RESUMEN
Four undescribed secocycloartane monoglycosides (1-4) were isolated from an ethanolic extract of the dry flowers of Cordia lutea Lam. Their structural assignment is based on NMR and MS analysis. Their stereochemistry is confirmed by molecular modelling studies using DFT-NMR calculations done for compound 3. In vitro antibacterial activity of the four compounds was moderate on Helicobacter pylori (MIC = 15.6 µg/mL), and much weaker on Staphylococcus aureus, Pseudomonas aeruginosa or Escherichia coli (MIC >125 µg/mL). Toxicity evaluated against RAW 264.7 cells was weak (IC50 values ranging from 24 to 41 µM i.e. 15 to 24 µg/mL), but in the same range as anti-Helicobacter activity.
Asunto(s)
Cordia , Antibacterianos , Cordia/química , Glicósidos/farmacología , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Extractos Vegetales/químicaRESUMEN
Four isocedrenes (1: â-â4: ), including one new compound (2: ), were isolated from an ethanolic extract of the aerial parts of Perezia multiflora by bioactivity-guided fractionation. For compounds 1: and 3: , a revised stereochemical assignment is proposed based on molecular modeling studies using DFT-NMR calculations. Antiparasitic activity of the four compounds was evaluated using an in vitro culture of Plasmodium falciparum and axenic amastigotes of Leishmania infantum. IC50 values ranged from 0.81 to 16.1 µM (P. falciparum) and 0.16 to 2.03 µM (L. infantum). Toxicity was evaluated against J774A.1 mouse macrophages or human macrophages generated from THP-1 monocytic cells (IC50 values ranging from 0.16 to 2.64 µM). Compound 4: exhibited weak selectivity against P. falciparum with a selectivity index (SI = CC50/IC50) of 3. No selectivity was observed for compounds 1: â-â3: against both parasites.
Asunto(s)
Antiprotozoarios , Asteraceae , Leishmania infantum , Malaria Falciparum , Humanos , Plasmodium falciparumRESUMEN
A series of novel hybrids of artemisinin (ART) with either a phytormone endoperoxide G factor analogue (GMeP) or chloroquine (CQ) and conjugates of the same compounds with the polyamines (PAs), spermidine (Spd), and homospermidine (Hsd) were synthesized and their antiplasmodial activity was evaluated using the CQ-resistant P. falciparum FcB1/Colombia strain. The ART-GMeP hybrid 5 and compounds 9 and 10 which are conjugates of Spd and Hsd with two molecules of ART and one molecule of GMeP, were the most potent with IC50 values of 2.6, 8.4, and 10.6 nM, respectively. The same compounds also presented the highest selectivity indexes against the primary human fibroblast cell line AB943 ranging from 16â¯372 for the hybrid 5 to 983 for the conjugate 10 of Hsd.
RESUMEN
A series of isoniazid derivatives bearing a phenolic or heteroaromatic coupled frame were obtained by mechanochemical means. Their pH stability and their structural (conformer/isomer) analysis were checked. The activity of prepared derivatives against Mycobacterium tuberculosis cell growth was evaluated. Some compounds such as phenolic hydrazine 1a and almost all heteroaromatic ones, especially 2, 5 and 7, are more active than isoniazid, and their activity against some M. tuberculosis MDR clinical isolates was determined. Compounds 1a and 7 present a selectivity index >1400 evaluated on MRC5 human fibroblast cells. The mechanism of action of selected hydrazones was demonstrated to block mycolic acid synthesis due to InhA inhibition inside the mycobacterial cell.
Asunto(s)
Antituberculosos/farmacología , Isoniazida/síntesis química , Isoniazida/farmacología , Antituberculosos/química , Muerte Celular/efectos de los fármacos , Línea Celular , Cromatografía en Capa Delgada , Humanos , Hidrazonas/síntesis química , Hidrazonas/química , Hidrazonas/farmacología , Concentración de Iones de Hidrógeno , Hidrólisis , Isomerismo , Isoniazida/química , Espectroscopía de Resonancia Magnética , Pruebas de Sensibilidad Microbiana , Modelos Moleculares , Conformación Molecular , Mycobacterium tuberculosis/efectos de los fármacos , Mycobacterium tuberculosis/crecimiento & desarrollo , Teoría Cuántica , Espectrofotometría Ultravioleta , TermodinámicaRESUMEN
Mechanism of the addition of molecular oxygen on the dienolic form of the 2-alkylidene-1,3-cyclohexadione was investigated by quantum chemical calculations using the approximate projection method developed by Yamaguchi. The complete reaction pathway of the formation of the endoperoxide is described. The crossing between triplet and singlet potential energy surfaces has been located. A multireference complete active space self-consistent field calculation has been performed to strengthen the results.
RESUMEN
A series of GEQ analogues bearing pyrrolidinone or pyrrolidine cores were synthesized and evaluated against InhA, essential target for Mycobacterium tuberculosis (M.tb) survival. The compounds were also evaluated against M.tb H37Rv growth. Interestingly, some of the compounds, not efficient as InhA inhibitors, are active against M.tb with MICs up to 1.4 µM. In particular, compound 4b was screened with different M.tb mutated strains in order to identify the cellular target, but without success, suggesting a new possible mode of action.
Asunto(s)
Proteínas Bacterianas/antagonistas & inhibidores , Diseño de Fármacos , Mycobacterium tuberculosis/efectos de los fármacos , Oxidorreductasas/antagonistas & inhibidores , Pirrolidinas/química , Pirrolidinas/farmacología , Pirrolidinonas/química , Pirrolidinonas/farmacología , Antituberculosos/química , Antituberculosos/metabolismo , Antituberculosos/farmacología , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Evaluación Preclínica de Medicamentos , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/metabolismo , Inhibidores Enzimáticos/farmacología , Escherichia coli/efectos de los fármacos , Proteínas de Transporte de Membrana/metabolismo , Pruebas de Sensibilidad Microbiana , Simulación del Acoplamiento Molecular , Mycobacterium tuberculosis/metabolismo , Oxidorreductasas/química , Oxidorreductasas/metabolismo , Conformación Proteica , Pirrolidinas/metabolismo , Pirrolidinonas/metabolismo , Relación Estructura-ActividadRESUMEN
Artemisinin and its derivatives are peroxide-containing compounds targeting P. falciparum. We review here structural analogues of bicyclic peroxides belonging to the G factors family presenting antimalarial properties. They were synthesised under Mannich type conditions, followed by an autoxidation step resulting exclusively in the peroxide. As the electron transfer from haem or free iron to the peroxide is the first step in the mode of action of artemisinin-like compounds, the redox properties of some endoperoxides were studied by electrochemistry allowing the evaluation of the reduction standard potentials. The Fe(II) induced reduction was also investigated and the reactivity of the C-centered radical intermediate formed was linked to the antimalarial activity. These bicyclic peroxides both with various hybrid molecules containing the endoperoxide framework were evaluated in vitro against Plasmodium falciparum. They exhibited moderate to good activities.
Asunto(s)
Antimaláricos/farmacología , Compuestos Bicíclicos con Puentes/farmacología , Hierro/química , Peróxidos/farmacología , Antimaláricos/química , Compuestos Bicíclicos con Puentes/química , Oxidación-Reducción , Peróxidos/químicaRESUMEN
Diastereoselective autoxidation allowed preparation of new tricyclic endoperoxides. These compounds and their methylated analogs were evaluated against the in vitro growth of Plasmodium falciparum, the malaria-causing parasite, showing moderate activities. However, hybrid molecules composed of the tricyclic peroxide moiety and 7-chloro-4-aminoquinoline were synthesized and displayed a marked increase in antiplasmodial activity.
Asunto(s)
Aminoquinolinas/química , Antimaláricos/síntesis química , Radicales Libres/química , Hierro/química , Peróxidos/síntesis química , Plasmodium falciparum/efectos de los fármacos , Antimaláricos/farmacología , Artemisininas/farmacología , Cloroquina/farmacología , Diseño de Fármacos , Eritrocitos/efectos de los fármacos , Eritrocitos/parasitología , Eritrocitos/patología , Humanos , Hipoxantina/metabolismo , Concentración 50 Inhibidora , Oxidación-Reducción , Peróxidos/farmacología , Plasmodium falciparum/crecimiento & desarrollo , TritioRESUMEN
Two series of streptocyanine dyes incorporating cyclic peroxide or 4-aminoquinoline moieties are prepared and X-ray diffraction structures for three compounds are determined. All hybrid dyes show good antiplasmodial activity (0.06 to 0.66 µM) and are not or are slightly cytotoxic, except 10a.
Asunto(s)
Aminoquinolinas/farmacología , Antimaláricos/farmacología , Carbocianinas/farmacología , Peróxidos/farmacología , Plasmodium falciparum/efectos de los fármacos , Aminoquinolinas/síntesis química , Aminoquinolinas/química , Animales , Antimaláricos/síntesis química , Antimaláricos/química , Carbocianinas/síntesis química , Carbocianinas/química , Línea Celular Tumoral , Cristalografía por Rayos X , Humanos , Modelos Moleculares , Estructura Molecular , Pruebas de Sensibilidad Parasitaria , Peróxidos/síntesis química , Peróxidos/química , Estereoisomerismo , Células VeroRESUMEN
We study structural analogues of endoperoxides belonging to the family of G factors which present moderate to good antimalarial activity. Their biological activity is related to the reduction and cleavage of the O-O bond. Generally, the O-O bond reduction of model endoperoxides, as well as artemisinin, occurs by a concerted dissociative electron transfer (ET) mechanism. For the G3 and G3Me compounds, the experimental counterpart indicates an unexpected competition between a concerted and a stepwise mechanism, but no intermediate species can be isolated. We thus perform DFT studies on the reduction of G3 and G3Me compounds. We confirm the formation of an intermediate radical anion followed by cleavage of the O-O bond in a second step. We characterize the stable conformations for the radical anions G(3)(*-) and G(3)Me(*-) resulting from the ET and the associated reaction pathway. We also calculate the reorganization energy upon ET in relation to the Marcus theory using the DFT method. These results provide valuable insight into understanding the biological activity of G-factor endoperoxides as potential therapeutic antimalarial agents.
Asunto(s)
Antimaláricos/química , Peróxidos/química , Artemisininas/química , Transporte de Electrón , Modelos Teóricos , Oxidación-Reducción , Teoría CuánticaRESUMEN
The title compound behaves as an efficient cheletropic trap for both NO and NO(2) radicals in the presence of oxygen, yielding EPR observable nitroxide and alkoxynitroxide, respectively.
Asunto(s)
Ciclohexanonas/química , Espectroscopía de Resonancia por Spin del Electrón , Óxido Nítrico/química , Oxidación-Reducción , Oxígeno/químicaRESUMEN
The spontaneous addition of air oxygen to a dienolic compound, yielding a cyclic peroxide, was followed by spin trapping (ST) combined with EPR spectroscopy and mass spectrometry (MS). Using two different nitrones, the ST/EPR study allowed the detection of the spin adduct of a radical intermediate, and the radical centre in the addend was identified after similar experiments performed with two different (13)C-labelled analogues of the substrate. The media were also submitted to electrospray ionisation, in both positive and negative modes, for structural characterisation of the spin adducts by tandem mass spectrometry. This allowed the structure of the hydroxylamine derivatives of the nitroxides formed to be identified. Following these results, a mechanism pathway was proposed for this autoxidation.
Asunto(s)
Alquenos/química , Espectrometría de Masas , Peróxidos/química , Espectroscopía de Resonancia por Spin del Electrón , Organofosfonatos/química , Oxidación-Reducción , Oxígeno/química , Piridinas/químicaRESUMEN
Several streptocyanine dyes were synthesized that contain polymethine chains of varying length. Their in vitro antimalarial activities were evaluated against the virulent P. falciparum parasite. In addition to the influence of polymethine chain length, the effects of structural modifications at nitrogen end groups, para substitution of the phenyl groups, and counter-anions were studied. The most potent antimalarial activities were found for heptacarbon chain streptocyanines, with an IC(50) value of 60 nM. Interestingly, most of the compounds were less cytotoxic toward the mammalian cells tested. The best selective toxicity profiles were found for pentacarbon chain streptocyanines, which have a good in vitro specificity index.
Asunto(s)
Antimaláricos/síntesis química , Carbocianinas/química , Animales , Antimaláricos/química , Antimaláricos/toxicidad , Línea Celular Tumoral , Humanos , Ratones , Plasmodium falciparum/efectos de los fármacos , Relación Estructura-ActividadRESUMEN
A rearrangement in basic medium of the natural endoperoxide G3-factor extracted from Eucalyptus grandis is described. Evidence to support a 1,2-dioxetane intermediate that decomposes with weak luminescence emission (quantum yield) is presented.
Asunto(s)
Eucalyptus/química , Luminiscencia , Peróxidos/química , Concentración de Iones de Hidrógeno , CinéticaRESUMEN
The reduction of the bicyclic G-factor endoperoxides G3 and G3Me was studied in N,N-dimethylformamide using cyclic voltammetry and convolution analysis. Electron transfer leads to irreversible cleavage of the O--O bond. Detailed analysis of the voltammetry curves reveals a non-linear dependence on the transfer coefficient indicating a mechanistic transition from a stepwise mechanism to one with more concerted character with increasing potential. By using quantum calculations to estimate the O--O bond dissociation energies, the experimental data was used to evaluate the standard reduction potentials and other pertinent thermochemical information.
RESUMEN
G-factor endoperoxides are natural products acting as phytohormones and contribute to root inhibition and frost resistance in Eucalyptus grandis and other Myrtaceae. Several (Z)- and (E)-configured cyclopentane-1,3-dione metabolites of G-factors have been found in some Eucalyptus extracts. Interestingly, these probable metabolites are identical to the products obtained by Ru(II)-catalyzed reduction of G-factors. In the present work, we, thus, studied the mechanism involved in the formation of these compounds by means of in-depth NMR distribution analysis of two differently 13C-labeled G3-factors. The observed CO2 release is underlined, and a comparison with the corresponding Fe(II)-induced degradation of G-factor endoperoxides is made. Also, the type of electron transfer proposed in the two processes is discussed and, tentatively, connected to the role of endoperoxides in plants.
Asunto(s)
Dióxido de Carbono/análisis , Espectroscopía de Resonancia Magnética/métodos , Peróxidos/análisis , Reguladores del Crecimiento de las Plantas/análisis , Rutenio/análisis , Dióxido de Carbono/farmacocinética , Isótopos de Carbono , Catálisis , Peróxidos/farmacocinética , Reguladores del Crecimiento de las Plantas/farmacocinética , Rutenio/farmacocinéticaRESUMEN
The behavior of G3 factor and of its methylated or fluorinated analogues G3Me and G3F, was studied under Fe(II) conditions. Degradation products were isolated and characterized in each case. The use of labelled compounds allowed us to propose mechanisms in which a tertiary radical is involved. This radical rearranges by 5-exo-trig cyclization, or disproportionates in the case of G3Me. A correlation between antiplasmodial activity and stability of this radical is proposed.
Asunto(s)
Éteres/química , Compuestos Ferrosos/química , Espectroscopía de Resonancia Magnética/métodos , Peróxidos/química , Oxidación-ReducciónRESUMEN
Alkylation of the peroxyhemiketal function is described and all synthesised endoperoxides show good antimalarial activity. New rearrangement reactions in the presence of CsCO3, and preliminary results on Fe(II) chemical reduction of the O-O bond are presented.
Asunto(s)
Antimaláricos/síntesis química , Antimaláricos/farmacología , Peróxidos/síntesis química , Peróxidos/farmacología , Alquilación , Animales , Antimaláricos/química , Peróxidos/química , Plasmodium falciparum/efectos de los fármacosRESUMEN
New endoperoxides, related to the natural phytohormones known as G factors (G1, G2, G3), were modified on the side chain and the ketalic position. An unexpected rearrangement, specific to one diastereoisomer was observed in the deprotection step of O-silylated compounds and attributed to a hexacoordinated fluorosilicon intermediate. The reduction potential of these new peroxides was determined. They exhibited good to moderate antimalarial activity, greatly related to the presence of peroxyketal function.