Antiviral activity of an N-allyl acridone against dengue virus

Background

Dengue virus (DENV), a member of the family Flaviviridae, is at present the most widespread causative agent of a human viral disease transmitted by mosquitoes. Despite the increasing incidence of this pathogen, there are no antiviral drugs or vaccines currently available for treatment or prevention. In a previous screening assay, we identified a group of N-allyl acridones as effective virus inhibitors. Here, the antiviral activity and mode of action targeted to viral RNA replication of one of the most active DENV-2 inhibitors was further characterized.

Results

The compound 10-allyl-7-chloro-9(10H)-acridone, designated 3b, was active to inhibit the in vitro infection of Vero cells with the four DENV serotypes, with effective concentration 50% (EC₅₀) values in the range 12.5-27.1 μM, as determined by virus yield inhibition assays. The compound was also effective in human HeLa cells. No cytotoxicity was detected at 3b concentrations up to 1000 μM. Mechanistic studies demonstrated that virus entry into the host cell was not affected, whereas viral RNA synthesis was strongly inhibited, as quantified by real time RT-PCR. The addition of exogenous guanosine together with 3b rescued only partially the infectivity of DENV-2.

Conclusions

The acridone derivative 3b selectively inhibits the infection of Vero cells with the four DENV serotypes without a direct interaction with the host cell or the virion but interfering specifically with the intracellular virus multiplication. The mode of antiviral action for this acridone apparently involves the cellular enzyme inosine-monophospahe dehydrogenase together with another still unidentified target related to DENV RNA synthesis.     

Synthetic peptides mimicking the binding site of human acetylcholinesterase for its inhibitor fasciculin 2

Molecules capable of mimicking protein binding and/or functional sites present useful tools for a range of biomedical applications, including the inhibition of protein–ligand interactions. Such mimics of protein binding sites can currently be generated through structure‐based design and chemical synthesis. Computational protein design could be further used to optimize protein binding site mimetics through rationally designed mutations that improve intermolecular interactions or peptide stability. Here, as a model for the study, we chose an interaction between human acetylcholinesterase (hAChE) and its inhibitor fasciculin‐2 (Fas) because the structure and function of this complex is well understood. Structure‐based design of mimics of the hAChE binding site for Fas yielded a peptide that binds to Fas at micromolar concentrations. Replacement of hAChE residues known to be essential for its interaction with Fas with alanine, in this peptide, resulted in almost complete loss of binding to Fas. Computational optimization of the hAChE mimetic peptide yielded a variant with slightly improved affinity to Fas, indicating that more rounds of computational optimization will be required to obtain peptide variants with greatly improved affinity for Fas. CD spectra in the absence and presence of Fas point to conformational changes in the peptide upon binding to Fas. Furthermore, binding of the optimized hAChE mimetic peptide to Fas could be inhibited by hAChE, providing evidence for a hAChE‐specific peptide–Fas interaction. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.     

Fullerene‐based inhibitors of HIV‐1 protease

A series of Fmoc‐Phe(4‐aza‐C₆₀)‐OH of fullerene amino acid derived peptides have been prepared by solid phase peptide synthesis, in which the terminal amino acid, Phe(4‐aza‐C₆₀)‐OH, is derived from the dipolar addition to C₆₀ of the Fmoc‐Nα‐protected azido amino acids derived from phenylalanine: Fmoc‐Phe(4‐aza‐C₆₀)‐Lys₃‐OH ( 1 ), Fmoc‐Phe(4‐aza‐C₆₀)‐Pro‐Hyp‐Lys‐OH ( 2 ), and Fmoc‐Phe(4‐aza‐C₆₀)‐Hyp‐Hyp‐Lys‐OH ( 3 ). The inhibition constant of our fullerene aspartic protease PRIs utilized FRET‐based assay to evaluate the enzyme kinetics of HIV‐1 PR at various concentrations of inhibitors. Simulation of the docking of the peptide Fmoc‐Phe‐Pro‐Hyp‐Lys‐OH overestimated the inhibition, while the amino acid PRIs were well estimated. The experimental results show that C₆₀‐based amino acids are a good base structure in the design of protease inhibitors and that their inhibition can be improved upon by the addition of designer peptide sequences. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.     

Taurine deficiency,synthesis and transport in the mdx mouse model for Duchenne Muscular Dystrophy

The amino acid taurine is essential for the function of skeletal muscle and administration is proposed as a treatment for Duchenne Muscular Dystrophy (DMD). Taurine homeostasis is dependent on multiple processes including absorption of taurine from food, endogenous synthesis from cysteine and reabsorption in the kidney. This study investigates the cause of reported taurine deficiency in the dystrophic mdx mouse model of DMD. Levels of metabolites (taurine, cysteine, cysteine sulfinate and hypotaurine) and proteins (taurine transporter [TauT], cysteine deoxygenase and cysteine sulfinate dehydrogenase) were quantified in juvenile control C57 and dystrophic mdx mice aged 18 days, 4 and 6 weeks. In C57 mice, taurine content was much higher in both liver and plasma at 18 days, and both cysteine and cysteine deoxygenase were increased. As taurine levels decreased in maturing C57 mice, there was increased transport (reabsorption) of taurine in the kidney and muscle. In mdx mice, taurine and cysteine levels were much lower in liver and plasma at 18 days, and in muscle cysteine was low at 18 days, whereas taurine was lower at 4: these changes were associated with perturbations in taurine transport in liver, kidney and muscle and altered metabolism in liver and kidney. These data suggest that the maintenance of adequate body taurine relies on sufficient dietary intake of taurine and cysteine availability and metabolism, as well as retention of taurine by the kidney. This research indicates dystrophin deficiency not only perturbs taurine metabolism in the muscle but also affects taurine metabolism in the liver and kidney, and supports targeting cysteine and taurine deficiency as a potential therapy for DMD.     

Bioactive natural products and chirality

Mori's synthetic works on bioactive natural products in general and pheromones in particular started about 40 years ago to establish their absolute configurations and also to clarify their stereochemistry-bioactivity relationships. Results indicate that bioactive natural products are not always enantiomerically pure, and the stereochemistry-bioactivity relationships are not simple but complicated. For example, neither (R)- nor (S)-sulcatol, the aggregation pheromone of an ambrosia beetle, is behaviorally bioactive, whereas their mixture is active. In the case of olean, the sex pheromone of the olive fruit fly, its (R)-isomer is active against the males and the (S)-isomer is active against the females. Recent synthesis of two new insect pheromones is discussed to illustrate the modern methods in enantioselective synthesis.     

Asymmetric synthesis of phenanthroindolizidine alkaloids with hydroxyl group at the C14 position and evaluation of their antitumor activities

The asymmetric total synthesis of the strongly cytotoxic phenanthroindolizidine alkaloid 3 was achieved. Using the same route, various derivatives were also synthesized. Cytotoxicity of those synthetic compounds was evaluated and compounds 19, 23, and 27 demonstrated potent cytotoxicities similar to that of 3. The in vivo antitumor efficacy of selected compounds was also evaluated and 23 demonstrated moderate antitumor efficacy.     

New branching inhibitors and their potential as strigolactone mimics in rice

Strigolactones (SLs) are rhizosphere communication chemicals. Recent studies of highly branched mutants revealed that SL or its metabolites work as a phytohormone to inhibit shoot branching. When SLs are exogenously applied to the rice d10-1 mutant that has a highly branched phenotype caused by a defect in the SL biosynthesis gene (CCD8), they inhibit tiller bud outgrowth (branching in rice) of the mutant. We focused our attention on the SL function as a phytohormone and tried to find new chemicals mimicking the hormonal action of SL by screening chemicals that inhibit branching of rice d10-1 mutant. Fortunately, we found 5-(4-chlorophenoxy)-3-methylfuran-2(5H)-one (3a) as a new chemical possessing SL-like activity against the rice d10-1 mutant. Then, we prepared several derivatives of 3a (3b-3k) to examine their ability to inhibit shoot branching of rice d10-1. These derivatives were synthesized by a one-pot coupling reaction between phenols and halo butenolide to give 5-phenoxy 3-methylfuran-2(5H)-one (3) derivatives, which possess a common substructure with SLs. Some of the derivatives showed SL-like activity more potently than GR24, a typical SL derivative, in a rice assay. As SLs also show activity by inducing seed germination of root parasitic plants, the induction activity of these derivatives was also evaluated. Here we report the structure-activity relationships of these compounds.     

A reverse method for diversity introduction of benzimidazole to synthesize H(+)/K(+)-ATP enzyme inhibitors

A series of 2-[(2-pyridylmethyl)sulfinyl]benzimidazole derivatives were synthesized via a solution phase synthetic route using a reversal method of diversity introduction. Using this synthetic strategy, we obtained two key intermediates (4-A and 4-B) simultaneously, which allows us to introduce diversity points onto the benzimidazole part of the final product under reliable reaction conditions to identify potent H⁺/K⁺-ATP enzyme inhibitors. Compound 14l (IC₅₀ = 1.6 × 10⁻⁵ M) was comparable with H⁺/K⁺-ATP enzyme inhibitor in vitro.