Interactions of isoorientin and its Semi-synthetic analogs with human serum albumin.

Isoorientin is a C-glycosyl flavone with a wide range of health beneficial effects and inhibits glycogen synthase kinase 3ß (GSK-3ß) potentially against Alzheimer's disease. Its semi-synthetic derivatives have greater potency than isoorientin. The present study was aimed to determine the mechanism of interactions of isoorientin and its derivatives with human serum albumin (HSA) using multi-spectroscopic, microscale thermophoresis (MST) and computational studies. Spectra of steady-state fluorescence, UV-Vis, and time-resolved fluorescence indicated that isoorientin and its derivatives quenched the intrinsic fluorescence of HSA through a static quenching process. Isoorientin and its derivatives had a moderate affinity with HSA (Ka 7.7-14.9 × 104 M-1). The binding process was accompanied by an exothermic phenomenon, ΔG° of HSA-isoorientin and its derivatives systems were calculated as from -29.51 kJ mol-1 to -27.87 kJ mol-1. Displacement experiments with site-specific markers revealed that isoorientin and its derivatives bind to HSA at site II (subdomain IIIA) only. A reduction in the α-helical content of HSA-isoorientin and its derivatives complex was observed, because the conformational changes was structurally perturbed by the hydrophilic groups of the compounds. Further molecular modeling studies confirmed that the binding of isoorientin and its derivatives to the site II via hydrophobic interaction. The MST results confirmed the interactions between HSA and the compounds of interest. The esterase-like assay studies indicated that isoorientin and its derivatives shared the same binding site in HSA, and their induced structural changes of HSA may have been caused by partial unfolding of HSA. This work helps to understand transport, distribution, bioactivity, and design of flavonoid-based GSK-3ß inhibitors.

Bis[N'-(3-cyano-benzyl-idene)isonicotino-hydrazide-κN]silver(I) trifluoro-methane-sulfonate.

In the title compound, [Ag(C(14)H(10)N(4)O)(2)]CF(3)SO(3), two N atoms from two independent pyridyl rings of two N'-3-cyano-benzyl-ideneisonicotinohydrazide ligands coordinate to the unique Ag(I) ion, forming a nearly linear coordination geometry. Adjacent silver complexes are primarily linked together by Ag⋯N inter-actions, with Ag⋯N separations of 2.877 (2) and 3.314 (2) Å. On the other hand, one CF(3)SO(3) (-) anion inter-acts with hydrazone groups of two neighbouring ligands via N-H⋯O hydrogen bonds. These weak inter-molecular inter-actions contribute to the formation of supra-molecular chains. In addition, there are Ag⋯O inter-actions [2.787 (2) Å] between Ag and O atoms from adjacent chains.

Dichlorido(2,9-dieth-oxy-1,10-phenanthroline-κN,N')zinc(II).

All non-H atoms except for the Cl atoms lie on a mirror plane in the title complex, [ZnCl(2)(C(16)H(16)N(2)O(2))]. The Zn(II) ion is coordinated by two N atoms from a bis-chelating 2,9-dieth-oxy-1,10-phenanthroline ligand and two symmetry-related Cl atoms in a distorted tetra-hedral environment. The two Zn-N bond lengths are significantly different from each other and the N-Zn-N angle is acute. In the crystal structure, there are weak but significant π-π stacking inter-actions between phenanthroline rings, with a centroid-centroid distance of 3.764 (1) Å.

Bis[µ-3-(1H-pyrazol-1-yl)benzonitrile-κN:N']bis-[perchloratosilver(I)].

In the title centrosymmetric complex, [Ag(2)(ClO(4))(2)(C(10)H(7)N(3))(2)], the unique Ag(I) ion is coordinated by an N atom from a carbonitrile group, an N atom from a symmetry-related pyrazole group and an O atom of a perchlorate ligand to form a distorted T-shaped environment. Two 3-(1H-pyrazol-1-yl)benzonitrile ligands each bridge two Ag(I) ions to form a dinuclear complex. In the crystal structure, there are weak Ag⋯O inter-actions within the range 2.70-3.01 Šlinking dimeric units into layers approximately parallel to (100). The O atoms of the perchlorate ligand are disordered over two sites with occupancies of 0.570 (11) and 0.430 (11), respectively.

catena-Poly[[(2,9-dieth-oxy-1,10-phen-anthroline-κN,N')cadmium(II)]-di-µ-dicyan-amido-κN:N].

In the title polymer, [Cd(C(2)N(3))(2)(C(16)H(16)N(2)O(2))](n), the Cd(II) ion is coordinated by two N atoms from one 2,9-dieth-oxy-1,10-phenanthroline mol-ecule and four N atoms from four symmetry-related dicyanamide ions in a distorted octa-hedral geometry. In the 2,9-dieth-oxy-1,10-phenanthroline ligand, the O and C atoms of the eth-oxy groups are located almost in the plane defined by the phenanthroline ring system. Two dicyanamide ions bridge two Cd(II) ions, which are located on a twofold axis, forming a one-dimensional zigzag chain along the [001] direction. The 2,9-dieth-oxy-1,10-phenanthroline mol-ecules act as bidentate terminal ligands. There are π-π inter-actions between polymeric chains, characterized by a centroid-centroid distance of 3.7624 (2) Šbetween the phenanthroline rings of two neighbouring chains.

A one-dimensional Ag coordination polymer: catena-poly[[[[N'-(4-cyano-benzyl-idene)nicotinohydrazide]silver(I)]-µ-N'-(4-cyano-benzyl-idene)nicotino-hydrazide] trifluoro-methane-sulfonate].

In the title compound, {[Ag(C(14)H(10)N(4)O)(2)]CF(3)SO(3)}(n), the unique Ag(I) ion is coordinated by two N atoms from two pyridine rings of two independent N'-(4-cyano-benzyl-idene)nicotinohydrazide ligands and one N atom of a carbonitrile group of a symmetry-related N'-(4-cyano-benzyl-idene)nicotino-hydrazide ligand, forming a distorted T-shaped coordination environment. One of the independent ligands acts as a bridge connecting Ag(I) ions, forming chains along the a axis. In the crystal structure, two neighbouring anti-parallel chains are connected through N-H⋯O hydrogen bonds. In addition, there are relatively short Ag⋯O contacts of 2.723 (3) Å, which connect the chains into a three-dimensional structure.

catena-Poly[[[N'-(4-cyano-benzyl-idene)nicotinohydrazide)silver(I)]-µ-N'-(4-cyano-benzyl-idene)nicotinohydrazide] hexa-fluorido-phosphate].

In the title polymer, {[Ag(C(14)H(10)N(4)O)(2)]PF(6)}(n), each Ag(I) ion is coordinated by two N atoms from two pyridyl rings of independent N'-(4-cyano-benzyl-idene)nicotinohydrazide ligands, and one N atom from one carbonitrile group of a symmetry-related ligand in a distorted T-shaped geometry. The ligands exhibit two modes of coordination. One acts as a bridge connecting Ag atoms to form one-dimensional chains along [01]. The other acts as a terminal monodentate ligand, coordinating to Ag through its pyridyl N atom. Two neighbouring anti-parallel chains in the crystal are connected through N-H⋯O hydrogen bonds. Other adjacent chains are packed via Ag⋯O inter-actions, with Ag⋯O separations of 2.876 (2) Å. In addition, PF(6) (-) counter-anions inter-act with the hydrazone groups through N-H⋯F hydrogen bonds. The PF(6) (-) anion is disordered over two sites, with occupancies of 0.773 (8) and 0.227 (8).

Chloridobis(2,9-dieth-oxy-1,10-phenanthroline-κN,N')copper(II) perchlorate.

In the title complex, [CuCl(C(16)H(16)N(2)O(2))(2)]ClO(4), the Cu(II) ion is coordinated by four N atoms from two chelating 2,9-dieth-oxy-1,10-phenanthroline ligands and one chloride ion in a slightly disorted trigonal-bipyramidal environment. Two N atoms and the Cl atom are in equatorial positions while the remaining two N atoms occupy apical sites, the equatorial Cu-N bonds being significantly longer than the two apical Cu-N bonds. The N=C-O-C torsion angles involving the four eth-oxy groups are in the range 161.5 (8) to 177.0 (5)°. In the crystal structure, there are significant π-π stacking inter-actions between inversion-related rings of phenanthroline groups with centroid-centroid distances in the range 3.649 (4)-3.790 (4) Å.