Diorganotin(IV) complexes ofD-galacturonic acid: solid-state and solution-phase structural study

Anti-cancer activity of di- and tri-organotin(IV) compounds with D-(+)-Galacturonic acid on human tumor cells

We have compared the anti-proliferative activity in vitro, of R₂SnGala (1-3) [R = Me, n-Bu, Ph] and novel R₃SnGala (4, 5) [R = Me, n-Bu] with D-(+)-Galacturonic acid [HGala; Gala^q-, q = (2) and (1) for R₂SnGala and R₃SnGala, respectively] compounds, towards human tumor cell lines of intestinal carcinoma (HCT-116) and breast adenocarcinoma (MCF-7). The new synthesized 4 and 5 compounds were characterized, in solution, by ¹H, ¹³C and ¹¹⁹Sn NMR, that showed that HGala acts as monoanionic moiety and evidenced the dynamic behavior of the compounds, due to inter-conversions involving the anomeric carbon atom of the ligand. Cell viability, apoptosis induction and cell cycle distribution were analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay and flow cytometry, respectively. The cytotoxicity of the compounds, in the micro-submicromolar range, changed in the order of the organotin(IV) moieties, according to 5 > 3 > 2, while 1 and 4, containing Me_nSn(IV) (n = 2,3) moieties, were ineffective. Compound 5 showed peculiar cytotoxic effects. It did not cause time dependent inhibition of cell growth nor accumulated into the cells. Cell death induced by the active 2, 3, and 5, was shown to be apoptotic by measuring the exposure of phosphatidylserine to the outer membrane and the loss of mitochondrial potential. All the cytotoxic compounds induced an accumulation of cells in the subG0/G1phase, while only 2 and 3 perturbed the cell cycle confining viable cells in G0/G1phase. Finally, none of the compounds investigated affected the viability of normal intestinal or liver cells, indicating selectivity towards tumor cells.

Synthesis and characterization of glucose-bis(pyrazole)-Cu(II)/Ni(II) complexes and their in vitro DNA binding studies

The D-glucose-bis pyrazolyl complexes of Cu(II) 1 and Ni(II) 2 were synthesized and characterized by elemental analysis, molar conductance measurements and spectroscopic methods. The solution structures of the complex have been assessed to square pyramidal using electronic absorption and electronic paramagnetic resonance (EPR) spectroscopy. The interaction of 1 and 2 with calf thymus DNA (CT DNA) has been carried out by absorption, emission, viscometric and electrochemical methods. The intrinsic binding constant K(b) was determined as 13.4x10(5) M(-1), 4.5x10(5) M(-1) for 1 and 2, respectively suggestive of strong binding of complexes with DNA. Furthermore, higher value of K(b) for 1 implies that this complex interacts more strongly with CT DNA in comparison to 2. The quenching constant "K" of 1 and 2 obtained from emission spectral methods was 1.33, 0.55, respectively. Complex 1 hydrolytically cleaved pBR322 supercoiled DNA in absence of an activating agent. The enhanced cleavage of pBR322 DNA was observed in presence of ascorbic acid as a reducing agent, 1 also displays efficient photonuclease activity through double strand DNA breaks when irradiated at 365 nm through mechanistic pathway involving hydroxyl radicals. In addition to the above binding studies, an in vitro binding study of complex 1 with protein human serum albumin (HSA), tyrptophan and mixtures of HSA, L-tryptophan with CT DNA was carried out. The in vitro "binding study" also supports that 1 shows higher binding affinity towards CT DNA.

Solution structure of R2Sn(iv)-β-N-acetyl-neuraminate (R = Me, Bu) complexes in D2O and DMSO-d6: Experimental NMR and DFT computational study

Two diorganotin(IV)-NANA complexes (NANA (1) = beta-N-acetyl-Neuraminic Acid = 5-amino-3,5-dideoxy-D-glycero-beta-D-galactononulosic acid) with formula Me(2)Sn(iv)NANA (2) and Bu(2)Sn(IV)NANA (3) were synthesized and characterized by (1)H, (13)C and (119)Sn NMR spectroscopy, both in D(2)O and DMSO-d(6) solutions. The experimental data in DMSO suggested the monosaccharide bidentate chelation via O1 carboxylate and vicinal O2 alkoxide atoms, which, in D(2)O, can be dynamically extended to a third binding site (O8 atom) of the pendant chain. Coordination at the tin atom is discussed on the basis of experimental NMR data and DFT calculation.