Influence of proline and hydroxyproline as antimicrobial and anticancer peptide components on the silver(I) ion activity: structural and biological evaluation with a new theoretical and experimental SAR approach

Silver(I) complexes with proline and hydroxyproline were synthesized and structurally characterized and crystal structure analysis shows that the formulas of the compounds are {[Ag2(Pro)2(NO3)]NO3}n (AgPro) (Pro = L-proline) and {[Ag2(Hyp)2(NO3)]NO3}n (AgHyp) (Hyp = trans-4-hydroxy-L-proline). Both complexes crystallize in the monoclinic lattice with space group P21 with a carboxylate bidentate-bridging coordination mode of the organic ligands Pro and Hyp (with NH2+ and COO- groups in zwitterionic form). Both complexes have a distorted seesaw (C2v) geometry around one silver(I) ion with τ4 values of 58% (AgPro) and 51% (AgHyp). Moreover, the results of spectral and thermal analyses correlate with the structural ones. 1H and 13C NMR spectra confirm the complexes species' presence in the DMSO biological testing medium and their stability in the time range of the bioassays. In addition, molar conductivity measurements indicate complexes' behaviour like 1 : 1 electrolytes. Both complexes showed higher or the same antibacterial activity against Bacillus cereus, Pseudomonas aeruginosa and Staphylococcus aureus as AgNO3 (MIC = 0.063 mM) and higher than silver(I) sulfadiazine (AgSD) (MIC > 0.5 mM) against Pseudomonas aeruginosa. In addition, complex AgPro exerted a strong cytotoxic effect against the tested MDA-MB-231 and Jurkat cancer cell lines (IC50 values equal to 3.7 and 3.0 μM, respectively) compared with AgNO3 (IC50 = 6.1 (5.7) μM) and even significantly higher selectivity than cisplatin (cisPt) against MDA-MB-231 cancer cell lines (SI = 3.05 (AgPro); 1.16 (cisPt), SI - selectivity index). The binding constants and the number of binding sites (n) of AgPro and AgHyp complexes with bovine serum albumin (BSA) were determined at four different temperatures, and the zeta potential of BSA in the presence of silver(I) complexes was also measured. The in ovo method shows the safety of the topical and intravenous application of AgPro and AgHyp. Moreover, the complexes' bioavailability was verified by lipophilicity evaluation from the experimental and theoretical points of view.

Silver(I) complexes with amino acid and dipeptide ligands - Chemical and antimicrobial relevant comparison (mini review)

Diseases caused by various microorganisms accompany humans (as well as animals) throughout their whole lives. After germs penetration to the body, the incubation period and infection developing, an infection can cause mild or severe symptoms, not infrequently even death. The immune system naturally defends itself against pathogens with various mechanisms. One of them is the synthesis of antimicrobial peptides. In the case of serious and severe infections, it is currently possible to help the natural immunity by administration of antimicrobial drugs (AMB) with good success since their discovery at the beginning of the last century. However, their excessive use leads to the development of pathogenic microorganisms' resistance to AMB drugs. Based on this, it is necessary to constantly develop new classes of AMB drugs that will be effective against pathogens, even resistant ones. The field of bioinorganic chemistry, similarly to other biological, chemical, or pharmaceutical sciences, discovers various options and approaches for antimicrobial treatment, from the development of new drugs to drug delivery systems. One of the approaches is the design and preparation of potential drugs based on metal ions and antimicrobial peptides. Various metal ions and amino acid or peptide ligands are used for this purpose. In this mini review, we focused on a reliable comparison of the chemical structure and biological properties of selected silver(I) complexes based on amino acids and dipeptides.

Ga(III) pyridinecarboxylate complexes: potential analogues of the second generation of therapeutic Ga(III) complexes?

A series of novel Ga(III)-pyridine carboxylates ([Ga(Pic)3]·H2O (GaPic; HPic = picolinic acid), H3O[Ga(Dpic)2]·H2O (GaDpic; H2Dpic = dipicolinic acid), [Ga(Chel)(H2O)(OH)]2·4H2O (GaChel; H2Chel = chelidamic acid) and [Ga(Cldpic)(H2O)(OH)]2 (GaCldpic; H2Cldpic = 4-chlorodipicolinic acid)) have been synthesized by simple one-step procedure. Vibrational spectroscopy (mid-IR), elemental analysis, thermogravimetric analysis and X-ray diffraction confirmed complexes molecular structure, inter and intramolecular interactions and their influence to spectral and thermal properties. Moreover, complex species speciation was described in Ga(III)-HPic and Ga(III)-H2Dpic systems by potentiometry and 1H NMR spectroscopy and mononuclear complex species were determined; [Ga(Pic)2]+ (logβ021 = 16.23(6)), [Ga(Pic)3] (logβ031 = 20.86(2)), [Ga(Dpic)2]- (logβ021 = 15.42(9)) and [Ga(Dpic)2(OH)]2- (logβ-121 = 11.08(4)). To confirm the complexes stability in 1% DMSO (primary solvent for biological testing), timescale 1H NMR spectra were measured (immediately after dissolution up to 96 h). Antimicrobial activity evaluated by IC50 (0.05 mM) is significant for GaDpic and GaCldpic against difficult to treat and multi-resistant P. aeruginosa. On the other hand, the GaPic complex is most effective against Jurkat, MDA-MB-231 and A2058 cancer cell lines and significantly also decreases the HepG2 cancer cells viability at 75 and 100 μM concentrations in a relatively short time (up to 48 h). In addition, fluorescence measurements have been used to elucidate bovine serum albumin binding activity between ligands, Ga(III) complexes and bovine serum albumin.

Silver(I) pyrrole- and furan-2-carboxylate complexes - From their design and characterization to antimicrobial, anticancer activity, lipophilicity and SAR

Two silver(I) complexes with biologically relevant heterocyclic ligands, pyrrole and furan-2- carboxylic acid, were synthesized and their composition was confirmed using elemental, spectral, thermal and structural analyses. The {[Ag(Py2c)]}n (AgPy2c, Py2c = pyrrole-2-carboxylate) and {[Ag(Fu2c)]}n (AgFu2c, Fu2c = furan-2-carboxylate) solubility and stability in biological test stock solution were confirmed by 1H NMR spectroscopy. The X-ray analysis has enabled us to determine typical argentophilic interactions and bridging carboxylate coordination mode of both ligands. Potentiometric data analysis by BSTAC program resulted in the determination of the stability constant of only one species, i.e., the ML (M = Ag+, L = Fu2c-), log βML = 0.59 ± 0.04. Antimicrobial and anticancer tests were performed against selected microorganisms and cell lines with new silver(I) complexes and compared with AgSD (silver(I) sulfadiazine) and cisplatin. From their microbial toxicity point of view, selectivity was determined against lactobacilli (AgPy2c is 8× more effective against S. aureus and E. coli and AgFu2c is 8× more effective against E. coli and 4× against S. aureus). AgFu2c significant anticancer activity was determined against Jurkat cell lines (IC50 = 8.00 μM) and was similar to cisPt (IC50 = 6.3 μM) similarly to its selectivity (SI (AgFu2c) = 7.3, SI (cisPt) = 6.4, SI = selectivity index). In addition, cell cycle arrest was observed already in the Sub-G0 phase during a flow cytometry experiment. To evaluate the AgPy2c and AgFu2c bioavailability we also discuss their Lipinski's Rule of Five.

Antibacterial activity, quality and stability study of creams with new potential silver(I) complexes and in vivo case report

The aim of this study was to evaluate the antibacterial activity, quality and stability of creams (at 1 % concentration) prepared with synthesized silver(I) complexes: [Ag(Nam)₂]NO₃·H₂O ( AgNam), [Ag₂(HGly)₂]_n(NO₃)_2n (AgGly) (Nam - nicotin-amide, Gly - glycine) and silver(I) sulfadiazine (AgSD), which is commercially available. Antibacterial activity was evaluated by agar well diffusion method and in in vivo case. The pure silver(I) complexes as well as all three tested creams loaded with AgGly, AgSD and AgNam showed antibacterial potential. Moreover, the creams loaded with AgGly and AgNam showed higher antibacterial effects against S. aureus and B. subtilis than the cream loaded with AgSD. In terms of appearance, all cream samples were opaque and odourless, and no phase separation was observed. Creams were soluble in water (o/w emulsions) and they had a pseudoplastic behaviour. The pH of the creams was in the range of 4.87-5.75. No visible changes were observed in the case of commercially used AgSD cream during one month testing period at conditions -16 ± 1 °C; 6 ± 1 °C and 56 % relative humidity; 20 ± 1 °C and 58 % relative humidity and 40 ± 1 °C and 75 % relative humidity. However, creams containing AgGly and AgNam changed their colour depending on the tested conditions.

An in vitro selective inhibitory effect of silver(i) aminoacidates against bacteria and intestinal cell lines and elucidation of the mechanism of action by means of DNA binding properties, DNA cleavage and cell cycle arrest

Novel silver(i) aminoacidate complexes {[Ag(HVal)(H₂O)(NO₃)]}_n (AgVal) and {[Ag₃(HAsp)₂(NO₃)]}_n·nH₂O (AgAsp) were prepared, investigated and fully characterized by vibrational spectroscopy (mid-IR), elemental analysis, thermogravimetric analysis, X-ray crystallography and mass spectrometry. Their stability in D₂O and PBS buffer was verified by time-dependent ¹H and ¹³C NMR measurements. Their in vitro antibacterial activity (against pathogenic Staphylococcus aureus CCM4223, Escherichia coli CCM4787) and that against probiotic bacteria Lactobacillus plantarum CCM7102 and Lactobacillus reuteri (L26) were determined and potential dosing concentration was evaluated. The cytotoxicity of both the complexes against intestinal porcine epithelial (IPEC-1) and human epithelial colorectal adenocarcinoma (CaCo-2) cell lines was determined using the colorimetric MTT assay and against human metastatic melanoma (A2058), human pancreatic adenocarcinoma (PaTu 8902), human cervical adenocarcinoma (HeLa), human colorectal carcinoma (HCT116), human leukaemic T cell lymphoma (Jurkat), and human dermal fibroblasts (HDF) using colorimetric MTS assay. The selectivity index (SI) was identified for intestinal cancer (CaCo-2) and healthy (IPEC-1) cells. The mechanism of action of AgVal and AgAsp was further elucidated and discussed by the study of their binding affinity toward the CT DNA, the ability to cleave the supercoiled form of pUC19 DNA and the ability to influence numbers of cells within each cell cycle.

Silver(i) pyridylphosphonates - synthesis, structure, stability and light-insensitivity investigation

Two silver(i) complexes, {[Ag7(2-pypo)3(NO3)]} n (1) and [Ag(3-pypoH)(3-pypoH2)] (2) (pypoH2 - pyridylphosphonic acid) were prepared and characterized by relevant methods in the solid state (elemental, spectral, thermal and structural analysis). Typical argentophilic interactions were observed in complex 1. The synthesized Ag(i) complexes were tested toward reduction to silver(0) using short wavelength UV-radiation and they revealed remarkable light-insensitivity in comparison to silver nitrate. SEM experiments were performed to observe the reduction of silver after the UV-light exposure of the samples. Light-insensitivity with the examined thermal stability and insolubility of the new complexes demonstrates their high potential to be used as light-insensitive materials in medical devices.

[Herbs for increasing breast-milk production]

Subjective perception of insufficient milk supply is one of the most common problems of nursing mothers. For centuries, herbs have been used to increase lactation and remain popular even today. There is only a limited number of studies proving their safety and effectivity, so their use is based primarily on previous experience. The use of certain herbs has shown that they could be effective and safe, but further research is needed to define terms of use. This paper describes preliminary findings on the mechanism of action, adverse effects and possible interactions observed in some herbs frequently used to promote lactation.Key words: phytotherapy lactation herbal galactagogue.

Interaction of the Zn(ii)–cyclen complex with aminomethylphosphonic acid: original simultaneous potentiometric and 31P NMR data treatment

The interaction of aminomethylphosphonic acid with the Zn(ii)–cyclen complex was evaluated by an original combination of potentiometry and multinuclear NMR.

Dipeptide interactions with Zn(II)-cyclen artificial model for molecular recognition

The Zn(II)-cyclen-dipeptide ternary systems (where cyclen is abbreviated as L and dipeptide is glycylglycine (HL(1)) or glycyl-(S)-alanine (HL(2))) were investigated by potentiometry applying both "out-of-cell" and direct titrations and by (1) H NMR spectroscopy. Especially, the (1)H NMR study was found to be very efficient to estimate speciation in the systems. The results obtained under full equilibria indicated two main species, [Zn(L)(HL(1,2))](2+) and [Zn(L)(L(1,2))](+), in both the systems. In the [Zn(L)(HL(1,2))](2+) complex, presence of carbonyl-carboxylate chelate was confirmed, and in the [Zn(L)(L(1,2))](+) species, the peptide coordination is re-organized to carbonyl-amine chelate or only terminal amino group is coordinated. Equilibrium constants describing [Zn(L)](2+)-dipeptide interaction are relatively low, log K = 3.4 for Gly-Gly and 4.1 for Gly-(S)-Ala, respectively. Nevertheless, the values are slightly higher than stability constants for interaction of Zn(II) with the dipeptides (i.e. [Zn(L(1,2))](+) species) where a chelate formation is expected. It indicates that interaction between Zn(II) ion in [Zn(L)](2+) and the dipeptides should be supported by some additional interactions. Potentiometry carried out under non-equilibrum condition showed different species where these additional stabilizing forces play more important role.

Utilization of IR spectral detailed analysis for coordination mode determination in novel Zn-cyclen-aminoacid complexes

The infrared spectra, elemental and thermal (TG/DTG and DTA) analyses of novel [Zn(cyclen-κ4N1,4,7,10)(HGly-κ2O,O')](ClO4)2 (1), and [Zn2(cyclen-κ4N1,4,7,10)2(μ-S-Ala-κ2N,O)](ClO4)(3)·2H2O (2) complexes (cyclen - 1,4,7,10-tetraazacyclododecane) were recorded and analyzed in the relation to their structural peculiarities. IR spectral data indicate both mono- or bidentate coordination mode of a carboxylate group in the prepared complexes (at pH≈9). The results indicate unusual bidentate carboxylate coordination mode (in complex (1)) toward to Zn2+-cyclen unit. Therefore the crystal structure determination of the crystalline complex [Zn(cyclen-κ4N1,4,7,10)(NO3-κ2O,O')](NO3) was attached in order to support the coordination mode assignment in complex (1).

Correlation of infrared spectra of zinc(II) carboxylates with their structures

The correlation of the infrared spectra of zinc(II) carboxylates with their structures was investigated in the paper. The complexes with different modes of the carboxylate binding, from chelating, through bridging (syn-syn, syn-anti, monatomic), ionic to monodentate were used for the study, namely [Zn(C6H5CHCHCOO)2(H2O)2] (I) with chelating carboxylate group (C6H5CHCHCOO=cinnamate), [Zn2(C6H5COO)4(pap)2] (II) with syn-syn bridging carboxylate (C6H5COO=benzoate; pap=papaverine), [Zn(C6H5CHCHCOO)2(mpcm)]n (III) with syn-anti carboxylate bridge (mpcm=methyl-3-pyridylcarbamate), [Zn(C5H4NCOO)2(H2O)4] (IV) with ionic carboxylate group (C5H4NCOO=nicotinate), [Zn(C6H5COO)2(pcb)2]n (V) with monodentate carboxylate coordination (pcb=3-pyridylcarbinol) and [Zn3(C6H5COO)6(nia)2] (VI) with syn-syn and monatomic carboxylate bridges (nia=nicotinamide). First, the mode of the carboxylate binding was assigned from the infrared spectra using the magnitude of the separation between the carboxylate stretches, Deltaexp=nuas(COO-)-nus(COO-). Then the values Deltaexp were compared with those calculated from structural data of the carboxylate anion (Deltacalc). The conclusions about the carboxylate binding which resulted from the Delta values, were confronted with the crystal structure of the complexes. The limitations and recommendations were formulated to assign the mode of the carboxylate binding from the infrared spectra. The dependence of the Deltaexp values on the magnitudes of Zn-O-C angles in bidentate carboxylate coordination was observed.