Design, Synthesis, and Antimicrobial Activity of Novel 1,4-Dihydropyridine-3,5-Dicarboxamides

The three-dimensional structure in dodecyl phosphocholine micelles of the 26-mer membrane-permeabilizing bacteriocin-like pheromone plantaricin A (PlnA) has been determined by use of nuclear magnetic resonance spectroscopy. The peptide was unstructured in water but became partly structured upon exposure to micelles. An amphiphilic alpha-helix stretching from residue 12 to 21 (possibly also including residues 22 and 23) was then formed in the C-terminal part of the peptide, whereas the N-terminal part remained largely unstructured. PlnA exerted its membrane-permeabilizing antimicrobial activity through a nonchiral interaction with the target cell membrane because the d-enantiomeric form had the same activity as the natural l-form. This nonchiral interaction involved the amphiphilic alpha-helical region in the C-terminal half of PlnA because a 17-mer fragment that contains the amphiphilic alpha-helical part of the peptide had antimicrobial potency that was similar to that of the l- and d-enantiomeric forms of PlnA. Also the pheromone activity of PlnA depended on this nonchiral interaction because both the l- and d-enantiomeric forms of the 17-mer fragment inhibited the pheromone activity. The pheromone activity also involved, however, a chiral interaction between the N-terminal part of PlnA and its receptor because high concentrations of the l-form (but not the d-form) of a 5-mer fragment derived from the N-terminal part of PlnA had pheromone activity. The results thus reveal a novel mechanism whereby peptide pheromones such as PlnA may function. An initial nonchiral interaction with membrane lipids induces alpha-helical structuring in a segment of the peptide pheromone. The peptide becomes thereby sufficiently structured and properly positioned in the membrane interface, thus enabling it to engage in a chiral interaction with its receptor in or near the membrane water interface. This membrane-interacting mode of action explains why some peptide pheromones/hormones such as PlnA sometimes display antimicrobial activity in addition to their pheromone activity.

Increasing attention has been given to tropical fruits not only due to their sensory attributes but also because of their functional and health-promoting properties associated with their bioactive composition. Flavonoids, phenolic acids, and carotenoids offer many health benefits in terms of antioxidant, antimicrobial, and anti-inflammatory activities. The purpose of the current study was to determine antimicrobial and antioxidant activities of kumquat (Fortunella spp.) and pomelo (Citrus maxima) fruits. The peel (edible exocarp) and seeds of kumquat and the inedible parts of pomelo fruit (albedo; white mesocarp, and segment peel; segment epidermis and juice sac stalk) were assessed with the aim of valorisation for waste management and contributing to the circular economy. The parts of the fruits mentioned were extracted with water and ethanol for kumquat and pomelo, respectively, and their antioxidant activities were assessed. Antimicrobial activities of the extracts were monitored against Staphylococcus aureus, Enterococcus spp., Escherichia coli, Klebsiella spp., and Candida albicans. Pomelo segment peel was studied at three concentrations (100%, 10%, and 1%), whereas the remaining extracts were used at 100% for antimicrobial evaluation. Pomelo segment peel showed higher antioxidant activity than pomelo albedo, kumquat peel, and kumquat seed. Pomelo segment peel at 1% concentration exhibited antimicrobial activity. While pomelo albedo only showed antimicrobial activity against E. coli. Aqueous extracts of kumquat peel and kumquat seed exhibited antioxidant activity but showed no antimicrobial activity against the microorganisms studied. Pomelo segment peel exhibited high antioxidant and antimicrobial activity, which promises significant contributions to the food industry. Using these wastes is believed to promote environmental sustainability and support the circular economy.

We have explored the possibility of generating peptides having antimicrobial and hemolytic activities or only antimicrobial activity, from a 16-residue peptide, GFFALIPKIISSPLFK, corresponding to the N-terminal region of the toxin pardaxin. This peptide does not exibit these activities, although it can permeabilize model membranes. Peptides were synthesized wherein either A4 or P7 were substituted by K and S11 replaced by K. Peptides in which P7 and S11 were replaced with K, (AK) and A4 and S11 replaced with K and A instead of P at position 7, (KA) showed potent antimicrobial and hemolytic activities. However, the peptide where S11 and A4 were replaced with K, (KP) showed pronounced antimicrobial activity with very weak hemolytic activity. Circular dichroism studies indicated that peptides AK and KA had a strong propensity to occur in a helical conformation, whereas KP did not. Peptides AK and KA were very effective in permeabilizing model membranes, whereas KP was relatively ineffective. Our studies thus suggest the requirements for a peptide to have only antimicrobial activity and also that selectivity in activity can be rationalized on the basis of biophysical principles. Thus, by judicious positioning of amino acids, especially positively charged ones, it should be possible to generate biologically active peptides without taking recourse to a combinatorial approach.

The aim of the research was to determine the antioxidant and antimicrobial activity, determination of chemical elements and heavy metals in seaweed extracts of wakame, arame, dulse, laminaria, kombu, and hijiki. Antioxidant activity was determined by DPPH method and the activity ranged from 0.00 to 2641.34 TEAC. The highest antioxidant activity was observed in kombu (2641.34 TEAC) and arame (2457.5 TEAC). Antimicrobial activity was analyzed by disk diffusion method and MIC method. Three G+ bacteria (Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis), three G- bacteria (Salmonella enterica, Pseudomonas aeruginosa, Yersinia enterocolitica), and four yeasts (Candida tropicalis, C. krusei, C. glabrata, C. albicans) were used as model organisms. The size of inhibition zones ranged from 0.00 to 8.67 mm. The minimum inhibitory concentrations of the selected seaweeds ranged from MIC50 98.46 (MIC90 100.25) to MIC50 3.43 µL/mL (MIC90 5.26 µL/mL). The content of selected elements was determined in seaweed samples by ICP-OES. The chemical composition of the algae showed differences between species and the presence of heavy metals. Arsenic, cadmium, and aluminum were confirmed. All seaweed samples contained arsenic ranging from 6.6546 to 76.48 mg/kg. Further investigation of seaweeds is needed to identify the active substances present in the algae that are responsible for antioxidant and antimicrobial activity. This study was carried out to evaluate the antimicrobial and antioxidant activity of extracts from five commonly consumed seaweeds for their ability to inhibit selected microorganisms and to determine the health risk due to heavy metals content. Our study contributes to the evidence that seaweeds have antimicrobial and antioxidant activity and seaweed extracts have for pharmacological applications.

Structure-activity analysis of brevinin 1E amide, an antimicrobial peptide from Rana esculenta

Simple SummaryThe global crisis of increased mortality rates due to the emergence of antimicrobial resistance and cancers has increased researchers’ efforts to find new, potent solutions through implementing natural products in the pharmaceutical industry. The present investigation produced echinenone (yellowish-orange pigment) from Micrococcus lylae MW407006 with potent pharmacological activities. A response surface methodology statistical design was used to optimize the biomass production, pigment concentration, and antimicrobial activity. The Spearman correlation coefficient was assessed, which indicated a strong linear relationship between biomass production, pigment concentration, and antimicrobial activity. Nano-echinenone was physically synthesized through the ball-milling technique. The synthesized nano-echinenone showed higher pharmacological activities (antimicrobial, antioxidant, and antitumor activities) in comparison with the crude pigment. The significantly high selectivity index of the synthesized nano-echinenone proved its safety and paved the way for its possible use in the pharmaceutical industry.Bacterial pigments (e.g., melanin and carotenoids) are considered to be among the most important secondary metabolites due to their various pharmacological activities against cancer and microbial resistance. Different pigmented bacterial strains were isolated from soil samples from El Mahmoudiyah governance and screened for their antimicrobial activity. The most promising pigment producer was identified as Micrococcus lylae MW407006; furthermore, the produced pigment was identified as echinenone (β-carotene pigment). The pigment production was optimized through a central composite statistical design to maximize the biomass production, pigment concentration, and the antimicrobial activity. It was revealed that the most significant fermentation parameters were the glucose (as a carbon source) and asparagine (as a nitrogen source) concentrations. Nano-echinenone was synthesized using the ball milling technique, characterized, and finally assessed for potential antimicrobial, antioxidant, and antitumor activities. The data revealed that the synthesized nano-echinenone had higher antimicrobial activity than the crude pigment. The cytotoxic potency of echinenone and nano-echinenone was investigated in different cell lines (normal and cancer cells). The inhibition of cell proliferation and induction of cell death was observed in Caco-2 and Hep-G2 cells. The data proved that nano-echinenone is a suitable candidate for use as a safe antimicrobial and anti-hepatocellular-carcinoma agent.

BackgroundReplacement of chloride ions in cyanuric chloride give several variants of 1,3,5-triazine derivatives which were investigated as biologically active small molecules. These compounds exhibit antimalarial, antimicrobial, anti-cancer and anti-viral activities, among other beneficial properties. On the other hand, treatment of bacterial infections remains a challenging therapeutic problem because of the emerging infectious diseases and the increasing number of multidrug-resistant microbial pathogens. As multidrug-resistant bacterial strains proliferate, the necessity for effective therapy has stimulated research into the design and synthesis of novel antimicrobial molecules.Results1,3,5-Triazine 4-aminobenzoic acid derivatives were prepared by conventional method or by using microwave irradiation. Using microwave irradiation gave the desired products in less time, good yield and higher purity. Esterification of the 4-aminobenzoic acid moiety afforded methyl ester analogues. The s-triazine derivatives and their methyl ester analogues were fully characterized by FT-IR, NMR (1H-NMR and 13C-NMR), mass spectra and elemental analysis. All the synthesized compounds were evaluated for their antimicrobial activity. Some tested compounds showed promising activity against Staphylococcus aureus and Escherichia coli.ConclusionsThree series of mono-, di- and trisubstituted s-triazine derivatives and their methyl ester analogues were synthesized and fully characterized. All the synthesized compounds were evaluated for their antimicrobial activity. Compounds (10), (16), (25) and (30) have antimicrobial activity against S. aureus comparable to that of ampicillin, while the activity of compound (13) is about 50% of that of ampicillin. Compounds (13) and (14) have antimicrobial activity against E. coli comparable to that of ampicillin, while the activity of compounds (9–12) and (15) is about 50% of that of ampicillin. Furthermore, minimum inhibitory concentrations values for clinical isolates of compounds (10), (13), (14), (16), (25) and (30) were measured. Compounds (10) and (13) were more active against MRSA and E. coli than ampicillin. Invitro cytotoxicity results revealed that compounds (10) and (13) were nontoxic up to 250 µg/mL (with SI = 10) and 125 µg/mL (with SI = 5), respectively.Graphical abstractThree series of mono-, di- and trisubstituted s-triazine derivatives and their methyl ester analogues were synthesized and evaluated for their antimicrobial activity. Several compounds have antimicrobial activity against S. aureus and E. coli comparable to that of ampicillin.

In a recent issue of the Journal of Clinical Microbiology, Kunin and Buesching (1) describe a novel technique to diagnose common urinary pathogens in office-collected samples. Using a three-layer circular sandwich with filter paper as the solid-phase dilution device, it was possible to pick up members of the family Enterobacteriaceae and staphylococci from urine specimens. The technology was standardized by monitoring the penetration of microbes through the filter paper onto MacConkey or Trypticase soy medium seeded onto a template. As a control to the sandwich technology, serial 10-fold dilutions of various organisms were cultured on the surfaces of agar plates. The sensitivity and specificity with 487 urine samples for gram-negative bacteria or with 405 samples for gram-positive bacteria were excellent. There is no information on any residual antimicrobial (AM) activity in 892 specimens. However, it would be pertinent to standardize the technology for urine samples with residual AM activity. Bacteriuria and AM activity are often encountered during clinical practice. Recent investigations of AM activity in Taiwan pointed to such an activity in 55.5% of 112 patients on their arrival at an emergency department (2). Furthermore, AM activity was also evident in 25.1% of 203 internal medicine outpatients, 7.6% of 471 high school students, and 7.4% of 202 people at a center for senior citizens. There was no correlation between the bacterial counts and sterility of a specimen and its AM activity. Residual AM activity in urine was likely to interfere in the three-layer sandwich technique during filtration of microbes onto culture medium. Antibacterial substances block the filter paper pores, lowering the number of microbes that filter through. The differently sized AMs may clog the pores in an unspecified manner. Any differential concentration of an antibacterial agent on the culture medium after filtration through the clogged filter paper would adversely affect sensitivity and specificity. Such an effect should be determined by soaking antibacterial agents and microbes onto filter paper. Well-designed experiments to address blockage of filter paper pores or any differential inhibition of bacterial growth are desirable. Such experiments would guarantee that concurrent bacteriuria and AM activity in urine would not interfere with a correct diagnosis, even in areas where AM drugs are freely available and histories of patients tend to be unreliable (2).

Morus alba L. (Moraceae) leaves are used effectively to treat fever, protect liver from damage, strengthen the joints, facilitate discharge of urine in Turkey folk medicine. In this study we aimed to determine in vitro antioxidant and antimicrobial activity with GC/MS analysis of the Morus alba L. leaves. Dried plant leaves samples are milled and extracted with distilled water and ethanol in Soxlet machine. After extraction, extract samples were concentrated in rotary evaporator machine. Total antioxidant status values were determined as mmol Trolox Equivalent/L spectrophotometrically by using Erel’s method. Sterile extracts used to avoid contamination in antimicrobial activity test. As test microorganisms Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 29212), Pseudomonas aeroginosa (ATCC 27853), Candida albicans (ATCC 90028) were used. Antimicrobial activity was determined with disk diffusion method. We used ethanol extracts of samples in GC/MS analysis. Ethanol and distilled water extracts showed antioxidant activity in different rate. Besides, ethanol extracts have an antimicrobial activity but water extracts have not antimicrobial activity on our test microorganisms. We determined four compounds (9,12,15-octadecatrienoic acid, ethyl ester, linolenic acid ethyl ester, gibberellic acid) with GC/MS analysis in ethanol extracts. In this researh we enlightened antimicrobial and antioxidant activities with GC/MS analysis of Morus alba L. leaves. So this research support of using this plant leaves in pharmacological and medical processes. Keywords: Antioxidant activity; Antimicrobial activity; GC/MS analysis; Morus alba L., extraction DOI: 10.17350/HJSE19030000006 Full Text:

Recently, nanocomposite materials containing nanoparticles of metals such as silver, copper and zinc oxide have attracted most attention due to their pronounced pharmacological properties, such as antimicrobial, antiviral, antiinflammatory, immunomodulatory ability and high stability in extreme conditions. Polyelectrolyte complexes based on polymers of natural origin, namely polysaccharides of chitosan and pectin, which can stabilize nanoparticles of a smaller size than individual polymers have significant potential for creation of silver-containing nanocomposites. The aim of this article is to study the antimicrobial and antiviral activity of silver-containing nanocomposites based on polyelectrolyte complexes. Methods. Peculiarities of the structural organization of silver-containing nanocomposites were investigated by the method of wide-angle scattering on an XRD-7000 diffractometer. The morphology of Ag nanoparticles in polymer matrixes were studied by transmission electron microscopy method (transmission electron microscope JEOL 100 CXII). The antimicrobial activity of silver-containing nanocomposites was determined by agar diffusion assays against opportunistic pathogens Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. Cytotoxicity and antiviral activity were investigated using the MTT method and staining by gentian violet. Results. Analysis of wide-angle X-ray diffractograms of silver-containing nanocomposites based on polyelectrolyte complexes Na-CMC (pectin) – chitosan showed that at reduction of Ag+ ions to metallic silver, there are two low-intensity diffraction maxima at 2θm ~ 380 and 440 in the diffractograms. These maxima correspond to the crystallographic planes of the face-centered cubic lattice of silver, are characterized by indices (111) and (200), respectively, and confirm the presence of metallic silver in the polymer system. Analysis of micrographs of silver-containing nanocomposites based on Na-CMC and chitosan showed that larger nanoparticles are formed with increasing the molecular weight of chitosan. The dependence of the size of silver nanoparticles on the wavelength of ultraviolet radiation at reduction of silver ion in polyelectrolyte-metal complexes Na-CMC–Ag+–chitosan of low molecular weight was also revealed. In particular, smaller particles are formed under irradiation by light with a shorter wavelength (λ =254 nm) than at λ=365 nm. Silver-containing nanocomposites Na-СMC-Ag-chitosan and pectin citrus-Ag-chitosan, obtained by reduction of Ag+ ions under ultraviolet irradiation at a wavelength λ = 365 nm and λ = 254 nm, exhibit high antimicrobial activity against the test cultures of microorganisms S. aureus, E. coli, and P. aeruginosa C. albicans. No significant dependence of antimicrobial activity on the molecular weight of the studied samples was noted: the obtained data were within close limits and had close values. In addition, no dependence of antimicrobial activity on the type of investigated test cultures of microorganisms was observed either. Nanocomposites based on Na-CMC-chitosan (λ = 365 nm) inhibited infection titer HSV-1 by (3.72–5.45) lgTCID50/mL, whereas the decrease in titer during incubation with samples based on citrus pectin-chitosan was within (2.39–2.42) lgTCID50/mL. A dose-dependent relationship between molecular weight of chitosan and reduction of infection titer was observed. It was found that silver-containing nanocomposites formed by reduction of silver ions in polyelectrolyte-metal complexes under ultraviolet radiation of different wavelengths had no cytotoxic effect on cells of MDCK and BHK. Conclusions. The investigated silver-containing nanocomposites based on Na-CMC (pectin)-chitosan polyelectrolyte complexes show antimicrobial activity against test cultures of S. aureus, E. coli P. aeruginosa, and C. albicans along with antiviral activity against herpes simplex virus type 1 and influenza virus. It was established that the obtained nanocomposites did not show a cytotoxic effect on MDCK and BHK cells. The obtained data allow us to assert that investigated silver-containing nanocomposites are promising antimicrobial means for the development of new effective strategies against microorganisms and viruses and improvement of the population health.

The present study aims to perform a comprehensive chemical characterization of the essential oils of Thymus pubescens var. pubescens (TPEO), Thymus leucotrichus var. leucotrichus (TLEO), and the endemic Thymus canoviridis (TCEO) using GC-MS, besides evaluating the potential antidiabetic, anticholinesterase, antimicrobial, antioxidant, antiglocouma, and antityrosinase activities of these essential oils. The antioxidant activity was assessed using various bioassays including DPPH, ABTS, DMPD, FRAP, CUPRAC, and Fe3+ reducing assays. The IC50 values of TPEO, TLEO, and TCEO for α-glycosidase were 28.32, 28.79, and 57.57 μg/mL, respectively. For tyrosinase, the IC50 values were 359.9, 270.87, and 597.43 μg/mL, respectively. The IC50 values for acetylcholinesterase were calculated as 44.15, 36.75, and 34.99 μg/mL, respectively, while for carbonic anhydrase, the IC50 values were 21.70, 24.75, and 24.45 μg/mL, respectively. The quantitiy of total phenolics present in TPEO, TLEO, and TCEO were determined to be 10.50, 34.50, and 32.50 μg GAE/mg essential oil, respectively. The TPEO, TLEO, and TCEO exhibited distinct antioxidant activities on DPPH, ABTS, and DMPD. TPEO showed antimicrobial activity against Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Acinetobacter baumannii bacterias. TLEO exhibited effective antimicrobial activity against S. aureus; The last of these TCEO demonstrated notable antimicrobial activity towards S. aureus, Enterococcus faecalis, E. coli, K. pneumoniae, Pseudomonas aeruginosa, P. mirabilis, A. baumannii. Additionaly, GC-MS revealed that the major components are TPEO (pulegone 29.01%, piperitenone 17.17%), TLEO (germacrene D 9.59%), and TCEO (carvacrol 52.87%). The essential oils possessed a range of biological activities, including antioxidant, antidiabetic, anticholinesterase, antityrosinase, antiglocouma and antimicrobial activities.

Antimicrobial and hemolytic activities of amphiphilic random copolymers were modulated by the structure of the cationic side chain spacer arms, including 2-aminoethylene, 4-aminobutylene, and 6-aminohexylene groups. Cationic amphiphilic random copolymers with ethyl methacrylate (EMA) comonomer were prepared with a range of comonomer fractions, and the library of copolymers was screened for antimicrobial and hemolytic activities. Copolymers with 4-aminobutylene cationic side chains showed an order of magnitude enhancement in their antimicrobial activity relative to those with 2-aminoethylene spacer arms, without causing adverse hemolysis. When the spacer arms were further elongated to hexylene, the copolymers displayed potent antimicrobial and hemolytic activities. The 4-aminobutylene side chain appears to be the optimal spacer arm length for maximal antimicrobial potency and minimal hemolysis, when combined with hydrophobic ethylmethacrylate in a roughly 70/30 ratio. The copolymers displayed relatively rapid bactericidal kinetics and broad-spectrum activity against a panel of Gram-positive and Gram-negative bacteria. The effect of the spacer arms on the polymer conformation in the membrane-bound state was investigated by molecular dynamics simulations. The polymer backbones adopt an extended chain conformation, parallel to the membrane surface. A facially amphiphilic conformation at the membrane surface was observed, with the primary ammonium groups localized at the lipid phoshophate region and the nonpolar side chains of EMA comonomers buried in the hydrophobic membrane environment. This study demonstrates that the antimicrobial activity and molecular conformation of amphiphilic methacrylate random copolymers can be modulated by adjustment of cationic side chain spacer arms.

MALAGASY AROMATIC PLANTS: ESSENTIAL OILS, ANTIOXIDANT AND ANTIMICROBIAL ACTIVITIES

Ethnopharmacological use of plant natural extracts has been known since ancient times. The optimization of plant molecule extraction is fundamental in obtaining relevant extraction yields. The main purpose of this study was to understand the role of different extraction techniques (solid-liquid, ultrasound, Soxhlet, and microwave) and solvents (water, methanol, ethanol, acetone, dichloromethane, and hexane) on the antimicrobial and antioxidant activities of extracts from Olea europaea (olive) and Acacia dealbata (mimosa). Crude plant extracts were evaluated for their antimicrobial activity against Staphylococcus aureus and Escherichia coli by the disk diffusion method. The antioxidant capacity of the extracts was determined by ABTS (2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid)) and DPPH (2,2-diphenyl-1-picrylhydrazyl) methods. In terms of extraction yield, ultrasound extraction and the solvents methanol, acetone (O. europaea) or water (A. dealbata) were found to be the best options. However, ethanol and acetone proved to be the best solvents to extract compounds with antimicrobial activity and antioxidant capacity, respectively (regardless of the extraction method employed). Soxhlet and microwave were the best techniques to extract compounds with antimicrobial activity, whereas any of the tested techniques showed the ability to extract compounds with antioxidant capacity. In most of the cases, both plant extracts (mimosa and olive) were more efficient against S. aureus than E. coli. In the present study, both mimosa and olive leaf crude extracts proved to have antimicrobial and antioxidant activities, increasing the demand of these natural products as a source of compounds with health benefits.

Attalea speciosa syn Orbignya phalerata Mart. (babassu) has been used in the treatment of inflammatory and infectious diseases. Aim of the study. To investigate the antimicrobial and immunological activity of babassu mesocarp extract (EE). Material and Methods. The in vitro antimicrobial activity was evaluated by disk diffusion assay and by determination of the minimum inhibitory concentration (MIC) to Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus (MRSA). The flavonoids and phenolic acids content were determined by chromatography. The in vivo assays were performed in Swiss mice submitted to sepsis by cecal ligation and puncture (CLP). The mice received EE subcutaneously (125 or 250 mg/Kg), 6 hours after the CLP. The number of lymphoid cells was quantified and the cytokines production was determined by ELISA after 12 h. Results. EE was effective as antimicrobial to E. faecalis, S. aureus, and MRSA. EE is rich in phenolic acids, a class of compounds with antimicrobial and immunological activity. An increased survival can be observed in those groups, possibly due to a significant inhibition of TNF-α and IL-6. Conclusions. The EE showed specific antimicrobial activity in vitro and an important antiseptic effect in vivo possibly due to the antimicrobial and immunomodulatory activity.