark. Conclusions: the activity-guided fractionation (A. salina) of dichloromethane extracts of the trunk and the inner bark of Tabebuia billbergii led to the isolation and the identification of five quinonoid compounds with antiplasmodial effect. The significant inhibitory activity in vitro against Plasmodium berghei observed for compound 2-acetyl-naphtho-[2,3b]-furan-4,9-dione allow us to present them as a potential antimalarial compound. Introducción: se evaluó la actividad antimalárica in vitro de una serie de naftoquinonas (1-5), aisladas de Tabebuia billbergii (Bureau & K. Schum.) Standl., que es conocida comúnmente como guayacán, una planta utilizada tradicionalmente en la Amazonía en numerosos problemas de salud como infecciones bacterianas y fúngicas, fiebre, sífilis, paludismo, tripanosomiasis, así como en problemas estomacales, tumores y trastornos de la vejiga. Objetivo: estudiar los extractos en diclorometano tanto del tronco como la corteza interna de Tabebuia billbergii y evaluar la actividad antimalárica de algunos de sus componentes bioactivos. Métodos: la actividad antimalárica contra Plasmodium berghei se evaluó en algunos componentes bioactivos, por la inhibición del ciclo de la diferenciación de la medida de los parásit
Mitragyna ciliata and its trypanocidal activity
HA Ogbunugafor, VI Okochi, J Okpuzor, T Adedayo, S Esue
African Journal of Biotechnology , 2007,
Abstract: The trypanocidal activity of different fractions of hydroethanolic root extract of Mitragyna ciliata Aubrev and Pellegr (Rubiaceae) were evaluated in rats infected with Trypanosoma brucei field isolates from a cow. Oral administration of the fractions at a dose of 100 mg/kg for 5 days (10 days post-infection) indicated that only butanol fraction showed trypanocidal activity with inhibition percent of 68.68. The activities of oxidative stress enzymes; superoxide dismutase (SOD) and catalase in the infected rats were determined. SOD activity was significantly higher than control (1.64 ± 0.026 I/U) in all fractions except ethyl acetate (1.56 ± 0.031 I/U). Catalase showed a significant decrease in activity in butanol (2.05 ± 0.015 I/U) and chloroform (2.18 ± 0.061 I/U) fractions compared to control (2.30 ± 0.015 I/U). Butanol fraction might have affected the redox equilibrium of the infected animals causing oxidative stress to the parasites. This is the basis of inhibition of growth of the parasites by the butanol fraction.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.