Interactions of the anti-tumor sesquiterpene hydroquinone avarol with DNA in vitro

Synthesis, Characterization, DFT Studies of Novel Cu(II), Zn(II), VO(II), Cr(III), and La(III) Chloro-Substituted Schiff Base Complexes: Aspects of Its Antimicrobial, Antioxidant, Anti-Inflammatory, and Photodegradation of Methylene Blue

A new chlorobenzylidene imine ligand, (E)-1-((5-chloro-2-hydroxybenzylidene)amino) naphthalen-2-ol (HL), and its [Zn(L)(NO₃)(H₂O)₃], [La(L)(NO₃)₂(H₂O)₂], [VO(L)(OC₂H₅)(H₂O)₂], [Cu(L)(NO₃)(H₂O)₃], and [Cr(L)(NO₃)₂(H₂O)₂], complexes were synthesized and characterized. The characterization involved elemental analysis, FT-IR, UV/Vis, NMR, mass spectra, molar conductance, and magnetic susceptibility measurements. The obtained data confirmed the octahedral geometrical structures of all metal complexes, while the [VO(L)(OC₂H₅)(H₂O)₂] complex exhibited a distorted square pyramidal structure. The complexes were found to be thermally stable based on their kinetic parameters determined using the Coats-Redfern method. The DFT/B3LYP technique was employed to calculate the optimized structures, energy gaps, and other important theoretical descriptors of the complexes. In vitro antibacterial assays were conducted to evaluate the complexes' potential against pathogenic bacteria and fungi, comparing them to the free ligand. The compounds exhibited excellent fungicidal activity against Candida albicans ATCC: 10231 (C. albicans) and Aspergillus negar ATCC: 16404 (A. negar), with inhibition zones of HL, [Zn(L)(NO₃)(H₂O)₃], and [La(L)(NO₃)₂(H₂O)₂] three times higher than that of the Nystatin antibiotic. The DNA binding affinity of the metal complexes and their ligand was investigated using UV-visible, viscosity, and gel electrophoresis methods, suggesting an intercalative binding mode. The absorption studies yielded K_b values ranging from 4.40 × 10⁵ to 7.30 × 10⁵ M^-1, indicating high binding strength to DNA comparable to ethidium bromide (value 10⁷ M^-1). Additionally, the antioxidant activity of all complexes was measured and compared to vitamin C. The anti-inflammatory efficacy of the ligand and its metal complexes was evaluated, revealing that [Cu(L)(NO₃)(H₂O)₃] exhibited the most effective activity compared to ibuprofen. Molecular docking studies were conducted to explore the binding nature and affinity of the synthesized compounds with the receptor of Candida albicans oxidoreductase/oxidoreductase INHIBITOR (PDB ID: 5V5Z). Overall, the combined findings of this work demonstrate the potential of these new compounds as efficient fungicidal and anti-inflammatory agents. Furthermore, the photocatalytic effect of the Cu(II) Schiff base complex/GO was examined.

Evaluation of genotoxic potential of tert-butylquinone and its derivatives in prokaryotic and eukaryotic test models

Tert-butylquinone (TBQ) and its alkylamino and aralkylamino derivatives are of high interest as a potential antitumor agent. Therefore, it was necessary to investigate if the compounds exert undesirable activities such as interaction with DNA molecule which could result in negative side effects in the case of their use in the diseases treatment. The major aim of this study was to investigate genotoxic potential of TBQ and selected derivatives in an acellular model by using plasmid DNA, in the prokaryotic model by the SOS/umuC assay in Salmonella typhimurium TA1535/pSK1002 and in eukaryotic models by using comet assay in human fetal lung cell line (MRC-5) and human liver cancer cell line (HepG2). Results indicated that in the acellular model TBQ and its derivatives do not interact with plasmid pUC19. In the prokaryotic model, only TBQ exerted weak genotoxic potential and only at highly cytotoxic concentrations. In eukaryotic models, genotoxic potential was detected mainly at the highest concentrations of the tested substances but the effect was lower in both cell lines in comparison with benzo[a]pyrene and etoposide which were used as positive controls. Weak genotoxic potential of tested compounds recommends them as good candidates for further testing in development of new antitumor agents.

Biological Activity of Flavonoids and Rare Sesquiterpene Lactones Isolated From Centaurea ragusina L

The endemic Croatian species Centaurea ragusina L., like other species from the genus Centaurea, has been traditionally used in Croatia as an antibacterial agent and for the treatment of gastrointestinal and urogenital disorders. In several chromatographic steps, three flavonoids and three sesquiterpene lactones (STLs) were isolated and identified from the most active fractions of the ethanol extract. Two STLs, one for which we created the trivial name ragusinin, and hemistepsin A are here reported for the first time as constituents of the genus Centaurea. All six compounds were screened for their effect on several tumor and one normal cell lines. Among them, ragusinin showed the best bioactivity and high specificity to affect tumor murine SCCVII, human HeLa and Caco-2 cell lines, but not the viability of normal V79 fibroblasts. Due to these characteristics the action of ragusinin was investigated in more detail. Since DNA is the primary target for many drugs with antibacterial and anticancer activity, we studied its interaction with ragusinin. Rather moderate binding affinity to DNA excluded it as the primary target of ragusinin. Due to the possibility of STL interaction with glutathione (GSH), the ubiquitous peptide that traps reactive compounds and other xenobiotics to prevent damage to vital proteins and nucleic acids, its role in deactivation of ragusinin was evaluated. Addition of the GSH precursor N-acetyl-cysteine potentiated the viability of HeLa cells, while the addition of GSH inhibitor L-buthionine sulfoximine decreased it. Moreover, pre-treatment of HeLa cells with the inhibitor of glutathione-S-transferase decreased their viability indicating the detoxifying role of GSH in ragusinin treated cells. Cell death, derived by an accumulation of cells in a G2 phase of the cell cylce, was shown to be independent of poly (ADP-ribose) polymerase and caspase-3 cleavage pointing toward an alternative cell death pathway.

Some new nano-sized Cr(III), Fe(II), Co(II), and Ni(II) complexes incorporating 2-((E)-(pyridine-2-ylimino)methyl)napthalen-1-ol ligand: Structural characterization, electrochemical, antioxidant, antimicrobial, antiviral assessment and DNA interaction

To estimate the biological preference of synthetic small drugs towards DNA target, new metal based chemotherapeutic agents of nano-sized Cr(III), Fe(II), Co(II) and Ni(II) Schiff base complexes having N,N,O donor system were synthesized and thoroughly characterized by physic-chemical techniques. The redox behavior of the Cr(III), Fe(II) and Co(II) complex was investigated by electrochemical method using cyclic voltammetry. IR results proven that the tridentate binding of Schiff base ligand with metal center during complexation reflects the proposed structure. Magnetic and spectroscopic data give support to octahedral geometry for Cr(III) and Fe(II) complexes and tetrahedral geometry for Ni(II) and Co(II) complexes. The activation thermodynamic parameters, such as, E(⁎), ΔH(⁎), ΔS(⁎) and ΔG(⁎) are calculated using Coats-Redfern method by analyzing the TGA data. The particle size of the investigated metal complexes was estimated by TEM. In addition to, the interaction of the nanosized complexes with CT-DNA was estimated by electronic absorption, viscosity and gel electrophoresis. These techniques revealed that the complexes could bind to CT-DNA through intercalation mode. Moreover, the in vitro cytotoxic and antiviral activities of the nanosized complexes were checked against Herpes Simplex virus and Tobacco Mosaic viruses. Moreover, investigation of antioxidant activities of the new nanosized compounds was done by ABTS assay. Among the compounds tested, Fe(II) complex showed the strongest potent radical scavenging activity with percent of 58.60%. Furthermore, the antimicrobial bustle of the prepared compounds was screened against different types of bacteria and fungi and the results show that all metal complexes have superior activity than its free ligand.

Metal based pharmacologically active agents: synthesis, structural characterization, molecular modeling, CT-DNA binding studies and in vitro antimicrobial screening of iron(II) bromosalicylidene amino acid chelates

In recent years, great interest has been focused on Fe(II) Schiff base amino acid complexes as cytotoxic and antitumor drugs. Thus a series of new iron(II) complexes based on Schiff bases amino acids ligands have been designed and synthesized from condensation of 5-bromosalicylaldehyde (bs) and α-amino acids (L-alanine (ala), L-phenylalanine (phala), L-aspartic acid (aspa), L-histidine (his) and L-arginine (arg)). The structure of the investigated iron(II) complexes was elucidated using elemental analyses, infrared, ultraviolet-visible, thermogravimetric analysis, as well as conductivity and magnetic susceptibility measurements. Moreover, the stoichiometry and the stability constants of the prepared complexes have been determined spectrophotometrically. The results suggest that 5-bromosalicylaldehyde amino acid Schiff bases (bs:aa) behave as dibasic tridentate ONO ligands and coordinate to Fe(II) in octahedral geometry according to the general formula [Fe(bs:aa)2]·nH2O. The conductivity values between 37 and 64 ohm(-1) mol(-1) cm(2) in ethanol imply the presence of nonelectrolyte species. The structure of the complexes was validated using quantum mechanics calculations based on accurate DFT methods. Geometry optimization of the Fe-Schiff base amino acid complexes showed that all complexes had octahedral coordination. In addition, the interaction of these complexes with (CT-DNA) was investigated at pH=7.2, by using UV-vis absorption, viscosity and agarose gel electrophoresis measurements. Results indicated that the investigated complexes strongly bind to calf thymus DNA via intercalative mode and showed a different DNA binding according to the sequence: bsari>bshi>bsali>bsasi>bsphali. Moreover, the prepared compounds are screened for their in vitro antibacterial and antifungal activity against three types of bacteria, Escherichia coli, Pseudomonas aeruginosa and Bacillus cereus and three types of anti fungal cultures, Penicillium purpurogenium, Aspergillus flavus and Trichotheium rosium. The results of these studies indicated that the metal complexes exhibit a stronger antibacterial and antifungal efficiency than their corresponding Schiff base amino acid ligands.

Synthesis and biological activity of derivatives of the marine quinone avarone

Nine alkyl(aryl)thio derivatives of the marine sesquiterpene quinone avarone were synthesized by nucleophilic addition of thiols or thiophenol to avarone. In most cases only one regioisomer was obtained. Their cytotoxic activities, brine shrimp lethality and antibacterial activity were evaluated, as well as those of some previously synthesized avarone derivatives. Anti-HIV activity of two derivatives was tested. Electrochemical properties were determined for all the derivatives in order to obtain more accurate information on structure-activity relationships. Most derivatives showed cytotoxic activity against tumor cell lines, with IC(50) values less than 10 microM for some of them, in particular those with electron-donating substituents. The most active compound was 4'-(methylamino)avarone, with IC(50) value of 2.4 microM to melanoma Fem-X cells, and no cytotoxicity to normal lymphocytes.

Natural sesquiterpenoids

This review covers the isolation, structural determination, synthesis and chemical and microbiological transformations of natural sesquiterpenoids. 423 references are cited.