[Show abstract][Hide abstract] ABSTRACT: Leaf extracts of Cassia roxburghii DC., prepared in petroleum ether,
chloroform, ethyl acetate, butanol, and methanol/water (70:30,
v/v), were evaluated as antioxidant, pro-oxidant, anti-infectious,
and cytotoxic agents. The major metabolite of each extract was
identified by chromatographic and spectroscopic means. The redox
properties were assessed with a battery of assays, which revealed
that the ethyl acetate extract demonstrated an interesting scavenging
activity of DPPH and superoxide radicals and an ascorbic
acid-like pro-oxidant activity. All the tested extracts showed moderate
antiplasmodial activity against a chloroquine-resistant strain
of Plasmodium falciparum, by possible disruption of parasite fine
redox balance. Cytotoxicity was evaluated against a human breast
cancer cell line. The antimicrobial activities of the extracts were
estimated against representative bacterial strains ( Staphylococcus
aureus, Enterococcus hirae, Pseudomonas aeruginosa, Escherichia
coli) and fungal species (Candida albicans, Aspergillus niger).
The ethylacetate extract possessed the highest redox properties and exhibited the highest antiplasmodial activity; there was no correlation
between antibacterial activity and the redox properties of the
Full-text · Article · Oct 2015 · Journal of Herbs Spices & Medicinal Plants
[Show abstract][Hide abstract] ABSTRACT: Objective: To investigate the antiplasmodial, antimicrobial, radical scavenging effects and to identifiy the phenolic constituents of Atriplex lindleyi (. A. lindleyi). Methods: A. lindleyi extracts and some isolated compounds were tested in vitro against the chloroquine-resistant strains of Plasmodium falciparum. The radical scavenging activity was quantified by using 2,2-diphenyl-2-picrylhydrazyl nitrogen-centered free radical. The IC50 of each extract was compared with references. The in vitro anti-infectious activity of extracts was evaluated against representative Gram-positive and Gram-negative bacterial strains [Staphylococcus aureus CIP 4.83, Enterococcus hirae CIP 5855, Pseudomonas aeruginosa (P. aeruginosa) CIP 82118, Escherichia coli CIP 53126], and fungal species [(Candida albicans (C. albicans) IP 48.72, Aspergillus niger IP 1431.83]. Ethanol extract was investigated for chemical composition through column and high performance liquid chromatography. The isolated compounds were identified by mass spectrometry and nuclear magnetic resonance. Results: Quercetin-7-O-arabinopyranoside-3-O-neohesperidosides (1), quercetin-3-O-arabinopyranosyl(1→6) glucopyranoside (2), quercetin-3-O-glucopyranoside-7-O-rhamnopyranoside (3), quercetin-3-O-glucopyranoside-7-O-arabinoside (4), schaftoside (5), quercetin-7-O-glucopyranoside (6) were isolated for the first time from the ethanol extract of A. lindleyi aerial parts in addition to isorhamnetin-3-O-β-glucopyranoside (7) and quercetin (8). The extracts exhibited moderate antiplasmodial activity with IC50≈ranging from 10-50 μg/mL. Quercetin was the most potent compound with IC50 of 9 μg/mL. P. aeruginosa and C. albicans were the most susceptible organisms. Conclusions: The study implies that A. lindelyi can contribute to the fight against malaria, and be useful as prophylactic against C. albicans and P. aeruginosa.
Full-text · Article · Oct 2015 · Asian Pacific Journal of Tropical Disease
[Show abstract][Hide abstract] ABSTRACT: More than 40 years after its discovery, artemisinin has become the most promising antimalarial agent. However, no intravenous formulation is available due to its poor aqueous solubility. Here, we report the preparation, characterization, and in vitro and in vivo biological evaluation of biodegradable albumin-bound artemisinin nanoparticles. The nanoparticles were prepared by a combination of a bottom-up and a top-down processes and characterized by different spectroscopic techniques. The preparation process was optimized to develop a nanoformulation with the smallest possible diameter and good homogeneity suitable for intravenous injection enabling direct contact of artemisinin with infected erythrocytes. Chemically and physically stable artemisinin nanoparticles were obtained with excellent entrapment efficiency. In in vitro experiments, the artemisinin nanoformulation was interestingly more effective than non-formulated artemisinin. In Plasmodiumm falciparum-infected 'humanized' mice, the nanoparticles proved to be highly effective with 96 % parasitemia inhibition at 10mg/kg/day, prolonging mean survival time without recrudescence. This nanoparticulate albumin-bound system allows the intravenous administration of artemisinin for the first time without harsh organic solvents or cosolvents with 100 % bioavailability.
Full-text · Article · Sep 2015 · International Journal of Pharmaceutics
[Show abstract][Hide abstract] ABSTRACT: Quinones are highly reactive molecules that readily undergo either one- or two-electron reduction. One-electron reduction of quinones or their derivatives by enzymes such as cytochrome P450 reductase or other flavoproteins generates unstable semiquinones, which undergo redox cycling in the presence of molecular oxygen leading to the formation of highly reactive oxygen species. Quinone reductases 1 and 2 (QR1 and QR2) catalyze the two-electron reduction of quinones to form hydroquinones, which can be removed from the cell by conjugation of the hydroxyl with glucuronide or sulfate thus avoiding its autoxidation and the formation of free radicals and highly reactive oxygen species. This characteristic confers a detoxifying enzyme role to QR1 and QR2, even if this character is strongly linked to the excretion capacity of the cell. Using EPR spectroscopy and confocal microscopy we demonstrated that the amount of reactive oxygen species (ROS) produced by Chinese hamster ovary (CHO) cells overexpressing QR1 or QR2 compared to naive CHO cells was determined by the quinone structural type. Indeed, whereas the amount of ROS produced in the cell was strongly decreased with para-quinones such as menadione in the presence of quinone reductase 1 or 2, a strong increase in ROS was recorded with ortho-quinones such as adrenochrome, aminochrome, dopachrome, or 3,5-di-tert-butyl-o-benzoquinone in cells overexpressing QR, especially QR2. These differences could originate from the excretion process, which is different for para- and ortho-quinones. These results are of particular interest in the case of dopamine considering the association of QR2 with various neurological disorders such as Parkinson disease.
No preview · Article · Sep 2015 · Free Radical Biology and Medicine
[Show abstract][Hide abstract] ABSTRACT: Binding of drugs to plasma proteins, such as albumin, is a major factor which determines their pharmacokinetics and pharmacological effects. Therefore, the interactions between human serum albumin (HSA) and four antimalarial compounds selected in the 2-aryl-3H-indol-3-one series have been investigated using UV-visible, fluorescence and circular dichroism (CD) spectroscopies. Compounds produced a static quenching of the intrinsic fluorescence of HSA. The thermodynamic parameters have shown that the binding reaction is endothermic for three compounds while exothermic for the 2-phenyl-3H-indol-3-one, 3. The interaction is entropically driven with predominant hydrophobic forces with binding affinities of the order of 104 M-1. The highest binding constant is observed for 3 (Kλ=280 nm = 4.53 104 M-1) which is also the less active compound against Plasmodium falciparum. Synchronous fluorescence gave qualitative information on the conformational changes of HSA while quantitative data were obtained with CD. Displacement experiments with site markers indicated that drugs bind to HSA at site I (subdomain IIA). In addition, the apparent binding constant and the binding site number were calculated in the presence of different ions.
Full-text · Article · Oct 2014 · The Journal of Physical Chemistry B
[Show abstract][Hide abstract] ABSTRACT: The search for antimalarial compounds continues to be an area of intensive investigation in medicinal chemistry. This review presents the structural variations around the indolone-N-oxide core. From these pharmacomodulation studies, new antiplasmodial agents with various structures have emerged. Most of the molecules generated from reduced forms of the indolone scaffold have led to compounds with antiplasmodial properties. These results confirm the importance of the redox reversibility of the bioreducible N=C bond in these series to obtain antimalarial activities.
No preview · Article · Aug 2014 · European Journal of Marketing
[Show abstract][Hide abstract] ABSTRACT: The synthesis of indolone derivatives and their antiplasmodial activity in vitro against Plasmodium falciparum at the blood stage are described. The 2-aryl-3H-indol-3-ones were synthesized via deoxygenation of indolone-N-oxides. Electrochemical behaviour, antiplasmodial activity and cytotoxicity on human tumor cell lines were compared to those of indolone-N-oxides. The antiplasmodial IC50 (concentrations at 50% inhibition) of these compounds ranged between 49 and 1327 nM. Among them, the 2-(4-dimethylaminophenyl)-5-methoxy-indol-3-one, 7, had the best antiplasmodial activity in vitro (IC50 = 49 nM; FcB1 strain) and selectivity index (SI (CC50 MCF7/IC50 FcB1) = 423.4). Thus, the hits identified in this deoxygenated series correspond to their structural homologs in the N-oxide series with comparable electrochemical behaviour at the nitrogen-carbon double bond.
Full-text · Article · May 2014 · European Journal of Medicinal Chemistry
[Show abstract][Hide abstract] ABSTRACT: There is an urgent need for new antimalarial drugs with novel mechanisms of action on novel targets. Indolone-N-oxides (INODs) display antimalarial properties in vitro and in vivo, but identified leads such as 6-(4-chloro-phenyl)-5-oxy-[1,3]dioxolo[4,5-f]indol-7-one 1, suffer from very poor aqueous solubility. In this study, structural modifications have been made by introducing various amino and bulky groups to produce sufficiently water soluble and active compounds for further pharmacological and pharmacokinetic studies. We report here the preparation of twelve novel amino derivatives and their antiplasmodial activities including those of two other structurally known compounds. The 5-methoxy-2-(4-morpholin-4-yl-phenyl)-1-oxy-indol-3-one, 9, has the highest antiplasmodial activity in vitro (IC₅₀ = 6.5 nM; FcB1 strain) and selectivity index (SI (CC₅₀ MCF7/IC₅₀ FcB1) = 4538.5). The 6-amino-2-(4-chloro-phenyl)-1-oxy-indol-3-one, 14, (IC₅₀ = 183 nM; SI = 60), is an excellent candidate for further mechanistic studies. Indeed, this is structurally the closest analogue to the current lead, 1, bearing an NH2 group at R(2) offering possibilities for functionalization and labeling.
Full-text · Article · Apr 2014 · European Journal of Medicinal Chemistry
[Show abstract][Hide abstract] ABSTRACT: We recently showed that the indolone-N-oxides can be promising candidates for the treatment of chloroquine-resistant malaria. However, the in vivo assays have been hampered by the very poor aqueous solubility of these compounds resulting in poor and variable activity. Here, we describe the preparation, characterization and in vivo evaluation of biodegradable albumin-bound indolone-N-oxide nanoparticles. Nanoparticles were prepared by precipitation followed by high-pressure homogenization and characterized by photon correlation spectroscopy, transmission electron microscopy, differential scanning calorimetry and X-ray powder diffraction. The process was optimized to yield nanoparticles of controllable diameter with narrow size distribution suitable for intravenous administration, which guarantees direct drug contact with parasitized erythrocytes. Stable nanoparticles showed greatly enhanced dissolution rate (complete drug release within 30min compared to 1.5% of pure drug) preserving the rapid antimalarial activity. The formulation achieved complete cure of Plasmodium berghei-infected mice at 25mg/kg with parasitemia inhibition (99.1%) comparable to that of artesunate and chloroquine and was remarkably more effective in prolonging survival time and inhibiting recrudescence. In 'humanized' mice infected with Plasmodium falciparum, the same dose proved to be highly effective: with parasitemia reduced by 97.5% and the mean survival time prolonged. This formulation can help advance the preclinical trials of indolone-N-oxides. Albumin-bound nanoparticles represent a new strategic approach to use this most abundant plasma protein to target malaria-infected erythrocytes.
No preview · Article · Jan 2014 · International Journal of Pharmaceutics
[Show abstract][Hide abstract] ABSTRACT: Uncatalyzed racemization processes in atropisomeric diphenyl-like frameworks are classically described as the result of the rotation around the pivotal single bond linking two planar frameworks. Severe constraints leading to more or less distorted transition states account for the experimental barrier to atropenantiomerization. In 1988, one of us hypothesized that in N-aryl-2(1H)-pyrimidin-(thi)ones, a ring-opening/ ring-closure process was contributing to the observed racemization process accounting for the lower barriers in the sulphur analogues than in oxygen analogues. Now a series of six novel 6-amino-5-cyano-1,4-disubstituted-2(1H)-pyrimidinones 5a-f and two 6-amino-5-cyano-4-p-tolyl-1-substituted-2(1H)-pyrimidinethiones 6a-b were synthesized and characterized through spectroscopic and X-ray diffraction studies. Semi-preparative HPLC chiral separation was achieved and enantiomerization barriers were obtained by thermal racemization. The rotational barriers of 6-amino-5-cyano-1-o-tolyl-4-p-tolyl-2(1H)-pyrimidinone (5b) and 6-amino-5-cyano-1-(naphthalen-1-yl)-4-p-tolyl-2(1H)-pyrimidinone (5e) were found to be 120.3 and 125.1 kJ.mol-1 (n-BuOH, 117 DegC), respectively and those of the corresponding thiones were 116.8 and 109.6 kJ.mol-1 (EtOH, 78 DegC), respectively. DFT calculations of the rotational barriers clearly ruled out the classical rotation around the pivotal bond with distorted transition states in the case of the sulphur derivatives. Instead, the ranking of the experimental barriers (sulphur versus oxygen, and O-tolyl versus 1-naphthyl in both series) were nicely reproduced by calculations when the rotation occurred via a ring-opened form in N-aryl-2(1H)-pyrimidinethiones.
Full-text · Article · Dec 2013 · The Journal of Organic Chemistry
[Show abstract][Hide abstract] ABSTRACT: New series of 10-anilino-9-alkyl-12-aryl-10,12-dihydro-11H-benzo[5,6] chromeno [2,3-d]pyrimidin-11-ones 5(a-e) and 9-anilino-10-alkyl-7-aryl-7,9-dihydro-8H-benzo[7,8]chromeno[2,3-d]pyrimidin-8-ones 6(a-f) were prepared in three steps with microwave irradiation. The procedure is easy, avoiding time-consuming syntheses are note costly.
Full-text · Article · Nov 2013 · Arabian Journal of Chemistry
[Show abstract][Hide abstract] ABSTRACT: In Alzheimer's disease, the redox‐active copper center bound to the amyloid‐beta peptide is able to produce reactive oxygen species by way of a low‐populated redox‐competent state. Insights into the coordination sphere of this state are reported by P. Faller, F. Collin, and co‐workers in their Communication on page 11110 ff. The copper atom is bound by the N‐terminal aspartate and the histidine dyad, while the third histidine acts as a gate keeper.
No preview · Article · Oct 2013 · Angewandte Chemie International Edition
[Show abstract][Hide abstract] ABSTRACT: Bei der Alzheimer‐Krankheit kann das am Amyloid‐beta‐Peptid gebundene, redoxaktive Kupfer reaktive Sauerstoffspezies über einen wenig bevölkerten redoxkompetenten Zustand produzieren. In ihrer Zuschrift auf S. 11316 ff. geben P. Faller, F. Collin et al. einen Einblick in die Koordinationssphäre dieses Zustands. Kupfer ist durch das N‐terminale Aspartat und die Histidindyade gebunden, während das dritte Histidin als “Gatekeeper” fungiert.
Full-text · Article · Oct 2013 · Angewandte Chemie
[Show abstract][Hide abstract] ABSTRACT: Copper-amyloid-β ROS production: Copper ions (red sphere, see picture) have been found to accumulate in amyloid-β plaques and play a role in the generation of reactive oxygen species (ROS) within this context. Mass spectrometry studies were able to detail the sites of oxidation damage and shed new light on the mechanism of ROS production, important for the understanding of the pathogenicity of amyloid-β peptides.
Full-text · Article · Oct 2013 · Angewandte Chemie International Edition
[Show abstract][Hide abstract] ABSTRACT: Targeting the redox metabolism of Plasmodium falciparum to create a fatal overload of oxidative stress is a route to explore the discovery of new antimalarial drugs. There are three main possibilities to target the redox metabolism of P. falciparum at the erythrocytic stage: selective targeting and inhibition of a redox P. falciparum protein or enzyme; oxidant drugs targeting essential parasite components and heme by-products; and redox cycler drugs targeting the parasitized red blood cell. Oxidants and redox cycler agents, with or without specific targets, may disrupt the fragile parasitized erythrocyte redox-dependent architecture given that: redox equilibrium plays a vital role at the erythrocytic stage; P. falciparum possesses major NADPH-dependent redox systems, such as glutathione and thioredoxin ones; and the protein-NADPH-dependent phosphorylation-dephosphorylation process is involved in building new permeation pathways and channels for the nutrient-waste import-export traffic of the parasite.
No preview · Article · Oct 2013 · Future medicinal chemistry
[Show abstract][Hide abstract] ABSTRACT: A new series of 3-substituted-2,1-benzisoxazoles (anthranils) were prepared by different methods and characterized by spectroscopic methods and mass spectrometry. These 2,1-benzisoxazoles were tested in vitro for their antiplasmodial activity on a chloroquine-resistant strain of Plasmodium falciparum (P.f.) (FcB1), and for antimicrobial activity against representative bacterial and fungal strains, as well as for cytotoxicity on MCF7 human breast cancer cells. Given the log Pcalc and selectivity index values (cytotoxicity/antiplasmodial activity ratio), the benzo[c]isoxazol-3-ylmethylene-phenyl-amine (11) (imino-benzisoxazole) was identified as the best hit against P.f. (FcB1), and the benzo[c]isoxazol-3-yl-phenyl-methanone (3) (3-acyl-2,1-benzisoxazole) against P.f. and the Geotrichum candidum fungal strain.
Full-text · Article · Sep 2013 · Arabian Journal of Chemistry
[Show abstract][Hide abstract] ABSTRACT: ETHNOPHARMACOLOGICAL RELEVANCE: Crinum latifolium L. (CL) leaf extracts have been traditionally used in Vietnam and are now used all over the world for the treatment of prostate cancer. However, the precise cellular mechanisms of the action of CL extracts remain unclear. AIM OF THE STUDY: To examine the effects of CL samples on the anti-tumour activity of peritoneal murine macrophages. MATERIALS AND METHODS: The properties of three extracts (aqueous, flavonoid, alkaloid), one fraction (alkaloid), and one pure compound (6-hydroxycrinamidine) obtained from CL, were studied i) for redox capacities (DPPH and bleaching beta-carotene assays), ii) on murine peritoneal macrophages (MTT assay) and on lymphoma EL4-luc2 cells (luciferine assay) for cytotoxicity, iii) on macrophage polarization (production of ROS and gene expression by PCR), and iv) on the tumoricidal functions of murine peritoneal macrophages (lymphoma cytotoxicity by co-culture with syngeneic macrophages). RESULTS: The total flavonoid extract with a high antioxidant activity (IC50=107.36mg/L, DPPH assay) showed an inhibitory action on cancer cells. Alkaloid extracts inhibited the proliferation of lymphoma cells either by directly acting on tumour cells or by activating of the tumoricidal functions of syngeneic macrophages. The aqueous extract induced mRNA expression of tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin 6 (IL-6) indicating differentiation of macrophages into pro-inflammatory M1 polarized macrophages. The total flavonoid, alkaloid extracts and an alkaloid fraction induced the expression of the formyl peptide receptor (FPR) on the surface of the polarized macrophages that could lead to the activation of macrophages towards the M1 phenotype. Aqueous and flavonoid extracts enhanced NADPH quinine oxido-reductase 1 (NQO1) mRNA expression in polarized macrophages which could play an important role in cancer chemoprevention. All the samples studied were non-toxic to normal living cells and the pure alkaloid tested, 6-hydroxycrinamidine, was not active in any of the models investigated. CONCLUSIONS: Our results indicate that CL extracts and alkaloid fraction (but not pure 6-hydroxycrinamidine) inhibit the proliferation of lymphoma cells in multiple pathways. Our results are in accordance with traditional usage and encourage further studies and in vivo assays.
No preview · Article · Jun 2013 · Journal of ethnopharmacology
[Show abstract][Hide abstract] ABSTRACT: Circulating blood monocytes belong to the first line of defense against pathogens and inflammation. Monocytes can be divided into three populations defined by the expression of the cell surface molecules, CD 14 and CD 16. The CD 14(++) CD 16(-) cells, called "classical" monocytes, represent 85% to 95% of the total monocytes in a healthy person whereas CD 14(-) CD 16(+), called "proinflammatory" monocytes, are found in greater numbers in the blood of patients with acute inflammation and infectious diseases. This increase in the concentration of proinflammatory monocytes can be a good indicator of an infectious state. This study presents an immunosensor based on impedance detection for specific cell trapping of classical and proinflammatory monocytes. The grafting of specific antibodies (CD 14 or CD 16) was based on the use of mixed SAM associated with protein G. Each step of the functionalization was characterized by electrochemical methods, quartz crystal microbalance and atomic force microscopy. Faradaic electrochemical impedance spectroscopy and voltametric analysis confirmed the success of the modification process with a surface coverage reaching 92% for the antibody layer. The increase in the deposited mass at each step of the modification process confirmed this results revealing that one protein G in two was bound to an antibody. The cell trapping capacity, evaluated by the variation in the film resistance using non-faradaic impedance spectroscopy revealed that the cell trapping is selective, depending on the specific antibody grafted and quantitative with the range of detection being 1000 to 30,000 infected cells. This range of detection is consistent with the application targeted.
No preview · Article · May 2013 · Biosensors & Bioelectronics
[Show abstract][Hide abstract] ABSTRACT: Indolone-N-oxides (INODs) are bioreducible and possess remarkable anti-malarial activities in the low nanomolar range in vitro against different Plasmodium falciparum (P. falciparum) strains and in vivo. INODs have an original mechanism of action: they damage the host cell membrane without affecting non-parasitized erythrocytes. These molecules produce a redox signal which activates SYK tyrosine kinases and induces a hyperphosphorylation of AE1 (band 3, erythrocyte membrane protein). The present work aimed to understand the early stages of the biochemical interactions of these compounds with some erythrocyte components from which the redox signal could originate. The interactions were studied in a biomimetic model and compared with those of chloroquine and artemisinin. The results showed that INODs i) do not enter the coordination sphere of the metal in the heme iron complex as does chloroquine; ii) do not generate iron-dependent radicals as does artemisinin; iii) generate stable free radical adducts after reduction at one electron; iv) cannot trap free radicals after reduction. These results confirm that the bioactivity of INODs does not lie in their spin-trapping properties but rather in their pro-oxidant character. This property may be the initiator of the redox signal which activates SYK tyrosine kinases.