Apoptosis Induction in HepG2 and HCT116 Cells by a Novel Quercetin-Zinc (II) Complex: Enhanced Absorption of Quercetin and Zinc (II)

Quercetin forms complexes with various metals due to its structural attributes. It predominantly exhibits chelating activity at the 3-hydroxy/4-carbonyl group. Previously, coordination in synthetically obtained quercetin-zinc (II) complexes has been limited to this group. However, the expanded coordination observed in quercetin-iron complexes has opened avenues for diverse applications. Thus, synthesizing novel quercetin-zinc complexes with different coordination positions is a significant advance. In our study, we not only synthesized and comprehensively characterized a new quercetin-zinc (II) complex, Zn-Q, but also evaluated the structure and bioactivity of chelate complexes (Q+Zn) derived from co-treatment in cell culture mediums. The structure of the new compound Zn-Q was comprehensively characterized using 1D 1H and 2D correlation spectroscopy (COSY), nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), electrospray ionization mass spectrometer (ESI-MS), and X-ray diffraction analysis (XRD) analysis. Subcellular localization and absorption of these zinc (II) complexes were determined using the ZnAF-2 DA zinc ion fluorescence probe. Throughout the experiments, both Zn-Q and Q+Zn exhibited significant antioxidant, cell growth inhibitory, and anticancer effects in HepG2 and HCT116 cells, with Zn-Q showing the highest potential for inducing apoptosis via the caspase pathway. Tracking intracellular zinc complex absorption using zinc fluorescent probes revealed zinc (II) localization around the cell nucleus. Interestingly, there was a proportional increase in intracellular quercetin absorption in conjunction with zinc (II) uptake. Our research highlights the advantages of quercetin complexation with zinc (II): enhanced anticancer efficacy compared to the parent compound and improved bioavailability of both quercetin and zinc (II). Notably, our findings, which include enhanced intracellular uptake of both quercetin and zinc (II) upon complex formation and its implications in apoptosis, contribute significantly to the understanding of metal-polyphenol complexes. Moving forward, comprehensive functional assessments and insights into its mechanism of action, supported by animal studies, are anticipated.

Overview of Research on Vanadium-Quercetin Complexes with a Historical Outline

The present review was conducted to gather the available literature on some issues related to vanadium-quercetin (V-QUE) complexes. It was aimed at collecting data from in vitro and in vivo studies on the biological activity, behavior, antioxidant properties, and radical scavenging power of V-QUE complexes. The analysis of relevant findings allowed summarizing the evidence for the antidiabetic and anticarcinogenic potential of V-QUE complexes and suggested that they could serve as pharmacological agents for diabetes and cancer. These data together with other well-documented biological properties of V and QUE (common for both), which are briefly summarized in this review as well, may lay the groundwork for new therapeutic treatments and further research on a novel class of pharmaceutical molecules with better therapeutic performance. Simultaneously, the results compiled in this report point to the need for further studies on complexation of V with flavonoids to gain further insight into their behavior, identify species responsible for their physiological activity, and fully understand their mechanism of action.

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.

Phenanthroline Complexation Enhances the Cytotoxic Activity of the VO-Chrysin System

Metal complexation in general improves the biological properties of ligands. We have previously measured the anticancer effects of the oxidovanadium(IV) cation with chrysin complex, VO(chrys)2. In the present study, we synthesized and characterized a new complex generated by the replacement of one chrysin ligand by phenanthroline (phen), VO(chrys)phenCl, to confer high planarity for DNA chain intercalation and more lipophilicity, giving rise to a better cellular uptake. In effect, the uptake of vanadium has been increased in the complex with phen and the cytotoxic effect of this complex proved higher in the human lung cancer A549 cell line, being involved in its mechanisms of action, the production of cellular reactive oxygen species (ROS), the decrease of the natural antioxidant compound glutathione (GSH) and the ratio GSH/GSSG (GSSG, oxidized GSH), and mitochondrial membrane damage. Cytotoxic activity studies using the non-tumorigenic HEK293 cell line showed that [VO(chrys)phenCl] exhibits selectivity action towards A549 cells after 24 h incubation. The interaction with bovine serum albumin (BSA) by fluorometric determinations showed that the complex could be carried by the protein and that the binding of the complex to BSA occurs through H-bond and van der Waals interactions.

Precise engineering of cetuximab encapsulated gadollium nanoassemblies: in vitro ultrasound diagnosis and in vivo thyroid cancer therapy

We report the formulation of nanoassemblies (NAs) comprising C225 conjugates Gd-PFH-NAs (C-Gd-PFH-NAs) for low-intensity focused ultrasound diagnosis ablation of thyroid cancer. C-Gd-PFH-NAs showed excellent stability in water, phosphate-buffered saline (PBS), and 20% rat serum. Transmission electron microscopy (TEM) images also revealed the effective construction of C-Gd-PFH-NAs as common spherical assemblies. The incubation of C625 thyroid carcinoma with C-Gd-PFH-NAs triggers apoptosis, as confirmed by flow cytometry analysis. The C-Gd-PFH-NAs exhibited antitumor efficacy in human thyroid carcinoma xenografts, where histopathological results further confirmed these outcomes. Furthermore, we were able to use low-intensity focused ultrasound diagnosis imaging (LIFUS) to examine the efficiency of C-Gd-PFH-NAs in thyroid carcinoma in vivo. These findings clearly show that the use of LIFUS agents with high performance imaging in different therapeutic settings will have extensive potential for future biomedical applications.

The Effects of Quercetin on the Apoptosis of Human Breast Cancer Cell Lines MCF-7 and MDA-MB-231: A Systematic Review

This systematic review was performed with a focus on the effects of quercetin (QT) on the human breast cancer cell lines MCF-7 and MDA-MB-231. PubMed, Scopus, Science Direct, and Google Scholar databases were searched up to May 2020 using relevant keywords. All articles written in English evaluating the effects of QT on the human breast cancer cell lines MCF-7 and/or MDA-MB-231 were eligible for the review. Totally, 31 articles were included in this review. Out of them, 23 studies investigated the effects of QT on MCF-7 cells and indicated that QT induces apoptosis in the cells. Of 15 studies that examined the effects of QT on MDA-MB-231 cells, 14 reports showed successful apoptosis. It is concluded that QT might be beneficial in the eliminating of breast cancer cells. However, further clinical trials are warranted to further verify these outcomes.

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.

Native Quercetin as a Chloride Receptor in an Organic Solvent

The binding properties of quercetin toward chloride anions were investigated by means of 1H-NMR, 13C-NMR, and electrospray ionization mass spectrometry (ESI-MS) measurements, as well as computational calculations. The results indicate that quercetin behaves primarily as a ditopic receptor with the binding site of the B ring that exhibits stronger chloride affinity compared to the A ring. However, these sites are stronger receptors than those of catechol and resorcinol because of their conjugation with the carbonyl group located on the C ring. The 1:1 and 1:2 complexation of this flavonoid with Cl− was also supported by ESI mass spectrometry.

Anti-Inflammatory and Antioxidant Properties of the Extract, Tiliroside, and Patuletin 3-O-β-D-Glucopyranoside from Pfaffia townsendii (Amaranthaceae)

Brazilian ginseng, including Pfaffia townsendii, is used in popular medicine as a natural anti-inflammatory, tonic, analgesic, and antidiabetic agent. In this study, we investigated the chemical composition and evaluated the antioxidant and anti-inflammatory activities of the P. townsendii ethanolic extract as well as the major isolated glycoside flavonoids tiliroside and patuletin 3-O-β-D-glucopyranoside. Chromatographic techniques and spectroscopic analysis were used for the isolation and identification of the major compounds. The antioxidant potential was determined through DPPH and ORAC-FL assays. The total phenolic content was measured using Folin-Ciocalteu reagent. The anti-inflammatory activity was determined based on a model of paw edema and carrageenan- (Cg-) induced pleurisy. We identified three phenolic acids, one carboxylic acid and two flavonoids, patuletin 3-O-β-D-glucopyranoside, and tiliroside. The ethanol crude extracts, partitions and isolated flavonoids (4581 μmol of Trolox equivalents/g of extract in ORAC and a SC₅₀ of approximately 31.9 μg/mL in the DPPH assay) demonstrated antioxidant activity, and the ethanolic extract as well as isolated flavonoids inhibited paw edema induced by Cg and leukocyte migration in the Cg-induced pleurisy model. The extract, tiliroside, and patuletin 3-O-β-D-glucopyranoside obtained from P. townsendii have therapeutic potential against oxidative stress-related and inflammatory disorders.

Vanadium quercetin complex attenuates mammary cancer by regulating the P53, Akt/mTOR pathway and downregulates cellular proliferation correlated with increased apoptotic events

Flavonoid metal ion complexes have been deliberated in recent years and are considered as a new class of medicinal agents with enhanced therapeutic activity and low toxicity. Our study deals with chemotherapeutic effects of vanadium, when coordinated with the flavonoid quercetin on a defined model of chemically induced rat mammary carcinogenesis in vivo and on human breast cancer cell line MCF-7 in vitro. The characterization of the complex was achieved through UV-Visible, IR, and Mass spectra and antioxidant activity was assessed by DPPH, FRAP and ABTS methods. In vitro studies established that the complex upregulated the expressions of p53, Caspase 3 and 9, whereas down regulating Akt, mTOR and VEGF expressions and also induced apoptosis and DNA fragmentation in a dose dependent manner. Acute and Sub-acute toxicity was performed to determine safe doses. 7,12-Dimethylbenz(α)anthracene (0.5 mg/100 g body weight) was used for induction of breast cancer in female Sprague-Dawley rats via single tail vein injection. The histopathological analysis after 24 weeks of carcinogenesis study depicted substantial repair of hyperplastic lesions. TUNEL assay showed an increase in apoptotic index (0.14 ± 0.03; 0.15 ± 0.01) in vanadium-quercetin treated groups as compared to the carcinogen control (0.02 ± 0.01) along with upregulation of Bcl-2 and downregulation of Bax and p53. Immunohistochemical analysis also exhibited decrease in cell proliferation in the vanadium-quercetin treated groups (11.3 ± 0.12; 11.8 ± 0.10). Thus, results from both in vivo and in vitro studies revealed that vanadium-quercetin complex could be a potential candidate for development of approved drug for breast cancer in the near future.

Research Progress in the Modification of Quercetin Leading to Anticancer Agents

The flavonoid quercetin (3,3′,4′,5,7-pentahydroxyflavone) is widely distributed in plants, foods, and beverages. This polyphenol compound exhibits varied biological actions such as antioxidant, radical-scavenging, anti-inflammatory, antibacterial, antiviral, gastroprotective, immune-modulator, and finds also application in the treatment of obesity, cardiovascular diseases and diabetes. Besides, quercetin can prevent neurological disorders and exerts protection against mitochondrial damages. Various in vitro studies have assessed the anticancer effects of quercetin, although there are no conclusive data regarding its mode of action. However, low bioavailability, poor aqueous solubility as well as rapid body clearance, fast metabolism and enzymatic degradation hamper the use of quercetin as therapeutic agent, so intense research efforts have been focused on the modification of the quercetin scaffold to obtain analogs with potentially improved properties for clinical applications. This review gives an overview of the developments in the synthesis and anticancer-related activities of quercetin derivatives reported from 2012 to 2016.

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.

Evaluation of cellular uptake, cytotoxicity and cellular ultrastructural effects of heteroleptic oxidovanadium(IV) complexes of salicylaldimines and polypyridyl ligands

Searching for prospective vanadium-based drugs for cancer treatment, a new series of structurally related [V^IVO(L-2H)(NN)] compounds (1-8) was developed. They include a double deprotonated salicylaldimine Schiff base ligand (L-2H) and different NN-polypyridyl co-ligands having DNA intercalating capacity. Compounds were characterized in solid state and in solution. EPR spectroscopy suggests that the NN ligands act as bidentate and bind through both nitrogen donor atoms in an axial-equatorial mode. The cytotoxicity was evaluated in human tumoral cells (ovarian A2780, breast MCF7, prostate PC3). The cytotoxic activity was dependent on type of cell and incubation time. At 24h PC3 cells presented low sensitivity, but at 72h all complexes showed high cytotoxic activity in all cells. Human kidney HEK293 and ovarian cisplatin resistant A2780cisR cells were also included to evaluate selectivity towards cancer cells and potency to overcome cisplatin resistance, respectively. Most complexes showed no detectable interaction with plasmid DNA, except 2 and 7 which depicted low ability to induce single strand breaks in supercoiled DNA. Based on the overall cytotoxic profile, complexes with 2,2´-bipyridine and 1,10-phenanthroline ligands (1 and 2) were selected for further studies, which consisted on cellular distribution and ultrastructural analyses. In the A2780 cells both depicted different distribution profiles; the former accumulates mostly at the membrane and the latter in the cytoskeleton. Morphology of treated cells showed nuclear atypia and membrane alterations, more severe for 1. Complexes induce different cell death pathways, predominantly necrosis for 1 and apoptosis for 2. Complexes alternative mode of cell death motivates the possibility for further developments.

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.

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

Chemotherapy using metal coordination compounds for cancer treatment is the work of the ongoing research. Continuing our research on the improvement of the anticancer activity of natural flavonoids by metal complexation, a coordination compound of the natural antioxidant flavone luteolin (lut) and the oxidovanadium(IV) cation has been synthesized and characterized. Using different physicochemical measurements some structural aspects of [VO(lut)(H2O)2]Na·3H2O (VOlut) were determined. The metal coordinated to two cis-deprotonated oxygen atoms (ArO(-)) of the ligand and two H2O molecules. Magnetic measurements in solid state indicated the presence of an effective exchange pathway between adjacent vanadium ions. VOlut improved the antioxidant capacity of luteolin only against hydroxyl radical. The antitumoral effects were evaluated on MDAMB231 breast cancer and A549 lung cancer cell lines. VOlut exhibited higher viability inhibition (IC50=17 μM) than the ligand on MDAMB231 cells but they have the same behavior on A549 cells (ca. IC50=60 μM). At least oxidative stress processes were active during cancer cell-killing. When metals chelated through the carbonyl group and one adjacent OH group of the flavonoid an effective improvement of the biological properties has been observed. In VOlut the different coordination may be the cause of the small improvement of some of the tested properties of the flavonoid. Luteolin and VOlut could be distributed and transported in vivo. Luteolin interacted in the microenvironment of the tryptophan group of the serum binding protein, BSA, by means of electrostatic forces and its complex bind the protein by H bonding and van der Waals interactions.

Insights into the mechanisms underlying the antitumor activity of an oxidovanadium(IV) compound with the antioxidant naringenin. Albumin binding studies

Naringenin, a natural antioxidant present in grapefruit, oranges and the skin of tomatoes showed low antioxidant properties among other flavonoids due to its structural characteristics. Since many flavonoids were shown to have cell-killing and antioxidant activities, naringenin was investigated herein. In parallel with its antioxidant activities the flavonoid showed very low cytotoxicity at concentrations up to 100 μM against lung (A549) and breast (SKBr3 and MDAMB231) cancer cell lines. Furthermore, a newly-synthesized and characterized complex of naringenin and oxidovanadium(IV) ([V(IV)O(nar)2] · 2H2O, VOnar, with weak ferromagnetic coupling) was also studied. As a result, VOnar acted as a better compound on cell-killing and antioxidant activities (in vitro) than naringenin. The anti-proliferative effect of VOnar was accompanied by reactive oxygen species (ROS) generation, cell membrane and DNA damages, cell cycle arrest, caspase 3/7 activation and mitochondrial potential reduction. The higher parameters observed for the MDAMB231 cell line have been related to its low glutathione (GSH) content. The assays of the interaction of bovine serum albumin (BSA) with the complex showed the affinity of protein toward it and that there is only one binding site on the BSA molecule. However, metal complexation decreased the binding affinity to BSA of naringenin probably due to a steric hindrance of the complex.

Electrochemistry-based chemotaxonomy in plants using the voltammetry of microparticles methodology

Characterization of vegetal taxa is achievedviacharacteristic voltammetric features displayed by leaf extracts.