Bovine serum albumin binding, antioxidant and anticancer properties of an oxidovanadium(IV) complex with luteolin

Optimized Chitosan-Based Nanoemulsion Improves Luteolin Release

Luteolin (LUT) is a flavonoid found in several edible and medicinal plants. It is recognized for its biological activities such as antioxidant, anti-inflammatory, neuroprotective, and antitumor effects. However, the limited water solubility of LUT leads to poor absorption after oral administration. Nanoencapsulation may improve the solubility of LUT. Nanoemulsions (NE) were selected for the encapsulation of LUT due to their biodegradability, stability, and ability to control drug release. In this work, chitosan (Ch)-based NE was developed to encapsulate luteolin (NECh-LUT). A 2³ factorial design was built to obtain a formulation with optimized amounts of oil, water, and surfactants. NECh-LUT showed a mean diameter of 67.5 nm, polydispersity index 0.174, zeta potential of +12.8 mV, and encapsulation efficiency of 85.49%. Transmission electron microscopy revealed spherical shape and rheological analysis verified the Newtonian behavior of NECh-LUT. SAXS technique confirmed the bimodal characteristic of NECh-LUT, while stability analysis confirmed NECh-LUT stability when stored at room temperature for up to 30 days. Finally, in vitro release studies showed LUT controlled release up to 72 h, indicating the promising potential of NECh-LUT to be used as novel therapeutic option to treat several disorders.

Recent updates on anticancer mechanisms of polyphenols

In today’s scenario, when cancer cases are increasing rapidly, anticancer herbal compounds become imperative. Studies on the molecular mechanisms of action of polyphenols published in specialized databases such as Web of Science, Pubmed/Medline, Google Scholar, and Science Direct were used as sources of information for this review. Natural polyphenols provide established efficacy against chemically induced tumor growth with fewer side effects. They can sensitize cells to various therapies and increase the effectiveness of biotherapy. Further pharmacological translational research and clinical trials are needed to evaluate theirs in vivo efficacy, possible side effects and toxicity. Polyphenols can be used to design a potential treatment in conjunction with existing cancer drug regimens such as chemotherapy and radiotherapy.

Double-Site Binding and Anti-/Pro-oxidation of Luteolin on Bovine Serum Albumin Mediated by Copper(II) Coordination

The interactions of luteolin (Lut) with bovine serum albumin (BSA) mediated by Cu(II) were investigated by spectroscopic, calorimetric, and molecular dynamic (MD) methods. Fluorescence studies showed that the binding of Lut to BSA was significantly enhanced by Cu(II) coordination with the number of binding sites and binding constant increasing from n = 1 and K _a = 3.2 × 10⁵ L·mol^-1 for Lut to n = 2 and K _a = 7.1 × 10⁵ L·mol^-1 for a 1:1 Cu(II)-luteolin complex, in agreement with the results from isothermal titration calorimetry (ITC). Site-specific experiments with warfarin and ibuprofen and MD confirmed that two binding sites of BSA were sequentially occupied by two Cu(II)-luteolin complexes. Cu(II) coordination increased the antioxidant activity of luteolin by 60% in the inhibition of carbonyl formation from the oxidation of amino groups in the side chain of BSA induced by the peroxyl radical ROO^•; however, it counteracted the antioxidant effects of luteolin and played pro-oxidative roles in BSA aggregation induced by ^•OH.

Antioxidant and Anticancer Activities and Protein Interaction of the Oxidovanadium(IV) Naringin Complex

The complex of oxidovanadium(IV) with naringin (Narg) [VO(Narg)2] 8H2O (VONarg) was prepared according to the literature improving the synthetic procedure and physicochemical characterization. In addition, biological activities (cytotoxic, antioxidant, and BSA interaction) were determined. The metal coordinated through the 5-hydroxy and 4-carbonyl groups of rings A and C of naringin, respectively. The antioxidant activity of VONarg, determined in vitro, was higher than those of the flavonoid against superoxide and peroxyl reactive oxygen species (ROS) and DPPH radical. The cytotoxic properties were determined by a MTT assay on adenocarcinoma human alveolar basal epithelial cells (A549). VONarg exerted a 20% decrease in cancer cells viability at 24 h incubation, while naringin and oxidovanadium(IV) cation did not show cytotoxicity. Measurements with the normal HEK293 cell line showed that the inhibitory action of the complex is selective. VONarg generated intracellular reactive oxygen species (ROS), depletion of reduced glutathione and depolarization of mitochondrial membrane potential, typical for apoptotic pathway, producing cell death by oxidative stress mechanism. Moreover, naringin interacted with bovine serum albumin (BSA) through hydrophobic interactions in a spontaneous process, and VONarg showed greater affinity for the protein but can still be transported and delivered by it (Ka 104 L·mol−1 order).

Study on the cytotoxic, antimetastatic and albumin binding properties of the oxidovanadium(IV) chrysin complex. Structural elucidation by computational methodologies

We have previously synthesized and characterized the chrysin coordination complex with the oxidovanadium(IV) cation (V^IVO(chrys)₂) and characterized in ethanolic solution and in solid state. Because suitable single crystals for X-ray diffraction determinations could not be obtained, in the present work, we elucidate the geometrical parameters of this complex by computational methodologies. The optimization and vibrational investigation were carried out both in ethanolic solution and in gas phase. The computational results support the experimentally proposed geometries of the V^IVO(chrys)₂ complex, thus leading to the conclusion that the complex exists as conformers with trans-octahedral geometry in ethanolic solution and as conformers with cis-octahedral geometry in the solid state. The complex also exists as conformers with trans-octahedral geometry in aqueous media. The active species formed after dissolution in DMSO showed anticancer and antimetastatic behavior in human lung cell line A549 with moderate binding (K_aca. 10⁵ M^-1) to bovine serum albumin (BSA). The interaction through hydrogen bonding and van der Waals forces resulted in a spontaneous process. Site marker competitive experiments showed binding sites for chrysin mainly located in site II (subdomain IIIA) and in site I (subdomain IIIA) for the complex. FT-IR spectral measurements showed evidences of the alterations of protein secondary structure in the presence of chrysin and V^IVO(chrys)₂.

The effect of Luteolin on DNA damage mediated by a copper catalyzed Fenton reaction

Luteolin has been reviewed as a flavonoid possessing potential cardioprotective, anti-inflammatory, anti-cancer activities. Having multiple biological effects, luteolin may act as either an antioxidant or a pro-oxidant. In this work, the protective role of copper(II)-chelation by luteolin on DNA damage via the Cu-Fenton reaction was studied. EPR and UV-vis spectroscopic data demonstrated that the luteolin, lacking 3-OH group, chelates to Cu(II) via the 5-OH and 4-CO groups, respectively. EPR spin trapping experiments using DMPO spin trap confirmed that the coordination of luteolin to Cu(II) significantly suppressed formation of hydroxyl and superoxide radicals (by 80%) in a Cu-Fenton system. Absorption titrations showed that the chelation of Cu(II) by luteolin slightly increased the mild intercalation strength of its interaction with DNA, as compared with free luteolin. Comparison with kaempferol and quercetin revealed, that the strength of the interaction between the free flavonoids/Cu-flavonoid complexes with DNA is only mildly affected by the presence/absence of 3-OH group. Due to the differences in the sensitivities of absorption titrations and viscometry, the latter confirmed weaker DNA intercalating efficiency of Cu-luteolin complex than does free luteolin. A dose dependent protective effect of luteolin against ROS-induced DNA damage was observed using gel electrophoresis. This effect was more pronounced compared to quercetin and kaempferol. In conclusion, the administration of luteolin to patients suffering from oxidative stress-related diseases with disturbed Cu-metabolism such as Alzheimer's diseases (antioxidant effect) and certain cancers (prooxidant effect) may have several health benefits.

Anticancer Activity of Half-Sandwich Ru, Rh and Ir Complexes with Chrysin Derived Ligands: Strong Effect of the Side Chain in the Ligand and Influence of the Metal

An important challenge in the field of anticancer chemotherapy is the search for new species to overcome the resistance of standard drugs. An interesting approach is to link bioactive ligands to metal fragments. In this work, we have synthesized a set of p-cymene-Ru or cyclopentadienyl-M (M = Rh, Ir) complexes with four chrysin-derived pro-ligands with different -OR substituents at position 7 of ring A. The introduction of a piperidine ring on chrysin led to the highly cytotoxic pro-ligand HL4 and its metal complexes L4-M (SW480 and A549 cell lines, cytotoxic order: L4-Ir > L4-Ru ≈ L4-Rh). HL4 and its complexes induce apoptosis and can overcome cis-platinum resistance. However, HL4 turns out to be more cytotoxic in healthy than in tumor cells in contrast to its metal complexes which displayed higher selectivity than cisplatin towards cancer cells. All L4-M complexes interact with double stranded DNA. Nonetheless, the influence of the metal is clear because only complex L4-Ir causes DNA cleavage, through the generation of highly reactive oxygen species (1O2). This result supports the hypothesis of a potential dual mechanism consisting of two different chemical pathways: DNA binding and ROS generation. This behavior provides this complex with a great effectivity in terms of cytotoxicity.

Vanadium-Flavonoid Complexes: A Promising Class of Molecules for Therapeutic Applications

Several reports have revealed the superior biological activity of metal ion-flavonoid complexes when compared with the parent flavonoid. Among the different metal ions explored, vanadium and its compounds are in the forefront because of their anticancer and antidiabetic properties. However, the toxicity of vanadium-based ions and their inorganic derivatives limits their therapeutic applications. Complexation of vanadium with flavonoids not only reduces its adverse effects but also augments its biological activity. This Review discusses the nature of coordination in vanadium-flavonoid complexes, their structure-activity correlations, with special emphasis on their therapeutic activities. Several investigations suggest that the superior biological activity of vanadium complexes arise because of their ability to regulate metabolic pathways distinct from those acted upon by vanadium alone. These studies serve to decipher the underlying molecular mechanism of vanadium-flavonoid complexes that can be explored further for generating a series of novel compounds with improved pharmacological and therapeutic performance.

Characterization and Quantification of Luteolin-Metal Complexes in Aqueous Extract of Lonicerae Japonicae Flos and Huangshan Wild Chrysanthemum

Luteolin is a flavonoid compound widely found in vegetables, fruits, and medicinal plants. In this study, the reaction conditions for luteolin and five metal ions (Ca²⁺, Mg²⁺, Zn²⁺, Fe³⁺, and Cu²⁺) to form complexes in hot water were optimized, which was at a molar ratio of 1 : 1 for luteolin and metal ions at 90°C in a volume of 20 mL for 2 h, and the ability of luteolin to form complexes with Cu²⁺ was the strongest. The DPPH scavenging test showed that luteolin exerted a dose-dependent effect on the clearance of free radicals; luteolin-Cu²⁺ complexes and luteolin-Fe³⁺ complexes accentuated the clearance of free radicals. Furthermore, we used high performance liquid chromatography (HPLC) to analyze luteolin in samples from two medicinal plants, obtained from the dissolution of aqueous extracts in two different solvents. The results showed that the peak areas for luteolin in the samples dissolved in 20% formic acid-methanol were significantly larger than those from the samples dissolved in methanol alone, with increases in the peak area being 135.6% (Lonicerae Japonicae Flos), and 161.16% (Huangshan wild chrysanthemum). The aforementioned results indicate that complexes formed from organic compounds and metal ions are present in the decoction of a plant.

Antimetastatic effects of VOflavonoid complexes on A549 cell line

BACKGROUND

Non-small-cell lung cancer (NSCLC) is the most frequent type of lung cancer and more than 90 % of mortality is due to metastasis-related deaths. Flavonoids are considered nutraceuticals due to the variety of pharmacological properties. In this paper, we studied the effects of baicalin, silibinin, apigenin, luteolin, and its oxidovanadium(IV) cation complexes on the viability, adhesion to fibronectin, invasion, and migration on human lung cancer cell line A549. In addition, in order to complete the study of the interaction of VOflavonoids and bovine serum albumin (BSA), the binding ability of silibinin and VOsil to the protein was evaluated.

METHOD

To establish the non-cytotoxic concentration range of the tested compounds, the cancer cell viability was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Cell migration and invasion assays were performed using Boyden chambers and adhesion assay using MTT method. The interaction of compounds with BSA were investigated in physiological buffer (pH = 7.4) by fluorescence spectroscopy.

RESULTS

All complexes inhibited the metastatic cascade steps to a greater extent than their respective ligands. Likewise, based on binding constant values (K_b) for BSA-silibinin and BSA-VOsil, we can suggest that both compounds can interact with the protein.

CONCLUSION

Although all the complexes suppressed cell adhesion, invasion and migration, VOlut can be considered as a good candidate to continue the trials because it presented encouraging results as a potential antitumor and antimetastatic agent, and can be transported by BSA.

Bioavailability and Pharmaco-therapeutic Potential of Luteolin in Overcoming Alzheimer's Disease

Luteolin is a naturally occurring, yellow crystalline flavonoid found in numerous dietary supplements we frequently have in our meals. Studies in the last 2 decades have revealed its therapeutic potential to reduce the Alzheimer's disease (AD) symptoms in various in vitro and in vivo models. The anti-Alzheimer's potential of luteolin is attributed to its ability to suppress Aβ as well as tau aggregation or promote their disaggregation, down-regulate the expression of COX-2, NOS, MMP-9, TNF-α, interleukins and chemokines, reduce oxidative stress by scavenging ROS, modulate the activities of transcription factors CREB, cJun, Nrf-1, NF-κB, p38, p53, AP-1 and β-catenine and inhibiting the activities of various protein kinases. In several systems, luteolin has been described as a potent antioxidant and anti-inflammatory agent. In addition, we have also discussed about the bio-availability of the luteolin in the plasma. After being metabolized luteolin persists in plasma as glucuronides and sulphate-conjugates. Human clinical trials indicated no dose limiting toxicity when administered at a dose of 100 mg/day. Improvements in the formulations and drug delivery systems may further enhance the bioavailability and potency of luteolin. The current review describes in detail the data supporting these studies.

Synthesis, characterization, and biological properties of oxidovanadium(IV) complexes of acetylsalicylhydroxamic acid (N-acetyloxy-2-hydroxybenzamide) as potential antimicrobials

New oxidovanadium(IV) complexes of composition [VO(AcSHA)2] 1 and [VO(acac)(AcSHA)] 2 are synthesized by reactions of VOSO4.5H2O and [VO(acac)2] with acetylsalicylhydroxamic acid AcSH2A (C6H4(OH)(CONHOCOCH3)) in a 1:2 molar ratio in absolute ethanol. The compounds are characterized by the Fourier-transform infrared spectroscopy, ultraviolet–visible spectroscopy, electron spin resonance, and mass spectrometry along with elemental analyses, molar conductivity, and magnetic moment measurements. The infrared spectra of the complexes suggest bonding through carbonyl and phenolic oxygen atoms (O,O coordination). The magnetic moment, electron spin resonance, and mass spectra of the complexes indicate that both exist as monomers, and a distorted square pyramidal geometry around vanadium is proposed. The thermal behavior of the complexes is studied by thermogravimetry and differential thermal analysis techniques under an N2 atmosphere, yielding VO2 as the decomposition product. The in vitro antimicrobial assays against pathogenic Gram-positive bacteria, Gram-negative bacteria, and fungi (minimum inhibitory concentration method) show the appreciable antimicrobial potential relative to the respective standard drugs, tetracycline hydrochloride, and fluconazole.

Ameliorating effect of troxerutin in unilateral ureteral obstruction induced renal oxidative stress, inflammation, and apoptosis in male rats

Unilateral ureteral obstruction (UUO) induces renal injury and troxerutin attenuates the inflammatory parameters and decreases oxidative stress. Accordingly, this study explored the renoprotective effect of troxerutin in UUO-induced renal oxidative stress, inflammation, and apoptosis in male Wistar rats. Animals were randomly separated into five groups (n = 8): control, UUO, and three UUO groups treated with troxerutin (1, 10, and 100 mg/kg). UUO-induced and vehicle/troxerutin administration was continued for 3 days. Then serum creatinine, mean arterial pressure (MAP), renal perfusion pressure (RPP), renal vascular resistance (RVR), and renal blood flow (RBF) were measured. Superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase activities, total antioxidant capacity (TAC), and malondialdehyde (MDA) levels as some oxidative stress parameters were measured in the left kidney. The immunoblotting method was applied to evaluate the cleaved caspase-3 Bax, Bcl-2, and TNF-α proteins level. The hematoxylin and eosin method was used to assess the kidney tissue damage score (KTDS). In 3 days, UUO significantly increased serum creatinine level, KTDS, RVR, MDA, Bax, cleaved caspase-3, and TNF-α protein levels (p < 0.05); and decreased RBF, TAC, SOD, catalase, GPx activity levels and Bcl-2 protein expression level in the left kidney (p < 0.05). Troxerutin (100 mg/kg) significantly attenuates the indicators alteration induced by UUO. Our findings represented that the renoprotective effect of troxerutin may be related to its anti-oxidative stress, anti-inflammation, anti-apoptosis, and RBF improver properties.

Synthesis, Characterisation, and Biological Properties of Oxidovanadium(IV) 3,5-Dinitrosalicylhydroxamate Complexes

The new oxidovanadium(iv) complexes of composition [VO(3,5(NO2)2C6H2(OH)CONHO)2] 1 and [VO(acac)(3,5(NO2)2C6H2(OH)CONHO)] 2 (where acac=(CH3COCHCOCH3)–] have been synthesised by the reactions of VOSO4·5H2O and [VO(acac)2] with potassium 3,5-dinitrosalicylhydroxamate (3,5-(NO2)2SHK) and characterised by elemental analyses, molar conductivity, magnetic moment measurements and FT-IR, UV-vis, and electron spin resonance (ESR) spectroscopies and mass spectrometry. Infrared spectra of complexes have indicated bonding through oxygen atoms of carbonyl and hydroxamic groups (O,O coordination). The magnetic moment, ESR, and mass spectra of the complexes suggested their monomeric nature, and a distorted square-pyramidal geometry around the vanadium has tentatively been proposed. The electrochemical behaviour of 1 and 2 has been studied by cyclic voltammetry. Thermal behaviour of the complexes studied by thermogravimetric and differential thermal analysis techniques has yielded VO2 as the decomposition product. The invitro antimicrobial activity of the ligand and complexes has been assayed against pathogenic bacteria and fungi by the minimum inhibitory concentration (MIC) method. The invitro antioxidant activity of the complexes has been determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging method.

Ternary copper(II) complex of 5-hydroxytryptophan and 1,10-phenanthroline with several pharmacological properties and an adequate safety profile

We report the synthesis and biological evaluation of a ternary copper complex, [Cu(5HTP)(phen)(H₂O)](NO₃).2H₂O, with the antioxidant agent 5-hydroxytryptophan (5-HTP) and phenanthroline (phen, added to improve its lipophilicity and membrane transport). The crystal structure of the complex was determined by X-ray diffraction methods. The complex showed antioxidant, antimicrobial, antitumor and antimetastatic properties with an adequate safety profile. The interaction of the metal with phen promotes cellular copper accumulation and cytotoxicity on human lung A549 cell line (IC₅₀ = 3.6 μM). Furthermore, the viability of the normal human fetal lung fibroblast cell line (MRC-5) is not altered by the complex. An oxidative stress mechanism for the anticancer effect has been determined: cellular increase of reactive oxygen species (ROS), decrease of the glutathione (GSH) and oxidized GSH (GSSG) ratio and alteration of the mitochondrial potential. The complex also displays antimetastatic activities with inhibition of cell adhesion, invasion and migration. It has not mutagenic behavior and no toxicity on Artemia salina indicating its potential to act as an effective and safety antimicrobial and antitumor drug.

Metal complexes of flavonoids: their synthesis, characterization and enhanced antioxidant and anticancer activities

Flavonoids are polyphenolic compounds of natural origin. They are extensively studied within drug discovery programs due to their wide ranging biological activities such as antimicrobial, antioxidant, antitumor, neuroprotective and cardioprotective properties. The ability of flavonoids to coordinate with metal atoms has provided new leads for drug discovery programs, with better pharmacological activities and clinical profiles than the parent flavonoids. In this review, the enhanced antioxidant and anticancer activities of flavonoid metal complexes versus the parent flavonoids are discussed. Possible mechanisms of action for the metal complexes, such as DNA binding and apoptosis induction, are also presented alongside an overview of the synthesis of the metal complexes, and the different techniques used for their characterization.

Vanadium Compounds as Enzyme Inhibitors with a Focus on Anticancer Effects

Vanadium salts and coordination compounds have desirable cellular anticancer effects, and although they have been investigated in detail as a potential treatment for diabetes, less attention has been given to the anticancer effects. The inhibition of some signal transduction enzymes is known, and studies of the metabolism and activation pathways both in vitro and in vivo are important for future investigations and development of vanadium's role as a new potential drug. In addition, a new approach has demonstrated that the enhancement of oncolytic viruses using vanadium salts and coordination complexes for immunotherapy is very promising. Some differences exist between this approach and current antidiabetic and anticancer studies because vanadium(iv) complexes have been found to be most potent in the latter approach, but the few compounds investigated with oncolytic viruses show that vanadium(v) systems are more effective. We conclude that recent studies demonstrate effects on signal transduction enzymes and anticancer pathways, thus suggesting potential applications of vanadium as anticancer agents in the future both as standalone treatments as well as combination therapies.

Vanadium in Biological Action: Chemical, Pharmacological Aspects, and Metabolic Implications in Diabetes Mellitus

Vanadium compounds have been primarily investigated as potential therapeutic agents for the treatment of various major health issues, including cancer, atherosclerosis, and diabetes. The translation of vanadium-based compounds into clinical trials and ultimately into disease treatments remains hampered by the absence of a basic pharmacological and metabolic comprehension of such compounds. In this review, we examine the development of vanadium-containing compounds in biological systems regarding the role of the physiological environment, dosage, intracellular interactions, metabolic transformations, modulation of signaling pathways, toxicology, and transport and tissue distribution as well as therapeutic implications. From our point of view, the toxicological and pharmacological aspects in animal models and humans are not understood completely, and thus, we introduced them in a physiological environment and dosage context. Different transport proteins in blood plasma and mechanistic transport determinants are discussed. Furthermore, an overview of different vanadium species and the role of physiological factors (i.e., pH, redox conditions, concentration, and so on) are considered. Mechanistic specifications about different signaling pathways are discussed, particularly the phosphatases and kinases that are modulated dynamically by vanadium compounds because until now, the focus only has been on protein tyrosine phosphatase 1B as a vanadium target. Particular emphasis is laid on the therapeutic ability of vanadium-based compounds and their role for the treatment of diabetes mellitus, specifically on that of vanadate- and polioxovanadate-containing compounds. We aim at shedding light on the prevailing gaps between primary scientific data and information from animal models and human studies.

Complexation of luteolin with lead (II): Spectroscopy characterization and theoretical researches

The interactions of (CH₃COO)₂Pb·3H₂O (lead acetate trihydrate) with luteolin, 5,7,3',4'-tetrahydroxyflavone, were investigated in methanol solution. The spectroscopy (UV-Vis, FT-IR, HPLC-MS, ¹H NMR) and elemental analysis were adopted to assess the interaction of luteolin and Pb(II). The results show that luteolin reacts with Pb(II) through the chelating sites of 4‑carbonyl and 5-hydroxy in two luteolin molecules. The structures, energies, CDA (charge decomposition analysis) and orbitals analysis of the ligand and complex have been analyzed according to quantum-chemical calculation, which is further proofed that luteolin molecule can effectively chelate Pb(II) by 5-hydroxyl-4-oxo chelating site. It is speculated that luteolin has a high potential of becoming a health care product to eliminate lead cation in the future.

Interactions of rutin with the oxidovanadium(iv) cation. Anticancer improvement effects of glycosylated flavonoids

This work reports the biological evaluation of the new complex Na₂[VO(rut)(OH)₂]·5H₂O (rut = rutin, a glycosylated flavonoid).

Metal Complexes of Natural Product Like-compounds with Antitumor Activity

Cancer continues to be one of the major causes of death worldwide. Despite many advances in the understanding of this complex disease, new approaches are needed to improve the efficacy of current therapeutic treatments against aggressive tumors. Natural products are one of the most consistently successful sources of drug leads. In recent decades, research activity into the clinical potential of this class of compounds in cancer has increased. Furthermore, a highly promising field is the use of metals and their complexes in the design and development of metal-based drugs for the treatment of cancer. Metal complexes offer unique opportunities due to their ability to alter pharmacology, improving the efficacy and/or reducing the negative side effects of drug molecules. In addition, transition metals as copper, iron, and manganese, among others, can interact with active sites of enzymes, playing important roles in multiple biological processes. Thus, these complexes not only possess higher activities but also reach their targets more efficiently. This review article highlights recent advances on the emerging and expanding field of metal-based drugs. The emphasis is on new therapeutic strategies consisting of metal complexes with natural product like-compounds as a starting point for the rational design of new antitumor agents.

Designing metallodrugs with nuclease and protease activity

The accidental discovery of cisplatin some 50 years ago generated renewed interest in metallopharmaceuticals. Beyond cisplatin, many useful metallodrugs have been synthesized for the diagnosis and treatment of various diseases, but toxicity concerns, and the propensity to induce chemoresistance and secondary cancers make it imperative to search for novel metallodrugs that address these limitations. The Amino Terminal Cu(ii) and Ni(ii) (ATCUN) binding motif has emerged as a suitable template to design catalytic metallodrugs with nuclease and protease activities. Unlike their classical counterparts, ATCUN-based metallodrugs exhibit low toxicity, employ novel mechanisms to irreversibly inactivate disease-associated genes or proteins providing in principle, a channel to circumvent the rapid emergence of chemoresistance. The ATCUN motif thus presents novel strategies for the treatment of many diseases including cancers, HIV and infections caused by drug-resistant bacteria at the genetic level. This review discusses their design, mechanisms of action and potential for further development to expand their scope of application.

Bioactivity In Vitro of Quercetin Glycoside Obtained in Beauveria bassiana Culture and Its Interaction with Liposome Membranes

Quercetin (Q) was used as substrate for regioselective glycosylation at the C-7 position catalyzed by Beauveria bassiana AM278 strain. As a result the glycoside quercetin 7-O-β-d-(4″-O-methyl)glucopyranoside (Q 7-MeGlu) was formed. The goal of the studies was to determine the anti-oxidative (liposome membrane protection against free radicals IC₅₀^{Q 7-MeGlu} = 5.47 and IC₅₀^Q = 4.49 µM) and anti-inflammatory (COX-1 and COX-2 enzymes activity inhibition) properties of Q 7-MeGlu as compared to Q. Every attempt was made to clarify the antioxidant activity of these molecules, which are able to interact with egg phosphatidylcholine liposomes, using a fluorometric method (by applying the probes MC540, TMA-DPH and DPH). The results indicated that Q 7-MeGlu and Q are responsible for increasing the packing order, mainly in the hydrophilic but also in hydrophobic regions of the membrane (Q > Q 7-MeGlu). These observations, confirmed by a ¹H-NMR method, are key to understanding their antioxidant activity which is probably caused by the stabilizing effect on the lipid membranes. The results showed that Q 7-MeGlu and Q have ability to quench the human serum albumin (HSA) intrinsic fluorescence through a static quenching mechanism. The results of thermodynamic parameters indicated that the process of formation complexes between studied molecules and HSA was spontaneous and caused through Van der Waals interactions and hydrogen bonding.

Stabilities and Biological Activities of Vanadium Drugs: What is the Nature of the Active Species?

Diverse biological activities of vanadium(V) drugs mainly arise from their abilities to inhibit phosphatase enzymes and to alter cell signaling. Initial interest focused on anti-diabetic activities but has shifted to anti-cancer and anti-parasitic drugs. V-based anti-diabetics are pro-drugs that release active components (e.g., H₂ VO₄^- ) in biological media. By contrast, V anti-cancer drugs are generally assumed to enter cells intact; however, speciation studies indicate that nearly all drugs are likely to react in cell culture media during in vitro assays and the same would apply in vivo. The biological activities are due to V^V and/or V^IV reaction products with cell culture media, or the release of ligands (e.g., aromatic diimines, 8-hydroxyquinolines or thiosemicarbazones) that bind to essential metal ions in the media. Careful consideration of the stability and speciation of V complexes in cell culture media and in biological fluids is essential to design targeted V-based anti-cancer therapies.

Enhanced antioxidant activity, antibacterial activity and hypoglycemic effect of luteolin by complexation with manganese(ii) and its inhibition kinetics on xanthine oxidase

A coordination compound with enhanced biological activities was synthesized with luteolin and manganese(ii) cation. The inhibition effect assay found that the complex reversibly inhibited xanthine oxidase in a competitive manner.

Antioxidant and anticancer effects and bioavailability studies of the flavonoid baicalin and its oxidovanadium(IV) complex

Based on the known antioxidant effect of flavonoids, baicalin (baic) found in roots of Scutellaria has been selected. Its coordination complex with the oxidovanadium(IV) cation, Na₄[VO(baic)₂].6H₂O (V^IVO(baic)), was synthesized at pH9 in ethanol and characterized by physicochemical methods. Spectrophotometric studies at pH9 showed a ligand: metal stoichiometry of 2:1. By vibrational spectroscopy a coordination mode through the cis 5-OH and 6-OH deprotonated groups is inferred. EPR spectroscopy shows an environment of four aryloxide (ArO^-) groups in the equatorial plane of the VO moiety, both in solution and in the solid complex. The antioxidant capacity against superoxide and peroxyl radicals of V^IVO(baic) resulted greater than for baicalin and correlated with previous results obtained for other VOflavonoid complexes. The coordination mode produces delocalization of the electron density and the stabilization of the radical formed by interaction with external radicals. The complex and the ligand displayed no toxic (Artemia salina test) and no mutagenic (Ames test) effects. The complex improved the ability of the ligand to reduce cell viability of human lung cancer cell lines (A549) generating reactive oxygen species (ROS) in cells, being this effect reversed by pre-incubation of the cells with antioxidants such as vitamins C and E. The addition of NAC (N-acetyl-l-cysteine, a sequestering agent of free radicals) suppresses the anticancer effect, confirming the oxidative stress mechanism. The complex interacted with bovine serum albumin (BSA) with stronger binding than baicalin and the mechanisms involved H bonding and van der Waals interactions.

Inhibition of the metastatic progression of breast and colorectal cancer in vitro and in vivo in murine model by the oxidovanadium(IV) complex with luteolin

The anticancer and antimetastatic behavior of the flavonoid luteolin and its oxidovanadium(IV) complex [VO(lut)(H₂O)₂]Na·3H₂O (VOlut) has been investigated. Considering that the complex displayed strong anticancer activity on MDAMB231 human breast cancer cell line we herein determined through in vitro assays that the complex would probably reduce breast cancer cell metastasis in a higher extent than the natural antioxidant. In the CT26 colon cancer cell line a stronger anticancer effect has also been determined for the complex (IC₅₀ 0.9μM) and in addition it did not exert toxic effects on normal colon epithelial cells at concentrations up to 10μM. Working with a murine model of highly aggressive, orthotopic colon cancer model (CT26 cancer cell lines) it has been determined that the complex might prevent metastatic dissemination of the colon cancer cells to the liver. The flavonoid luteolin also exerted anticancer effects (at a low degree, IC₅₀ 5.9μM) on CT26 cell line and produced a 24% reduction of colon cancer liver metastasis.

Effect of oleuropein against chemotherapy drug-induced histological changes, oxidative stress, and DNA damages in rat kidney injury

Cisplatin-based chemotherapy is responsible for a large number of renal failures, and it is still associated with high rates of mortality today. Oleuropein (OLE) presents a plethora of pharmacological beneficial properties. In this study we investigated whether OLE could provide sufficient protection against cisplatin-induced nephrotoxicity. With this aim, Sprague-Dawley rats were divided into eight groups: control; 7 mg/kg/d cisplatin, 50 mg/kg, 100 mg/kg, and 200 mg/kg OLE; and treatment with OLE for 3 days starting at 24 hours following cisplatin injection. After exposure to the chemotherapy agent and OLE, oxidative DNA damage was quantitated in the renal tissue of experimental animals by measuring the amount of 8-hydroxy-2′-deoxyguanosine (8-OHdG) adducts. Malondialdehyde (MDA) level, total oxidative stress (TOS), and total antioxidant status (TAS) were assessed to determine the oxidative injury in kidney cells. The histology of the kidney was examined using four different staining methods: hematoxylin-eosin (H&E), periodic acid Schiff (PAS), Masson trichrome, and amyloid. In addition, the blood urea nitrogen (BUN), uric acid (UA), and creatinine (CRE) levels were established. Our experimental data showed that tissue 8-OHdG levels were significantly higher in the cisplatin group when compared to the control group. The glomerular cells were sensitive to cisplatin as tubular cells. In addition, treatment with cisplatin elevated the levels of BUN, UA, CRE, and TOS, but lowered the level of TAS compared to the control group. The OLE therapy modulated oxidative stress in order to restore normal kidney function and reduced the formation of 8-OHdG induced by cisplatin. Furthermore, the OLE treatment significantly reduced pathological findings in renal tissue. We demonstrate for the first time that OLE presents significant cytoprotective properties against cisplatin-induced genotoxicity by restoring the antioxidant system of the renal tissue. According to our findings, OLE is a promising novel natural source for the prevention of serious kidney damage in current chemotherapies.

Antioxidant, anticancer activities and mechanistic studies of the flavone glycoside diosmin and its oxidovanadium(IV) complex. Interactions with bovine serum albumin

The natural antioxidant flavonoid diosmin, found in citric fruits, showed low antioxidant properties among other flavonoids due to its structural characteristics and low cytotoxicity against lung (A549) and breast (T47D, SKBR3 and MDAMB231) cancer cell lines. The anticancer behavior has been improved by the metal complex generated with the flavonoid and the oxidovanadium(IV) ion. This new complex, [VO(dios)(OH)3]Na5·6H2O (VOdios), has been synthesized and characterized both in solid and solution states. The interaction of the metal ion through the sugar moiety of diosmin precluded the improvement of the antioxidant effects. However, the cell-killing effects tested in human lung A549 and breast T47D, SKBR3 and MDAMB231 cancer cell lines, were enhanced by complexation. The anti-proliferative effects on the human lung cancer cell line were accompanied by cellular ROS generation and an increase in cytoplasm condensation. The breast cancer cell lines did not produce caspase3/7 activation, mitochondrial potential reduction and ROS generation. Therefore, a non-apoptotic form of cell death in a caspase- and oxidative stress-independent manner has been proposed. The protein binding ability has been monitored by the quenching of tryptophan emission in the presence of the compounds using bovine serum albumin (BSA) as a model protein. Both compounds could be distributed and transported in vivo and the complex displayed stronger binding affinity and higher contributions to the hydrogen bond and van der Waals forces.