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

Structural related oxidovanadium(IV)-flavonoid complexes. Influence on their anticancer effects

Flavonoids, known for their antioxidant properties in plants, can also act as pro-oxidants in cancer cells, an effect that intensifies when coordinated with metal cations. Among them, oxidovanadium(IV) (VO) complexes with flavonoids have shown promising anticancer potential, following a clear relationship of the ligand structure with the activity. Quercetin and troxerutin share a common core structure; however, in troxerutin, four of the five hydroxyl (-OH) groups of quercetin are blocked, which may influence its metal coordination properties. In this study, we synthesized and fully characterized the VOtroxerutin complex using FTIR, EPR, UV-Vis, and reflectance spectroscopies, along with elemental, thermal, and conductivity analyses. Additionally, we prepared the reported VOquercetin complex, which shares the same coordination sphere as VOtroxerutin, to explore a relationship between the structure of the complexes and their activities. Their anticancer potential was tested through in vitro cytotoxicity assays against the A549 human lung cancer cells and HaCaT normal human keratinocytes. Both complexes exhibited anticancer activities (viability inhibition at 100 μM: 32.1 %, VOtroxerutin; 39.5 %,VOquercetin) and selectivity, highlighting their therapeutic potential. Notably, their pro-oxidant effects were activated upon incubation with cancer cells, leading to oxidative stress-induced cytotoxicity and mitochondrial membrane disruption. Further comparisons with the VOrutin complex provided additional insights into the correlation between anticancer activity and the coordination environment of the VOFlavonoid complexes. Additionally, we evaluated the safety profile of VOtroxerutin, finding no acute toxicity or mutagenic effects, supporting its potential as a targeted anticancer therapy with normal cells viability inhibition only at 100 μM (10 %).

Synthesis, crystal structure, computational and solution studies of a new phosphotetradecavanadate salt. Assessment of its effect on U87 glioblastoma cells

The new benzylammonium (C7H10N) salt of the phosphotetradecavanadate (PV14) anion PV14O429-, (C7H10N)6[H3PV14O42]∙7H2O (1), is synthesized under mild conditions and characterized by a combination of physicochemical techniques such as Fourier transform infrared spectroscopy, powder X-ray diffraction, elemental analyses and cyclic voltammetry. As evaluated by 51V NMR spectroscopy, at milimolar concentrations and pH ∼2.5 the PV14 anions decompose slowly, thus demonstrating kinetic stability, but at pH ∼7 this process takes place much faster. However, in the presence of human serum albumin, the 51V NMR peaks of PV14 anions broaden significantly and their decomposition becomes much slower, this being due to a direct interaction between both components. The structure of 1 is elucidated by single-crystal X-ray diffraction and reveals the presence of three-fold protonated, bicapped Keggin type [H3PV14O42]6- anions. The supramolecular interactions governing the crystal packing are further studied using the Hirshfeld surface analysis. Computational studies using density functional theory were effective in determining the electronic and protonation states of PV14 clusters, as well as the multi-electron redox behavior of compound 1 in acidic aqueous solutions. Molecular dynamics calculations confirm the high hydrophilicity and absence of aggregation between protonated PV14 anions in aqueous medium. Notably, this compound shows high inhibitory effect on the viability of the U87 glioblastoma cell line with IC50 values of 3.2 ± 0.6 μM and 1.10 ± 0.04 μM after 24 h and 72 h treatments. The mode of action of compound 1 is mediated by the pro-apoptotic process. These data provide evidence on the potential therapeutic use of PV14 compounds against glioblastoma.

Phytochemicals as Novel Therapeutics for Triple-Negative Breast Cancer: A Comprehensive Review of Current Knowledge

Triple-negative breast cancer is a characteristic subtype of breast cancer that lacks the estrogen receptor, human epidermal growth factor receptor 2, and progesterone receptor. Because of its highly diverse subtypes, increased metastasis capability, and poor prognosis, the risk of mortality for people with triple-negative breast cancers is high as compared with other cancers. Chemotherapy is currently playing a major role in treating triple-negative breast cancer patients; however, poor prognosis due to drug resistance is causing serious concern. Recent studies on several phytochemicals derived from various plants being used in Traditional Chinese Medicine, Traditional Korean Medicine, Ayurveda (Traditional Indian Medicine), and so on, have demonstrated to be a promising agent as a viable therapy against triple-negative breast cancer. Phytochemicals categorized as alkaloids, polyphenols, terpenoids, phytosterols, and organosulfur compounds have been demonstrated to reduce cancer cell proliferation and metastasis by activating various molecular pathways, thereby reducing the spread of triple-negative breast cancer. This review analyzes the molecular mechanisms by which various phytochemicals fight triple-negative breast cancer and offers a perspective on the difficulties and potential prospects for treating triple-negative breast cancer with various phytochemicals.

Synthesis, physicochemical and pharmacological characterizations of a tetra-[methylimidazolium] dihydrogen decavanadate, inhibiting the IGR39 human melanoma cells development

Melanoma is a skin cancer that arises from melanocytes and can spread quickly to the other organs of the body, if not treated early. Generally, melanoma shows an inherent resistance to conventional therapies. In this regard, new potential drugs are being developed as possible treatments for melanoma. In this paper, we report the synthesis of a new decavanadate compound with organic molecules for a potential therapeutic application. The tetra-[methylimidazolium] dihydrogen decavanadate(V) salt (C4H7N2)4[H2V10O28] is characterized by single-crystal X-ray diffraction, by FT-IR, UV-Vis and 51V NMR spectroscopy, as well as by thermal analysis (TGA and DSC). The compound crystallizes in the monoclinic centrosymmetric space group P21/c. Its formula unit consists of one dihydrogen decavanadate anion [H2V10O28]4- and four organic 4-methylimidazolium cations (C4H7N2)+. Important intermolecular interactions are N-H···O and O-H···O hydrogen bonds and π-π stacking interactions between the organic cations, revealed by analysis of the Hirshfeld surface and its two-dimensional fingerprint plots. Interestingly, this compound inhibits the viability of IGR39 cells with IC50 values of 14.65 μM and 4 μM after 24 h and 72 h of treatment, respectively. The analysis of its effect by flow cytometry using an Annexin V-FITC/IP cell labeling, showed that (C4H7N2)4H2V10O28 compound induced IGR39 cell apoptosis and necrosis. Molecular docking studies performed against TNFR1 and GPR40, as putative targets, suggest that the (C4H7N2)4[H2V10O28] compound may act as inhibitor of these proteins, known to be overexpressed in melanoma cells. Therefore, we could consider it as a new potential metallodrug against melanoma.

Naringenin Alleviates Radiation-Induced Intestinal Injury by Inhibiting TRPV6 in Mice

SCOPE

Naringenin (NAR) possesses unique anti-inflammatory, antiapoptosis effects and various bioactivities; however, its role against radiation-induced intestinal injury (RIII) remains unclear. This study aims to investigate whether NAR has protective effects against radiation-induced intestinal injury and the underlying mechanisms.

METHODS AND RESULTS

C57BL/6J mice are exposed to a single dose of 13 Gy X-ray total abdominal irradiation (TAI), then gavaged with NAR for 7 days. NAR treatment prolongs the survival rate, protects crypts and villi from damage, alleviates the level of radiation-induced inflammation, and mitigates intestinal barrier damage in the irradiated mice. Additionally, NAR reduces immune cell infiltration and intestinal epithelial cell apoptosis. NAR also shows radioprotective effects in human colon cancer cells (HCT116) and human intestinal epithelial cells (NCM460). It reduces cell damage by reducing intracellular calcium ion levels and reactive oxygen species (ROS) levels. NAR-mediated radioprotection is associated with the downregulation of transient receptor potential vanilloid 6 (TRPV6), and inhibition of apoptosis pathway. Notably, treatment with NAR fails to further increase the protective effects of the TRPV6 inhibitor 2-APB, indicating that TRPV6 inhibition is essential for NAR activity.

CONCLUSION

NAR inhibits the apoptosis pathway by downregulating TRPV6 and reducing calcium ion level, thereby alleviating RIII. Therefore, NAR is a promising therapeutic drug for RIII.

Copper(II) cation and bathophenanthroline coordination enhance therapeutic effects of naringenin against lung tumor cells

The development of new anticancer compounds is one of the challenges of bioinorganic and medicinal chemistry. Naringenin and its metal complexes have been recognized as promising inhibitors of cell proliferation, having enormous potential to act as an antioxidant and antitumorigenic agent. Lung cancer is the second most commonly diagnosed type of cancer. Therefore, this study is devoted to investigate the effects of Cu(II), naringenin (Nar), binary Cu(II)-naringenin complex (CuNar), and the Cu(II)-naringenin containing bathophenanthroline as an auxiliary ligand (CuNarBatho) on adenocarcinoma human alveolar basal epithelial cells (A549 cells) that are used as models for the study of drug therapies against lung cancer. The ternary complex shows selectivity being high cytotoxic against malignant cells. The cell death generated by CuNarBatho involves ROS production, loss of mitochondrial membrane potential, and depletion of GSH level and GSH/GSSG ratio. The structure-relationship activity was assessed by comparison with the reported Cu(II)-naringenin-phenanthroline complex. The CuNarBatho complex was synthesized and characterized by elemental analysis, molar conductivity, mass spectrometry, thermogravimetric measurements and UV-VIS, FT-IR, EPR, Raman and ¹H-NMR spectroscopies. In addition, the binding to bovine serum albumin (BSA) was studied at the physiological conditions (pH = 7.4) by fluorescence spectroscopy.

Naringenin: A potential flavonoid phytochemical for cancer therapy

Naringenin is an important phytochemical which belongs to the flavanone group of polyphenols, and is found mainly in citrus fruits like grapefruits and others such as tomatoes and cherries plus medicinal plants derived food. Available evidence demonstrates that naringenin, as herbal medicine, has important pharmacological properties, including anti-inflammatory, antioxidant, neuroprotective, hepatoprotective, and anti-cancer activities. Collected data from in vitro and in vivo studies show the inactivation of carcinogens after treatment with pure naringenin, naringenin-loaded nanoparticles, and also naringenin in combination with anti-cancer agents in various malignancies, such as colon cancer, lung neoplasms, breast cancer, leukemia and lymphoma, pancreatic cancer, prostate tumors, oral squamous cell carcinoma, liver cancer, brain tumors, skin cancer, cervical and ovarian cancer, bladder neoplasms, gastric cancer, and osteosarcoma. Naringenin inhibits cancer progression through multiple mechanisms, like apoptosis induction, cell cycle arrest, angiogenesis hindrance, and modification of various signaling pathways including Wnt/β-catenin, PI3K/Akt, NF-ĸB, and TGF-β pathways. In this review, we demonstrate that naringenin is a natural product with potential for the treatment of different types of cancer, whether it is used alone, in combination with other agents, or in the form of the naringenin-loaded nanocarrier, after proper technological encapsulation.

Comprehensive review on naringenin and naringin polyphenols as a potent anticancer agent

Though the incidence of several cancers in Western societies is regulated wisely, some cancers such as breast, lung, and colorectal cancer are currently rising in many low- and middle-income countries due to increased risk factors triggered by societal and development problems. Surgery, chemotherapy, hormone, radiation, and targeted therapies are examples of traditional cancer treatment approaches. However, multiple short- and long-term adverse effects may also significantly affect patient prognosis depending on treatment-associated clinical factors. More and more research has been carried out to find new therapeutic agents in natural products, among which the bioactive compounds derived from plants have been increasingly studied. Naringin and naringenin are abundantly found in citrus fruits, such as oranges and grapefruits. A variety of cell signaling pathways mediates their anti-carcinogenic properties. Naringin and naringenin were also documented to overcome multidrug resistance, one of the major challenges to clinical practice due to multiple defense mechanisms in cancer. The effective parameters underlying the anticancer effects of naringenin and naringin include GSK3β inactivation, suppression of the gene and protein activation of NF-kB and COX-2, JAK2/STAT3 downregulation, downregulation of intracellular adhesion molecules-1, upregulation of Notch1 and tyrocite-specific genes, and activation of p38/MAPK and caspase-3. Thus, this review outlines the potential of naringin and naringenin in managing different types of cancers.

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.

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.

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.

Therapeutic potential of vanadium complexes with 1,10-phenanthroline ligands, quo vadis? Fate of complexes in cell media and cancer cells

V^IVO-complexes formulated as [V^IVO(OSO₃)(phen)₂] (1) (phen = 1,10-phenanthroline), [V^IVO(OSO₃)(Me₂phen)₂] (2) (Me₂phen = 4,7-dimethyl-1,10-phenanthroline) and [V^IVO(OSO₃)(amphen)₂] (3) (amphen = 5-amino-1,10-phenanthroline) were prepared and stability in cell incubation media evaluated. Their cytotoxicity was determined against the A2780 (ovarian), MCF7 (breast) and PC3 (prostate) human cancer cells at different incubation times. While at 3 and 24 h the cytotoxicity differs for complexes and corresponding free ligands, at 72 h incubation all compounds are equally active presenting low IC₅₀ values. Upon incubation of A2780 cells with 1-3, cellular distribution of vanadium in cytosol, membranes, nucleus and cytoskeleton, indicate that the uptake of V is low, particularly for 1, and that the uptake pattern depends on the ligand. Nuclear microscopic techniques are used for imaging and elemental quantification in whole PC3 cells incubated with 1. Once complexes are added to cell culture media, they decompose, and with time most V^IV oxidizes to V^V-species. Modeling of speciation when [V^IVO(OSO₃)(phen)₂] (1) is added to cell media is presented. At lower concentrations of 1, V^IVO- and phen-containing species are mainly bound to bovine serum albumin, while at higher concentrations [V^IVO(phen)_n]²⁺-complexes become relevant, being predicted that the species taken up and mechanisms of action operating depend on the total concentration of complex. This study emphasizes that for these V^IVO-systems, and probably for many others involving oxidovanadium or other labile metal complexes, it is not possible to identify active species or propose mechanisms of cytotoxic action without evaluating speciation occurring in cell media.

Vanadium compounds and cellular death mechanisms in the A549 cell line: The relevance of the compound valence

Non-small lung cell carcinoma has a high morbidity and mortality rates. The elective treatment for stage III and IV is cisplatinum that conveys serious toxic side effects. Vanadium compounds are metal molecules with proven antitumor activity that depends on its valence. Therefore, a better understanding of the mechanism of action of vanadium compounds is required. The aim of our study was to investigate the mechanisms of cell death induced by sodium metavanadate (NaVO₃ [V(+5)]) and vanadyl sulfate (VOSO₄ [(+4)]), both of which have reported apoptotic-inducing activity. We exposed the A549 cell line to various concentrations (0-100 μM) and to different exposure times to each compound and determined the cell viability and expression of caspases, reactive oxygen species (ROS) production, Bcl2, Bax, FasL and NO. Our results showed that neither compounds modified the basal expression of caspases or pro- and anti-apoptotic proteins. The only change observed was the 12- and 14-fold significant increase in ROS production induced by NaVO₃ and VOSO₄ , respectively, at 100 μm concentrations after 48 hours. Our results suggest that classical apoptotic mechanisms are not related to the cell death induced by the vanadium compounds evaluated here, and showed that the higher ROS production was induced by the [(+4)] valence compound. It is possible that the difference will be secondary to its higher oxidative status and thus higher ROS production, which leads to higher cell damage. In conclusion, our results suggest that the efficacy of the cell death mechanisms induced by vanadium compounds differ depending on the valence of the compound.

Vanadium: History, chemistry, interactions with α-amino acids and potential therapeutic applications

In the last 30 years, since the discovery that vanadium is a cofactor found in certain enzymes of tunicates and possibly in mammals, different vanadium-based drugs have been developed targeting to treat different pathologies. So far, the in vitro studies of the insulin mimetic, antitumor and antiparasitic activity of certain compounds of vanadium have resulted in a great boom of its inorganic and bioinorganic chemistry. Chemical speciation studies of vanadium with amino acids under controlled conditions or, even in blood plasma, are essential for the understanding of the biotransformation of e.g. vanadium antidiabetic complexes at the physiological level, providing clues of their mechanism of action. The present article carries out a bibliographical research emphaticizing the chemical speciation of the vanadium with different amino acids and reviewing also some other important aspects such as its chemistry and therapeutical applications of several vanadium complexes.

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.

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.

Naringenin ameliorates LPS-induced acute lung injury through its anti-oxidative and anti-inflammatory activity and by inhibition of the PI3K/AKT pathway

The aim of the present study was to explore the effect of naringenin on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in a mouse model, as well as the underlying mechanism. The animals were randomly assigned to four groups: PBS-treated healthy control (Control), LPS-induced ALI (LPS), vehicle-treated ALI (LPS + Vehicle), and naringenin-treated ALI (LPS + Nar) group. Naringenin (100 mg/kg) was administered orally for 4 consecutive days, starting 3 days prior to induction of ALI. The survival rates of mice, lung wet/dry weight ratios, lung injury score, protein levels of bronchoalveolar lavage fluid (BALF), lactate dehydrogenase (LDH) activity in the BALF, lung myeloperoxidase (MPO) activity, the number of infiltrated neutrophils and reactive oxygen species (ROS) levels (H₂O₂ and malondialdehyde) were assessed. In addition, the serum and BALF levels of inflammatory cytokines [tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and macrophage inflammatory protein 2] were determined, along with the total and the phosphorylated protein levels of phosphatidylinositol 3-hydroxy kinase (PI3K) and AKT in lung tissues. The results showed that naringenin pre-treatment significantly increased the survival rate, improved histopathologic changes, alleviated pulmonary edema and lung vascular leak, downregulated the levels of ROS and reduced neutrophil infiltration as well as the levels of inflammatory cytokines in the serum and BALF. Moreover, naringenin pre-treatment reduced the total and the phosphorylated protein levels of PI3K and AKT. The present study suggested that naringenin pre-treatment ameliorated LPS-induced ALI through its anti-oxidative and anti-inflammatory activity and by inhibition of the PI3K/AKT pathway in mice.

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.

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.

Behavior of the potential antitumor V(IV)O complexes formed by flavonoid ligands. 3. Antioxidant properties and radical production capability

The radical production capability and the antioxidant properties of some V(IV)O complexes formed by flavonoid ligands were examined. In particular, the bis-chelated species of quercetin (que), [VO(que)2](2-), and morin (mor), [VO(mor)2], were evaluated for their capability to reduce the stable radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) and produce the hydroxyl radical (•)OH by Fenton-like reactions, where the reducing agent is V(IV)O(2+). The results were compared with those displayed by other V(IV)O complexes, such as [VO(H2O)5](2+), [VO(acac)2] (acac=acetylacetonate) and [VO(cat)2](2-) (cat=catecholate). The capability of the V(IV)O flavonoids complexes to reduce DPPH is much larger than that of the V(IV)O species formed by non-antioxidant ligands and it is due mainly to the flavonoid molecule. Through the 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin trapping assay of the hydroxyl radical it was possible to demonstrate that in acidic solution V(IV)O(2+) has an effectiveness in producing (•)OH radicals comparable to that of Fe(2+). When V(IV)O complexes of flavonoids were taken into account, the amount of hydroxyl radicals produced in Fenton-like reactions depends on the specific structure of the ligand and on their capability to reduce H2O2 to give (•)OH. Both the formation of reactive oxygen species (ROS) under physiological conditions by V(IV)O complexes of flavonoid ligands and their radical scavenging capability can be put in relationship with their antitumor effectiveness and it could be possible to modulate these actions by changing the features of the flavonoid coordinated to the V(IV)O(2+) ion, such as the entity, nature and position of the substituents and the number of phenolic groups.

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.