Design, synthesis and antitumor activity of novel artemisinin derivatives using hybrid approach

Molecular Hybridization as a Strategy for Developing Artemisinin-Derived Anticancer Candidates

Artemisinin is a natural compound extracted from Artemisia species belonging to the Asteraceae family. Currently, artemisinin and its derivatives are considered among the most significant small-molecule antimalarial drugs. Artemisinin and its derivatives have also been shown to possess selective anticancer properties, however, there are several limitations and gaps in knowledge that retard their repurposing as effective anticancer agents. Hybridization resulting from a covalent combination of artemisinin with one or more active pharmacophores has emerged as a promising approach to overcome several issues. The variety of hybridization partners allows improvement in artemisinin activity by tuning the ability of conjugated artemisinin to interact with various molecule targets involved in multiple biological pathways. This review highlights the current scenario of artemisinin-derived hybrids with potential anticancer activity. The synthetic approaches to achieve the corresponding hybrids and the structure-activity relationships are discussed to facilitate further rational design of more effective candidates.

Synthesis and Antiproliferative Activity of Novel Dehydroabietic Acid-Chalcone Hybrids

Dehydroabietic Acid (DHA, 1) derivatives are known for their antiproliferative properties, among others. In the context of this work, DHA was initially modified to two key intermediates bearing a C18 methyl ester, a phenol moiety at C12, and an acetyl or formyl group at C13 position. These derivatives allowed us to synthesize a series of DHA-chalcone hybrids, suitable for structure-activity relationship studies (SARS), following their condensation with a variety of aryl-aldehydes and methyl ketones. The antiproliferative evaluation of the synthesized DHA-chalcone hybrids against three breast cancer cell lines (the estrogen-dependent MCF-7 and the estrogen-independent MDA-MB-231 and Hs578T) showed that eight derivatives (33, 35, 37, 38, 39, 41, 43, 44) exhibit low micromolar activity levels (IC50 2.21-11.5 μΜ/MCF-7). For instance, some of them showed better activity compared to the commercial anticancer drug 5-FU against MCF-7 cells (33, 41, 43, 44) and against MDA-MB231 (33 and 41). Hybrid 38 is a promising lead compound for the treatment of MCF-7 breast cancer, exhibiting comparable activity to 5-FU and being 12.9 times less toxic (SI = 22.7). Thus, our findings suggest that DHA-chalcone hybrids are drug candidates worth pursuing for further development in the search for novel breast cancer therapies.

Artemisinin and Derivatives-Based Hybrid Compounds: Promising Therapeutics for the Treatment of Cancer and Malaria

Cancer and malaria are major health conditions around the world despite many strategies and therapeutics available for their treatment. The most used strategy for the treatment of these diseases is the administration of therapeutic drugs, which suffer from several shortcomings. Some of the pharmacological limitations associated with these drugs are multi-drug resistance, drug toxicity, poor biocompatibility and bioavailability, and poor water solubility. The currently ongoing preclinical studies have demonstrated that combination therapy is a potent approach that can overcome some of the aforementioned limitations. Artemisinin and its derivatives have been reported to exhibit potent efficacy as anticancer and antimalarial agents. This review reports hybrid compounds containing artemisinin scaffolds and their derivatives with promising therapeutic effects for the treatment of cancer and malaria.

Chalcone Derivatives: Role in Anticancer Therapy

Chalcones (1,3-diaryl-2-propen-1-ones) are precursors for flavonoids and isoflavonoids, which are common simple chemical scaffolds found in many naturally occurring compounds. Many chalcone derivatives were also prepared due to their convenient synthesis. Chalcones as weandhetic analogues have attracted much interest due to their broad biological activities with clinical potentials against various diseases, particularly for antitumor activity. The chalcone family has demonstrated potential in vitro and in vivo activity against cancers via multiple mechanisms, including cell cycle disruption, autophagy regulation, apoptosis induction, and immunomodulatory and inflammatory mediators. It represents a promising strategy to develop chalcones as novel anticancer agents. In addition, the combination of chalcones and other therapies is expected to be an effective way to improve anticancer therapeutic efficacy. However, despite the encouraging results for their response to cancers observed in clinical studies, a full description of toxicity is required for their clinical use as safe drugs for the treatment of cancer. In this review, we will summarize the recent advances of the chalcone family as potential anticancer agents and the mechanisms of action. Besides, future applications and scope of the chalcone family toward the treatment and prevention of cancer are brought out.

Chalcone hybrids as potential anticancer agents: Current development, mechanism of action, and structure-activity relationship

The continuous emergency of drug-resistant cancers and the low specificity of anticancer agents have been the major challenges in the control and treatment of cancer, making an urgent need to develop novel anticancer agents with high efficacy. Chalcones, precursors of flavonoids and isoflavonoids, exhibit structural heterogeneity and can act on various drug targets. Chalcones which demonstrated potential in vitro and in vivo activity against both drug-susceptible and drug-resistant cancers, are useful templates for the development of novel anticancer agents. Hybridization of chalcone moiety with other anticancer pharmacophores could provide the hybrids which have the potential to overcome drug resistance and improve the specificity, so it represents a promising strategy to develop novel anticancer agents. This review emphasizes the development, the mechanisms of action as well as structure-activity relationships of chalcone hybrids with potential therapeutic application for many cancers in recent 10 years.

Artemisinin-derived hybrids and their anticancer activity

The emergence of drug-resistance and the low specificity of anticancer agents are the major challenges in the treatment of cancer and can result in many side effects, creating an urgent demand to develop novel anticancer agents. Artemisinin-derived compounds, bearing a peroxide-containing sesquiterpene lactone moiety, could form free radicals with high reactivity and possess diverse pharmaceutical properties including in vitro and in vivo anticancer activity besides their typical antimalarial activity. Hybrid molecules have the potential to improve the specificity and overcome the drug resistance, therefore hybridization of artemisinin skeleton with other anticancer pharmacophores may provide novel anticancer candidates with high specificity and great potency against drug-resistant cancers. The review outlines the recent advances of artemisinin-derived hybrids as potential anticancer agents, and the structure-activity relationships are also discussed to provide an insight for rational designs of novel hybrids with high activity.

Novel 1,3,4-thiadiazole-chalcone hybrids containing catechol moiety: synthesis, antioxidant activity, cytotoxicity and DNA interaction studies

Hybrid compounds that combine the 1,3,4-thiadiazole-containing catechol moiety with a chalcone motif were synthesized and examined for their antioxidant activity, cytotoxicity, and DNA-binding activity. A series of thirteen compounds showed strong antioxidant and cytotoxic effects on human acute promyelocytic leukemia HL-60 cells. Several compounds exerted good cytotoxic activities on cervical adenocarcinoma HeLa cells. The treatment of HeLa cells with IC₅₀ and double IC₅₀ concentrations of the compounds 5a, 5c, 5f, and 5m induced a statistically significant increase in the percentage of cells within a subG1 cell cycle phase. The examined compounds caused G2/M cell cycle arrest in HeLa cells. Each of these compounds triggered apoptosis in HeLa cells through activation of caspase-3, the main effector caspase, caspase-8, which is involved in the extrinsic apoptotic pathway, and caspase-9, which is involved in the intrinsic apoptotic pathway. All of the examined compounds decreased the expression levels of MMP2 in HeLa cells and levels of protumorigenic miR-133b. Compounds 5a and 5m lowered the expression level of oncogenic miR-21 in HeLa cells. In addition, compounds 5a, 5f, and 5m decreased the expression levels of oncogenic miR-155 while the treatment of HeLa cells with compounds 5a, 5c, and 5f increased expression of tumor-suppressive miR-206. Observed effects of these compounds on expression levels of four examined miRNAs suggest their prominent cancer-suppressive activity. An investigation by absorption and fluorescence spectroscopy showed more efficient calf thymus DNA binding activity of the compound 5m in comparison to other tested compounds. Results of a pUC19 plasmid cleavage study and comet assay showed DNA damaging activities of compounds 5a and 5c.

Preclinical Efficacy and Safety Assessment of Artemisinin-Chemotherapeutic Agent Conjugates for Ovarian Cancer

Artemisinin (ARS) and its derivatives, which are clinically used antimalarial agents, have shown antitumor activities. Their therapeutic potencies, however, are limited by their low solubility and poor bioavailability. Here, through a pharmacophore hybridization strategy, we synthesized ARS-drug conjugates, in which the marketed chemotherapeutic agents chlorambucil, melphalan, flutamide, aminoglutethimide, and doxifluridine, were separately bonded to Dihydroartemisinin (DHA) through various linkages. Of these, the artemisinin-melphalan conjugate, ARS4, exhibited most toxicity to human ovarian cancer cells but had low cytotoxicity to normal cells. ARS4 inhibited the growth and proliferation of ovarian cancer cells and resulted in S-phase arrest, apoptosis, and inhibition of migration; these effects were stronger than those of its parent drugs, DHA and melphalan. Furthermore, ARS4 modulated the expression of proteins involved in cell cycle progression, apoptosis, and the epithelial–mesenchymal transition (EMT). Moreover, in mice, ARS4 inhibited growth and intraperitoneal dissemination and metastasis of ovarian cancer cells without observable toxic effects. Our results provide a basis for development of the compound as a chemotherapeutic agent.

Research in context

Artemisinin compounds have recently received attention as anticancer agents because of their clinical safety profiles and broad efficacy. However, their therapeutic potencies are limited by low solubility and poor bioavailability. Here, we report that ARS4, an artemisinin-melphalan conjugate, possesses marked in-vitro and in-vivo antitumor activity against ovarian cancer, the effects of which are stronger than those for its parent drugs, Dihydroartemisinin and melphalan. In mice, ARS4 inhibits localized growth of ovarian cancer cells and intraperitoneal dissemination and metastasis without appreciable host toxicity. Thus, for patients with ovarian cancer, ARS4 is a promising chemotherapeutic agent.

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Artemisinin-drug conjugates were designed via pharmacophore hybridization strategy

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ARS4 induced apoptosis of ovarian cancer cells and cell cycle arrest and reversed the EMT polarity

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In mice, ARS4 inhibited growth and intraperitoneal dissemination of ovarian cancer cells with no appreciable host toxicity

Design, synthesis, and biological evaluation of artemisinin-indoloquinoline hybrids as potent antiproliferative agents

A series of artemisinin-indoloquinoline hybrids were designed and synthesized in an attempt to develop potent and selective anti-tumor agents. Compounds 7a–7f, 8 and 9 were prepared and characterized. Their antiproliferative activities against MV4-11, HCT-116, A549, and BALB/3T3 cell lines in vitro were tested. Nearly all of the tested compounds (7–9, except for compounds 7d and 7e against HCT-116) showed an increased antitumor activity against HCT-116 and A549 cell lines when compared to the dihydroartemisinin control. Especially for the artemisinin-indoloquinoline hybrid 8, with an 11-aminopropylamino-10H-indolo[3,2-b]quinoline substituent, the antiproliferative activity against the A549 cell line had improved more than ten times. The IC₅₀ value of hybrid 8 against A549 cell lines was decreased to 1.328 ± 0.586 μM, while dihydroartemisin showed IC₅₀ value of >20 µM in the same cell line. Thus, these results have proven that the strategy of introducing a planar basic fused aromatic moiety, such as the indoloquinoline skeleton, could improve the antiproliferative activity and selectivity towards cancer cell lines.

Synthesis and synergetic anti-tumor activity evaluation of dihydroartemisinin-organogermanium(IV) compound

Dihydroartemisinin (DHA), a semi-synthetic derivative of the herb artemisinin, has shown commendable bioactivity. In this paper, a novel dihydroartemisinin-organogermanium (DHA-Ge) compound was synthesized, characterized and its potential anti-tumor activity was evaluated by various methods. MTT results demonstrated that DHA-Ge could effectively inhibit the proliferation of HepG2 cells and showed their dose-dependent properties. The IC50 value of inhibition effect on HepG2 cells of DHA-Ge was 10.23 μg/ml which was lower than 39.44 μg/ml of DHA. Flow cytometric results suggested that DHA-Ge could induce apoptosis of HepG2 cells and the apoptosis rate was 20.26% after 24h treatment with 56.8 μg/ml DHA-Ge concentration. Atomic force microscopy images showed that HepG2 cells were collapsed and the cell nucleus were fragmented after 24h treatment. All these results together showed that the DHA-Ge possessed desirable synergetic enhanced anti-tumor effects and could be developed as a suitable tumor therapeutic agent.

Compounds from Chinese herbal medicines as reversal agents for P-glycoprotein-mediated multidrug resistance in tumours

Multidrug resistance (MDR) is a major obstacle to successful cancer chemotherapy. One of the main underlying mechanisms of this resistance is the over-expression of P-glycoprotein (P-gp), an ATP-dependent transmembrane transporter protein encoded by the MDR1 gene. P-gp might transport anti-cancer drugs out of cancer cells and decrease effective intracellular drug concentrations. An effective approach to overcome MDR is to inhibit the function of P-gp or its expression on the surface of cancer cells. Thus, application of MDR reversal agents can be seen as a potentially important means by which to overcome the clinical drug resistance of tumour cells and improve the efficacy of chemotherapy. Recently, research efforts worldwide have focused on reversal mechanisms for MDR and on the identification of reversal agents. Chinese scholars have performed a great deal of exploratory work by screening for efficacy and low toxicity in drug resistance reversal compounds. These compounds may provide more lead compounds with greater activity, leading to the development of more effective therapies for MDR cancer cells. In this review, the function and efficiency of novel compounds derived from traditional Chinese medicines are described.

Synthesis and cytotoxicity of novel 10-substituted dihydroartemisinin derivatives containing N-arylphenyl-ethenesulfonamide groups

The manuscript describes the synthesis of 10-substituted dihydroartemisinin derivatives containing N-aryl phenylethenesulfonamide groups and their in vitro anti-tumor activities against the HT-29, MDA-MB-231, U87MG, H460, A549 and HL-60 cancer cell lines and the normal WI-38 cell line. Most tested compounds showed enhanced cytotoxic activities and good selectivity toward the MDA-MB-231, HT-29 and HL-60 cell lines, with IC₅₀ values in the single-digit μM range as compared with dihydroartemisinin (DHA), and all of them displayed less toxicity towards WI-38 cells. Among them, compounds 3c and 6c with trifluoromethoxy groups on the N-phenyl ring were found to be most active compounds against the six tested cancer cell lines.

Recent advances on structural modifications of benzothiazoles and their conjugate systems as potential chemotherapeutics

INTRODUCTION

Benzothiazole scaffold comprises a bicyclic ring system and is known to exhibit a wide range of biological properties including antimicrobial and anticancer activities. Benzothiazole derivatives have long been therapeutically used for the treatment of various diseases. However, in recent years, 2-arylbenzothiazoles have emerged as an important pharmacophore in the development of antitumor agents. The promising biological profile and synthetic accessibility have been attractive in the design and development of new benzothiazoles and their conjugate systems as potential chemotherapeutics.

AREAS COVERED

This review mainly focuses on the structural modifications of benzothiazole scaffold, development of various series of benzothiazoles and their conjugates as new antitumor agents. Furthermore, heterocyclic derivatives bearing benzothiazole moiety and their in vitro as well as in vivo screening, structure-activity relationships (SAR), mechanism, pharmacokinetics, clinical use and their future therapeutic applications are discussed here.

EXPERT OPINION

A large number of benzothiazole derivatives discussed here possess potent anticancer activity and can be further developed as drug candidates. Benzothiazole conjugates could also display synergistic effect and still there is a need to use the drug combinations permitting lower dose and development of new generation of drugs. Despite encouraging results that have been observed for their response to tumor in clinical studies, full characterization of their toxicity is further required for their clinical usage as safe drugs for the treatment of cancer. We believe that this review gives a better understanding and scope for future drug design and development of benzothiazole-based compounds to implicate their use in cancer chemotherapy.