Ruthenium(II)–Arene RAPTA Type Complexes Containing Curcumin and Bisdemethoxycurcumin Display Potent and Selective Anticancer Activity

Biomolecular Interactions and Anticancer Mechanisms of Ru(II)-Arene Complexes of Cinnamaldehyde-Derived Thiosemicarbazone Ligands: Analysis Combining In Silico and In Vitro Approaches

Our study focuses on synthesizing and exploring the potential of three N-(4) substituted thiosemicarbazones derived from cinnamic aldehyde, alongside their Ru(II)-(η6 -p-cymene)/(η6-benzene) complexes. The synthesized compounds were comprehensively characterized using a range of analytical techniques, including FT-IR, UV-visible spectroscopy, NMR (1H, 13C), and HRMS. We investigated their electronic and physicochemical properties via density functional theory (DFT). X-ray crystal structures validated structural differences identified by DFT. Molecular docking predicted promising bioactivities, supported by experimental observations. Notably, docking with EGFR suggested an inhibitory potential against this cancer-related protein. Spectroscopic titrations revealed significant DNA/BSA binding affinities, particularly with DNA intercalation and BSA hydrophobic interactions. RuPCAM displayed the strongest binding affinity with DNA (Kb = 6.23 × 107 M-1) and BSA (Kb = 9.75 × 105 M-1). Assessed the cytotoxicity of the complexes on cervical cancer cells (HeLa), and breast cancer cells (MCF-7 and MDA-MB 231), revealing remarkable potency. Additionally, selectivity was assessed by examining MCF-10a normal cell lines. The active complexes were found to trigger apoptosis, a vital cellular process crucial for evaluating their potential as anticancer agents utilizing staining assays and flow cytometry analysis. Intriguingly, complexation with Ru(II)-arene precursors significantly amplified the bioactivity of thiosemicarbazones, unveiling promising avenues toward the creation of powerful anticancer agents.

Organoruthenium metallocycle induced mutation in gld-1 tumor suppression gene in JK1466 strain and appreciable lifespan expansion

Four Ru(II) complexes (A2-A5) were synthesized from the reaction of coumarin Schiff base ligands (7da2-tsc, 7da3-mtsc, 7da4-etsc and 7da5-ptsc) with [RuHCl(CO)(PPh3)3]. The compounds were characterized by FT-IR, UV-Vis, 1H, 13C and 31P NMR, mass spectrometry and crystallographic analysis. Calf Thymus DNA (CT-DNA) binding studies revealed the intercalative mode of binding of the complexes with DNA. The results of Bovine serum albumin (BSA) binding studies established the interaction between BSA followed static quenching mechanism. The cytotoxic effects of the complexes and the ligands were evaluated against breast (MCF-7 and MDA-MB-231) and lung carcinoma cell lines (A549 and NCI-H460) using MTT assay. Complex A4 demonstrated potent cytotoxic effects on both breast and lung cancer cells. Furthermore, morphological observations and FACS analysis showed the decrease in cell density by complex A4 by induced morphological changes and apoptotic body formation and cell death in both breast and lung cancer cells. Moreover, the invertebrate model Caenorhabditis elegans was employed to assess the in vivo anticancer activity of compound A4. The findings indicated that the treatment with A4 reduced tumor development and significantly extended organismal lifespan by 64 % in the tumoral strain JK1466 without adversely affecting essential physiological functions of the worm. Additionally, A4 demonstrated an upregulation of two crucial antioxidant defense genes. Overall, these results suggested that the compound A4 can be a potential candidate with novel chemotherapeutic applications.

Ruthenium(II) complexes of curcumin and β-diketone derivatives: effect of structural modifications on their cytotoxicity

Ruthenium(II) complexes (Ru1-Ru3) with the general formula [Ru(O-O)(PPh3)2(bipy)]PF6, bearing two triphenylphosphine (PPh3), bipyridine (bipy) and a series of natural and synthetic β-diketones (O,O) ligands were synthesized and characterized using various analytical techniques. The interaction between the complexes and calf thymus DNA (CT-DNA) was investigated and demonstrated a weak interaction. The cytotoxicity of the complexes was investigated against breast cancer cells (MDA-MB-231 and MCF-7), lung cancer cells (A549), cisplatin-resistant ovarian cancer cells (A2780cis), as well as non-tumour lung (MRC-5) and non-tumour breast (MCF-10A) cell lines. All complexes exhibited cytotoxic activity against all the cell lines studied, with half maximal inhibitory concentration (IC50) values ranging from 0.39 to 13 µM. Notably, the three complexes demonstrated selectivity against the A2780cis cell line, with IC50 ranging from 0.39 to 0.82 µM. Among them, Ru2 exhibited the highest cytotoxicity, with an IC50 value of 0.39 µM. Consequently, this new class of complexes shows good selectivity towards cisplatin-resistant ovarian cancer cells and it is promising for further investigation as anti-cancer agents.

Pd(II)/diphosphine/curcumin complexes as potential anticancer agents

Palladium(II) complexes have stimulated research interest mainly due to their in vitro cytotoxicity against various cancer cell lines and their low cytotoxicity in healthy cells. Thus, in this work, we combined Pd(II)/phosphine systems with the natural product curcumin as a ligand, obtaining a series of complexes, [Pd(cur)(PPh3)2]PF6 (A1), [Pd(cur)(dppe)]PF6 (A2), [Pd(cur)(dppp)]PF6 (A3), [Pd(cur)(dppb)]PF6 (A4) and [Pd(cur)(dppf)]PF6 (A5), where dppe = 1,2-bis(diphenylphosphino)ethane, dppp = 1,3-bis(diphenylphosphino)propane, dppb = 1,4-bis(diphenylphosphino)butane, and dppf = 1,1'-bis(diphenylphosphino)ferrocene (P-P), which were characterized by elemental analysis, molar conductivity analysis, and mass, NMR (1H, 13C, 31P{1H}), UV-vis, and IR spectroscopies, and four of them (A1, A2, A4, and A5) by X-ray crystallography. The in vitro cell viability of the complexes A1-A5, cisplatin, and the free ligand curcumin against MDA-MB-231 (human triple-negative breast tumor cells), SK-BR-3 (human breast tumor cells), A549 (human lung tumor cells), MRC-5 (non-tumor human lung cells), A2780 (human ovarian carcinoma cells), and A2780cis (cisplatin-resistant human ovarian carcinoma cells), was evaluated by the MTT colorimetric assay. For the tumor cell lines tested, the complexes showed good anticancer activities. The results showed that in general the complexes had lower IC50 values than free curcumin and the precursors [PdCl2(P-P)]. IC50 results obtained for the A1-A5 complexes, in the MCF-7 cell line, are similar to those that had already been observed for some Pd/bipy/curcumin complexes. In the MDA-MB-231 cell line, complexes A1 and A5 stood out, with their lowest IC50 values, around 5 μmol L-1, and the complexes appeared to be more active (lower IC50 values) against the ovarian cell lines. Complex A1 was 23 and 22-fold more cytotoxic than cisplatin, against the A2780 and A2780cis cells, respectively. The complex A1 was studied on A2780cis cells and it was found that this complex inhibits colony formation and induces cell cycle arrest in the sub-G1 phase in a concentration-dependent manner and leads to cell death by apoptosis. The DCFDA assay revealed a potent ROS induction for complex A1.

Ru(II)-Arene Complexes of Curcumin and Bisdesmethoxycurcumin Metabolites

Curcuminoids and their complexes continue to attract attention in medicinal chemistry, but little attention has been given to their metabolic derivatives. Here, the first examples of (arene)Ru(II) complexes with curcuminoid metabolites, tetrahydrocurcumin (THcurcH), and tetrahydrobisdesmethoxycurcumin (THbdcurcH) were prepared and characterized. The neutral complexes [Ru(arene)(THcurc)Cl] and [Ru(arene)(THbdcurc)Cl] (arene = cymene, benzene, or hexamethylbenzene) were characterized by NMR spectroscopy and ESI mass spectrometry, and the crystal structures of the three complexes were determined by X-ray diffraction analysis. Compared to curcuminoids, these metabolites lose their conjugated double bond system responsible for their planarity, showing unique closed conformation structures. Both closed and open conformations have been analyzed and rationalized by using density functional theory (DFT). The cytotoxicity of the complexes was evaluated in vitro against human ovarian carcinoma cells (A2780 and A2780cisR), human breast adenocarcinoma cells (MCF-7 and MCF-7CR), as well as against non-tumorigenic human embryonic kidney cells (HEK293) and human breast (MCF-10A) cells and compared to the free ligands, cisplatin, and RAPTA-C. There is a correlation between cellular uptake and the cytotoxicity of the compounds, suggesting that cellular uptake and binding to nuclear DNA may be the major pathway for cytotoxicity. However, the levels of complex binding to DNA do not strictly correlate with the cytotoxic potency, indicating that other mechanisms are also involved. In addition, treatment of MCF-7 cells with [Ru(cym)(THcurc)Cl] showed a significant decrease in p62 protein levels, which is generally assumed as a noncisplatin-like mechanism of action involving autophagy. Hence, a cisplatin- and a noncisplatin-like concerted mechanism of action, involving both apoptosis and autophagy, is possible.

Development of Half-Sandwich Ru, Os, Rh, and Ir Complexes Bearing the Pyridine-2-ylmethanimine Bidentate Ligand Derived from 7-Chloroquinazolin-4(3H)-one with Enhanced Antiproliferative Activity

Kinesin spindle protein (KSP) inhibitors are one of the most promising anticancer agents developed in recent years. Herein, we report the synthesis of ispinesib-core pyridine derivative conjugates, which are potent KSP inhibitors, with half-sandwich complexes of ruthenium, osmium, rhodium, and iridium. Conjugation of 7-chloroquinazolin-4(3H)-one with the pyridine-2-ylmethylimine group and the organometallic moiety resulted in up to a 36-fold increased cytotoxicity with IC50 values in the micromolar and nanomolar range also toward drug-resistant cells. All studied conjugates increased the percentage of cells in the G2/M phase, simultaneously decreasing the number of cells in the G1/G0 phase, suggesting mitotic arrest. Additionally, ruthenium derivatives were able to generate reactive oxygen species (ROS); however, no significant influence of the organometallic moiety on KSP inhibition was observed, which suggests that conjugation of a KSP inhibitor with the organometallic moiety modulates its mechanism of action.

Interaction of gallium, indium, and vanadyl curcumin complexes with hen egg-white lysozyme (HEWL): Mechanistic aspects and evaluation of antiamyloidogenic activity

Many proteins and peptides can aggregate into amyloid fibrils with high-ordered and cross-β rich structure characteristics. Amyloid deposition is a common feature of neurodegenerative diseases called amyloidosis. Various natural polyphenolic compounds such as curcumin exhibited antiamyloidogenic activities, but less researches were focused on the metal complexes of these compounds. In this study, the inhibitory effects of gallium curcumin (Ga(cur)3), indium curcumin (In(cur)3), and vanadyl curcumin (VO(cur)2) on the amyloid fibrillation of hen egg white lysozyme (HEWL) have been investigated. Moreover, the details of binding interactions of these metal complexes with HEWL have been explored. The results of fluorescence quenching analyses revealed that In(cur)3 and VO(cur)2 have much higher binding affinities than Ga(cur)3 toward HEWL. The interactions of these metal complexes were accompanied by partial conformational changes in the tertiary structure of HEWL. The kinetic curves of the fibrillation process demonstrated that In(cur)3 and VO(cur)2 have higher inhibitory effects than Ga(cur)3 on the amyloid fibrillation of HEWL. The strength of binding to HEWL is completely in accordance with inhibitory activities of these metal complexes of curcumin.

Ruthenium complexes of 1,4-diazabutadiene ligands with a cis-RuCl2 moiety for catalytic acceptorless dehydrogenation of alcohols: DFT evidence of chemically non-innocent ligand participation

The acceptorless dehydrogenative coupling (ADC) of primary alcohols to esters by diazabutadiene-coordinated ruthenium compounds is reported. Treatment of cis-Ru(dmso)4Cl2 in acetone at 56 °C with different 1,4-diazabutadienes [p-XC6H4N[double bond, length as m-dash]C(H)(H)C[double bond, length as m-dash]NC6H4X-p; X = H, CH3, OCH3, and Cl; abbreviated as DAB-X], gives trans-Ru[κ2-N,N-DAB-X]2Cl2 as the kinetic product of substitution. Heating these products in o-xylene at 144 °C gives the thermodynamically favored cis-Ru[κ2-N,N-DAB-X]2Cl2 isomers. Electronic structure calculations confirm the greater stability of the cis diastereomer. The molecular structures for each pair of geometric isomers have been determined by X-ray diffraction analyses. Cyclic voltammetry experiments on the complexes show an oxidative response and a reductive response within 0.50 to 0.93 V and -0.76 to -1.24 V vs. SCE respectively. The cis-Ru[κ2-N,N-DAB-X]2Cl2 complexes function as catalyst precursors for the acceptorless dehydrogenative coupling of primary alcohols to H2 and homo- and cross-coupled esters. When 1,4-butanediol and 1,5-pentanediol are employed as substrates, lactones and hydroxyaldehydes are produced as the major dehydrogenation products, while secondary alcohols afforded ketones in excellent yields. The mechanism for the dehydrogenation of benzyl alcohol to benzyl benzoate and H2 using cis-Ru[κ2-N,N-DAB-H]2Cl2 (cis-1) as a catalyst precursor was investigated by DFT calculations. The data support a catalytic cycle that involves the four-coordinate species Ru[κ2-N,N-DAB-H][κ1-N-DAB-H](κ1-OCH2Ph) whose protonated κ1-diazabutadiene moiety functions as a chemically non-innocent ligand that facilitates a β-hydrogen elimination from the κ1-O-benzoxide ligand to give the corresponding hydride HRu[κ2-N,N-DAB-H][κ1-N-DAB-H](κ2-O,C-benzaldehyde). H2 production follows a Noyori-type elimination to give (H2)Ru[κ2-N,N-DAB-H][κ1-N-DAB-H](κ1-O-benzaldehyde) as an intermediate in the catalytic cycle.

Monofunctional dimetallic Ru(η6-arene) complexes inhibit NOTCH1 signaling pathway and synergistically enhance anticancer effect in combination with cisplatin or vitamin C

ONS donor ligands L1-L4 were utilized in the preparation of monofunctional dimetallic Ru(η6-arene) complexes (C1-C4). These ONS donor ligand based novel tricoordinated Ru(II) complexes bearing η6-arene co-ligand were prepared for the first time. The current methodology resulted in excellent isolated yields and these complexes were characterized in detail by different spectroscopic and spectrometric techniques. The structures of C1-C2 and C4 were characterized in solid state by single crystal X-ray analysis. The in vitro anticancer analyses showed these novel complexes suppressed the growth of breast (MCF-7), liver (HepG2) and lung (A549) cancer cells. C2 suppressed the growth of these cells in dose-dependent manner revealed form the MTT and crystal violet cell viability assays. Moreover, C2 was observed the most potent complex that was used further in detailed mechanistic analyses in cancer cells. C2 showed good cytotoxic activity at 10 μM dose level as compared to cisplatin or oxaliplatin in these cancer cells. We observed morphological changes in cancer cells upon treatment with C2. Moreover, C2 suppressed the invasion and migration ability of cancer cells. C2 induced cellular senescence to retard cell growth and suppressed the formation of cancer stem cells. Importantly, C2 showed synergistic anticancer effect in combination with cisplatin and Vitamin C to further inhibit cell growth which suggested the potential role of C2 in cancer therapy. Mechanistically, C2 inhibited NOTCH1 dependent signaling pathway to suppress cancer cell invasion, migration and cancer stem cells formation. Thus, these data suggested potential role of C2 in cancer therapy by targeting NOTCH1-dependent signaling to suppress tumorigenesis. The results obtained in this study for these novel monofunctional dimetallic Ru(η6-arene) complexes showed their high anticancer potency and this study will pave to further cytotoxicity exploration on this class of complexes.

Therapeutic potential and limitations of curcumin as antimetastatic agent

Treatment of metastatic cancer is one of the biggest challenges in anticancer therapy. Curcumin is interesting nature polyphenolic compound with unique biological and medicinal effects, including repression of metastases. High impact studies imply that curcumin can modulate the immune system, independently target various metastatic signalling pathways, and repress migration and invasiveness of cancer cells. This review discusses the potential of curcumin as an antimetastatic agent and describes potential mechanisms of its antimetastatic activity. In addition, possible strategies (curcumin formulation, optimization of the method of administration and modification of its structure motif) to overcome its limitation such as low solubility and bioactivity are also presented. These strategies are discussed in the context of clinical trials and relevant biological studies.

Ionic mononuclear [Fe] and heterodinuclear [Fe,Ru] bis(diphenylphosphino)alkane complexes: Synthesis, spectroscopy, DFT structures, cytotoxicity, and biomolecular interactions

Iron(II) and Ru(II) half-sandwich compounds encompass some promising pre-clinical anticancer agents whose efficacy may be tuned by structural modification of the coordinated ligands. Here, we combine two such bioactive metal centres in cationic bis(diphenylphosphino)alkane-bridged heterodinuclear [Fe²⁺, Ru²⁺] complexes to delineate how ligand structural variations modulate compound cytotoxicity. Specifically, Fe(II) complexes of the type [(η⁵-C₅H₅)Fe(CO)₂(κ¹-PPh₂(CH₂)_nPPh₂)]{PF₆} (n = 1-5), compounds 1-5, and heterodinuclear [Fe²⁺, Ru²⁺] complexes, [(η⁵-C₅H₅)Fe(CO)₂(μ-PPh₂(CH₂)_nPPh₂))(η⁶-p-cymene)RuCl₂]{PF₆} (n = 2-5) (compounds 7-10), were synthesized and characterised. The mononuclear complexes were moderately cytotoxic against two ovarian cancer cell lines (A2780 and cisplatin resistant A2780cis) with IC₅₀ values ranging from 2.3 ± 0.5 μM to 9.0 ± 1.4 μM. For 7-10, the cytotoxicity increased with increasing Fe⋅⋅⋅Ru distance, consistent with their DNA affinity. UV-visible spectroscopy suggested the chloride ligands in heterodinuclear 8-10 undergo stepwise substitution by water on the timescale of the DNA interaction experiments, probably affording the species [RuCl(OH₂)(η⁶-p-cymene)(PRPh₂)]²⁺ and [Ru(OH)(OH₂)(η⁶-p-cymene)(PRPh₂)]²⁺ (where PRPh₂ has R = [-(CH₂)₅PPh₂-Fe(C₅H₅)(CO)₂]⁺). One interpretation of the combined DNA-interaction and kinetic data is that the mono(aqua) complex may interact with dsDNA through nucleobase coordination. Heterodinuclear 10 reacts with glutathione (GSH) to form stable mono- and bis(thiolate) adducts, 10-SG and 10-SG₂, with no evidence of metal ion reduction (k₁ = 1.07 ± 0.17 × 10^-1 min^-1 and k₂ = 6.04 ± 0.59 × 10^-3 min^-1 at 37 °C). This work highlights the synergistic effect of the Fe²⁺/Ru²⁺ centres on both the cytotoxicity and biomolecular interactions of the present heterodinuclear complexes.

"Half-Sandwich" Ruthenium Complexes with Alizarin as Anticancer Agents: In Vitro and In Vivo Studies

Upon exploration of the chemistry of the combination of ruthenium/arene with anthraquinone alizarin (L), three new complexes with the general formulas [Ru(L)Cl(η⁶-p-cymene)] (C1), [Ru(L)(η⁶-p-cymene)(PPh₃)]PF₆ (C2), and [Ru(L)(η⁶-p-cymene)(PEt₃)]PF₆ (C3) were synthesized and characterized using spectroscopic techniques (mass, IR, and 1D and 2D NMR), molar conductivity, elemental analysis, and X-ray diffraction. Complex C1 exhibited fluorescence, such as free alizarin, while in C2 and C3, the emission was probably quenched by monophosphines and the crystallographic data showed that hydrophobic interactions are predominant in intermolecular contacts. The cytotoxicity of the complexes was evaluated in the MDA-MB-231 (triple-negative breast cancer), MCF-7 (breast cancer), and A549 (lung) tumor cell lines and MCF-10A (breast) and MRC-5 (lung) nontumor cell lines. Complexes C1 and C2 were more selective to the breast tumor cell lines, and C2 was the most cytotoxic (IC₅₀ = 6.5 μM for MDA-MB-231). In addition, compound C1 performs a covalent interaction with DNA, while C2 and C3 present only weak interactions; however, internalization studies by flow cytometry and confocal microscopy showed that complex C1 does not accumulate in viable MDA-MB-231 cells and is detected in the cytoplasm only after cell permeabilization. Investigations of the mechanism of action of the complexes indicate that C2 promotes cell cycle arrest in the Sub-G₁ phase in MDA-MB-231, inhibits its colony formation, and has a possible antimetastatic action, impeding cell migration in the wound-healing experiment (13% of wound healing in 24 h). The in vivo toxicological experiments with zebrafish indicate that C1 and C3 exhibit the most zebrafish embryo developmental toxicity (inhibition of spontaneous movements and heartbeats), while C2, the most promising anticancer drug in the in vitro preclinical tests, revealed the lowest toxicity in in vivo preclinical screening.

Anticancer evaluation of new organometallic ruthenium(ii) flavone complexes

Targeting multiple malignancy features such as angiogenesis, proliferation and metastasis with one molecule is an effective strategy in developing potent anticancer agents. Ruthenium metal complexation to bioactive scaffolds is reported to enhance their biological activities. Herein, we evaluate the impact of Ru chelation on the pharmacological activities of two bioactive flavones (1 and 2) as anticancer candidates. The novel Ru complexes (1Ru and 2Ru) caused a loss of their parent molecules' antiangiogenic activities in an endothelial cell tube formation assay. 1Ru enhanced the antiproliferative and antimigratory activities of its 4-oxoflavone 1 on MCF-7 breast cancer cells (IC₅₀ = 66.15 ± 5 μM and 50% migration inhibition, p < 0.01 at 1 μM). 2Ru diminished 4-thioflavone's (2) cytotoxic activity on MCF-7 and MDA-MB-231 yet significantly enhanced 2's migration inhibition (p < 0.05) particularly on the MDA-MB-231 cell line. The test derivatives also showed non-intercalative interaction with VEGF and c-myc i-motif DNA sequences.

NRF2 and Bip Interconnection Mediates Resistance to the Organometallic Ruthenium-Cymene Bisdemethoxycurcumin Complex Cytotoxicity in Colon Cancer Cells

Organometallic ruthenium (Ru)(II)-cymene complexes display promising pharmacological properties and might represent alternative therapeutic agents in medical applications. Polyphenols, such as curcumin and curcuminoids, display beneficial properties in medicine, including chemoprevention. Here we analyzed the anticancer effect of a cationic Ruthenium (Ru)(II)-cymene Bisdemethoxycurcumin (Ru-bdcurc) complex. The experimental data show that Ru-bdcurc induced cell death of colon cancer cells in vitro. In response to treatment, cancer cells activated the endoplasmic reticulum (ER)-resident chaperone GRP78/BiP and NRF2, the master regulators of the unfolded protein response (UPR) and the antioxidant response, respectively. Pharmacologic targeting of either NRF2 or BiP potentiated the cytotoxic effect of Ru-bdcurc. We also found that NRF2 and UPR pathways were interconnected as the inhibition of NRF2 reduced BiP protein levels. Mechanistically, the increased Ru-bdcurc-induced cell death, following NRF2 or BiP inhibition, correlated with the upregulation of the UPR apoptotic marker CHOP and with increased H2AX phosphorylation, a marker of DNA damage. The findings reveal that BiP and NRF2 interconnection was a key regulator of colon cancer cells resistance to Ru-bdcurc cytotoxic effect. Targeting that interconnection overcame the protective mechanism and enhanced the antitumor effect of the Ru-bdcurc compound.

Antioxidant conjugated metal complexes and their medicinal applications

Antioxidants are naturally available and man-made substances have the ability to protect cells from damage due to a number of intracellular redox activities. Moreover, Antioxidants such as α-lipoic acid, curcumin and catechin are good anticancer agents. In recent years, the usage of metal complexes as therapeutic agents is gaining importance due to their useful biological properties. Most of the metal ions act as the essential components in building drug molecules that serve as medicines for cancer and neurodegenerative diseases. In particular, metals like copper, gold, ruthenium, and platinum have adequate anticancer properties at both micro- and nano-levels. Hence, conjugation of antioxidants with metals and metal-based compounds results in hybrid bioactive materials with improved anticancer properties. In this chapter, medicinal applications of antioxidant conjugated metal complexes are reviewed and discussed.

Transition metallo-curcumin complexes: a new hope for endometriosis?

Endometriosis is a debilitating gynecological disorder in women of reproductive age. Laparoscopy, a minimally invasive surgical procedure, provides a definitive diagnosis of the disease. Current treatments, including hormonal therapy and pain medication, are often associated with undesirable side effects limiting their long-term usage. This calls for exploring newer diagnostic and therapeutic options with minimal side effects. Curcumin is an established anti-endometriotic agent with inherent fluorescent properties; however, poor bioavailability limits its clinical utility. To address this shortcoming, various transition metals were conjugated with curcumin to improve its stability, specificity and pharmacological properties. The chemical stability, hemocompatibility and ability of the synthesized metallo-curcumin complexes (MCCs) to ameliorate endometriotic lesions were investigated. While all of the MCCs exhibited low hemolytic activity, their chemical and biological activities were largely dependent on the nature of the metal ion conjugated to the curcumin molecule. Copper-curcumin and nickel-curcumin complexes demonstrated superior therapeutic efficacy evidenced by enhanced antioxidant activity, selective cytotoxicity and increased accumulation in endometriotic cells mediated by an energy-dependent active transport process.

Potent and selective anticancer activity of half-sandwich ruthenium and osmium complexes with modified curcuminoid ligands

We have recently reported a series of half-sandwich ruthenium(II) complexes with curcuminoid ligands showing excellent cytotoxic activities (particularly ionic derivatives containing PTA (PTA = 1,3,5-triaza-7-phosphaadamantane). In the present study, new members of this family of compounds have been prepared with the objective to investigate the effect of a long hydrophobic chain obtained by replacing the OH-groups, present in curcumin and bisdemethoxycurcumin, with the palmitic acid ester. We report the synthesis of ruthenium(II) and osmium(II) p-cymene derivatives containing palmitic acid curcumin ester ligands ((1E,3Z,6E)-3-hydroxy-5-oxohepta-1,3,6-triene-1,7-diyl)bis(2-methoxy-4,1-phenylene)dipalmitate (p-curcH) and ((1E,3Z,6E)-3-hydroxy-5-oxohepta-1,3,6-triene-1,7-diyl)bis(4,1-phenylene)dipalmitate (p-bdcurcH). Complexes [M(II)(cym)(p-curc)/(p-bdcurc)(Cl)] 1-4 (M = Ru or Os) are neutral, whereas [M(II)(cym)(p-curc)/(p-bdcurc)(PTA)][SO₃CF₃] 5-8 are salts obtained when the chloride ligand is replaced by the PTA ligand. Stability studies performed on 1-8 in DMSO-PBS under physiological conditions (pH = 7.4) indicate that the complexes remain intact. The complexes exhibit potent and selective cytotoxic activity against an ovarian carcinoma cell line and its cisplatin-resistant form (A2780 and A2780cis), and non-cancerous human embryonic kidney (HEK293T) cells. To define the structure-activity relationships (SAR), the compounds have been compared with other Ru(II) and Os(II) complexes with curcuminoid ligands previously reported. SAR data reveal that the bisdemethoxycurcumin complexes are generally more active and selective than analogous curcumin-containing complexes.

Design, Synthesis, and Anticancer Studies of a p-Cymene-Ru(II)-Curcumin Organometallic Conjugate Based on a Fluorescent 4-Amino-1,8-naphthalimide Tröger's Base Scaffold

A unique V-shaped "chiral" supramolecular scaffold, N-(4-pyridyl)-4-amino-1,8-naphthalimide Tröger's base (TBNap), was synthesized in good yield from a precursor N-(4-pyridyl)-4-amino-1,8-naphthalimide (Nap). TBNap was characterized using different spectroscopic methods and the molecular structure was elucidated by diffraction analysis. A new p-cymene-Ru(II)-curcumin conjugate (TB-Ru-Cur) was designed by reacting TBNap dipyridyl donor and ruthenium-curcuminato acceptor [RuCur = (p-cymene)Ru-(curcuminato)Cl] in the presence of silver triflate. TB-Ru-Cur was isolated in quantitative yield and characterized using Fourier transform infrared (FT-IR), NMR (¹H, ¹³C, and ¹⁹F), and electrospray ionization mass spectrometry (ESI-MS), and the molecular structure has been predicted using a computational study. Both TBNap and TB-Ru-Cur exhibited intramolecular charge transfer (ICT)-based fluorescence emission. Furthermore, the anticancer properties of TBNap, Ru-Cur, and TB-Ru-Cur were assessed in different cancer cell lines. Gratifyingly, the conjugate TB-Ru-Cur displayed fast-cellular internalization and good cytotoxicity against HeLa, HCT-116, and HepG2 cancer cells and the estimated IC₅₀ value was much lower than that of the precursors (TBNap and Ru-Cur) and the well-known chemotherapeutic drug cisplatin.

Nanoencapsulation of Ru(p-cymene) Complex Bearing Ginger-based Natural Product into Liposomal Nanoformulation to Improve Its Cellular Uptake and Antiproliferative Activity

The organometallic compounds are prospective candidates in the row of developing metallochemotherapeutics with the aim of overcoming the limitations of platinum drugs. In order to explore the anticancer properties of organometallic compounds with the natural medicines, two Ru(II)-p-cymene complexes containing the natural products, viz., 6-gingerol (6G) and benzylated-6-gingerdione (B-6GD) have been synthesized and characterized well. The phenolic group of the Ru(6G) complex facilitates its higher cell-free antioxidant activity than its analogue complex. Also, the same complex shows higher cytotoxicity toward A549 lung and HeLa-S3 cervical cancer cells than the Ru(B-6GD) complex but lower cytotoxicity toward A2058 metastatic melanoma cancer cells. Both complexes are shown to easily accumulate in melanoma cancer cells, and their degree of cytotoxicity in the same cells is found to be positively correlated with cell uptake. The cytotoxicity of complexes arises from their intracellular activity, mainly due to the induction of singlet oxygen production in cancer cells. The subcellular fractionation study shows that mitochondria and ER-Golgi membranes might be their predominant targets. Also, the mechanistic investigation revealed that Ru(B-6GD) induces caspase-dependent non-apoptotic cell death whereas Ru(6G) can induce caspase-independent non-apoptotic cell death. Furthermore, both complexes are found to moderately alter the adhesion properties of cancer cells, which is beneficial for antimetastatic treatment. Despite the potential pharmacological activity, Ru(6G) is encapsulated into polymer-supported liposomes to reduce its toxicity and further improve its anticancer potency. The π-conjugated yne-ene chain of polydiacetylene aids in the development of a stable nanoformulation, which achieved a slow release of the complex. Most importantly, the cancer cell uptake of the liposome-encapsulated Ru(6G) complex is 20 times enhanced and the total ROS formation in cancer cells is significantly increased compared to the non-encapsulated complex. However, the nanoformulation does not alter the antimetastatic potency of the encapsulated complex.

Systematic Study on the Cytotoxic Potency of Commonly Used Dimeric Metal Precursors in Human Cancer Cell Lines

The cytotoxicities of seven dimeric metal species of the general formula [M(arene)Cl2 ]2 , commonly used as precursors for complex synthesis and deemed biologically inactive, are investigated in seven commonly employed human cancer cell lines. Four of these complexes featured a ruthenium(II) core, where p-cymene, toluene, benzene and indane were used as arenes. Furthermore, the osmium(II) p-cymene dimer, as well as the Cp* dimers of rhodium(III) and its heavier analogue iridium(III) were included in this work (Cp*=1,2,3,4,5-pentamethylcyclopentadienide). While the cytotoxic potencies of the ruthenium(II) and osmium(II) dimers are very low (or not even detectable at applicable concentrations), surprising activity, especially in cells from ovarian malignancies (with one or two-digit micromolar IC50 values), have been found for the rhodium(III) and iridium(III) representatives. This publication is aimed at all researchers using synthetic procedures based on functionalization of these dimeric starting materials to rationalize changes in biological properties, especially cytotoxicity in cancer cells.

Complexes of Zn(II) with a mixed tryptanthrin derivative and curcumin chelating ligands as new promising anticancer agents

In this study, two novel curcumin (H-Cur)-tryptanthrin metal compounds-[Zn(TA)Cl₂], i.e., Zn(TA), and [Zn(TA)(Cur)]Cl, i.e., Zn(TAC)-were synthesized and investigated using 5-(bis-pyridin-2-ylmethyl-amino)-pentanoic acid (6,12-dioxo-6,12-dihydro-indolo[2,1-b]quinazolin-8-yl)-amide (TA) and H-Cur as the targeting and high-activity anticancer chemotherapeutic moieties, respectively. They were then compared with the di-(2-picolyl)amine (PA) Zn(II) complex [Zn(PA)Cl₂], i.e., Zn(PA). When compared with Zn(PA) and cisplatin, the IC₅₀ values of Zn(TA) and Zn(TAC) indicated that the compounds had high cytotoxicity against A549/DDP cancer cells, implying that the H-Cur-tryptanthrin Zn(II) compounds have the potential for use as anticancer drugs. We propose the use of synthesized theragnostic H-Cur-tryptanthrin Zn(II) complexes with nuclear-targeting and DNA-damaging capabilities as a simple therapeutic strategy against tumors. The Zn(TA) and Zn(TAC) complexes could be traced via red fluorescence and were found to accumulate in the cell nuclei and induce DNA damage, cell cycle arrest, mitochondrial dysfunction, and cell apoptosis both in vitro and in vivo. In addition, Zn(TAC) exhibited a higher antiproliferative effect on A549/DDP than Zn(TA) and Zn(PA), which was undoubtedly associated with the key roles of the novel tryptanthrin derivative TA and H-Cur in the Zn(TAC) complex.

Tuning the Cytotoxicity of Bis-Phosphino-Amines Ruthenium(II) Para-Cymene Complexes for Clinical Development in Breast Cancer

Despite some limitations such as long-term side effects or the potential presence of intrinsic or acquired resistance, platinum compounds are key therapeutic components for the treatment of several solid tumors. To overcome these limitations, maintaining the same efficacy, organometallic ruthenium(II) compounds have been proposed as a viable alternative to platinum agents as they have a more favorable toxicity profile and represent an ideal template for both, high-throughput and rational drug design. To support the preclinical development of bis-phoshino-amine ruthenium compounds in the treatment of breast cancer, we carried out chemical modifications in the structure of these derivatives with the aim of designing less toxic and more efficient therapeutic agents. We report new bis-phoshino-amine ligands and the synthesis of their ruthenium counterparts. The novel ligands and compounds were fully characterized, water stability analyzed, and their in vitro cytotoxicity against a panel of tumor cell lines representative of different breast cancer subtypes was evaluated. The mechanism of action of the lead compound of the series was explored. In vivo toxicity was also assessed. The results obtained in this article might pave the way for the clinical development of these compounds in breast cancer therapy.

Biological Investigations of Ru(II) Complexes With Diverse β-diketone Ligands

The β-diketone scaffold is a commonly used synthetic intermediate, and is a functional group found in natural products such as curcuminoids. This core structure can also act as a chelating ligand for a variety of metals. In order to assess the potential of this scaffold for medicinal inorganic chemistry, seven different κ2-O,O'-chelating ligands were used to construct Ru(II) complexes with polypyridyl co-ligands, and their biological activity was evaluated. The complexes demonstrated promising structure-dependent cytotoxicity. Three complexes maintained high activity in a tumor spheroid model, and all complexes demonstrated low in vivo toxicity in a zebrafish model. From this series, the best compound exhibited a ~ 30-fold window between cytotoxicity in a 3-D tumor spheroid model and potential in vivo toxicity. These results suggest that κ2-O,O'-ligands can be incorporated into Ru(II)-polypyridyl complexes to create favorable candidates for future drug development.

Photoactivated Osmium Arene Anticancer Complexes

Half-sandwich Os-arene complexes exhibit promising anticancer activity, but their photochemistry has hardly been explored. To exploit the photocytotoxicity and photochemistry of Os-arenes, O,O-chelated complexes [Os(η⁶-p-cymene)(Curc)Cl] (OsCUR-1, Curc = curcumin) and [Os(η⁶-biphenyl)(Curc)Cl] (OsCUR-2), and N,N-chelated complexes [Os(η⁶-biphenyl)(dpq)I]PF₆ (OsDPQ-2, dpq = pyrazino[2,3-f][1,10]phenanthroline) and [Os(η⁶-biphenyl)(bpy)I]PF₆ (OsBPY-2, bpy = 2,2'-bipyridine), have been investigated. The Os-arene curcumin complexes showed remarkable photocytotoxicity toward a range of cancer cell lines (blue light IC₅₀: 2.6-5.8 μM, photocytotoxicity index PI = 23-34), especially toward cisplatin-resistant cancer cells, but were nontoxic to normal cells. They localized mainly in mitochondria in the dark but translocated to the nucleus upon photoirradiation, generating DNA and mitochondrial damage, which might contribute toward overcoming cisplatin resistance. Mitochondrial damage, apoptosis, ROS generation, DNA damage, angiogenesis inhibition, and colony formation were observed when A549 lung cancer cells were treated with OsCUR-2. The photochemistry of these Os-arene complexes was investigated by a combination of NMR, HPLC-MS, high energy resolution fluorescence detected (HERFD), X-ray adsorption near edge structure (XANES) spectroscopy, total fluorescence yield (TFY) XANES spectra, and theoretical computation. Selective photodissociation of the arene ligand and oxidation of Os(II) to Os(III) occurred under blue light or UVA excitation. This new approach to the design of novel Os-arene complexes as phototherapeutic agents suggests that the novel curcumin complex OsCUR-2, in particular, is a potential candidate for further development as a photosensitizer for anticancer photoactivated chemotherapy (PACT).

Acid-assisted hydrogenation of CO2 to methanol using Ru(II) and Rh(III) RAPTA-type catalysts under mild conditions

A highly efficient homogeneous catalyst system for production of CH3OH from CO2 using single molecular defined ruthenium and rhodium RAPTA-type catalysts [Ru(η6-p-cymene)X2(PTA)] (X = I(1), Cl(2); PTA = 1,3,5-triaza-7-phosphaadamantane) and rhodium catalysts [Rh(η5-C5Me5)X2(PTA/PTA-BH3)] (X = Cl(3), H(4) and PTA-BH3, H(5)) developed in acidic media under mild conditions. A TON of 4752 is achieved using a [Ru(η6-p-cymene)I2(PTA)] catalyst which represents the first example of CO2 hydrogenation to CH3OH using single molecular defined Ru and Rh RAPTA-type catalysts.

Organoruthenium Complexes with Benzo-Fused Pyrithiones Overcome Platinum Resistance in Ovarian Cancer Cells

Drug resistance to existing anticancer agents is a growing clinical concern, with many first line treatments showing poor efficacy in treatment plans of some cancers. Resistance to platinum agents, such as cisplatin, is particularly prevalent in the treatment of ovarian cancer, one of the most common cancers amongst women in the developing world. Therefore, there is an urgent need to develop next generation of anticancer agents which can overcome resistance to existing therapies. We report a new series of organoruthenium(II) complexes bearing structurally modified pyrithione ligands with extended aromatic scaffold, which overcome platinum and adriamycin resistance in human ovarian cancer cells. The mechanism of action of such complexes appears to be unique from that of cisplatin, involving G1 cell cycle arrest without generation of cellular ROS, as is typically associated with similar ruthenium complexes. The complexes inhibit the enzyme thioredoxin reductase (TrxR) in a model system and reduce cell motility towards wound healing. Importantly, this work highlights further development in our understanding of the multi-targeting mechanism of action exhibited by transition metal complexes.

Piano-Stool Ruthenium(II) Complexes with Delayed Cytotoxic Activity: Origin of the Lag Time

We have recently reported a series of piano-stool ruthenium(II) complexes of the general formula [RuCl₂(η⁶-arene)(P(1-pyrenyl)R²R³)] showing excellent cytotoxic activities (particularly when R² = R³ = methyl). In the present study, new members of this family of compounds have been prepared with the objective to investigate the effect of the steric hindrance of a bulky phosphane ligand, namely diisopropyl(1-pyrenyl)phosphane (L), on exchange reactions involving the coordinated halides (X = Cl, I). Two η⁶-arene rings were used, i.e. η⁶-methyl benzoate (mba) and η⁶-p-cymene (p-cym), and four complexes were synthesized, namely [RuCl₂(mba)(L)] (1_Cl2^iPr), [RuI₂(mba)(L)] (1_I2^iPr), [RuCl₂(p-cym)(L)] (2_Cl2^iPr), and [RuI₂(p-cym)(L)] (2_I2^iPr). Unexpectedly, all of the complexes exhibited poor cytotoxic activities after 24 h of incubation with cells, in contrast to the related compounds previously reported. However, it was observed that aged DMSO solutions of 2_I2^iPr (from 2 to 7 days) exhibited better activities in comparison to freshly prepared solutions and that the activity improved over “aging” time. Thorough studies were therefore performed to uncover the origin of this lag time in the cytotoxicity efficiency. The data achieved clearly demonstrated that compounds 2_I2^iPr and 2_Cl2^iPr were undergoing a series of transformation reactions in DMSO (with higher rates for the iodido complex 2_I2^iPr), ultimately generating cyclometalated species through a mechanism involving DMSO as a coordinated proton abstractor. The cyclometalated complexes detected in solution were subsequently prepared; hence, pure [RuCl(p-cym)(κ²C-diisopropyl(1-pyrenyl)phosphane)] (3_Cl^iPr), [RuI(p-cym)(κ²C-diisopropyl(1-pyrenyl)phosphane)] (3_I^iPr), and [Ru(p-cym)(κS-dmso)(κ²C-diisopropyl(1-pyrenyl)phosphane)]PF₆ (3_dmso^iPr) were synthesized and fully characterized. Remarkably, 3_Cl^iPr, 3_I^iPr, and 3_dmso^iPr are all very efficient cytotoxic agents, exhibiting slightly better activities in comparison to the chlorido noncyclometalated complexes [RuCl₂(η⁶-arene)(P(1-pyrenyl)R²R³)] described in an earlier report. For comparison purposes, the iodido compounds [RuI₂(mba)(dimethyl(1-pyrenyl)phosphane)] (1_I2^Me) and [RuI₂(p-cym)(dimethyl(1-pyrenyl)phosphane)] (2_I2^Me), bearing the less hindered dimethyl(1-pyrenyl)phosphane ligand, have also been prepared. The cytotoxic and chemical behaviors of 1_I2^Me and 1_I2^Me were comparable to those of their chlorido counterparts reported previously.

DMSO gradually converts half-sandwich, 1-pyrenyl-containing ruthenium(II) complexes into cyclometalated species showing notable cytotoxic properties.

Lead (Pb) exposure induces physiological alterations in the serotoninergic and vasopressin systems causing anxiogenic-like behavior in Meriones shawi: Assessment of BDMC as a neuroprotective compound for Pb-neurotoxicity and kidney damages

BACKGROUND

Studies have shown that lead (Pb) is one of hazardous heavy metals with various adverse effects on human health including mental health; Pb can induce psychiatric disorders like anxiety. In the present work, we examined the potential of bisdemethoxycurcumin (BDMC) as a neuroprotective agent against lead induced anxiety inMeriones shawi (M. shawi).

METHODS

We asses, the potential of three consecutive day exposure to Pb (25 mg/kg body weight) in inducing anxiogenic effect, serotoninergic and vasopressinergic disruptions inM. shawi. This was done using neurobehavioral tests (open field, elevated plus maze), immunohistochemestry by anti-serotonin (5-HT), and anti-vasopressin (AVP) antibodies. We also measured the possible restorative potential of BDMC (30 mg/kg body weight), delivered by oral gavage. After that, a biochemical and histopathological studies were done.

RESULTS

Our results showed that lead exposure for three consecutive days increases significantly the 5-HT-immunoreactivity in dorsal raphe nucleus (DRN) accompanied with a significant enhancement of AVP-immunoreactivity in the cell bodies and fibers in the supraoptic (SON) and paraventricular (PVN) nuclei of the hypothalamus. In the collecting tube, AVP binds to the V2 receptor of the epithelial cells and increases the water permeability. Our results showed clearly the epithelial cells degeneration after lead exposure, then we suggest that the increased AVP could be a response to the hydric balance disrupted after degenerative effect of lead exposure on epithelial cells. BDMC produced an anxiolytic effect in meriones. Moreover, it restored 5-HT and AVP immunoreactivity within studying nuclei. The biochemical and histopathological studies showed that Pb induced renal damages. In addition, BDMC restored the renal alterations.

CONCLUSION

According to the obtained results, we suggest new pharmacological effects of BDMC; while it has an anxiolytic effect against Pb-induced anxiety by working on serotoninergic and vasopressinergic systems with an obvious restoration of the renal injuries induced by lead exposure.

Ruthenium(II) 1,4,7-trithiacyclononane complexes of curcumin and bisdemethoxycurcumin: Synthesis, characterization, and biological activity

Two cationic ruthenium(II) 1,4,7-trithiacyclononane ([9]aneS₃) complexes of curcumin (curcH) and bisdemethoxycurcumin (bdcurcH), namely [Ru(curc)(dmso-S)([9]aneS₃)]Cl (1) and [Ru(bdcurc)(dmso-S)([9]aneS₃)]Cl (2) were prepared from the [RuCl₂(dmso-S)([9]-aneS₃)] precursor and structurally characterized, both in solution and in the solid state by X-ray crystallography. The corresponding PTA complexes [Ru(curc)(PTA)([9]aneS₃)]Cl (3) and [Ru(bdcurc)(PTA)([9]aneS₃)]Cl (4) have been also synthesized and characterized (PTA = 1,3,5-triaza-7-phosphaadamantane). Bioinorganic studies relying on mass spectrometry were performed on complexes 1-4 to assess their interactions with the model protein lysozyme. Overall, a rather limited reactivity with lysozyme was highlighted accompanied by a modest cytotoxic potency against three representative cancer cell lines. The moderate pharmacological activity is likely connected to the relatively high stability of these complexes.

Mitochondria-localizing curcumin-cryptolepine Zn(II) complexes and their antitumor activity

Many metal complexes are potent candidates as mitochondrial-targeting agents. In this study, four novel Zn(II) complexes, [Zn(BPQA)Cl₂] (Zn1), [Zn(BPQA)(Curc)]Cl (Zn2), [Zn(PQA)Cl₂] (Zn3), and [Zn(PQA)(Curc)]Cl (Zn4), containing N,N-bis(pyridin-2-ylmethyl)benzofuro[3,2-b]quinolin-11-amine (BPQA), N-(pyridin-2-ylmethyl)benzofuro[3,2-b]quinolin-11-amine (PQA), and curcumin (H-Curc) were synthesized. An MTT assay showed that Zn1-Zn4 had strong anticancer activities against SK-OV-3/DDP and T-24 tumor cells with IC₅₀ values of 0.03-6.19 μM. Importantly, Zn1 and Zn2 displayed low toxicities against normal HL-7702 cells. Mechanism experiments demonstrated that probe Zn2 showed appreciable fluorescence in the red region of the spectrum, and substantial accumulation of Zn2 occurred in the mitochondria after treatment, indicating increases in Ca²⁺ and reactive oxygen species levels, loss of the mitochondrial membrane potential, and consequent induction of mitochondrial dysfunction at low concentrations. In addition, the probe Zn2 effectively (50.7%) inhibited the growth of T-24 bladder tumor cells in vivo. The probe Zn2 shows potential for use in cancer therapy while retaining the H-Curc as an imaging probe.

N,N-Ru(II)-p-cymene-poly(N-vinylpyrrolidone) surface functionalized gold nanoparticles: from organoruthenium complex to nanomaterial for antiproliferative activity

Organometallic Ru-arene complexes are promising as anticancer agents, but the lack of tumor uptake and poor solubility in the physiological medium impede their development. In order to deal with these challenges, we developed gold nanoparticles coated with Ru(arene)-functionalized PNVP-Py, where PNVP-Py is pyridine end-functionalized poly(N-vinylpyrrolidone). It is demonstrated that these particles exhibit higher anti-proliferative activity than the individual organometallic ruthenium(ii) complex of the type [Ru(η6-p-cymene)(NN)Cl]PF6, where NN is bis(4-methoxyphenylimino)acenaphthene, against colorectal adenocarcinoma cell lines. More specifically, a RuII(η6-p-cymene) complex containing a NN bidentate ligand has been prepared and characterized by spectral studies and X-ray crystallography. To tether the isolated complex onto the surface of the AuNPs, PNVP-Py, which contains a pyridine group at one end to coordinate to the Ru-complex and a suitable functional group at the other end to bind on the surface of the AuNPs, has been prepared and utilized to obtain the macromolecular complex [Ru(η6-p-cymene)(NN)(PNVP-Py)]Cl2. Next, stable Ru(p-cym)(NN)(PNVP-Py)@AuNPs were obtained via a ligand exchange reaction of citrate-stabilized AuNPs with a macromolecular complex by a direct 'grafting to' approach and characterized well. Despite the lower DNA cleavage activity, the nanoconjugate exhibits better cytotoxicity than the individual complex against HT-29 colorectal adenocarcinoma cells on account of its enhanced permeability across the cell membrane. The AO/EB staining assay revealed that the nanoconjugate is able to induce an apoptotic mode of cell death, which was further quantitatively evaluated by Annexin V-FITC/PI double assay. An immunofluorescence assay indicated the higher potency of the nanoconjugate to inhibit cyclin D1 gene expression that is required for cancer cell growth. To the best of our knowledge, this is the first report of the modification of an organometallic Ru(arene) complex into a Ru(arene)metallopolymer-gold nanoconjugate for the development of ruthenium-based nanomedicine for cancer treatment.

Mononuclear Mn complexes featuring N,S-/N,N-donor and 1,3,5-triaza-7-phosphaadamantane ligands: synthesis and electrocatalytic properties

Mononuclear Mn(i) carbonyl complexes incorporating 2-mercaptobenzothiazole or 2-mercaptobenzimidazole and phosphaadamantane ligands were evaluated as electrocatalysts for the HER both in acetonitrile and acetonitrile/water.

Ruthenium Complexes as Anticancer Agents: A Brief History and Perspectives

Platinum (Pt)-based anticancer drugs such as cisplatin have been used to treat various cancers. However, they have some limitations including poor selectivity and toxicity towards normal cells and increasing chemoresistance. Therefore, there is a need for novel metallo-anticancers, which has not been met for decades. Since the initial introduction of ruthenium (Ru) polypyridyl complex, a number of attempts at structural evolution have been conducted to improve efficacy. Among them, half-sandwich Ru-arene complexes have been the most prominent as an anticancer platform. Such complexes have clearly shown superior anticancer profiles such as increased selectivity toward cancer cells and ameliorating toxicity against normal cells compared to existing Pt-based anticancers. Currently, several Ru complexes are under human clinical trials. For improvement in selectivity and toxicity associated with chemotherapy, Ru complexes as photodynamic therapy (PDT), and photoactivated chemotherapy (PACT), which can selectively activate prodrug moieties in a specific region, have also been investigated. With all these studies on these interesting entities, new metallo-anticancer drugs to at least partially replace existing Pt-based anticancers are anticipated. This review covers a brief description of Ru-based anticancer complexes and perspectives.

Synthesis, characterization and photodynamic activity of half-sandwich rhodium(III) complexes with curcuminoids

Half-sandwich Cp*-Rh complexes containing curcuminoids ([Rh(η⁵-Cp*)(L)(Py)]PF₆, 1-3, L = curcuminoid ligands L¹-L³) were prepared, characterized and studied for anticancer activity. Complex 1 was structurally characterized by single-crystal X-ray crystallography. Complex 3 presented excellent photodynamic anticancer effect in light (>400 nm) showing IC₅₀ values of 7.5 and 4.3 μM against HepG2, SKOV3 and HeLa, respectively, along with the 12.4, 7.9 and 4.7-fold lower toxicity in the dark. Confocal fluorescence images show that the complex primarily targeted mitochondrial localization. These results suggest that the complex 3 was a valuable agent with higher efficacy for chemotherapy and photodynamic therapy, which can achieve real-time image guidance in cancer therapy for the fluorescence of the complex as imaging signals. This investigation provides a valuable route to design novel half-sandwich Cp*-Rh complexes with higher efficacy for photodynamic anticancer chemotherapy.

Protein binding studies with human serum albumin, molecular docking and in vitro cytotoxicity studies using HeLa cervical carcinoma cells of Cu(ii)/Zn(ii) complexes containing a carbohydrazone ligand

The interaction of two binuclear mixed ligand Cu(ii) complexes [Cu(o-phen)LCu(OAc)] (1) and [Cu(o-phen)LCu(o-phen)](OAc) (2) (H3L = o-HOC6H4C(H)[double bond, length as m-dash]N-NH-C(OH)[double bond, length as m-dash]N-N[double bond, length as m-dash]C(H)-C6H4OH-o) and a new mononuclear Zn(ii) complex [Zn(HL)(o-phen)(H2O)](OAc)·H2O (3) (H2L = o-HOC6H4-C(H)[double bond, length as m-dash]N-NH-C([double bond, length as m-dash]O)-NH-N[double bond, length as m-dash]C(H)-C6H4OH-o, o-phen = 1,10-phenanthroline, and OAc = CH3COO-) with human serum albumin (HSA) was studied using fluorescence quenching, synchronous and 3D fluorescence measurements and UV-vis spectroscopy. 3D fluorescence studies showed that the HSA structure was altered at the secondary and tertiary levels upon binding with the complexes. This was further supported by the electronic absorption spectral studies of HSA in the absence and presence of the compounds. The average binding distance (r) between HSA and the complexes was obtained by Förster's resonance energy transfer theory. Complex 3 was structurally characterized by X-ray crystallography. Molecular docking studies indicated that all three complexes primarily bind to HSA in subdomain IIA with amino acid residues such as Arg218 and Lys199 which are located at the entrance of Sudlow's site I. The in vitro cytotoxicities of complexes 1-3 against HeLa cells showed promising anticancer activity (IC50 = 3.5, 3.9 and 16.9 μM for 1, 2 and 3, respectively). Live cell time lapse imaging for 1 was done to capture the dynamic behavior of the cells upon treatment with the complex. Cell cycle analysis by flow cytometry with HeLa cells indicated that 1 and 2 induced cell cycle arrest in the G2/M phase while 3 induced arrest in the G0/G1 phase leading to cell death. Compounds 1 and 2 but not 3 induced apoptosis through the mitochondrial pathway as suggested from the relative p53, caspase3 and bcl2 mRNA levels measured by real-time quantitative PCR analysis.

Investigating the reactivity of neutral water-soluble Ru(ii)-PTA carbonyls towards the model imine ligands pyridine and 2,2'-bipyridine

As a continuation of our strategy for preparing new Ru(ii) precursors to be exploited as building blocks in the construction of metal-mediated supramolecular assemblies with improved solubility in water, here we describe the reactivity of selected neutral Ru(ii)-PTA carbonyls (PTA = 1,3,5-triaza-7-phosphaadamantane) towards the model imine ligands pyridine (py) and 2,2'-bipyridine (bpy) and the preparation and characterization of several neutral and cationic water-soluble derivatives: trans,trans,trans-[RuCl2(CO)(py)(PTA)2] (7), cis,cis,trans-[RuCl2(CO)2(py)(PTA)] (9), cis,trans-[Ru(bpy)Cl(CO)(PTA)2]Cl (10), mer-[Ru(bpy)(CO)(PTA)3](Cl)2 (12), cis,trans-[Ru(bpy)(CO)2Cl(PTA)]Cl (13), cis,trans-[Ru(bpy)(CO)2(PTA)2](NO3)2 (14NO3). In addition, we found that light-induced isomerization in some bpy compounds could be induced. The following species, either side-products isolated in low yield or compounds obtained exclusively in solution, were also unambiguously identified: cis,cis,trans-[RuCl2(CO)(py)(PTA)2] (8), trans-[RuCl2(bpy)(CO)(PTA)] (11), cis,cis-[Ru(bpy)Cl(CO)(PTA)2]Cl (15) and cis,cis-[Ru(bpy)(CO)2Cl(PTA)]Cl (16). The X-ray structures of 7, 11·H2O, and 12·7H2O are also reported. All compounds are new and - with few exceptions - show a good solubility in water.

A ruthenium(II)-curcumin compound modulates NRF2 expression balancing the cancer cell death/survival outcome according to p53 status

Abstract

Background

Tumor progression and tumor response to anticancer therapies may be affected by activation of oncogenic pathways such as the antioxidant one induced by NRF2 (nuclear factor erythroid 2-related factor 2) transcription factor and the pathways modified by deregulation of oncosuppressor p53. Often, oncogenic pathways may crosstalk between them increasing tumor progression and resistance to anticancer therapies. Therefore, understanding that interplay is critical to improve cancer cell response to therapies. In this study we aimed at evaluating NRF2 and p53 in several cancer cell lines carrying different endogenous p53 status, using a novel curcumin compound since curcumin has been shown to target both NRF2 and p53 and have anti-tumor activity.

Methods

We performed biochemical and molecular studies by using pharmacologic of genetic inhibition of NRF2 to evaluate the effect of curcumin compound in cancer cell lines of different tumor types bearing wild-type (wt) p53, mutant (mut) p53 or p53 null status.

Results

We found that the curcumin compound induced a certain degree of cell death in all tested cancer cell lines, independently of the p53 status. At molecular level, the curcumin compound induced NRF2 activation, mutp53 degradation and/or wtp53 activation. Pharmacologic or genetic NRF2 inhibition further increased the curcumin-induced cell death in both mutp53- and wtp53-carrying cancer cell lines while it did not increase cell death in p53 null cells, suggesting a cytoprotective role for NRF2 and a critical role for functional p53 to achieve an efficient cancer cell response to therapy.

Conclusions

These findings underline the prosurvival role of curcumin-induced NRF2 expression in cancer cells even when cells underwent mutp53 downregulation and/or wtp53 activation. Thus, NRF2 inhibition increased cell demise particularly in cancer cells carrying p53 either wild-type or mutant suggesting that p53 is crucial for efficient cancer cell death. These results may represent a paradigm for better understanding the cancer cell response to therapies in order to design more efficient combined anticancer therapies targeting both NRF2 and p53.