Synthesis, structural studies and antimicrobial evaluation of nickel (II) complexes of NNS tridentate thiosemicarbazone based ligands

New iron(III) complexes with 2-formylpyridine thiosemicarbazones: Synthetic aspects, structural and spectral analyses and cytotoxicity screening against MCF-7 human cancer cells

2-Formylpyridine thiosemicarbazone - iron (III) chelates [ F e L 2 ] C l • 2 H 2 O {L = L¹ (C1) [HL ¹  = 4-(4-Nitrophenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide] and L = L² (C2) [HL ²  = 4-(2,5-Dimethoxyphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide]} were prepared. The two ligand anions in each complex resulted in saturation of the iron coordination number and consequently the existence of these complexes as 1:1 electrolytes. As well, the iron in these complexes exhibits low-spin electronic configuration. X-ray crystallography of complex C1 indicated its triclinic crystal system and P 1 ‾ space group. In addition, it proved the ligation through a thiol sulfur atom and two nitrogen atoms of pyridine and azomethine groups. This is while the presence of two water molecules of crystallization in the complex structure was also indicated. The ligand HL ¹ was selected for cytotoxicity screening against human MCF-7, A-549, HEPG-2 and HCT-116 cancer cells and the most enhanced activities were detected against the breast cells. Against these cells, the compounds HL ¹ , HL ² , C1 and C2 induced cytotoxicity, respectively, with IC₅₀ values of 52.4, 145.4, 34.3 and 62.0 μM. However, against the healthy BHK cells, HL ¹ and HL ² caused cytotoxicity, respectively, with IC₅₀ values of 54.8 and 110.6 μM and cytotoxicity with percent viabilities of 56.7 and 55.4% of the BHK cells by the complexes (137.4 μM of C1 and 131.9 μM of C2) was determined. These activities against MCF-7 cells are less significant compared with the measured value for doxorubicin. But this standard is more toxic to normal cells than the thiosemicarbazones (IC₅₀ (doxorubicin) = 9.66 μM against MCF-7 cells and 36.42 μM against BHK cells).

Thiosemicarbazones and Derived Antimony Complexes: Synthesis, Structural Analysis, and In Vitro Evaluation against Bacterial, Fungal, and Cancer Cells

Two antimony complexes {[Sb(L1)Cl2] C1 and [Sb(L2)Cl2] C2} with the thiosemicarbazone ligands {HL1 = 4-(2,4-dimethylphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide and HL2 = 4-(2,5-dimethoxyphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide} were introduced. The structures were elucidated on the basis of a CHNS analysis, spectroscopic techniques (UV-Vis and FT-IR), and DMF solution electrical conductivities. Single crystal X-ray diffraction analysis of complex C1 assigned the complex pseudo-octahedral geometry and triclinic P-1 space group. Only the ligand HL1 and its derived complex C1 displayed antifungal activities against Candida albicans and this activity was enhanced from 10 mm to 21 mm for the respective complex, which is the same activity given by the drug “Amphotericin B”. The ligands HL1 and HL2 gave inhibitions, respectively, of 14 and 10 mm against Staphylococcus aureus and 15 and 10 mm against Escherichia coli; however, complexes C1 and C2 increased these inhibitions to 36 and 32 mm against Staphylococcus aureus and 35 and 31 mm against Escherichia coli exceeding the activities given by the ampicillin standard (i.e., 21 mm against Staphylococcus aureus and 25 mm against Escherichia coli). Against MCF-7 human breast cancer cells, the IC50 values of HL1 (68.9 μM) and HL2 (145.4 μM) were notably enhanced to the values of 34.7 and 37.4 μM for both complexes, respectively. Further, the complexes induced less toxicity in normal BHK cells (HL1 (126.6 μM), HL2 (110.6 μM), C1 (>210.1 μM), and C2 (160.6 μM)). As a comparison, doxorubicin gave an IC50 value of 9.66 μM against MCF-7 cells and 36.42 μM against BHK cells.

Trivalent Cobalt Complexes with NNS Tridentate Thiosemicarbazones: Preparation, Structural Study and Investigation of Antibacterial Activity and Cytotoxicity against Human Breast Cancer Cells

New complexes of trivalent cobalt with substituted thiosemicarbazone ligands having an NNS donor system {HL1 = 4-(4-nitrophenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide and HL2 = 4-(2,5-dimethoxyphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide} were synthesized via the in situ oxidation of divalent cobalt chloride accompanying its addition to the ligands. The complexes C1 and C2 were characterized via elemental (CHNS) analysis and 1H NMR, FT-IR and UV-Vis. spectroscopic data. Further, conductometric studies on the DMF solutions of the complexes indicated their 1:1 nature, and their diamagnetism revealed the low-spin trivalent oxidation state of the cobalt in the complexes. The X-ray diffraction analysis of complex C1 indicated that it crystallizes in the triclinic space group P-1. The metal exhibits an octahedral environment built by two anionic ligands bound via pyridine nitrogen, imine nitrogen and thiol sulfur atoms. The complex is counterbalanced by a chloride ion. In addition, two lattice water molecules were detected in the asymmetric unit of the unit cell. The ligand HL2 (20 mg/mL in DMSO) displayed inhibition zones of 10 mm against both S. aureus and E. coli, and the same concentration of the respective complex raised this activity to 15 and 12 mm against these bacterial strains, respectively. As a comparison, ampicillin inhibited these bacterial strains by 21 and 25 mm, respectively. Screening assay by HL1 on four human cancer cells revealed the most enhanced activity against the breast MCF-7 cells. The induced growth inhibitions in the MCF-7 cells by all compounds (0–100 μg/mL) have been detected. The ligands {HL1 and HL2} and complex C2 gave inhibitions with IC50 values of 52.4, 145.4 and 49.9 μM, respectively. These results are more meaningful in comparison with similar cobalt complexes, but less efficient compared with the inhibition with IC50 of 9.66 μM afforded by doxorubicin. In addition, doxorubicin, HL1 and HL2 induced cytotoxicity towards healthy BHK cells with IC50 values of 36.42, 54.8 and 110.6 μM, but surviving fractions of 66.1% and 62.7% of these cells were detected corresponding to a concentration of 100 μg/mL of the complexes (136.8 μM of C1 and 131.4 μM of C2).

Zn(II) and Cd(II) thiosemicarbazones for stimulation/inhibition of kojic acid biosynthesis from Aspergillus flavus and the fungal defense behavior against the metal complexes' excesses

The complexes {[ZnL¹Cl] C1, [ZnL²Cl].0.5H₂O C2, [CdL¹Cl] C3, and [CdL²Cl] C4} were prepared from tridentate thiosemicarbazones {HL¹ = 4-(3-nitrophenyl)-1-((pyridin-2-yl)methylene) thiosemicarbazide and HL² = 4-(2,4-dimethoxyphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide} and identified by elemental CHNS, spectroscopic {IR and UV-Vis.}, thermal and DMF solution electrical conductivity data. On another hand, kojic acid (KA) which represents important secondary metabolite with numerous hot spot applications was successfully biosynthesized from Aspergillus flavus and structurally analyzed by single crystal analysis. The Zn(II) complexes C1&C2 (0.3 mM) enhanced the KA biosynthesis by 70.87% and 42.26%, while 76.09% of C1 and 72.78% of C2 were absorbed by the fungal cells. The Cd(II) complexes C3&C4 at 0.3 mM inhibited KA production by 87.95% and 97.03% with Cd(II) consumption reaching to 40.09% & 37.3%, while 0.4 mM of C3&C4 resulted in 100% inhibition of kojic acid biosynthesis. Light microscopic analysis showed the fungal structural abnormalities and the cell antioxidant behavior was detected. These complexes could be highly applicable as new stimulators and inhibitors of kojic acid production.