2-Substituted-3H-indol-3-one-1-oxides: Preparation and Radical Trapping Properties

Albumin-bound nanoparticles of practically water-insoluble antimalarial lead greatly enhance its efficacy

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 30 min 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.

Azide trapping of metallocarbenes: generation of reactive C-acylimines and domino trapping with nucleophiles

Diazocarbonyl compounds react with pendent azides under copper catalysis to generate reactive C-acylimines that can be trapped with carbon π-nucleophiles in situ.

Antibacterial, antifungal and antileishmanial activities of indolone-N-oxide derivatives

An alarming increase in microbial resistance to traditional drugs and classical pharmacophores has spurred the search for new antimicrobial compounds. Indolone-N-oxides (INODs) possess a redox pharmacophore with promising, recently established, antimalarial activities. In this study, the anti-infectious properties of a series of INODs were investigated. The antibacterial activity was evaluated against five bacterial strains Gram-positive (Staphylococcus aureus, Enterococcus hirae), Gram-negative (Pseudomonas aeruginosa, Escherichia coli) and acid-fast (Mycobacterium tuberculosis). The antifungal activity was assessed using two fungal strains (Aspergillus niger, Candida albicans). The antileishmanial activity was tested against two leishmanial strains, axenically-cultured amastigote (Leishmania infantum, Leishmania amazonensis). The pharmacological activities are discussed as a function of structural and lipophilic characteristics. The Gram-positive bacterial strain E. hirae was found to be the most sensitive strain, whereas the Gram-negative E. coli was resistant to this family of compounds. One compound (64) was more potent than nalidixic acid against E. hirae, whereas another one (52) was equipotent as clotrimazole against C. albicans. INODs were microbe -cidal rather than -static. INODs showed good antitubercular activity in the low micromolar range (similar to ciprofloxacin). In addition, INOD-antiprotozoal potencies were confirmed against the leishmania parasite. INODs showed a broad spectrum of antimicrobial activity and offer a promising anti-infectious prototype worthy of being developed.

Synthesis and antiplasmodial activity of new indolone N-oxide derivatives

A series of 66 new indolone-N-oxide derivatives was synthesized with three different methods. Compounds were evaluated for in vitro activity against CQ-sensitive (3D7), CQ-resistant (FcB1), and CQ and pyrimethamine cross-resistant (K1) strains of Plasmodium falciparum (P.f.), as well as for cytotoxic concentration (CC(50)) on MCF7 and KB human tumor cell lines. Compound 26 (5-methoxy-indolone-N-oxide analogue) had the most potent antiplasmodial activity in vitro (<3 nM on FcB1 and = 1.7 nM on 3D7) with a very satisfactory selectivity index (CC(50) MCF7/IC(50) FcB1: 14623; CC(50) KB/IC(50) 3D7: 198823). In in vivo experiments, compound 1 (dioxymethylene derivatives of the indolone-N-oxide) showed the best antiplasmodial activity against Plasmodium berghei, 62% inhibition of the parasitaemia at 30 mg/kg/day.