Facile green approach towards the synthesis of some phenyl piperazine based dithiocarbamates as potent hemolytic and thrombolytic agents.

The facile and efficient protocol for the synthesis of N-phenyl piperazine based di-thio-carbamates has been reported under neat conditions. A library of novel piperazine based di-thio-carbamates (3a-h) in excellent yields has been prepared. Solvent free, catalyst free and easy work up conditions make this protocol an attractive synthetic protocol to achieve novel biologically active di-thio-carbamates. The synthesized molecules have been characterized by FT-IR, 1HNMR and 13CNMR spectroscopic techniques. The pharmacological aspects of these derivatives have been evaluated via hemolysis and thrombolysis. All the target molecules (3a-h) exhibit mild to medium potential as hemolytic and thrombolytic agents. Among the synthesized derivatives, compound 3c showed least cytotoxicity and better thrombolytic potential.

Synthesis, spectral analysis and biological evaluation of 2-{[(morpholin-4-yl)ethyl]thio}-5-phenyl/aryl-1,3,4-oxadiazole derivatives.

A series of new derivatives of 4-(2-chloroethyl)morpholine hydrochloride (5) were efficiently synthesized. Briefly, different aromatic organic acids (1a-f) were refluxed to acquire respective esters (2a-f) using conc. H2SO4 as catalyst. The esters were subjected to nucleophillic substitution by monohydrated hydrazine to acquire hydrazides (3a-f). The hydrazides were cyclized with CS2 in the presence of KOH to yield corresponding oxadiazoles (4a-f). Finally, the derivatives, 6a-f, were prepared by reacting oxadiazoles (4a-f) with 5 using NaH as activator. Structures of all the derivatives were elucidated through 1D-NMR EI-MS and IR spectral data. All these molecules were subjected to antibacterial and hemolytic activities and showed good antibacterial and hemolytic potential relative to the reference standards.

α-Glucosidase inhibitory potential and hemolytic evaluation of newly synthesized 3,4,5-trisubstituted-1,2,4-triazole derivatives.

A series of 1, 2, 4-triazole derivatives bearing piperidine moiety has been introduced as new anti-diabetic drug candidates with least cytotoxicity. p-Chlorophenylsulfonyl chloride (1) and ethyl nipecotate (2) were the starting reagents that resulted into corresponding 3,4,5-trisubstituted-1,2,4-triazole (6) through a series of steps. A series of electrophiles, 9a-e, were synthesized by reacting 4-bromobutyryl chloride (7) with differently substituted aromatic amines (8a-e) under basic aqueous medium. Target derivatives, 10a-e, were synthesized by the reaction of compound 6 with N-aryl-4-bromobutanamides (9a-e) in an aprotic solvent. Structures of all the derivatives were verified by spectroscopic analysis using IR, 1H-NMR, 13C-NMR and EIMS. Most of the derivatives revealed moderate to good α-glucosidase inhibitory activity with reference to acarbose. The moderate hemolytic potential demonstrated least toxicity.

Synthesis, pharmacological screening and computational analysis of some 2-(1H-Indol-3-yl)-N'-[(un)substituted phenylmethylidene] acetohydrazides and 2-(1H-Indol-3-yl)-N'-[(un)substituted benzoyl/2-thienylcarbonyl]acetohydrazides.

The undertaken research was initiated by transforming 2-(1H-Indol-3-yl)acetic acid (1) in catalytic amount of sulfuric acid and ethanol to ethyl 2-(1H-Indol-3-yl)acetate (2), which was then reacted with hydrazine monohydrate in methanol to form 2-(1H-Indol-3-yl)acetohydrazide (3). Further, The reaction scheme was designed into two pathways where, first pathway involved The reaction of 3 with substituted aromatic aldehydes (4a-o) in methanol with few drops of glacial acetic acid to generate 2-(1H-Indol-3-yl)-N'-[(un)substitutedphenylmethylidene]acetohydrazides (5a-o) and in second pathway 3 was reacted with acyl halides (6a-e) in basic aqueous medium (pH 9-10) to afford 2-(1H-Indol-3-yl)-N'-[(un)substitutedbenzoyl/2-thienylcarbonyl]acetohydrazides (7a-e). All The synthesized derivatives were characterized by IR, EI-MS and 1H-NMR spectral techniques and evaluated for their anti-bacterial potentials against Gram positive and Gram negative bacterial strains and it was found that compounds 7a-d exhibited antibacterial activities very close to standard Ciprofloxacin. The synthesized derivatives demonstrated moderate to weak anti-enzymatic potential against α-Glucosidase and Butyrylcholinesterase (BChE) where, compounds 7c and 5c exhibited comparatively better inhibition against these enzymes respectively. Compounds 7a, 7d and 7e showed excellent anti-enzymatic potentials against Lipoxygenase (LOX) and their IC50 values were much lower than the reference standard Baicalein. Enzyme inhibitory activities were also supported by computational docking results. Compounds 5c, 7a, 7b and 7c also showed low values of % hemolytic activity as well, showing that these molecules were not toxic, indicating that these molecules can be utilized as potential therapeutic agents against inflammatory ailments.

Efficient Double Suzuki Cross-Coupling Reactions of 2,5-Dibromo-3-hexylthiophene: Anti-Tumor, Haemolytic, Anti-Thrombolytic and Biofilm Inhibition Studies.

The present study describes several novel 2,5-biaryl-3-hexylthiophene derivatives (3a-i) synthesized via a Pd(0)-catalyzed Suzuki cross-coupling reaction in moderate to good yields. The novel compounds were also analyzed for their anti-thrombolytic, haemolytic, and biofilm inhibition activities. In addition, the anti-tumor activity was also evaluated in vitro for newly-synthesized compounds, where 3-hexyl-2,5-bis(4-(methylthio)phenyl)thiophene exhibited the best anti-tumor activity against 4T1 cells with IC50 value of 16 µM. Moreover, 2,5-bis(4-methylphenyl)-3-hexylthiophene showed the highest activity against MCF-7 cells with an IC50 value of 26.2 µM. On the other hand, the compound 2,5-bis(4-chloropheny)-3-hexylthiophene exhibited excellent biofilm inhibition activity. Furthermore, the compound 2,5-bis(3-chloro-4-fluorophenyl)-3-hexylthiophene also exhibited better anti-thrombolytic and hemolytic activity results as compared to the other newly-synthesized compounds.

Synthesis of 2-{(5-phenyl-1,3,4-Oxadiazol-2-yl)sulfanyl}-N-substituted acetamides as potential antimicrobial and hemolytic agents.

A new series of N-substituted derivatives of 2-{(5-phenyl-1,3,4-Oxadiazol-2-yl)sulfanyl}acetamides was synthesized. The synthesis was carried out by converting benzoic acid (1) into ethyl benzoate (2), benzohydrazide (3) and then 5-pheny-1,3,4-Oxadiazol-2-thiol (4) step by st0ep. The target compounds 6a-p were synthesized by reaction of compound 4 with equimolar ratios of different N-alkyl/aryl substituted 2-bromoacetamide (5a-p) in the presence of DMF and sodium hydride (NaH). The spectral (EI-MS, IR, (1)H-NMR) characterization of all the synthesized compounds reveal their successful synthesis. The compounds were also screened for antimicrobial & hemolytic activity and most of them were found to be active against the selected microbial species at variable extent relative to reference standards. But 6h was the most active against the selected panel of microbes. This series showed less toxicity and may be considered for further biological screening and application trial except 6m, possessing higher cytotoxicity.

Converting a Staphylococcus aureus toxin into effective cyclic pseudopeptide antibiotics.

Staphylococcus aureus produces peptide toxins that it uses to respond to environmental cues. We previously characterized PepA1, a peptide toxin from S. aureus, that induces lytic cell death of both bacterial and host cells. That led us to suggest that PepA1 has an antibacterial activity. Here, we demonstrate that exogenously provided PepA1 has activity against both Gram-positive and Gram-negative bacteria. We also see that PepA1 is significantly hemolytic, thus limiting its use as an antibacterial agent. To overcome these limitations, we converted PepA1 into nonhemolytic derivatives. Our most promising derivative is a cyclic heptapseudopeptide with inconsequential toxicity to human cells, enhanced stability in human sera, and sharp antibacterial activity. Mechanistically, linear and helical PepA1 derivatives form pores at the bacterial and erythrocyte surfaces, while the cyclic peptide induces bacterial envelope reorganization, with insignificant action on the erythrocytes. Our work demonstrates that bacterial toxins might be an attractive starting point for antibacterial drug development.

Selective C-arylation of 2,5-dibromo-3-hexylthiophene via Suzuki cross coupling reaction and their pharmacological aspects.

The present study reports the synthesis of various new derivatives based on 5-aryl-2-bromo-3-hexylthiophene with moderate-to-good yields via a palladium-catalyzed Suzuki cross-coupling reaction. This coupling method involved the reaction of 2,5-dibromo-3-hexylthiophene with several arylboronic acids in order to synthesize corresponding thiophene derivatives under controlled and optimal reaction conditions. The different substituents (CH3, OCH3, Cl, F etc.) present on arylboronic acids are found to have significant electronic effects on the overall properties of new products. The synthesized thiophene molecules were studied for their haemolytic, biofilm inhibition and anti-thrombolytic activities, and almost all products showed potentially good properties. The compound 2-bromo-5-(3-chloro-4-fluorophenyl)-3-hexylthiophenein particular exhibited the highest values for haemolytic and bio-film inhibition activities among all newly synthesized derivatives. In addition, the compound 2-bromo-3-hexyl-5-(4-iodophenyl)thiophene also showed high anti-thrombolytic activity, suggesting the potential medicinal applications of these newly synthesized compounds.

Synthesis of analogs of peptides from Buthus martensii scorpion venom with potential antibiotic activity.

Five analogs of a natural peptide (BmKn1) found in the venom of scorpion Buthus martensii Karsh have been synthesized and tested to compare their antimicrobial and hemolytic activity with the wild type. Circular dichroism spectra show that these peptides form an alpha helix structure and its amino acid positions predict an amphipathic nature. Results show that increasing hydrophobicity by substituting successively positions 5 and 9 of the sequence (on the hydrophobic side of the helix) with alanine, valine and leucine enhances antimicrobial activity and hemolysis. When changes are done on positions 7 and 10 (on the hydrophilic side) by introducing more positive charges with addition of lysine, both activities also increase. However, when negative charges are introduced instead (with glutamic acids), antimicrobial activity is observed but hemolysis is reduced to zero under the concentrations studied. Although strong inhibitory activity begins at low concentrations (10µg/mL), some peptides level off inhibition and no change is observed as concentrations are increased.

Synthesis, characterization, in vitro anti-proliferative and hemolytic activity of hydroxyapatite.

Hydroxyapatite (Ca10(PO4)6(OH)2, HAP) nanoparticles are widely used in several biomedical applications due to its compositional similarities to bone mineral, excellent biocompatibility and bioactivity, osteoconductivity. In this present investigation, HAP nanoparticles synthesized by precipitation technique using calcium nitrate and di-ammonium phosphate. The crystalline nature and the functional group analysis are confirmed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Fourier transform Raman spectroscopy (FT-Raman) respectively. The morphological observations are ascertained from field emission electron scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). In vitro anti-proliferative and hemolytic activities are carried out on the synthesized HAP samples and the studies reveals that HAP have mild activity against erythrocytes.

Synthetic analogs of anoplin show improved antimicrobial activities.

We present the antimicrobial and hemolytic activities of the decapeptide anoplin and 19 analogs thereof tested against methicillin-resistant Staphylococcus aureus ATCC 33591 (MRSA), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), vancomycin-resistant Enterococcus faecium (ATCC 700221) (VRE), and Candida albicans (ATCC 200955). The anoplin analogs contain substitutions in amino acid positions 2, 3, 5, 6, 8, 9, and 10. We use these peptides to study the effect of altering the charge and hydrophobicity of anoplin on activity against red blood cells and microorganisms. We find that increasing the charge and/or hydrophobicity improves antimicrobial activity and increases hemolytic activity. For each strain tested, we identify at least six anoplin analogs with an improved therapeutic index compared with anoplin, the only exception being Enterococcus faecium, against which only few compounds are more specific than anoplin. Both 2Nal(6) and Cha(6) show improved therapeutic index against all strains tested.

Polymers with tunable side-chain amphiphilicity as non-hemolytic antibacterial agents.

Quaternized polymers mimicking the antimicrobial peptides were created by tuning the side-chain amphiphilicity using a first-time approach of post-functionalization. They displayed excellent efficacy against pathogenic bacteria even in human plasma and membrane disruptive mode of action. The optimized polymers and degraded products were non-hemolytic.

Direct access to side chain N,N'-diaminoalkylated derivatives of basic amino acids suitable for solid-phase peptide synthesis.

A simple and efficient one-pot procedure that enables rapid access to orthogonally protected N,N'-diaminoalkylated basic amino acid building blocks fully compatible with standard Boc and Fmoc solid-phase peptide synthesis is reported. Described synthetic approach includes double reductive alkylation of N (α)-protected diamino acids with N-protected amino aldehydes in the presence of sodium cyanoborohydride. This approach allows preparation of symmetrical, as well as unsymmetrical, basic amino acid derivatives with branched side-chains that can be further modified, enhancing their synthetic utility. The suitability of the synthesized branched basic amino acid building blocks for use in standard solid-phase peptide synthesis has been demonstrated by synthesis of an indolicidin analogue in which the lysine residue was substituted with the synthetic derivative N (α)-(9H-fluorenyl-9-methoxycarbonyl)-N (ß),N (ß) '-bis[2-(tert-butoxycarbonylamino)ethyl]-L-2,3-diaminopropionic acid. This substitution resulted in an analogue with more ordered secondary structure in 2,2,2-trifluoroethanol and enhanced antibacterial activity without altering hemolytic activity.

Structure-activity relationships of a snake cathelicidin-related peptide, BF-15.

Cathelicidin-BF15 (BF-15) is a 15-mer peptide derived from Cathelicidin-BF (BF-30), which is found in the venom of the snake Bungarus fasciatus and exhibits broad antimicrobial activity. Since BF-15 retains most part of the antimicrobial activity of BF-30 but has significantly reduced haemolytic activity and a much shorter sequence length (and less cost), it is a particularly attractive template around which to design novel antimicrobial peptides. However, the structure-activity relationship of it is still unknown. We designed and synthesized a series of C-terminal amidated analogs of BF-15 based on its amphipathic α-helix structure. And we characterized their antimicrobial potency and haemolytic activity. We identified the amidated BF-15 (analog B1) with potent antimicrobial activity against several antibiotic-resistant bacteria (MICs between 1 and 64 µg/mL, 2-16-folds higher than BF-30) and much lower haemolytic activity. The subsequent circular dichroism study results showed a typical α-helix pattern of analog B1 and the content of the α-helix structure of it increased significantly comparing with BF-30, which indicates the peptide sequence of BF-15 may provide a major contribution to the α-helix content of the whole BF-30 sequence. The peptide induced chaotic membrane morphology and cell debris as determined by electron microscopy. This suggests that the antimicrobial activity of B1 is based on cytoplasmic membrane permeability. Taken together, our results suggested that peptide B1 should be considered as an excellent candidate for developing therapeutic drugs.

Diacyl glycerol arginine-based surfactants: biological and physicochemical properties of catanionic formulations.

In this paper, we report on a catanionic vesicles-based strategy to reduce the cytotoxicity of the diacyl glycerol arginine-based synthetic surfactants 1,2-dimyristoyl-rac-glycero-3-O-(N(α)-acetyl-L-arginine) hydrochloride (1414RAc) and 1,2-dilauroyl-rac-glycero-3-O-(N(α)-acetyl-L-arginine) hydrochloride (1212RAc). The behavior of these surfactants was studied either as pure components or after their formulation as pseudo-tetra-chain catanionic mixtures with phosphatidylglycerol (PG) and as cationic mixtures with 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) used as control. The antimicrobial activity of the negatively charged formulations against Acinetobacter baumannii was maintained with respect to the surfactant alone, while a significant improvement of the antimicrobial activity against Staphylococcus aureus was observed, together with a strong decrease of hemolytic activity. The influence of the net charge of the catanionic vesicles on membrane selectivity was studied using model membranes. The dynamics of surface tension changes induced by the addition of 1414RAc/PG aqueous dispersions into phospholipid monolayers composed of zwitterionic DPPC as model system for mammalian membranes and of negatively charged PG mimicking cytoplasmic membrane of gram-positive bacteria was followed by tensiometry. Our results constitute a proof of principle that tuning formulation can reduce the cytotoxicity of many surfactants, opening their possible biological applications.

Design of antimicrobially active small amphiphilic peptide dendrimers.

Novel polyfunctional small amphiphilic peptide dendrimers characterized by incorporation of a new core compounds - tris-amino acids or tetrakis-amino alcohols that originated from a series of basic amino acids - were efficiently synthesized. These new core elements yielded molecules with multiple branching and (+5)/(+6) charge at the 1-st dendrimer generation. Dendrimers exhibited significant antimicrobial potency against Gram(+) and Gram(-) strains involving also multiresistant reference strains (S. aureus ATCC 43300 and E. coli ATCC BAA-198). In addition, high activity against fungi from the Candida genus was detected. More charged and more hydrophobic peptide dendrimers expressed hemolytic properties.

Novel echinocandin antifungals. Part 1: novel side-chain analogs of the natural product FR901379.

A series of novel acylated analogs of the novel water-soluble echinocandin FR901379 have been prepared and evaluated for antifungal and hemolytic activity. A relationship between antifungal activity and lipophilicity of the acyl side chain, expressed as ClogP was demonstrated, and an analog (3c) with 5.5- to 8-fold superior in vivo activity relative to the previously disclosed 4-(n-octyloxy)benzoyl side chain analog, FR131535 obtained.

Cathelicidin-derived Trp/Pro-rich antimicrobial peptides with lysine peptoid residue (Nlys): therapeutic index and plausible mode of action.

Recently, we designed a novel cell-selective antimicrobial peptide (TPk) with intracellular mode of action from Pro --> Nlys (Lys peptoid residue) substitution in a noncell-selective cathelicidin-derived Trp/Pro-rich antimicrobial peptide, tritrpticin-amide (TP; VRRFPWWWPFLRR-NH(2)) (Biochemistry 2006; 45: 13007-13017). In this study, to elucidate the effect of Pro --> Nlys substitution on therapeutic index and mode of action of other noncell-selective cathelicidin-derived Trp/Pro-rich antimicrobial peptides and develop novel short antimicrobial peptides with high cell selectivity/therapeutic index, we synthesized Nlys-substituted antimicrobial peptides, TPk, STPk and INk, in which all proline residues of TP, symmetric TP-analogue (STP; KKFPWWWPFKK-NH(2)) and indolicidin (IN; ILPWKWPWWPWRR-NH(2)) were replaced by Nlys, respectively. Compared to parent Pro-containing peptides (TP, STP and IN), Nlys substituted peptides (TPk, STPk and Ink) had 4- to 26-fold higher cell selectivity/therapeutic index. Parent Pro-containing peptides induced a significant depolarization of the cytoplasmic membrane of intact Staphylococcus aureus at their MIC, whereas Nlys-substituted antimicrobial peptides did not cause visible membrane depolarization at their MIC. These results suggest that the antibacterial action of Nlys-substituted peptides is probably not due to the disruption of bacterial cytoplasmic membranes but the inhibition of intracellular components. Taken together, our results showed that Pro --> Nlys substitution in other noncell-selective Trp/Pro-rich antimicrobial peptides such as STP and IN as well as TP can improve the cell selectivity/therapeutic index and change the mode of antibacterial action from membrane-disrupting to intracellular targeting. In conclusion, our findings suggested that Pro --> Nlys substitution in noncell-selective Trp/Pro-rich antimicrobial peptides is a promising method to develop cell-selective antimicrobial peptides with intracellular target mechanism.

Role of micafungin in the antifungal armamentarium.

Serious infections caused by opportunistic molds remain a major problem for public health. Immune deficiency following organ transplantation and aggressive cancer treatment has greatly increased the incidence of systemic mycoses, and invasive aspergillosis in patients with AIDS is associated with significant morbidity and mortality. Amphotericin B is the first-line therapy for systemic infection because of its broad-spectrum and fungicidal activity. However, considerable side effects limit its clinical utility. The echinocandins are large lipopeptide molecules that inhibit the synthesis of 1,3-beta-D-glucan, a key component of the fungal cell wall. Three echinocandins have reached the market, and some others are in early clinical development. Caspofungin was the first echinocandin to be licensed for clinical use in most countries. Micafungin is licensed for clinical use in Japan, China, Taiwan, Jordan, Korea, Hong-Kong and the US, and anidulafungin is currently licensed in the US. The novel class of echinocandins represents a milestone in antifungal drug research that has further expanded our therapeutic options. Studies to date have shown that micafungin exhibits extremely potent antifungal activity against clinically important fungi, including Aspergillus and azole-resistant strains of Candida. In animal studies, micafungin is as efficacious as amphotericin B with respect to improvement of survival rate. Micafungin is also characterized by a linear pharmacokinetic profile and substantially fewer toxic effects. Micafungin is a poor substrate for the cytochrome P450 enzymes, and compared to azoles, fewer drug interactions are described. No dose adjustments of the drug are required in the presence of mycophenolate mofetil, cyclosporin, tacrolimus, prednisolone, or sirolimus. Strategies using this new echinocandin agent will benefit a large number of patients with severe immune dysfunction.

Synthesis, antifungal and haemolytic activity of a series of bis(pyridinium)alkanes.

A series of bis(pyridinium)alkanes have been prepared and their antifungal activity, haemolytic activity and ability to inhibit fungal phospholipase B1 have been investigated, together with those of the commercially available antiseptics octenidine and dequalinium. Removal of the amino substituents from the pyridinium rings resulted in a significant decrease in antifungal activity. However, shortening or removing the alkyl chains attached to the amino groups had little effect on antifungal activity and significantly reduced haemolytic activity. Only octenidine was a strong inhibitor of fungal phospholipase B1.