Antitumor activity of a Trans-thiosemicarbazone schiff base palladium (II) complex on human gastric adenocarcinoma cells

Schiff bases and their metal complexes to target and overcome (multidrug) resistance in cancer

Overcoming multidrug resistance (MDR) is one of the major challenges in cancer therapy. In this respect, Schiff base-related compounds (bearing a R1R2CNR3 bond) gained high interest during the past decades. Schiff bases are considered privileged ligands for various reasons, including the easiness of their preparation and the possibility to form complexes with almost all transition metal ions. Schiff bases and their metal complexes exhibit many types of biological activities and are used for the treatment and diagnosis of various diseases. Until now, 13 Schiff bases have been investigated in clinical trials for cancer treatment and hypoxia imaging. This review represents the first collection of Schiff bases and their complexes which demonstrated MDR-reversal activity. The areas of drug resistance covered in this article involve: 1) Modulation of ABC transporter function, 2) Targeting lysosomal ABCB1 overexpression, 3) Circumvention of ABC transporter-mediated drug efflux by alternative routes of drug uptake, 4) Selective activity against MDR cancer models (collateral sensitivity), 5) Targeting GSH-detoxifying systems, 6) Overcoming apoptosis resistance by inducing necrosis and paraptosis, 7) Reactivation of mutated p53, 8) Restoration of sensitivity to DNA-damaging anticancer therapy, and 9) Overcoming drug resistance through modulation of the immune system. Through this approach, we would like to draw attention to Schiff bases and their metal complexes representing highly interesting anticancer drug candidates with the ability to overcome MDR.

Synthesis, Characterization, Antimicrobial and Antimalarial Activities of Azines Based Schiff Bases and their Pd(II) Complexes

Herein, we report synthesis, characterization, antimicrobial and antimalarial activities of azines Schiff base ligands (L1 -L4 ) and their palladium (II) complexes (C1 -C4 ) of [Pd(L)(OAc)2 ] type. The azine ligands (L1 -L4 ) were prepared by condensation of carbonyl compounds with hydrazine hydrate and their complexes by the reaction of palladium acetate with L1 -L4 ligands in 1 : 1 molar ratio. The prepared ligands and their complexes were characterized by spectral characterization using 1 H &13 C-NMR, FT-IR and mass spectral studies, which revealed that the ligands coordinates via azomethine nitrogen and heteroatom or aryl carbon with palladium. Moreover, Schiff bases and their palladium (II) complexes have been screened for their antibacterial (S. aureus, B. subtillis, and S. typhi, P. aeruginosa), antifungal (C. albicans, A. niger, and A. clavatus) and antimalarial (P. falciparum) activities. The Schiff base L4 showed good results for antibacterial against S. aureus (MIC, 50 μg/mL) and antimalarial against P. falciparum (IC50 , 0.83 μg/mL). The complex C1 showed best antibacterial activity (MIC, 62.5 μg/mL) against S. typhi and the complex C4 exhibited remarkable antimalarial activity (IC50 , 0.42 μg/mL) among the tested compounds. Thus, azines based ligands and their Pd complexes can be good antimicrobial and antimalarial agents if explored further.

Newly synthesized palladium(II) complexes with aminothiazole derivatives: in vitro study of antimicrobial activity and antitumor activity on the human prostate cancer cell line

Five new complexes of the palladium(II) ion (C1-C5) having the general formula [(PdL₂)]Cl₂ with some 2-aminothiazoles (L1-L5), where L1 = 2-amino-4-(3,4-difluorophenyl)thiazole, L2 = 2-amino-5-methyl-4-phenylthiazole, L3 = 2-amino-4-phenylthiazole, L4 = 2-amino-4-(4-chlorophenyl)thiazole, and L5 = 2-amino-4-(2,4-difluorophenyl)thiazole, have been synthesized and characterized by elemental microanalysis and infrared, ¹H NMR and ¹³C NMR spectroscopy. The in vitro antimicrobial activity of the five ligands and the corresponding Pd(II) complexes is investigated. Testing is performed by the microdilution method and the minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) have been determined. Testing is conducted against 11 microorganisms (nine strains of pathogenic bacteria and two yeast species). The tested ligands and palladium(II) complexes show selective, high and moderate activity. There is a difference in antimicrobial activity between the ligands and the corresponding palladium(II) complexes. The complexes have significant anti-staphylococcal activity and activity on Pseudomonas aeruginosa which is better than the positive control. The interactions of newly synthesized palladium(II) complexes with calf thymus DNA (CT-DNA) were investigated using UV-Vis absorption and fluorescence spectroscopy. Analysis of UV-absorption and fluorescence spectra indicates the formation of a complex between the palladium(II) complexes and DNA. The high values of intrinsic binding constants, K_b, of the order 10⁴ M^-1 and Stern-Volmer quenching constants, K_SV, of the order 10⁵ M^-1 indicated very good binding of all complexes to CT-DNA. Also, the new Pd(II) complexes show high cytotoxic activity towards the human prostate cancer cell line and insignificant activity towards non-cancerous human fibroblasts. Future research could additionally explore the biological activity of Pd(II) complexes presented in this paper and investigate the possibility of their implementation in clinical practice.

Schiff Bases and Complexes: A Review on Anti-Cancer Activity

Development in the field of bio-inorganic chemistry increased the interest in Schiff base and its complexes due to its biological importance in many fields, including anticancer activity. Discovery of the antitumor activity of Schiff base and its complexes against various tumor cell lines fascinates the researchers to develop new anticancer drugs without any side effects. Thus, the present review focuses on the anticancer activity of Schiff bases and their metal complexes.

Enhancement of Chemical Stability and Dermal Delivery of Cordyceps militaris Extracts by Nanoemulsion

This study aimed to develop nanoemulsions for enhancing chemical stability and dermal delivery of Cordyceps militaris extracts. C. militaris was extracted by maceration and infusion. The extracts were investigated for cordycepin, phenolic, and flavonoid content. The antioxidant activity was investigated by in vitro spectrophotometric methods. The irritation profile was investigated by hen's egg-chorioallantoic membrane test. Nanoemulsions were developed using high-pressure homogenizer. C. militaris extract was incorporated into the nanoemulsion and investigated for safety, release profile, permeation, and skin retention. The results demonstrated that water extract (CW) contained the significantly highest content of cordycepin, phenolics, and flavonoids, which were responsible for antioxidant activity. CW was the most potent antioxidant. CW possessed comparable 2,2'-diphenyl-1-picrylhydrazyl radical scavenging activity and lipid peroxidation inhibition to l-ascorbic acid (96.9 ± 3.1%) and alpha-tocopherol (87.2 ± 1.0%). Consequently, ten mg/mL of CW was incorporated into nanoemulsions composing of sugar squalene, Tween® 85, and deionized water. Nanoemulsion, which had the smallest internal droplet size (157.1 ± 2.6 nm), enhanced the stability of CW, had no cytotoxicity effect and no skin irritation, released the most CW (0.9 ± 0.0% w/w after 24 h), and delivered the highest CW into the skin layer (33.5 ± 0.7% w/w). Therefore, nanoemulsion was suggested for enhancing the stability and dermal delivery of CW.

New Palladium(II) and Platinum(II) Complexes Based on Pyrrole Schiff Bases: Synthesis, Characterization, X-ray Structure, and Anticancer Activity

New palladium (Pd)II and platinum (Pt)II complexes (C1-C5) from the Schiff base ligands, R-(phenyl)methanamine (L1), R-(pyridin-2-yl)methanamine (L2), and R-(furan-2-yl)methanamine (L3) (R-(E)-N-((1H-pyrrol-2-yl) methylene)) are herein reported. The complexes (C1-C5) were characterized by FTIR, 1H and 13C NMR, UV-vis, and microanalyses. Single-crystal X-ray crystallographic analysis was performed for the two ligands (L1-L2) and a Pt complex. Both L1 and L2 belong to P21/n monoclinic and P-1 triclinic space systems, respectively. The complex C5 belongs to the P21/c monoclinic space group. The investigated molar conductivity of the complexes in DMSO gave the range 4.0-8.8 μS/cm, suggesting neutrality, with log P values ≥ 1.2692 ± 0.004, suggesting lipophilicity. The anticancer activity and mechanism of the complexes were investigated against various human cancerous (Caco-2, HeLa, HepG2, MCF-7, and PC-3) and noncancerous (MCF-12A) cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Apopercentage assays, respectively. C5 demonstrated strong DNA-binding affinity for calf thymus DNA (CT-DNA) with a binding constant of 8.049 × 104 M-1. C3 reduced cell viability of all the six cell lines, which included five cancerous cell lines, by more than 80%. The C5 complex also demonstrated remarkably high selectivity with no cytotoxic activity toward the noncancerous breast cell line but reduced the viability of the five cancerous cell lines, which included one breast cancer cell line, by more than 60%. Further studies are required to evaluate the selective toxicity of these two complexes and to fully understand their mechanism of action.

Synthesis, characterization, spectroscopic studies and biological evaluation of Schiff bases derived from 1-hydroxy-2-acetonapthanone

The four Schiff bases (I - IV) were synthesized by the condensation reaction of 1(1-hydroxynaphthalen-2-yl)ethanone, 1-(4-chloro-1hydroxynaphthalen-2-yl)ethanone and 1-(4-bromo-1-hydroxynaphthalen-2-yl)ethanone with propane-1,3-diamine and pentane-1,3-diamine. The structural analysis is done by UVvis., FT-IR, 1H NMR, 13C NMR, LCMS and elemental analyses. These compounds were assayed for antibacterial (Escherichia coli and Salmonella Typhi) activity and antioxidant (2,2-Diphenyl-1-Picryl Hydrazyl(DPPH) and Hydroxyl radical scavenging method) activity. The antibacterial and antioxidant activities of synthesized Schiff bases exhibited better degrees of inhibitory effects. Among these, Schiff base 2,2'-((propane-1,3-diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(4-chloronaphthalen-1-ol) (II) exhibited excellent antibacterial activity with MICs of 0.12, 0.25, 0.5 and 1 mg/ml against E. coli and Salmonella Typhi. Furthermore, two Schiff bases such as, 2,2'-((propane-1,3-diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(naphthalen-1-ol) (I) and 2,2'-((pentane-1,3-diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(4-bromonaphthalen-1-ol) (IV) exhibited promising antioxidant activity.

Novel pyridinecarboxaldehyde thiosemicarbazone conjugated magnetite nanoparticulates (MNPs) promote apoptosis in human lung cancer A549 cells

The present study highlights the apoptotic activity of magnetic Fe₃O₄ nanoparticulates functionalized by glutamic acid and 2-pyridinecarboxaldehyde thiosemicarbazone (PTSC) toward human lung epithelial carcinoma A549 cell line. To this aim, the Fe₃O₄ nanoparticulates were prepared using co-precipitation method. Then, the glutamic acid and Fe₃O₄ nanoparticulates were conjugated to each other. The product was further functionalized with bio-reactive PTSC moiety. In addition, the synthesized Fe₃O₄@Glu/PTSC nanoparticulates were characterized by physico-chemical techniques including scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy and zeta potential analysis. The effects of in vitro cell viability in Fe3O4@Glu/PTSC nanoparticulate indicated the anti-proliferative properties in a dose-dependent manner (IC₅₀ = 135.6 µM/mL). The high selectivity for tumor cells and far below of activity in HEK293 non-tumorigenic cells is considered as an important feature for this complex (SI, 3.48). Based on the results, PTSC failed to reveal any activity against A549 cells alone. However, Fe₃O₄ nanoparticulates had some effects in inhibiting the growth of lung cancer cell. Furthermore, Bax and Bcl-2 gene expressions were quantified by real-time PCR method. The expression of Bax increased 1.62-fold, while the expression of Bcl-2 decreased 0.76-fold at 135.6 µM/mL concentration of Fe₃O₄@Glu/PTSC compared to untreated A549 cells. Furthermore, the Fe₃O₄@Glu/PTSC nanoparticulate-inducing apoptosis properties were evaluated by Hoechst 33258 staining, Caspase-3 activation assay and Annexin V/propidium iodide staining. The results of the present study suggest that Fe₃O₄@Glu/PTSC nanoparticulates exhibit effective anti-cancer activity against lung cancer cells.

New dinuclear palladium(II) complexes with benzodiazines as bridging ligands: interactions with CT-DNA and BSA, and cytotoxic activity

Three new dinuclear Pd(II) complexes with general formula [{Pd(en)Cl}₂(μ-L)](NO₃)₂ [L is bridging ligand quinoxaline (Pd1), quinazoline (Pd2) and phthalazine (Pd3)] were synthesized and characterized by elemental microanalyses, UV-Vis, IR and NMR (¹H and ¹³C) spectroscopy. The interaction of dinuclear Pd1-Pd3 complexes with calf thymus DNA (CT-DNA) has been monitored by viscosity measurements, UV-Vis and fluorescence emission spectroscopy in aqueous phosphate buffer solution (PBS) at pH 7.40 and 37 °C. In addition, these experimental conditions have been applied to investigate the binding affinities of Pd1-Pd3 complexes to the bovine serum albumin (BSA) by fluorescence emission spectroscopy. In vitro antiproliferative and apoptotic activities of the dinuclear Pd(II) complexes have been tested on colorectal and lung cancer cell lines. All tested Pd(II) complexes had lower cytotoxic effect than cisplatin against colorectal cancer cells, but also had similar or even higher cytotoxicity than cisplatin against lung cancer cells. All complexes induced apoptosis of colorectal and lung cancer cells, while the highest antiproliferative effect exerted Pd2 complex.

DNA Binding Properties and Antibacterial Activity of Heterolyptic Transition Metal Complexes with 2,2-Bipyridyl and 2-Acetylthiophene Thiosemicarbazone

Metal complexes having the composition M(Bipy)Cl2 (where, M = Cu(II), Ni(II) and Co(II); Bipy = 2,2-bipyridyl) are reacted with 2-acetylthiophene thiosemicarbazone (ATT) to produce heteroleptic transition metal complexes with molecular formula [M(Bipy)ATT]. The complexes are characterized by mass spectra, molar conductivity, infrared and electronic spectra. Electrochemical behaviour of these metal complexes was investigated by cyclic voltammetric studies. The metal complexes show quasi reversible cyclic voltammetric responses for the Cu(II)/Cu(I) couple. The binding properties of these complexes with calf-thymus DNA have been investigated by using absorption spectrophotometry. Metal complexes are screened for their antibacterial activity by using agar well diffusion method against pathogenic bacterial strains viz. Escherichia coli and Staphylococcus aureus. Antibacterial activity of the present complexes are comparable with the activity of ciprofloxacin. The Cu(Bipy)Cl2 complex inhibits bacteria more strongly than any other complex. The Ni(Bipy)ATT complex shows more activity than the parent complex, Ni(Bipy)Cl2.

Novel thiosemicarbazones induce high toxicity in estrogen-receptor-positive breast cancer cells (MCF7) and exacerbate cisplatin effectiveness in triple-negative breast (MDA-MB231) and lung adenocarcinoma (A549) cells

Cis-diamminedichloroplatinum(II) (CDDP), known as cisplatin, has been extensively used against breast cancer, which is the most frequent cancer among women, and lung cancer, the leading cancer that causes death worldwide. Novel compounds such as thiazole derivatives have exhibited antiproliferative activity, suggesting they could be useful against cancer treatment. Herein, we synthesized two novel thiosemicarbazones and an aldehyde to combine with CDDP to enhance efficacy against ER-positive breast MCF7 cancer cells, triple-negative/basal-B mammary carcinoma cells (MDA-MB231) and lung adenocarcinoma (A549) human cells. We synthesized 2,3,5,6-tetrafluoro-4-(2-mercaptoetanothiolyl)benzaldehyde (ALD), 5-[(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenyl)thio]-2-furaldehyde thiosemicarbazone (TSC1) and 5-[(4-(trifluoromethyl)phenyl)thio]-2-furaldehyde thiosemicarbazone (TSC2) and used them alone or in combination with subtoxic CDDP concentrations to evaluate cytotoxicity, cytoskeleton integrity and mitochondrial function. We found that none of the synthesized compounds improved CDDP activity against MCF7 cell cultures; however, TSC2 was effective in enhancing the cytotoxicity of CDDP against MDA-MB231 and A549 cancer cell cultures. We demonstrated that the cytotoxic effect is related to the TSC2 capacity to induce disruption in the cytoskeleton network and to decrease mitochondrial function.