Amino porphyrins as photoinhibitors of Gram-positive and -negative bacteria

Synthesis of pyrimidine-6-carbonitriles, pyrimidin-5-ones, and tetrahydroquinoline-3-carbonitriles by new superb oxovanadium(V)-[5,10,15,20-tetrakis(pyridinium)-porphyrinato]-tetra(tricyanomethanide) catalyst via anomeric based oxidation

Oxovanadium(V)-[5,10,15,20-tetrakis(pyridinium)-porphyrinato]-tetra(tricyanomethanide) [(VO)TPP][(TCM)₄] was designed, synthesized and characterized by various techniques such as FT-IR, EDX, SEM equipped with EDX mappings, CHN elemental analysis, ICP-OES, XRD, SEM, TEM, TGA, DTA, DRS, Kubelka-Munk function (Tauc's plot), and UV-Vis analyses. Then, [(VO)TPP][(TCM)₄] was used as a benign and expedient catalyst for the synthesis of numerous heterocyclic compounds such as 5-amino-7-(aryl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carbonitriles, 5-amino-7-(aryl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carbonitriles, 7-(aryl)-7,12-dihydro-5H-isochromeno[4,3-d][1,2,4]triazolo[1,5-a]pyrimidin-5-ones, and 4-(aryl)-2-(1H-indol-3-yl)-5,6,7,8-tetrahydroquinoline-3-carbonitriles under solvent-free conditions at 100 °C via a cooperative geminal-vinylogous anomeric based oxidation.

Photophysical and Bactericidal Properties of Pyridinium and Imidazolium Porphyrins for Photodynamic Antimicrobial Chemotherapy

Despite advances achieved over the last decade, infections caused by multi-drug-resistant bacterial strains are increasingly becoming important societal issues that need to be addressed. New approaches have already been developed in order to overcome this problem. Photodynamic antimicrobial chemotherapy (PACT) could provide an alternative to fight infectious bacteria. Many studies have highlighted the value of cationic photosensitizers in order to improve this approach. This study reports the synthesis and the characterization of cationic porphyrins derived from methylimidazolium and phenylimidazolium porphyrins, along with a comparison of their photophysical properties with the well-known N-methylpyridyl (pyridinium) porphyrin family. PACT tests conducted with the tetracationic porphyrins of these three families showed that these new photosensitizers may offer a good alternative to the classical pyridinium porphyrins, especially against S.aureus and E.coli. In addition, they pave the way to new cationic photosensitizers by the means of derivatization through amide bond formation.

Antimicrobial activity of different substituted meso-porphyrin derivatives

The increasing resistance against classical antibiotic treatment forces the researchers to develop novel non-toxic antimicrobial agents. The aim of this study was to determine the antimicrobial properties of seven different porphyrins having distinctive hydrophobicity/hydrophilicity: P1 meso-tetra(4-methoxy-phenyl)porphyrin, P2 Zn(II)-meso-5,10,15,20-tetrapyridylporphyrin, P3 meso-tetra(p-tolyl)porphyrin, P4 5,10,15,20-tetraphenylporphyrin; P5 (5,10,15,20-tetraphenylporphinato) dichlorophosphorus(V) chloride, P6 5,10,15,20-tetrakis-(N-methyl-4-pyridyl) porphyrin-Zn(II) tetrachloride, P7 Zn(II)-5,10,15,20-meso-tetrakis-(4-aminophenyl)porphyrin. The meso-porphyrin derivatives were screened for their antimicrobial activity against six reference strains: Streptococcus pyogenes ATCC 19615, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 700603, Pseudomonas aeruginosa ATCC27853 and Candida albicans ATCC 10231. The antimicrobial activity of these samples was evaluated by the agar disk diffusion method and dilution method, with the determination of the minimum inhibitory concentration (MIC), the minimum bactericidal concentration (MBC) and the minimum fungicidal concentration (MFC). The most significant result is provided by the water-soluble P5 manifesting an obvious antimicrobial activity against Streptococcus pyogenes. On the other hand, P6 is a moderately active derivative against Streptococcus pyogenes and Escherichia coli and P7 presents moderate activity against Streptococcus pyogenes and Staphylococcus aureus. All the tested porphyrin bases, presenting hydrophobic character, have no antimicrobial activity under the investigated conditions. The common characteristics of the porphyrins that act as promising antimicrobial agents in the non-irradiated methods are: the cationic nature, the increased hydrophilicity and the presence of both amino functional groups grafted on the porphyrin ring and the coordination with Zn or phosphorus in the inner core.

Synthesis and characterization of novel porphyrin-cinnamic acid conjugates

A series of novel porphyrin-cinnamic acid (porphyrin/CA) conjugates (4a-4c) have been synthesized by condensation of 5-(4-Hydroxyphenyl)-10,15,20-triphenyl- porphyrin (1) with different substituted cinnamic acids (CAs) through an alkyl linker due to the biological activities of CAs and the application of porphyrins in photodynamic therapy (PDT) of cancer. Their related zinc (II) complexes (5a-5c) were also prepared. These novel compounds have been fully characterized by ¹H NMR, Infrared (IR), Mass spectra (Ms) and Elemental analysis. The photophysical properties of these target molecules were studied by absorption and Fluorescence spectroscopy. In solution, the effect of pH, ionic strength in acid media and concentration on the aggregation behaviors of 4a has also been investigated by UV-Vis spectra. The broadened and red shifted Soret band indicated the formation of J-aggregates when the pH value was up to 2.0 in THF-aqueous solution. Furthermore, the higher ionic strength of 0.3 M NaCl in acid media resulted in the generation of J-aggregates in THF-aqueous solution. And the significant blue shift of Soret band also demonstrated the formation of H-aggregates of 4a at 1.1 × 10^-4 M in THF.

Antibacterial activity of a photosensitive hybrid cellulose fabric

A new photosensitive hybrid cellulose material, synthesized by polymerization of methacrylic acid (MAA) and PpIX, showed photoantibacterial activity against Staphylococcus aureus.

Synthesis, characterization and in vitro photodynamic antimicrobial activity of basic amino acid-porphyrin conjugates

Photodynamic antimicrobial chemotherapy (PACT), as a novel and effective modality for the treatment of infection with the advantage of circumventing multidrug resistance, receives great attention in recent years. The photosensitizer is the crucial element in PACT, and cationic porphyrins have been demonstrated to usually be more efficient than neutral and negatively charged analogues towards bacteria in PACT. In this work, three native basic amino acids, l-lysine, l-histidine and l-arginine, were conjugated with amino porphyrins as cationic auxiliary groups, and 13 target compounds were synthesized. This paper reports their syntheses, structural characterizations, oil-water partition coefficients, singlet oxygen generation yields, photo-stability, as well as their photo inactivation efficacies against methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli and Pseudomonas aeruginosa in vitro. The preliminary structure-activity relationship was discussed. Compound 4i, with porphyrin bearing four lysine moieties, displays the highest photo inactivation efficacy against the tested bacterial strains at 3.91 μM with a low light dose (6 J/cm(2)), and it is stable in serum and lower cytotoxicity to A929 cells. These basic amino acid-porphyrin conjugates are potential photosensitizers for PACT.

Theoretical investigation of the absorption spectra and singlet-triplet energy gap of positively charged tetraphenylporphyrins as potential photodynamic therapy photosensitizers

DFT and TD-DFT calculations have been performed on a series of positively charged tetraphenylporphyrins with the aim to check whether these compounds can be used as photosensitizers in photodynamic therapy (PDT). Absorption spectra and singlet-triplet energy gaps have been computed by using the BP86, PBE0, and ωB97XD exchange-correlation functionals. Polarizable continuum model (PCM) has been used to take into account solvent effects. A careful analysis has been made on the Q-band, localized in the near-red visible region of the spectrum, since it plays a fundamental role in the drug design of new photodynamic therapy photosensitizers. Our results show that all the examined molecules have an adsorption band that falls in the so-called therapeutic window and possess a singlet-triplet energy gap able to promote the excitation of molecular oxygen from its ground triplet to the excited singlet state. The use of the ωB97XD exchange correlation functional, which accounts for dispersion interactions, allows calculating excitation energy values close to the experimental values.

Syntheses and properties of trimethylaminophenoxy-substituted Zn((II))-phthalocyanines

The syntheses, photophysical properties and in vitro biological behavior of a series of nine Zn((II))-phthalocyanines (ZnPcs) bearing one to eight positively-charged trimethylaminophenoxy groups are reported. All ZnPcs are highly soluble in polar organic solvents, and show fluorescence and singlet oxygen quantum yields in the ranges 0.11-0.21 and 0.16-0.47, respectively. The cytotoxicity of the ZnPcs depends on both the number of charges and their site of substitution (α vs. β) on the Pc isoindole units; the most promising for PDT application are the α-substituted di-cationic ZnPcs 6a and 17a.

Vicente MG, Luguya R, Norton J, Fronczek FR, Smith KM. Effect of overall charge and charge distribution on cellular uptake, distribution and phototoxicity of cationic porphyrins in HEp2 cells

Five cationic porphyrins bearing one to four -N(CH(3))(3)(+) groups linked to the p-phenyl positions of 5,10,15,20-tetraphenylporphyrin (TPP) were synthesized in order to study the effect of overall charge and its distribution on the cellular uptake, phototoxicity and intracellular localization using human carcinoma HEp2 cells. The di-cationic porphyrins DADP-o and DADP-a accumulated the most within cells and preferentially localize within vesicular compartments and in mitochondria. Of these two only DADP-a was phototoxic to the cells (IC(50)=3 microM at 1 J/cm(2)). The mono-cationic porphyrin MAP was found to be the most phototoxic of the series, and it localized mainly in lipid membranes, including the plasma membrane, ER, mitochondria, and Golgi. Both the tri-cationic porphyrin TRAP and the tetra-cationic porphyrin TEAP localized subcellularly mainly in the mitochondria, but of the two only TEAP showed moderate phototoxicity (IC(50)=8 microM at 1 J/cm(2)). Our results suggest that MAP is the most promising PDT photosensitizer, and that both DADP-o and TRAP might find application as transport vehicles for therapeutics into cells.

Squalamine: an appropriate strategy against the emergence of multidrug resistant gram-negative bacteria?

We reported that squalamine is a membrane-active molecule that targets the membrane integrity as demonstrated by the ATP release and dye entry. In this context, its activity may depend on the membrane lipid composition. This molecule shows a preserved activity against bacterial pathogens presenting a noticeable multi-resistance phenotype against antibiotics such as polymyxin B. In this context and because of its structure, action and its relative insensitivity to efflux resistance mechanisms, we have demonstrated that squalamine appears as an alternate way to combat MDR pathogens and by pass the gap regarding the failure of new active antibacterial molecules.

Novel ebselen–porphyrin conjugates: Synthesis and nucleic acid interaction study

Novel porphyrins bearing ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]-one) moiety were synthesized and characterized. Their interactions with herring sperm DNA were studied by means of UV-visible, fluorescence, circular dichroism spectroscopy, and gel electrophoresis.

Antibacterial Effects of a Monoporphyrinato Ytterbium(III) Complex and Its Free Components onStaphylococcus aureus as Determined by Stop-Flow Microcalorimetry

The antibacterial effect of Yb3+, the free porphyrin base 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin (H2TMP; 1), and the corresponding Yb3+ porphyrinato complex [Yb(III)(TMP)(H2O)3]+ Cl- (Yb(TMP); 2) towards Staphylococcus aureus was investigated by stop-flow microcalorimetry. By analyzing the obtained metabolic thermogenic curves, crucial parameters such as rate constant of bacterial growth (k), half inhibitory concentration (IC50), and generation time (t(G)) were determined. The antibacterial activities of the three compounds tested was 2>1>Yb3+, with an IC50 value of 273 mg/l for complex 2. The Yb3+ porphyrinato complex is proposed to benefit from synergetic effects of Yb3+ and the free porphyrin 1.

Photoinactivation of bacteria in wastewater by porphyrins: bacterial beta-galactosidase activity and leucine-uptake as methods to monitor the process

The increasing interest in photodynamic antimicrobial chemotherapy as a promising technology for wastewater treatment demands more efficient photosensitizers and faster methods for the monitorization of the photoinactivation process. Two sets of neutral and cationic porphyrins were used as photosensitizers for the photoinactivation of sewage bacteria. Two of the cationic porphyrins revealed to be highly active, even against Gram-negative bacteria, inactivating ca. 94-99.8% of these at 5 microM and after 270 min of irradiation with white light (9 mW cm(-2)). In addition, two expeditious methods for the evaluation of the bacteria photoinactivation were developed. These methods are based on beta-galactosidase activity and on leucine incorporation and give an excellent relation with faecal coliform counts. The evaluation of these two descriptors of bacterial activity, directly related with bacterial abundance, is an easy and fast way to monitor the micro-organisms during the photoinactivation process.

Anti-MRSA agents: under investigation, in the exploratory phase and clinically available

Staphylococcal infections are difficult to treat due to the rapid emergence of methicillin-resistant staphylococci and, unfortunately, vancomycin-intermediate or -resistant staphylococci. Numerous alternative treatments are urgently required. In this special report, intensive research of new molecules is highlighted--in known antibacterial families and new medicinal chemical entities.

New photoantimicrobial films composed of porphyrinated lipophilic cellulose esters

Porphyrinated cellulose laurate esters have been prepared in homogeneous DMA/LiCl medium by "one-pot, two-step" reactions starting from cellulose, protoporphyrin IX, and lauric acid and using a TsCl/Pyridine system. The plastic films obtained after casting were shown to display photobactericidal activity against Gram positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. This new photobactericidal polymer has potential for industrial, medical, or household applications.