QuatCy: A Heptamethine Cyanine Modification With Improved Characteristics.

A major restriction on optical imaging techniques is the range of available fluorophores that are compatible with aqueous media without aggregation, absorb light above 750 nm with high extinction coefficients, fluoresce with relatively high quantum yields, and resist photodecomposition. Indocyanine green (ICG or A in this paper) is an important example of a fluorophore that fits this description. Other dyes that are becoming increasingly prevalent are select heptamethine cyanine dyes (Cy7) which feature a cyclohexyl framework to rigidify the conjugated alkenes, and meso-chlorine substitution; MHI-148 (B) is one example. Methods: Research described here was initiated to uncover the consequences of a simple isoelectronic substitution to MHI-148 that replaces a cyclohexyl methylene with a dialkyl ammonium fragment. Solubility experiments were carried out in aqueous and cell culture media, photophysical properties including fluorescence quantum yields, brightness and stability were measured. Moreover, in vivo pharmacokinetics, distribution and tumor seeking properties were also explored. Results: Modification to incorporate dialkyl ammonium fragment leads to a brighter, more photostable fluorophore, with a decreased tendency to aggregation, complementary solubility characteristics, and a lower cytotoxicity. Conclusion: All the above-mentioned parameters are favorable for many anticipated applications of the new dye we now call quaternary cyanine-7 or QuatCy.

Synthesis and biological activity investigation of azole and quinone hybridized phosphonates.

Phosphonates, azoles and quinones are pharmacophores found in bioactive compounds. A series of phosphonates conjugated to azoles and quinones with variable carbon chain lengths were synthesized in 3-4 steps with good yield. Antifungal assay of these compounds showed that ethyl protected phosphates have excellent inhibitory activity against phytopathogenic fungus Fusarium graminearum, and the free-base phosphates have good activity against human pathogenic fungi Aspergillus flavus and Candida albicans. Structure- activity relationship (SAR) studies showed activity increases with longer carbon chain length between phosphonate and anthraquinone analogs consisting of azole and quinone moieties. These newly synthesized compounds also have mild antibacterial activities to Gram positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Cytotoxicity analysis of these compounds against HeLa cells reveals that the phosphoric acid analogs are less toxic compared to ethyl protected phosphonates. Three leads compounds have been identified with prominent antifungal activity and low cytotoxicity.

Tuning the biological activity of cationic anthraquinone analogues specifically toward Staphylococcus aureus.

Development of new antibacterial agents against drug resistant bacteria is an imminent task, especially against methicillin-resistant Staphylococcus aureus (MRSA). While MRSA can still be treated with broad spectrum antibiotics, the use of which often leads to the disruption of normal microbial flora leading to Clostridium difficile infection (CDI). Herein, a new class of antibacterial agent, cationic anthraquinone analogues specifically against MRSA, has been developed. Through the variation and optimization of substituents, these agents are selective toward MRSA, and not Gram negative bacteria which may avoid the problem of CDI. In addition, newly discovered lead compounds also show significantly reduced cytotoxicity against normal mammalian cells than cancerous cells. This interesting finding can alleviate the toxicity and side effect problems often associate with the use of antibiotics.

One-step synthesis of carbohydrate esters as antibacterial and antifungal agents.

Carbohydrate esters are biodegradable, and the degraded adducts are naturally occurring carbohydrates and fatty acids which are environmentally friendly and non-toxic to human. A simple one-step regioselective acylation of mono-carbohydrates has been developed that leads to the synthesis of a wide range of carbohydrate esters. Screening of these acylated carbohydrates revealed that several compounds were active against a panel of bacteria and fungi, including Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Candida albicans, Cryptococcus neoformans, Aspergillus flavus and Fusarium graminearum. Unlike prior studies on carbohydrate esters that focus only on antibacterial applications, our compounds are found to be active against both bacteria and fungi. Furthermore, the synthetic methodology is suitable to scale-up production for a variety of acylated carbohydrates. The identified lead compound, MAN014, can be used as an antimicrobial in applications such as food processing and preservation and for treatment of bacterial and fungal diseases in animals and plants.

Aminoglycoside interactions and impacts on the eukaryotic ribosome.

Aminoglycosides are chemically diverse, broad-spectrum antibiotics that target functional centers within the bacterial ribosome to impact all four principle stages (initiation, elongation, termination, and recycling) of the translation mechanism. The propensity of aminoglycosides to induce miscoding errors that suppress the termination of protein synthesis supports their potential as therapeutic interventions in human diseases associated with premature termination codons (PTCs). However, the sites of interaction of aminoglycosides with the eukaryotic ribosome and their modes of action in eukaryotic translation remain largely unexplored. Here, we use the combination of X-ray crystallography and single-molecule FRET analysis to reveal the interactions of distinct classes of aminoglycosides with the 80S eukaryotic ribosome. Crystal structures of the 80S ribosome in complex with paromomycin, geneticin (G418), gentamicin, and TC007, solved at 3.3- to 3.7-Å resolution, reveal multiple aminoglycoside-binding sites within the large and small subunits, wherein the 6'-hydroxyl substituent in ring I serves as a key determinant of binding to the canonical eukaryotic ribosomal decoding center. Multivalent binding interactions with the human ribosome are also evidenced through their capacity to affect large-scale conformational dynamics within the pretranslocation complex that contribute to multiple aspects of the translation mechanism. The distinct impacts of the aminoglycosides examined suggest that their chemical composition and distinct modes of interaction with the ribosome influence PTC read-through efficiency. These findings provide structural and functional insights into aminoglycoside-induced impacts on the eukaryotic ribosome and implicate pleiotropic mechanisms of action beyond decoding.

Synthesis and bioactivity investigation of quinone-based dimeric cationic triazolium amphiphiles selective against resistant fungal and bacterial pathogens.

A series of synthetic dimeric cationic anthraquinone analogs (CAAs) with potent antimicrobial activities against a broad range of fungi and bacteria were developed. These compounds were prepared in 2-3 steps with high overall yield and possess alkyl chain, azole, quinone, and quaternary ammonium complexes (QACs). In vitro biological evaluations reveal prominent inhibitory activities of lead compounds against several drug-susceptible and drug-resistant fungal and bacterial strains, including MRSA, VRE, Candida albicans and Aspergillus flavus. Mode of action investigation reveals that the synthesized dimeric CAA's can disrupt the membrane integrity of fungi. Computational studies reveal possible designs that can revive the activity of QACs against drug-resistant bacteria. Cytotoxicity assays in SKOV-3, a cancer cell line, show that the lead compounds are selectively toxic to fungi and bacteria over human cells.

Divergent Synthesis of Three Classes of Antifungal Amphiphilic Kanamycin Derivatives.

A concise and novel method for site-selective alkylation of 1,3,6',3″-tetraazidokanamycin has been developed that leads to the divergent synthesis of three classes of kanamycin A derivatives. These new amphiphilic kanamycin derivatives bearing alkyl chains length of 4, 6, 7, 8, 9, 10, 12, 14, and 16 have been tested for their antibacterial and antifungal activities. The antibacterial effect of the synthesized kanamycin derivatives declines or disappears as compared to the original kanamycin A. Several compounds, especially those with octyl chain at O-4″ and/or O-6″ positions on the ring III of kanamycin A, show very strong activity as antifungal agents. In addition, these compounds display no toxicity toward mammalian cells. Finally, computational calculation has revealed possible factors that are responsible for the observed regioselectivity. The simplicity in chemical synthesis and the fungal specific property make the lead compounds ideal candidates for the development of novel antifungal agents.

Antifungal amphiphilic aminoglycoside K20: bioactivities and mechanism of action.

K20 is a novel amphiphilic antifungal aminoglycoside that is synthetically derived from the antibiotic kanamycin A. Reported here are investigations of K20's antimicrobial activities, cytotoxicity, and fungicidal mechanism of action. In vitro growth inhibitory activities against a variety of human and plant pathogenic yeasts, filamentous fungi, and bacteria were determined using microbroth dilution assays and time-kill curve analyses, and hemolytic and animal cell cytotoxic activities were determined. Effects on Cryptococcus neoformans H-99 infectivity were determined with a preventive murine lung infection model. The antifungal mechanism of action was studied using intact fungal cells, yeast lipid mutants, and small unilamellar lipid vesicles. K20 exhibited broad-spectrum in vitro antifungal activities but not antibacterial activities. Pulmonary, single dose-administration of K20 reduced C. neoformans lung infection rates 4-fold compared to controls. Hemolysis and half-maximal cytotoxicities of mammalian cells occurred at concentrations that were 10 to 32-fold higher than fungicidal MICs. With fluorescein isothiocyanate (FITC), 20-25 mg/L K20 caused staining of >95% of C. neoformans and Fusarium graminearum cells and at 31.3 mg/L caused rapid leakage (30-80% in 15 min) of calcein from preloaded small unilamellar lipid vesicles. K20 appears to be a broad-spectrum fungicide, capable of reducing the infectivity of C. neoformans, and exhibits low hemolytic activity and mammalian cell toxicity. It perturbs the plasma membrane by mechanisms that are lipid modulated. K20 is a novel amphiphilic aminoglycoside amenable to scalable production and a potential lead antifungal for therapeutic and crop protection applications.

Synthesis and anticancer structure activity relationship investigation of cationic anthraquinone analogs.

We have synthesized a series of novel 4,9-dioxo-4,9-dihydro-1H-naphtho[2,3-d][1,2,3]triazol-3-ium salts, which can be viewed as analogs of cationic anthraquinones. Unlike the similar analogs that we have reported previously, these compounds show relatively weak antibacterial activities but exert strong anticancer activities (low µM to nM GI50), in particular, against melanoma, colon cancer, non-small cell lung cancer and central nervous system (CNS) cancer. These compounds are structurally different from their predecessors by having the aromatic group, instead of alkyl chains, directly attached to the cationic anthraquinone scaffold. Further investigation in the structure-activity relationship (SAR) reveals the significant role of electron donating substituents on the aromatic ring in enhancing the anticancer activities via resonance effect. Steric hindrance of these groups is disadvantageous but is less influential than the resonance effect. The difference in the attached groups at N-1 position of the cationic anthraquinone analog is the main structural factor for the switching of biological activity from antibacterial to anticancer. The discovery of these compounds may lead to the development of novel cancer chemotherapeutics.

Safe and easy route for the synthesis of 1,3-dimethyl-1,2,3-triazolium salt and investigation of its anticancer activities.

We have developed a new safe and easy route for the synthesis of 1,3-dimethyl-1,2,3-triazolium derivatives. We have reported the synthesis of 4,9-dioxo-1,3-dimethylnaphtho[2,3-d][1,2,3]triazol-3-ium chloride from methylation of 1-methyl-1H-naphtho[2,3-d][1,2,3]triazole-4,9-dione. The synthesis of 1-methyl-1H-naphtho[2,3-d][1,2,3]triazole-4,9-dione is inefficient as a significant amount of by-product is formed that is difficult to separate and also unsafe as it requires the use of hazardous methylazide as a starting material. It is, however, important to develop an improved method for the synthesis of 4,9-dioxo-1,3-dimethylnaphtho[2,3-d][1,2,3]triazol-3-ium salt due to its significant anticancer activities. Herein, we report a safe and convenient route for the synthesis of this compound, which lead to more detailed exploration of its profound anticancer activities. The improved method can be applicable for the synthesis of other 1,3-dimethyl-1,2,3-triazolium salts of interest without the use of potentially explosive methylazide. The compound synthesized in this new method shows significant anticancer activities against melanoma, colon cancer, non-small cell lung cancer and central nervous system (CNS) cancer with GI50 values ranging from low µM to nM.