Naphthylisoquinoline alkaloids, validated as hit multistage antiplasmodial natural products.

The discovery and development of multistage antimalarial drugs targeting intra-erythrocytic asexual and sexual Plasmodium falciparum parasites is of utmost importance to achieve the ambitious goal of malaria elimination. Here, we report the validation of naphthylisoquinoline (NIQ) alkaloids and their synthetic analogues as multistage active antimalarial drug candidates. A total of 30 compounds were tested, of which 17 exhibited IC50 values <1 µM against drug-sensitive P. falciparum parasites (NF54 strain); 15 of these retained activity against a panel of drug-resistant strains. These compounds showed low in vitro cytotoxicity against HepG2 cells, with selectivity indices of >10. The tested compounds showed activity in vitro against both early- and late-stage P. falciparum gametocytes while blocking male gamete formation (>70% inhibition of exflagellation at 2 µM). Additionally, five selected compounds were found to have good solubility (≥170 µM in PBS at pH 6.5), while metabolic stability towards human, mouse, and rat microsomes ranged from >90% to >7% after 30 min. Dioncophylline C (2a) emerged as a front runner from the study, displaying activity against both asexual parasites and gametocytes, a lack of cross-resistance to chloroquine, good solubility, and microsomal stability. Overall, this is the first report on the multistage activity of NIQs and their synthetic analogues including gametocytocidal and gametocidal effects induced by this class of compounds.

A new class of synthetic retinoid antibiotics effective against bacterial persisters.

A challenge in the treatment of Staphylococcus aureus infections is the high prevalence of methicillin-resistant S. aureus (MRSA) strains and the formation of non-growing, dormant 'persister' subpopulations that exhibit high levels of tolerance to antibiotics and have a role in chronic or recurrent infections. As conventional antibiotics are not effective in the treatment of infections caused by such bacteria, novel antibacterial therapeutics are urgently required. Here we used a Caenorhabditis elegans-MRSA infection screen to identify two synthetic retinoids, CD437 and CD1530, which kill both growing and persister MRSA cells by disrupting lipid bilayers. CD437 and CD1530 exhibit high killing rates, synergism with gentamicin, and a low probability of resistance selection. All-atom molecular dynamics simulations demonstrated that the ability of retinoids to penetrate and embed in lipid bilayers correlates with their bactericidal ability. An analogue of CD437 was found to retain anti-persister activity and show an improved cytotoxicity profile. Both CD437 and this analogue, alone or in combination with gentamicin, exhibit considerable efficacy in a mouse model of chronic MRSA infection. With further development and optimization, synthetic retinoids have the potential to become a new class of antimicrobials for the treatment of Gram-positive bacterial infections that are currently difficult to cure.

Identification of Saccharomyces cerevisiae Tub1 alpha-tubulin as a potential target for NKH-7, a cytotoxic 1-naphthol derivative compound.

In a screening for small-molecule compounds that alleviate the deleterious effects of external CaCl(2) on zds1 Delta strain yeast, we found 2-((1-(hydroxymethyl) cyclohexyl) methyl) naphthalen-1-ol (NKH-7) to be an active compound. NKH-7 also inhibited cell growth at higher concentrations. To identify its target in growth inhibition, we isolated NKH-7-resistant mutants and selected those mutants that exhibited dominant or semi-dominant resistance specifically to NKH-7. By gene cloning, a TUB1 mutant gene encoding alpha-tubulin with a Ser248Pro mutation was identified. Deletion of the TUB3 gene, a minor gene encoding alpha-tubulin, led to supersensitivity to NKH-7. Cellular tubulin-containing arrays as visualized by green fluorescent protein (GFP)-labeled alpha-tubulin diminished rapidly on exposure to the inhibitor. The mutation was situated proximal to the alpha-beta interface of alpha-tubulin in microtubule protofilaments, suggesting the possibility that NKH-7 affects the hydrolysis of GTP bound to beta-tubulin. A functional connection perhaps exists between the tubulin inhibition and Ca(2+)-dependent cell-cycle regulation.

A study of ambrein treatment for the evaluation of change in plasma biochemical parameters in rats.

Biochemical effects of acute and subacute treatments with ambrein were investigated in rats by measuring the total proteins, cholesterol, triglycerides, GOT, GPT and alkaline phosphatase in the blood plasma. Also, determinations of prothrombin time (PT), partial thrombin time (PTT), thrombin time (TT) and fibrinogen level were performed. Furthermore, changes in plasma electrolyte concentration were studied. Ambrein administered i.p. did not cause any toxic symptoms in the liver as revealed by the histology of the liver tissue both in acute and subacute treatments. Ambrein itself did not significantly affect the plasma protein, cholesterol, GOT and GPT profiles, but lowered alkaline phosphatase at high doses (50 and 250 mg/kg) after subacute treatment. Thus far, no specific pattern of action of ambrein in electrolyte control has been found. However, it increased PT, PTT and TT and decreased fibrinogen levels in both the acute and subacute studies, pointing towards its potential as an anticoagulant and antifibrinogenic agent.

Isoxazolynaphthoquinone effects on the growth of Trypanosoma cruzi

Frente a la necessidad de hallar neuveos fármacos contra el agente etiológico de la enfermedad de Chagas y en base a las propiedades biológicas y terapéuticas de naftoquinonas e isoxazoles, se resolvió estudiar el efecto de tres isoxazolilnaftoquinonas (Fig. 1) sobre el desarrollo del Trypanosoma cruzi in-vitro e in-vivo. Para evaluar la acción de las drogas sobre los epimastigotes se realizaron curvas de crecimiento con distintas concentraciones de 2-hidroxi-N-(3,4-dimetil-5-isoxazolil)-1,4-naftoquinina-4-imina (I), N-(3,4-dimetil-5-isoxazolil)-4-amino-1,2 naftoquinona (II), 2-acetil-N-(3,4-dimetil-5-isoxazolil)-1,4-naftoquinona-imina (III) y Nifurtimox como droga de referencia. Los estudios sobre la forma de tripomastigote se realizaron sobre ratones BALB/c de dos meses de edad, evaluado parasistemia en el día 13 post-infección. Los resultados obtenidos con epimastigotes mostraron que todas las drogas indujeron alteraciones consistentes es disminución de movilidad, vacuolización, pérdida de viabilidad y/o lisis de los parásitos (Fig. 2 y 3). En los tratamientos sobre tripomastigotes los resultados más concluyentes se presentaron con I que produjo una reducción de la parasitemia respecto a los controles no tratados (Fig 4)

Isoxazolynaphthoquinone effects on the growth of Trypanosoma cruzi

Frente a la necessidad de hallar neuveos fármacos contra el agente etiológico de la enfermedad de Chagas y en base a las propiedades biológicas y terapéuticas de naftoquinonas e isoxazoles, se resolvió estudiar el efecto de tres isoxazolilnaftoquinonas (Fig. 1) sobre el desarrollo del Trypanosoma cruzi in-vitro e in-vivo. Para evaluar la acción de las drogas sobre los epimastigotes se realizaron curvas de crecimiento con distintas concentraciones de 2-hidroxi-N-(3,4-dimetil-5-isoxazolil)-1,4-naftoquinina-4-imina (I), N-(3,4-dimetil-5-isoxazolil)-4-amino-1,2 naftoquinona (II), 2-acetil-N-(3,4-dimetil-5-isoxazolil)-1,4-naftoquinona-imina (III) y Nifurtimox como droga de referencia. Los estudios sobre la forma de tripomastigote se realizaron sobre ratones BALB/c de dos meses de edad, evaluado parasistemia en el día 13 post-infección. Los resultados obtenidos con epimastigotes mostraron que todas las drogas indujeron alteraciones consistentes es disminución de movilidad, vacuolización, pérdida de viabilidad y/o lisis de los parásitos (Fig. 2 y 3). En los tratamientos sobre tripomastigotes los resultados más concluyentes se presentaron con I que produjo una reducción de la parasitemia respecto a los controles no tratados (Fig 4) (AU)

Isoxazolylnaphthoquinone effects on the growth of Trypanosoma cruzi.

Knowing the need for new drugs against the etiologic agent of Chagas disease and considering the biological properties of naphthoquinones and isoxazoles, the effect of three isoxazolyl-naphthoquinones on the growth of Trypanosoma cruzi was studied. To evaluate the activity of the compounds on epimastigote forms, growth curves with different concentrations of 2-hydroxi-N-(3,4-dimethyl-5-isoxazolyl)-1,4-naphthoquinone-4 -imine (I), N-(3,4-dimethyl-5-isoxazolyl)-4-amino-1,2-naphthoquinone (II), 2-acetyl-N-(3,4-dimethyl-5-isoxazolyl)-1,4-naphthoquinone-imine (III) and Nifurtimox as reference drug were made. The studies on the trypomastigote form were performed on two month old BALB/c mice, evaluating parasitemia on day 13 post infection. The results obtained with epimastigotes showed that all drugs induced alterations in motility, morphology, viability and/or lysis of parasites. For the treatments on trypomastigotes the best results were obtained with (I) which reduced parasitemia compared to untreated controls.