Dinuclear zinc(II) complexes containing (benzimidazol-2-yl)benzene that overcome drug resistance in hepatocellular carcinoma cells through induction of mitochondria fragmentation

Anticancer properties of complexes derived from bidentate ligands

Cancer is the abnormal division and multiplication of cells in an organ or tissue. It is the second leading cause of death globally. There are various types of cancer such as prostate, breast, colon, lung, stomach, liver, skin, and many others depending on the tissue or organ where the abnormal growth originates. Despite the huge investment in the development of anticancer agents, the transition of research to medications that improve substantially the treatment of cancer is less than 10%. Cisplatin and its analogs are ubiquitous metal-based anticancer agents notable for the treatment of various cancerous cells and tumors but unfortunately accompanied by large toxicities due to low selectivity between cancerous and normal cells. The improved toxicity profile of cisplatin analogs bearing bidentate ligands has motivated the synthesis of vast metal complexes of bidentate ligands. Complexes derived from bidentate ligands such as β-diketones, diolefins, benzimidazoles and dithiocarbamates have been reported to possess 20 to 15,600-fold better anticancer activity, when tested on cell lines, than some known antitumor drugs currently on the market, e.g. cisplatin, oxaliplatin, carboplatin, doxorubicin, and 5-fluorouracil. This work discusses the anticancer properties of various metal complexes derived from bidentate ligands, for possible application in chemotherapy. The results discussed were evaluated by the IC50 values as obtained from cell line tests on various metal-bidentate complexes. The structure-activity relationship study of the complexes discussed, revealed that hydrophobicity is a key factor that influences anticancer properties of molecules.

Novel glycosylation zinc(II)-cryptolepine complexes perturb mitophagy pathways and trigger cancer cell apoptosis and autophagy in SK-OV-3/DDP cells

With the aim of shedding some light on the mechanism of action of zinc(II) complexes in antiproliferative processes and molecular signaling pathways, three novel glycosylated zinc(II)-cryptolepine complexes, i.e., [Zn(QA1)Cl₂] (Zn(QA1)), [Zn(QA2)Cl₂] (Zn(QA2)), and [Zn(QA3)Cl₂] (Zn(QA3)), were prepared by conjugating a glucose moiety with cryptolepine, followed by complexation of the resulting glycosylated cryptolepine compounds N-((1-(2-morpholinoethyl)-1H-1,2,3-triazol-4-yl)methyl)-benzofuro[3,2-b]quinolin-11-amine (QA1), 2-(4-((benzofuro[3,2-b]quinolin-11-ylamino)methyl)-1H-1,2,3-triazol-1-yl)ethan-1-ol (QA2), and (2S,3S,4R,5R,6S)-2-(4-((benzofuro[3,2-b]quinolin-11-ylamino)-methyl)-1H-1,2,3-triazol-1-yl)-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol (QA3) with zinc(II), and their anticancer activity was evaluated. In MTT assays, Zn(QA1)-Zn(QA3) were more active against cisplatin-resistant ovarian SK-OV-3/DDP cancer cells (SK-OV-3cis) than ZnCl₂ and the QA1-QA3 ligands, with IC₅₀ values of 1.81 ± 0.50, 2.92 ± 0.32, and 1.01 ± 0.11 μM, respectively. Complexation of glycosylated cryptolepine QA3 with zinc(II) increased the antiproliferative activity of the ligand, suggesting that Zn(QA3) could act as a chaperone to deliver the active ligand intracellularly, in contrast with other cryptolepine metal complexes previously reported. In vivo and in vitro investigations suggested that Zn(QA3) exhibited enhanced anticancer activity with treatment effects comparable to those of the clinical drug cisplatin. Furthermore, Zn(QA1)-Zn(QA3) triggered SK-OV-3cis cell apoptosis through mitophagy pathways in the order Zn(QA1) > Zn(QA1) > Zn(QA2). These results demonstrate the potential of glycosylated zinc(II)-cryptolepine complexes for the development of chemotherapy drugs against cisplatin-resistant SK-OV-3cis cells.

Mitochondria-Targeting Anticancer Metal Complexes

Background:

Since the serendipitous discovery of the antitumor activity of cisplatin there has been a continuous surge in studies aimed at the development of new cytotoxic metal complexes. While the majority of these complexes have been designed to interact with nuclear DNA, other targets for anticancer metallodrugs attract increasing interest. In cancer cells the mitochondrial metabolism is deregulated. Impaired apoptosis, insensitivity to antigrowth signals and unlimited proliferation have been linked to mitochondrial dysfunction. It is therefore not surprising that mitochondria have emerged as a major target for cancer therapy. Mitochondria-targeting agents are able to bypass resistance mechanisms and to (re-) activate cell-death programs.

Methods:

Web-based literature searching tools such as SciFinder were used to search for reports on cytotoxic metal complexes that are taken up by the mitochondria and interact with mitochondrial DNA or mitochondrial proteins, disrupt the mitochondrial membrane potential, facilitate mitochondrial membrane permeabilization or activate mitochondria-dependent celldeath signaling by unbalancing the cellular redox state. Included in the search were publications investigating strategies to selectively accumulate metallodrugs in the mitochondria.

Results:

This review includes 241 references on antimitochondrial metal complexes, the use of mitochondria-targeting carrier ligands and the formation of lipophilic cationic complexes.

Conclusion:

Recent developments in the design, cytotoxic potency, and mechanistic understanding of antimitochondrial metal complexes, in particular of cyclometalated Au, Ru, Ir and Pt complexes, Ru polypyridine complexes and Au-N-heterocyclic carbene and phosphine complexes are summarized and discussed.

Structure of 2,2'-(5-tert-butyl-1,3-phenyl-ene)bis-(1-pentyl-1H-benzimidazol-3-ium) tetra-chlorido-mercurate(II)

In the title salt, (C34H44N4)[HgCl4], the [C34H44N4]2+ cations and [HgCl4]2- anions are linked by N-H⋯Cl hydrogen bonds. One of the two n-pentyl side chains was refined as disordered over two sets of sites, with occupancies of 0.733 (18) and 0.267 (18). The geometry around the HgII atom in the [HgCl4]2- anion is distorted tetra-hedral, with bond angles ranging from 98.16 (3) to 120.68 (3)°. In the [HgCl4]2- anion, there are two short Hg-Cl bonds [2.4120 (9) and 2.4171 (11) Å], one inter-mediate Hg-Cl bond [2.4716 (12) Å] and one long Hg-Cl bond [2.6579 (13) Å] for the Cl atom involved in a trifurcated hydrogen bond as an acceptor, including two N-H⋯Cl⋯H-N interactions as well as one C-H⋯Cl inter-action. There are several C-H⋯Cl inter-actions, with C⋯Cl distances ranging from 3.492 (3) to 3.796 (3) Å. These link the cations and anions into a zigzag chain along the c-axis direction. In addition, there are Cl⋯Cl halogen bonds, as well as π-π inter-actions, with centroid-to-centroid distances of 3.4765 (18) Å, which link one of the two benzimidazole moieties into dimeric units.

Synthesis and structure of the mercury chloride complex of 2,2'-(2-bromo-5-tert-butyl-1,3-phenyl-ene)bis-(1-methyl-1H-benzimidazole)

In the title mercury complex, catena-poly[[di-chlorido-mercury(II)]-μ-2,2'-(2-bromo-5-tert-butyl-1,3-phenyl-ene)bis-(1-methyl-1H-benzimidazole)-κ2N3:N3'], [HgCl2(C26H25BrN4)] n , the HgII atom is coordinated by two Cl atoms and by two N atoms from two 2,2'-(2-bromo-5-tert-butyl-1,3-phenyl-ene)bis-(1-methyl-1H-benzimidazole) ligands. The metal cation adopts a distorted tetrahedral coordination geometry with with bond angles around mercury of 100.59 (15)° [N-Hg-N] and 126.35 (7)° [Cl-Hg-Cl]. This arrangement gives rise to a zigzag helical 1-D polymer propagating along the b-axis direction.

Structure of the mercury(II) mixed-halide (Br/Cl) complex of 2,2'-(5-tert-butyl-1,3-phenyl-ene)bis-(1-pentyl-1H-benzo[d]imidazole)

The mercury(II) complex of 2,2'-(5-tert-butyl-1,3-phenyl-ene)bis-(1-pentyl-1H-benz-imidazole), namely catena-poly[[dihalogenido-mercury(II)]-μ-2,2'-(5-tert-butyl-1,3-phenyl-ene)bis-(1-pentyl-1H-benzimidazole)-κ2N3:N3'], [HgBr1.52Cl0.48(C34H42N4)], 2, has a polymeric structure bridging via the N atoms from the benzimidazole moieties of the ligand. The compound crystallizes in the ortho-rhom-bic space group Pca21 and is a racemic twin [BASF = 0.402 (9)]. The geometry around the HgII atom is distorted tetra-hedral, with the HgII atom coordinated to two N atoms, one Br atom, and a fourth coordination site is occupied by a mixed halide (Br/Cl). For the two ligands in the asymmetric unit, there is disorder with one of the two tert-butyl groups and benzimidazole moieties showing twofold disorder, with occupancy factors of 0.57 (2):0.43 (2) for the tert-butyl group and 0.73 (3):0.27 (3) for the benzimidazole group. In addition, there is threefold disorder for two of the four n-pentyl groups, with occupancy factors of 0.669 (4):0.177 (4):0.154 (4) and 0.662 (4):0.224 (4):0.154 (4), respectively. The mol-ecules form a one-dimensional helical polymer propagating in the b-axis direction. The helices are held together by intra-strand C-H⋯Br and C-H⋯Cl inter-actions. Each strand is further linked by inter-strand C-H⋯Br and C-H⋯Cl inter-actions. In addition, there are weak C-H⋯N inter-strand inter-actions which further stabilize the structural arrangement.

Synthesis, structure, photoluminescence and antitumour activity of zinc complex based on 2-(2-(1H-benzo-[d]imidazol-2-yl)benzyl)-1H-benzo-[d]imidazole

A new complex [Zn(bbb)Cl2]·DMF, where bbb is 2-(2-(1H-benzo[d]imidazol-2-yl)benzyl)-1H-benzo[d]imidazole, was synthesized and characterized by element analysis, (1)H NMR and X-ray single crystal structure analyses. For complex: crystal system, triclinic, space group, P-1, a=9.4661(13), b=10.3534(14), c=13.0025(18)Å, α=73.477(2), β=80.743(2), γ=88.658(2)°, V=1205.5(3)Å(3), Z=2. In this complex, the Zn(2+) distorted tetrahedron geometry is coordinated by two nitrogen atoms from 2-(2-(1H-benzo[d]imidazol-2-yl)benzyl)-1H-benzo[d]imidazole and two Cl(-). The complex emits yellow green luminescence with the maximal emission peak at 550 nm in DMF solution. The complex exhibits inhibition on the growth of Eca109 cancer cell with IC50 value of 8.9±1.1 μM, which was lower than that of cisplatin (14.3±1.4 μM). This complex has potential application in treatment of esophageal cancer.