Synthesis and Structural Investigation of New Bio-Relevant Complexes of Lanthanides with 5-Hydroxyflavone: DNA Binding and Protein Interaction Studies

CuAAC "Click"-Derived Luminescent 2-(2-(4-(4-(Pyridin-2-yl)-1H-1,2,3-triazol-1-yl)butoxy)phenyl)benzo[d]thiazole-Based Ru(II)/Ir(III)/Re(I) Complexes as Anticancer Agents

To enhance the cytoselective behavior of the complexes, we intended to develop a CuAAC "click"-derived synthetic protocol for the preparation of 2-(2-(4-(4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl)butoxy)phenyl)benzo[d]thiazole-based Ru(II)/Ir(III)/Re(I) complexes, and their cytotoxicity against three different cancer cell lines (MCF-7, HeLa, and U87MG) in consort with one normal cell line (HEK-293) was evaluated. In our detailed investigations, the significant cytotoxic nature of the Ru(II) complex 7a compared to Ir(III) and Re(I) complexes (7b and 7c, respectively) was observed. Complex 7a was capable of MCF-7 cell apoptosis via the inhibition of both S- and G2/M-phase cell cycle arrest in association with a substantial quantity of ROS production and DNA intercalation.

Optimization of Sintering Conditions to Enhance the Dielectric Performance of Gd3+ and Ho3+ Codoped BaTiO3 Ceramics

BaTiO3 dielectric capacitors, one of the important energy storage devices, play critical roles in storing electricity from renewable energies of water, wind, solar, etc. The synthesis of BaTiO3 ceramics with weak temperature dependence and a high dielectric constant at room temperature (εRT′) is an urgent problem to meet the miniaturization and large capacity of dielectric capacitors. Doping rare earth elements into BaTiO3 can solve this problem, but it is still challenging. In this work, we adopt a synergistic strategy of increasing εRT′ and improving the temperature stability by codoping Gd3+ and Ho3+, respectively, to address this challenge. By carefully adjusting the synthesis conditions in the solid-state reaction, codoping 7% Gd3+ and 7% Ho3+ in BaTiO3 (BGTH7) ceramics were synthesized. The temperature-dependent dielectric constant reveals that the obtained optimal BGTH7 ceramic satisfies the X7U specification and displays a stable ε′ in the temperature range of −55~125 °C. The optimal BGTH7 ceramic after sintering at 1400 °C for 6 h exhibits a high dielectric constant of 5475 and low dielectric loss (tan δ) of 0.0176, hitherto exhibiting the best performance in X7U ceramics. The findings in this work are conducive to the miniaturization and stabilization of dielectric energy storage devices.

Metallophenolomics: A Novel Integrated Approach to Study Complexation of Plant Phenolics with Metal/Metalloid Ions

Plant adaptive strategies have been shaped during evolutionary development in the constant interaction with a plethora of environmental factors, including the presence of metals/metalloids in the environment. Among adaptive reactions against either the excess of trace elements or toxic doses of non-essential elements, their complexation with molecular endogenous ligands, including phenolics, has received increasing attention. Currently, the complexation of phenolics with metal(loid)s is a topic of intensive studies in different scientific fields. In spite of the numerous studies on their chelating capacity, the systemic analysis of phenolics as plant ligands has not been performed yet. Such a systematizing can be performed based on the modern approach of metallomics as an integral biometal science, which in turn has been differentiated into subgroups according to the nature of the bioligands. In this regard, the present review summarizes phenolics–metal(loid)s’ interactions using the metallomic approach. Experimental results on the chelating activity of representative compounds from different phenolic subgroups in vitro and in vivo are systematized. General properties of phenolic ligands and specific properties of anthocyanins are revealed. The novel concept of metallophenolomics is proposed, as a ligand-oriented subgroup of metallomics, which is an integrated approach to study phenolics–metal(loid)s’ complexations. The research subjects of metallophenolomics are outlined according to the methodology of metallomic studies, including mission-oriented biometal sciences (environmental sciences, food sciences and nutrition, medicine, cosmetology, coloration technologies, chemical sciences, material sciences, solar cell sciences). Metallophenolomics opens new prospects to unite multidisciplinary investigations of phenolic–metal(loid) interactions.

A Study on Repositioning Nalidixic Acid via Lanthanide Complexation: Synthesis, Characterization, Cytotoxicity and DNA/Protein Binding Studies

“Drug repositioning” is a modern strategy used to uncover new applications for out-of-date drugs. In this context, nalidixic acid, the first member of the quinolone class with limited use today, has been selected to obtain nine new metal complexes with lanthanide cations (La³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺); the experimental data suggest that the quinolone acts as a bidentate ligand, binding to the metal ion via the keto and carboxylate oxygen atoms, findings that are supported by DFT calculations. The cytotoxic activity of the complexes has been studied using the tumoral cell lines, MDA-MB-231 and LoVo, and a normal cell line, HUVEC. The most active compounds of the series display selective activity against LoVo. Their affinity for DNA and the manner of binding have been tested using UV–Vis spectroscopy and competitive binding studies; our results indicate that major and minor groove binding play a significant role in these interactions. The affinity towards serum proteins has also been evaluated, the complexes displaying higher affinity towards albumin than apotransferrin.

Impact of cationic surfactant-induced DNA compaction on the characteristics of a minor groove bound flavonol

3-Hydroxyflavone (3-HF), which binds to the minor groove of DNA, is a strong antioxidant and hence a potent therapeutic and diagnostic agent. A special photo-property, called excited state intramolecular proton transfer (ESIPT), makes the 3-HF derivatives sensitive to the cellular hydrophobic microenvironment. The present study depicts the various changes in the ESIPT of 3-HF due to cationic surfactant-induced compaction of DNA.

Rare-Earth Metal Complexes of the Antibacterial Drug Oxolinic Acid: Synthesis, Characterization, DNA/Protein Binding and Cytotoxicity Studies

"Drug repositioning" is a current trend which proved useful in the search for new applications for existing, failed, no longer in use or abandoned drugs, particularly when addressing issues such as bacterial or cancer cells resistance to current therapeutic approaches. In this context, six new complexes of the first-generation quinolone oxolinic acid with rare-earth metal cations (Y³⁺, La³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺) have been synthesized and characterized. The experimental data suggest that the quinolone acts as a bidentate ligand, binding to the metal ion via the keto and carboxylate oxygen atoms; these findings are supported by DFT (density functional theory) calculations for the Sm³⁺ complex. The cytotoxic activity of the complexes, as well as the ligand, has been studied on MDA-MB 231 (human breast adenocarcinoma), LoVo (human colon adenocarcinoma) and HUVEC (normal human umbilical vein endothelial cells) cell lines. UV-Vis spectroscopy and competitive binding studies show that the complexes display binding affinities (K_b) towards double stranded DNA in the range of 9.33 × 10⁴ - 10.72 × 10⁵. Major and minor groove-binding most likely play a significant role in the interactions of the complexes with DNA. Moreover, the complexes bind human serum albumin more avidly than apo-transferrin.

Interaction of flavonoids with serum albumin: A review

Flavonoids are plant products abundant in every day diet and claimed to be beneficial for human health. After absorption, flavonoids are transported by the serum albumin (SA), the most abundant carrier blood protein, through formation of flavonoids-SA complex. This review deals with the current state of knowledge on flavonoids-SA complex over the past 10 years, mainly involved multi-spectroscopic techniques and molecular dynamics simulation studies to explore the binding mechanism, thermodynamics and structural aspects of flavonoids binding to SA. Especially, the novel method, capillary electrophoresis, high performance affinity chromatography approach, native mass spectrometry and microscale thermophoresis used in characterization of the interaction between flavonoids and SA as well as flavonoid-based fluorescent probe for SA measurement are also included in this review.

Improving the odds of success in antitumoral drug development using scoring approaches towards heterocyclic scaffolds

One of the most commonly discussed topics in the field of drug discovery is the continuous search for anticancer therapies, in which small-molecule development plays an important role. Although a number of techniques have been established over the past decades, one of the main methods for drug discovery and development is still represented by rational, ligand-based drug design. However, the success rate of this method could be higher if not affected by cognitive bias, which renders many potential druggable scaffolds and structures overlooked. The present study aimed to counter this bias by presenting an objective overview of the most important heterocyclic structures in the development of anti-proliferative drugs. As such, the present study analyzed data for 91,438 compounds extracted from the Developmental Therapeutics Program (DTP) database provided by the National Cancer Institute. Growth inhibition data from these compounds tested on a panel of 60 cancer cell lines representing various tissue types (NCI-60 panel) was statistically interpreted using 6 generated scores assessing activity, selectivity, growth inhibition efficacy and potency of different structural scaffolds, Bemis-Murcko skeletons, chemical features and structures common among the analyzed compounds. Of the most commonly used rings, the most prominent anti-proliferative effects were produced by quinoline, tetrahydropyran, benzimidazole and pyrazole, while overall, the optimal results were produced by complex ring structures that originate from natural compounds. These results highlight the impact of certain ring structures on the anti-proliferative effects in drug design. In addition, considering that medicinal chemists usually focus their research on simpler scaffolds the majority of the time with no significant pay-off, the present study indicates several unused complex scaffolds that could be exploited when designing anticancer therapies for optimal results in the fight against cancer.

Parent and nano-encapsulated ytterbium(iii) complex toward binding with biological macromolecules, in vitro cytotoxicity, cleavage and antimicrobial activity studies

To determine the chemotherapeutic and pharmacokinetic aspects of an ytterbium complex containing 2,9-dimethyl-1,10-phenanthroline (Me₂Phen), in vitro binding studies were carried out with FS-DNA/BSA by employing multiple biophysical methods and a molecular modeling study. There are different techniques including absorption spectroscopy, fluorescence spectroscopy, circular dichroism studies, viscosity experiments (only in the case of DNA), and competitive experiments used to determine the interaction mode between DNA/BSA and the ytterbium-complex. The results showed that the Yb-complex exhibited a high propensity for the interaction of BSA and DNA via hydrophobic interactions and van der Waals forces. Further, a competitive examination and docking study showed that the interaction site of the ytterbium complex on BSA is site III. The results of docking calculations for DNA/BSA were in good agreement with experimental findings. The complex displays efficient DNA cleavage in the presence of hydrogen peroxide. Moreover, antimicrobial studies of different bacteria and fungi indicated its promising antibacterial activity. In vitro cytotoxicity studies of the Yb-complex, starch nano-encapsulated, and lipid nano-encapsulated were carried out in MCF-7 and A-549 cell lines, which revealed significantly good activity. The results of anticancer activity studies showed that the cytotoxic activity of the Yb-complex was increased when encapsulated with nanocarriers. Based on biological applications of the Yb-complex, it can be concluded that this complex and its nanocarriers can act as novel anticancer and antimicrobial candidates.

The biological applications of Yb-complexes including anticancer, antimicrobial and DNA cleavage ability, and their interaction with FS-DNA and BSA were examined.

Molecular Structure-Affinity Relationship of Flavonoids in Lotus Leaf (Nelumbo nucifera Gaertn.) on Binding to Human Serum Albumin and Bovine Serum Albumin by Spectroscopic Method

Lotus leaf has gained growing popularity as an ingredient in herbal formulations due to its various activities. As main functional components of lotus leaf, the difference in structure of flavonoids affected their binding properties and activities. In this paper, the existence of 11 flavonoids in lotus leaf extract was confirmed by High Performance Liquid Chromatography (HPLC) analysis and 11 flavonoids showed various contents in lotus leaf. The interactions between lotus leaf extract and two kinds of serum albumins (human serum albumin (HSA) and bovine serum albumin (BSA)) were investigated by spectroscopic methods. Based on the fluorescence quenching, the interactions between these flavonoids and serum albumins were further checked in detail. The relationship between the molecular properties of flavonoids and their affinities for serum albumins were analyzed and compared. The hydroxylation on 3 and 3’ position increased the affinities for serum albumins. Moreover, both of the methylation on 3’ position of quercetin and the C₂=C₃ double bond of apigenin and quercetin decreased the affinities for HSA and BSA. The glycosylation lowered the affinities for HSA and BSA depending on the type of sugar moiety. It revealed that the hydrogen bond force played an important role in binding flavonoids to HSA and BSA.