Coordination polymers
have emerged as a new class of potent biologically
active agents due to a variety of important characteristics such as
the presence of bioactive metal centers and linkers, low toxicity,
stability, tailorable structures, and bioavailability. The research
on intermediate metabolites has also been explored with implications
toward the development of selective anticancer, antimicrobial, and
antiviral therapeutic strategies. In particular, quinolinic acid (H
2
quin) is a recognized metabolite in kynurenine pathway and
potent neurotoxic molecule, which has been selected in this study
as a bioactive building block for assembling a new silver(I) coordination
polymer, [Ag(Hquin)(μ-PTA)]
n
·H
2
O (
1
). This product has been prepared from silver
oxide, H
2
quin, and 1,3,5-triaza-7-phosphaadamantane
(PTA), and fully characterized by standard methods including single-crystal
X-ray diffraction. Compound
1
has revealed distinctive
bioactive features, namely (i) a remarkable antiviral activity against
herpes simplex virus type 1 (HSV-1) and adenovirus 36 (Ad-36), (ii)
a significant antibacterial activity against clinically important
bacteria (
Staphylococcus aureus
,
Escherichia coli
, and
Pseudomonas
aeruginosa
), and (iii) a selective cytotoxicity against
HeLa (human cervix carcinoma) cell line. The present work widens a
growing family of bioactive coordination polymers with potent antiviral,
antibacterial, and antiproliferative activity.
A series of novel silver polypyridine complexes containing PTA or PTAS have been synthesized and fully characterized. Representative light-stable and water-soluble complexes were evaluated for their cytotoxic and the antitumor activity.
From the well-known 1,3,5-triaza-phosphaadamantane (PTA, 1a), the novel N-allyl and N-benzyl tetrafuoroborate salts 1-allyl-1-azonia-3,5-diaza-7-phosphaadamantane (APTA(BF4), 1b) and 1-benzyl-1-azonia-3,5-diaza-7-phosphaadamantane (BzPTA(BF4), 1c) were obtained. These phosphines were then allowed to react with (Pt(μ-Cl)(C6F5)(tht))2 (tht = tetrahydrothiophene) affording the water soluble Pt(II) complexes trans-(PtCl(C6F5)(PTA)2) (2a) and its bis-cationic congeners trans-(PtCl(C6F5)(APTA)2)(BF4)2 (2b) and trans-(PtCl(C6F5)(BzPTA)2)(BF4)2 (2c). The compounds were fully characterized by multinuclear NMR, ESI-MS, elemental analysis and (for 2a) also by single crystal X-ray diffraction, which proved the trans configuration of the phosphine ligands. Furthermore, in order to evaluate the cytotoxic activities of all complexes the normal human dermal fibroblast (NHDF) cell culture were used. The antineoplastic activity of the investigated compounds was checked against the human lung carcinoma (A549), epithelioid cervix carcinoma (HeLa) and breast adenocarcinoma (MCF-7) cell cultures. Interactions between the complexes and human serum albumin (HSA) using fluorescence spectroscopy and circular dichroism spectroscopy (CD) were also investigated.
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