Preparation of 6/8/11-Amino/Chloro-Oxoisoaporphine and Group-10 Metal Complexes and Evaluation of Their in Vitro and in Vivo Antitumor Activity

Advances in anticancer alkaloid-derived metallo-chemotherapeutic agents in the last decade: Mechanism of action and future prospects

Metal-based complexes have occupied a pioneering niche in the treatment of many chronic diseases, including various types of cancers. Despite the phenomenal success of cisplatin for the treatment of many solid malignancies, a limited number of metallo-drugs are in clinical use against cancer chemotherapy till date. While many other prominent platinum and non‑platinum- based metallo-drugs (e.g. NAMI-A, KP1019, carboplatin, oxaliplatin, titanocene dichloride, casiopeinas® etc) have entered clinical trials, many have failed at later stages of R&D due to deleterious toxic effects, intrinsic resistance and poor pharmacokinetic response and low therapeutic efficacy. Nonetheless, research in the area of medicinal inorganic chemistry has been increasing exponentially over the years, employing novel target based drug design strategies aimed at improving pharmacological outcomes and at the same time mitigating the side-effects of these drug entities. Over the last few decades, natural products became one of the key structural motifs in the anticancer drug development. Many eminent researchers in the area of medicinal chemistry are devoted to develop new 3d-transition metal-based anticancer drugs/repurpose the existing bioactive compounds derived from myriad pharmacophores such as coumarins, flavonoids, chromones, alkaloids etc. Metal complexes of natural alkaloids and their analogs such as luotonin A, jatrorrhizine, berberine, oxoaporphine, 8-oxychinoline etc. have gained prominence in the anticancer drug development process as the naturally occurring alkaloids can be anti-proliferative, induce apoptosis and exhibit inhibition of angiogenesis with better healing effect. While some of them are inhibitors of ERK signal-regulated kinases, others show activity based on cyclooxygenases-2 (COX-2) and telomerase inhibition. However, the targets of these alkaloid complexes are still unclear, though it is well-established that they demonstrate anticancer potency by interfering with multiple pathways of tumorigenesis and tumor progression both in vitro and in vivo. Over the last decade, many significant advances have been made towards the development of natural alkaloid-based metallo-drug therapeutics for intervention in cancer chemotherapy that have been summarized below and reviewed in this article.

4-Hydroxyl-oxoisoaporphine, one small molecule as theranostic agent for simultaneous fluorescence imaging and photodynamic therapy as type II photosensitizer

Oxoisoaporphine (OA) is a plant phototoxin isolated from Menispermaceae, however, its weak fluorescence and low water solubility impede it for theranostics. We developed here 4-hydroxyl-oxoisoaporphine (OHOA), which has good singlet oxygen-generating ability (0.06), strong fluorescence (0.72) and improved water solubility. OHOA displays excellent fluorescence for cell imaging and exhibits light-induced cytotoxicity against cancer cell. In vitro model of human cervical carcinoma (HeLa) cell proved that singlet oxygen generated by OHOA triggered photosensitized oxidation reactions and exert toxic effect on tumor cells. The MTT assay using HeLa cells verified the low cytotoxicity of OHOA in the dark and high phototoxicity. Confocal experiment indicates that OHOA mainly distributes in mitochondria and western blotting demonstrated that OHOA induces cell apoptosis via the mitochondrial pathway in the presence of light. Our molecule provides an alternative choice as a theranostic agent against cancer cells which usually are in conflict with each other for most traditional theranostic agents.

Oxoisoaporphines and Aporphines: Versatile Molecules with Anticancer Effects

Cancer is a disease that involves impaired genome stability with a high mortality index globally. Since its discovery, many have searched for effective treatment, assessing different molecules for their anticancer activity. One of the most studied sources for anticancer therapy is natural compounds and their derivates, like alkaloids, which are organic molecules containing nitrogen atoms in their structure. Among them, oxoisoaporphine and sampangine compounds are receiving increased attention due to their potential anticancer effects. Boldine has also been tested as an anticancer molecule. Boldine is the primary alkaloid extract from boldo, an endemic tree in Chile. These compounds and their derivatives have unique structural properties that potentially have an anticancer mechanism. Different studies showed that this molecule can target cancer cells through several mechanisms, including reactive oxygen species generation, DNA binding, and telomerase enzyme inhibition. In this review, we summarize the state-of-art research related to oxoisoaporphine, sampangine, and boldine, with emphasis on their structural characteristics and the relationship between structure, activity, methods of extraction or synthesis, and anticancer mechanism. With an effective cancer therapy still lacking, these three compounds are good candidates for new anticancer research.

Synthesis, Characterization, and Cytotoxicity of the Cobalt (III) Complex with N,N-Diethyl-4-(2,2':6',2''-terpyridin-4'-yl)aniline

A cobalt(III) complex, [Co(L)₂ ](ClO₄ )₃ (1), in which the ligand L was N,N-diethyl-4-(2,2':6',2''-terpyridin-4'-yl)aniline (L), was synthesized and fully characterized. This new cobalt(III) complex 1 exhibited selective cytotoxicity against HeLa, T-24, A549, MGC80-3, HepG2, and SK-OV-3 cells with IC₅₀ values in the micromolar range (0.52 - 4.33 μm), and it exhibited low cytotoxicity against normal HL-7702 cells. The complex 1 was the most potent against the T-24 cells. It was found that 1 could cause the cell cycle arrest in G1 phase, and it exerted its antitumor activity mainly via disruption of mitochondrial function.

Syntheses, Crystal Structures, and Antitumor Activities of Copper(II) and Nickel(II) Complexes with 2-((2-(Pyridin-2-yl)hydrazono)methyl)quinolin-8-ol

Two transition metal complexes with 2-((2-(pyridin-2-yl)hydrazono)methyl)quinolin-8-ol (L), [Cu(L)Cl₂]₂ (1) and [Ni(L)Cl₂]·CH₂Cl₂ (2), were synthesized and fully characterized. Complex 1 exhibited high in vitro antitumor activity against SK-OV-3, MGC80-3 and HeLa cells with IC50 values of 3.69 ± 0.16, 2.60 ± 0.17, and 3.62 ± 0.12 μM, respectively. In addition, complex 1 caused cell arrest in the S phase, which led to the down-regulation of Cdc25 A, Cyclin B, Cyclin A, and CDK2, and the up-regulation of p27, p21, and p53 proteins in MGC80-3 cells. Complex 1 induced MGC80-3 cell apoptosis via a mitochondrial dysfunction pathway, as shown by the significantly decreased level of bcl-2 protein and the loss of Δψ, as well as increased levels of reactive oxygen species (ROS), intracellular Ca2+, cytochrome C, apaf-1, caspase-3, and caspase-9 proteins in MGC80-3 cells.

Oxoisoaporphine Alkaloids: Prospective Anti-Alzheimer's Disease, Anticancer, and Antidepressant Agents

Oxoisoaporphine alkaloids are a family of oxoisoquinoline-derived alkaloids that were first isolated from the rhizome of Menispermum dauricum DC. (Menispermaceae). It has been demonstrated that oxoisoaporphine alkaloids possess various biological properties, such as cholinesterase and β-amyloid inhibition, acting as a topoisomerase intercalator, monoamine oxidase A inhibition, and are expected to become anti-Alzheimer's disease, anticancer, and antidepressant drugs. This review provides an overview of natural sources, synthetic routes, bioactivities, structure-function relationship, and modification investigations into oxoisoaporphine alkaloids, with the aim of providing references to the structure-activity relationships for the design and development of oxoisoaporphine derivatives with higher efficacy and therapeutic potential.

Synthesis, characterization and biological evaluation of six highly cytotoxic ruthenium(ii) complexes with 4'-substituted-2,2':6',2''-terpyridine

Herein, six ruthenium(ii) terpyridine complexes, i.e. [RuCl2(4-EtN-Phtpy)(DMSO)] (Ru1), [RuCl2(4-MeO-Phtpy)(DMSO)] (Ru2), [RuCl2(2-MeO-Phtpy)(DMSO)] (Ru3), [RuCl2(3-MeO-Phtpy)(DMSO)] (Ru4), [RuCl2(1-Bip-Phtpy)(DMSO)] (Ru5), and [RuCl2(1-Pyr-Phtpy)(DMSO)] (Ru6) with 4'-(4-diethylaminophenyl)-2,2':6',2''-terpyridine (4-EtN-Phtpy), 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine (4-MeO-Phtpy), 4'-(2-methoxyphenyl)-2,2':6',2''-terpyridine (2-MeO-Phtpy), 4'-(3-methoxyphenyl)-2,2':6',2''-terpyridine (3-MeO-Phtpy), 4'-(1-biphenylene)-2,2':6',2''-terpyridine (1-Bip-Phtpy), and 4'-(1-pyrene)-2,2':6',2''-terpyridine (1-Pyr-Phtpy), respectively, were synthesized and fully characterized. The MTT assay demonstrates that the in vitro anticancer activity of Ru1 is higher than that of Ru2-Ru6 and more selective for Hep-G2 cells than for normal HL-7702 cells. In addition, various biological assays show that Ru1 and Ru6, especially the Ru1 complex, are telomerase inhibitors targeting c-myc G4 DNA and also cause apoptosis of Hep-G2 cells. With the same Ru center, the in vitro antitumor activity and cellular uptake ability of the 4-EtN-Phtpy and 1-Bip-Phtpy ligands follow the order 4-EtN-Phtpy > 1-Bip-Phtpy.

Facile total synthesis of lysicamine and the anticancer activities of the RuII, RhIII, MnII and ZnII complexes of lysicamine

Lysicamine is a natural oxoaporphine alkaloid, which isolated from traditional Chinese medicine (TCM) herbs and has been shown to possess cytotoxicity to hepatocarcinoma cell lines. Reports on its antitumor activity are scarce because lysicamine occurs in plants at a low content. In this work, we demonstrate a facile concise total synthesis of lysicamine from simple raw materials under mild reaction conditions, and the preparation of the Ru(II), Rh(III), Mn(II) and Zn(II) complexes 1–4 of lysicamine (LY). All the compounds were fully characterized by elemental analysis, IR, ESI-MS, ¹H and ¹³C NMR, as well as single-crystal X-ray diffraction analysis. Compared with the free ligand LY, complexes 2 and 3 exhibited superior in vitro cytotoxicity against HepG2 and NCI-H460. Mechanistic studies indicated that 2 and 3 blocked the cell cycle in the S phase by decreasing of cyclins A2/B1/D1/E1, CDK 2/6, and PCNA levels and increasing levels of p21, p27, p53 and CDC25A proteins. In addition, 2 and 3 induced cell apoptosis via both the caspase-dependent mitochondrial pathway and the death receptor pathway. in vivo study showed that 2 inhibited HepG2 tumor growth at 1/3 maximum tolerated dose (MTD) and had a better safety profile than cisplatin.

Oxoaporphine Metal Complexes (CoII, NiII, ZnII) with High Antitumor Activity by Inducing Mitochondria-Mediated Apoptosis and S-phase Arrest in HepG2

Three new oxoaporphine Co(II), Ni(II) and Zn(II) complexes 1–3 have been synthesized and fully characterized. 1–3 have similar mononuclear structures with the metal and ligand ratio of 1:2. 1–3 exhibited higher cytotoxicity than the OD ligand and cisplatin against HepG2, T-24, BEL-7404, MGC80–3 and SK-OV-3/DDP cells, with IC₅₀ value of 0.23−4.31 μM. Interestingly, 0.5 μM 1–3 significantly caused HepG2 arrest at S-phase, which was associated with the up-regulation of p53, p21, p27, Chk1 and Chk2 proteins, and decrease in cyclin A, CDK2, Cdc25A, PCNA proteins. In addition, 1–3 induced HepG2 apoptosis via a caspase-dependent mitochondrion pathway as evidenced by p53 activation, ROS production, Bax up-regulation and Bcl-2 down-regulation, mitochondrial dysfunction, cytochrome c release, caspase activation and PARP cleavage. Furthermore, 3 inhibited tumor growth in HepG2 xenograft model, and displayed more safety profile in vivo than cisplatin.

Synthesis and antitumor mechanism of a new iron(iii) complex with 5,7-dichloro-2-methyl-8-quinolinol as ligands

A new iron(iii) complex with 5,7-dichloro-2-methyl-8-quinolinol (HClMQ) as ligands, i.e., [Fe(ClMQ)2Cl] (1), was synthesized and evaluated for its anticancer activity. Compared to the HClMQ ligand, complex 1 showed a higher cytotoxicity towards a series of tumor cell lines, including Hep-G2, BEL-7404, NCI-H460, A549, and T-24, with IC50 values in the range of 5.04-14.35 μM. Notably, the Hep-G2 cell line was the most sensitive to complex 1. Mechanistic studies indicated that complex 1 is a telomerase inhibitor targeting c-myc G-quadruplex DNA and can trigger cell apoptosis via inducing cell cycle arrest and DNA damage.

Three novel transition metal complexes of 6-methyl-2-oxo-quinoline-3-carbaldehyde thiosemicarbazone: synthesis, crystal structure, cytotoxicity, and mechanism of action

Complex 1 was more selective for MGC80-3 tumor cells versus normal cells (HL-7702). Importantly, 1 triggered MGC80-3 cells apoptosis via a mitochondrial dysfunction pathway.