Stereospecific ligands and their complexes. Part VII. Synthesis, characterization and in vitro antitumoral activity of platinum(II) complexes with O,O′-dialkyl esters of (S,S)-ethylenediamine-N,N′-di-2-(4-methyl)pentanoic acid

Synthesis and Biological Evaluation of Amino Acid and Peptide Conjugates of 5-Bromovaleric Acid

BACKGROUND

Among various carboxylic acid derivatives, valeric acid or pentanoic acid is found to be widely distributed in nature. It is a straight-chain alkyl carboxylic acid containing five carbon atoms. Due to the therapeutic value of valeric acid, it is used as a versatile nucleus in the pharmaceutical field. Valeric acid derivatives are associated with a broad spectrum of biological activities, like anticonvulsant, antiplatelet, antidiabetic, and plant growth activities.

AIM

It has previously been revealed that peptide derivatives of carboxylic acids are accountable for enhanced antimicrobial activity. Therefore, it was hypothesized that coupling peptides with valeric acid would increase the antimicrobial properties of the target compounds. So, the objective of the present study was to synthesize peptide derivatives of 5-bromovaleric acid and evaluate their antibacterial and antifungal activities.

METHODS

5-bromovaleric acid was synthesized by the reaction of cyclopentanone and hydrogen peroxide in the presence of copper bromide and sodium bromide. Additionally, 5-bromovaleric acid was coupled with amino acid methyl esters, dipeptides, tripeptides, and tetrapeptides in the presence of dicyclohexylcarbodimide (DCC) and N-methylmorpholine (NMM) as a base under continuous stirring for 36 hours to produce its peptide derivatives.

RESULTS

The results obtained showed that 5-bromovaleric acid possesses more potent antibacterial activity than N-terminal 5-bromovaleric acid conjugates of selected di-, tri, and tetra peptide Cterminal methyl esters against ciprofloxacin as a standard. The selected dipeptide and tripeptide Nterminal 5-bromovaleric acid-conjugated C-terminal methyl ester derivatives were more active than the selected tetrapeptide methyl ester analogue. Using fluconazole as a reference, the antifungal efficacy of 5-bromovaleric acid against C. albicans and A. niger declined as it was combined with C-terminal methyl esters of selected dipeptides, tripeptides, and tetrapeptides.

CONCLUSION

The novel selected peptide derivatives had less antibacterial and antifungal action than the parent 5-bromovaleric acid. Antibacterial and antifungal investigations showed that 5- bromopentanoic acid peptide derivatives might impair antimicrobial efficacy. Further, attaching 5- bromopentanoic acid to di, tri, and tetra peptides did not boost their antibacterial potential.

Synthesis, characterization, HSA binding, molecular docking, cytotoxicity study, and antimicrobial activity of new palladium(II) complexes with propylenediamine derivatives of phenylalanine

The four new ligands, propylenediamine derivatives of phenylalanine (R2-S,S-pddbaˑ2HCl; L1-L4) and their palladium(II) complexes (C1-C4) were synthesized and characterized by elemental analysis, infrared, 1H and 13C NMR spectroscopy. The interactions of new palladium(II) complexes with human serum albumin (HSA) were studied by fluorescence spectroscopy. All investigated compounds can be transported to target cells by binding to HSA, but complex C4 interacts most strongly. Molecular docking simulations were applied to comprehend the binding of the complex to the molecular target of HSA. Obtained results are in good correlations with experimental data regarding binding affinity by HSA. In vitro cytotoxicity activities were investigated on four tumor cell lines (mouse mammary (4 T1) and colon (CT26), human mammary (MDA-MD-468) and colon (HCT116)) and mouse mesenchymal stem cells as non-tumor control cells. Cytotoxic capacity was determined by MTT test and according to obtained results ligand L4 stands out as the most active and selective compound and as a good candidate for future in vivo testing. Further examination of the ligand L4 and corresponding complex C4 led to the conclusion that both induced cell death mainly by apoptosis. Ligand L4 facilitated cycle arrest in G0/G1 phase and decreased proliferative capacity of tumor cells. In vitro antimicrobial activity for ligands and corresponding Pd(II) complexes was investigated against eleven microorganisms (eight strains of pathogenic bacteria and three yeast species) using microdilution method. The minimum inhibitory concentration and minimum microbicidal concentration were determined.

Biotin-Avidin System-Based Delivery Enhances the Therapeutic Performance of MSC-Derived Exosomes

Exosomes (EXs) shed by mesenchymal stem cells (MSCs) are potent therapeutic agents that promote wound healing and regeneration, but when used alone in vivo, their therapeutic potency is diminished by rapid clearance and bioactivity loss. Inspired by the biotin-avidin interaction, we developed a simple yet versatile method for the immobilization of MSC-derived EXs (MSC-EXs) into hydrogels and achieved sustained release for regenerative purposes. First, biotin-modified gelatin methacryloyl (Bio-GelMA) was fabricated by grafting NHS-PEG₁₂-biotin onto the amino groups of GelMA. Biotin-modified MSC-EXs (Bio-EXs) were then synthesized using an in situ self-assembling biotinylation strategy, which provided sufficient binding sites for MSC-EX delivery with little effect on their cargo composition. Thereafter, Bio-EXs were immobilized in Bio-GelMA via streptavidin to generate Bio-GelMA@Bio-EX hydrogels. An in vitro analysis demonstrated that Bio-EXs could be taken up by macrophages and exerted immunomodulatory effects similar to those of MSC-EXs, and Bio-GelMA@Bio-EX hydrogels provided sustained release of MSC-EXs for 7 days. After subcutaneous transplantation, a more constant retention of MSC-EXs in Bio-GelMA@Bio-EX hydrogels was observed for up to 28 days. When placed in an artificial periodontal multitissue defect, the functionalized hydrogels exhibited an optimized therapeutic performance to regrow complex periodontal tissues, including acellular cementum, periodontal ligaments (PDLs), and alveolar bone. In this context, Bio-GelMA@Bio-EX hydrogels exerted a robust immunomodulatory effect that promoted macrophage polarization toward an M2 phenotype. Our findings demonstrate that MSC-EXs delivered with the aid of the biotin-avidin system exhibit robust macrophage-modulating and repair-promoting functions and suggest a universal approach for the development of MSC-EX-functionalized biomaterials for advanced therapies.

Toxicity study of DE-EDCP as a potential drug for cancer therapy: Toxicity profile of DE-EDCP

It was reported that novel O, O'-diethyl-(S, S)-ethylenediamine- N, N'-di-2-(3-cyclohexyl) propanoate dihydrochloride (DE-EDCP) displayed in vitro antiproliferative activity on several human and mouse cancer cell lines, which was comparable to that of the prototypical anticancer drug cisplatin. In order to reveal its toxicity profile, acute and repeated-dose toxicity studies were performed in Naval Medical Research Institute (NMRI) Han mice. The intravenous LD₅₀ values of DE-EDCP were found to be 95.3 and 101.3 mg/kg body weight in female and male mice, respectively. In the subacute toxicity study, DE-EDCP was administered intravenously at the doses of 15, 25, and 40 mg/kg/day for a period of 28 days. There were no adverse effects on general condition, growth, feed and water consumption, and hematological parameters. There was a significant increase in urea and alanine aminotransferase in female mice and aspartate aminotransferase and alkaline phosphatase in both genders in 40 mg/kg/day dose-treated group. The histopathological changes confined to the liver and kidney, but in other organs were not found. Satellite group revealed that changes in the kidney and liver were less pronounced, suggesting their reversibility. Interactions with DNA could also be of importance for understanding DE-EDCP toxic side effects. Hyperchromic effect obtained with ultraviolet-visible, suggested electrostatic interactions between DE-EDCP and calf thymus DNA. The toxicity testing of DE-EDCP was conducted to predict human outcomes.

Stereospecific ligands and their complexes. XXIV. Synthesis, characterization and some biological properties of Pd(ii) and Pt(ii) complexes with R2-S,S-eddtyr

In vitro activity of ligands and corresponding platinum(ii) and palladium(ii) complexes.

Platinum Complexes with Edda (Ethylenediamine -N, N - Diacetate) Ligands as Potential Anticancer Agents

The design of platinum based drugs is not a new field of interest. Platinum complexes are widely used as anticancer agents and currently, approximately 30 platinum(II) and platinum(IV) entered into some of the phases of clinical trials. A special place in today’s research belongs to platinum complexes with diammine ligands. A large number of edda (ethylenediamine- N, N’-diacetate)-type ligands and their corresponding metal complexes has been successfully synthesized. This article summarizes recent progress in research on edda-type-platinum complexes. Some of these agents achieves better effect compared to the gold standard (cisplatin). It has been shown that there is a possible relationship between the length of the ligand ester group carbon chain and its cytotoxic effect. In most cases the longer the ester chain is the greater is the antitumor activity. Of particular interest are the noticeable effects of some new platinum compound with edda-type ligand on cell lines that are known to have a high level of cisplatin-resistance. Exanimate complexes appear to have a different mode of mechanism of action compared with cisplatin which includes apoptotic and necrotic cell death. There are indications that further investigations of these compounds may be very useful in overcoming the problems associated global cancer statistic.

Improved in vitro antitumor potential of (O,O'-Diisobutyl-ethylenediamine-N,N'-di-3-propionate)tetrachloridoplatinum(IV) complex under normoxic and hypoxic conditions

(O,O'-Diisobutyl-ethylenediamine-N,N'-di-3-propionate)tetrachloridoplatinum(IV), [PtCl4(iBu2eddp)], shows an improved pharmacological profile in comparison to cisplatin. This is manifested through accelerated dying process led by necrotic cell death, reflected through mitochondrial collapse, strong ATP depletion and reactive oxygen species production. Loss of mitochondrial potential was further followed with intensive apoptosis that finalized with DNA fragmentation. Different dynamic of tumoricidal action could be partly ascribed to less affected repair mechanisms in comparison to cisplatin. Importantly, [PtCl4(iBu2eddp)] did not induce necrosis in primary fibroblasts suggesting different intracellular response of normal vs. tumor cells. This selectivity toward malignant phenotype is further confirmed by retained tumoricidal potential in hypoxic conditions, while cisplatin became completely inefficient.

Oxidative Reactivity and Cytotoxic Properties of a Platinum(II) Complex Prepared by Outer-Sphere Amide Bond Coupling

Benzyl amine was coupled to the dangling carboxylic acid groups of the platinum(II) complex [Pt(edda)Cl₂], where edda = ethylenediamine-N,N'-diacetic acid, to give the diamidetethered complex [Pt(L)Cl₂] (1), where L = ethylenediamine-N,N'-bis(N-benzylacetamide). Complex 1 was oxidized with both PhICl₂ and Br₂. Oxidation with PhICl₂ cleanly afforded the tetrachloride complex, [Pt(L)Cl₄] (2), whereas oxidation with Br₂ gave rise to several mixed halide complexes of the general formula, [Pt(L)Cl_xBr_4-x], where x = 1, 2, or 3. Complexes 1 and 2 were fully characterized by ¹H, ¹³C, and ¹⁹⁵Pt NMR spectroscopy, as well as by ESI-MS. These compounds exist as a mixture of diastereomers that arise from the chirality of the two coordinated nitrogen atoms. Crystal structures of 1, 2, and [Pt(L)Cl_xBr_y] (3) are reported. Although refined as the tetrabromide complex [Pt(L)Br₄], the crystal structure of 3 is a mixture of species with site-occupancy disorder of chloride and bromide ligands. DFT calculations indicate that the two sets of diastereomers of 1 and 2 are effectively thermoneutral, a conclusion that is also supported by the observation of both members of each pair by NMR spectroscopy. The cytotoxicity of 1 and 2 was measured by the MTT assay in HeLa cells and compared to that of cisplatin. Both exhibit IC₅₀ values close to 50 μM and are therefore substantially less toxic than cisplatin, for which the IC₅₀ is 1 μM.