Synthesis and Biological evaluation of novel 4β-[(5-substituted)-1,2,3,4-tetrazolyl] podophyllotoxins as anticancer compounds

Tetrazoles: A multi-potent motif in drug design

The unique physicochemical properties and fascinating bioisosterism of tetrazole scaffolds have received significant attention in medicinal chemistry. We report recent efforts using tetrazoles in drug design strategies in this context. Despite the increasing prevalence of tetrazoles in FDA-approved drugs for various conditions such as cancer, bacterial viral and fungal infections, asthma, hypertension, Alzheimer's disease, malaria, and tuberculosis, our understanding of their structure-activity relationships, multifunctional mechanisms, binding modes, and biochemical properties remains limited. We explore the potential of tetrazole bioisosteres in optimising lead molecules for innovative therapies, discussing applications, trends, advantages, limitations, and challenges. Additionally, we assess future research directions to drive further progress in this field.

Organo NHC catalyzed aqueous synthesis of 4β-isoxazole-podophyllotoxins: in vitro anticancer, caspase activation, tubulin polymerization inhibition and molecular docking studies

We present, for the first time, the organo-N-heterocyclic carbene (NHC) catalyzed 1,3-dipolar cycloaddition of 4β-O-propargyl podophyllotoxin (1) with in situ aromatic nitrile oxides to afford regioselective 4β-isoxazolepodophyllotoxin hybrids (6a-n) in benign aqueous-organic media. Preliminary anticancer activity results showed that compound 6e displayed superior activity against MCF-7, HeLa and MIA PaCa2 human cell lines compared with podophyllotoxin. Compounds 6j and 6n showed greater activity against the MCF-7 cell line than the positive control. Caspase activation studies revealed that compound 6e at 20 μg ml-1 concentration had greater caspase 3/7 activation in MCF-7 and MIAPaCa2 cells than podophyllotoxin. Furthermore, in vitro tubulin polymerization inhibition studies revealed that compound 6e showed comparable activity with podophyllotoxin. Finally, in silico molecular docking studies of compounds 6e, 6j, 6n and podophyllotoxin on α,β-tubulin (pdb id 1SA0) revealed that compound 6n showed excellent binding energies and inhibition constants compared with podophyllotoxin.

Design, Synthesis, and Biological Evaluation of SSE1806, a Microtubule Destabilizer That Overcomes Multidrug Resistance

Microtubules are dynamic structures that form spindle fibers during cell division; pharmacological inhibition of microtubule dynamics arrests cells in mitosis, leading to apoptosis, and they have been extensively used to treat various cancers. However, the efficacy of such drugs is often limited by multidrug resistance. This study synthesized and evaluated 30 novel derivatives of podophyllotoxin, a natural antimitotic compound, for their antiproliferative activities. Compound SSE1806 exhibited the most potent antiproliferative activity with GI50 values ranging from 1.29 ± 0.01 to 21.15 ± 2.1 μM in cancer cell lines of different origins; it directly inhibited microtubule polymerization, causing aberrant mitosis and G2/M arrest. Prolonged treatment with SSE1806 increased p53 expression, induced cell death in monolayer cultures, and reduced the growth of mouse- and patient-derived human colon cancer organoids. Importantly, SSE1806 overcame multidrug resistance in a cell line overexpressing MDR-1. Thus, SSE1806 represents a potential anticancer agent that can overcome multidrug resistance.

Natural product inspired leads in the discovery of anticancer agents: an update

Natural products have emerged as major leads for the discovery and development of new anti-cancer drugs. The plant-derived anti-cancer drugs account for approximately 60% and the quest for new anti-cancer agents is in progress. Anti-cancer leads have been isolated from plants, animals, marine organisms, and microorganisms from time immemorial. The process of semisynthetic modifications of the parent lead has led to the generation of new anti-cancer agents with improved therapeutic efficacy and minimal side effects. The various chemo-informatics tools, bioinformatics, high-throughput screening, and combinatorial synthesis are able to deliver the new natural product lead molecules. Plant-derived anticancer agents in either late preclinical development or early clinical trials include taxol, vincristine, vinblastine, topotecan, irinotecan, etoposide, paclitaxel, and docetaxel. Similarly, anti-cancer agents from microbial sources include dactinomycin, bleomycin, mitomycin C, and doxorubicin. In this review, we highlighted the importance of natural products leads in the discovery and development of novel anti-cancer agents. The semisynthetic modifications of the parent lead to the new anti-cancer agent are also presented. Further, the leads in the preclinical settings with the potential to become effective anticancer agents are also reviewed.Communicated by Ramaswamy H. Sarma.

Insight Into the Molecular Mechanism of Podophyllotoxin Derivatives as Anticancer Drugs

Podophyllotoxin (PTOX) is a biologically active compound derived from the podophyllum plant, and both it and its derivatives possess excellent antitumor activity. The PTOX derivatives etoposide (VP-16) and teniposide (VM-26) have been approved by the U.S. Food and Drug Administration (FDA) for cancer treatment, but are far from perfect. Hence, numerous PTOX derivatives have been developed to address the major limitations of PTOX, such as systemic toxicity, drug resistance, and low bioavailability. Regarding their anticancer mechanism, extensive studies have revealed that PTOX derivatives can induce cell cycle G2/M arrest and DNA/RNA breaks by targeting tubulin and topoisomerase II, respectively. However, few studies are dedicated to exploring the interactions between PTOX derivatives and downstream cancer-related signaling pathways, which is reasonably important for gaining insight into the role of PTOX. This review provides a comprehensive analysis of the role of PTOX derivatives in the biological behavior of tumors and potential molecular signaling pathways, aiming to help researchers design and develop better PTOX derivatives.

Recent advances of podophyllotoxin/epipodophyllotoxin hybrids in anticancer activity, mode of action, and structure-activity relationship: An update (2010-2020)

Podophyllotoxins and epipodophyllotoxins, possess excellent activity against both drug-sensitive and drug-resistant even multidrug-resistant cancer cells via inhibition of tubulin polymerization. Several podophyllotoxin/epipodophyllotoxin derivatives such as etoposide and teniposide have already been applied for cancer therapy, revealing their potential as putative anticancer drugs. Hybridization of podophyllotoxin/epipodophyllotoxin moiety with other anticancer pharmacophores is a promising strategy to develop novel drug candidates so as to overcome drug resistance and improve the specificity, and numerous of podophyllotoxin/epipodophyllotoxin hybrids exhibit excellent in vitro antiproliferative and in vivo anticancer potency. This review emphasizes the recent development of podophyllotoxin/epipodophyllotoxin hybrids with potential application for cancer therapy covering articles published between 2010 and 2020. The mechanisms of action, the critical aspects of design as well as structure-activity relationships were also summarized.

Tetrazole hybrids with potential anticancer activity

Cancer is one of the main causes of death throughout the world. The anticancer agents are indispensable for the treatment of various cancers, but most of them currently on the market are not specific, resulting in series of side effects of chemotherapy. Moreover, the emergency of drug-resistance towards cancers has already increased up to alarming level in the recent decades. Therefore, it's imperative to develop novel anticancer candidates with excellent activity against both drug-susceptible and drug-resistant cancers, and low toxicity as well. Tetrazole is the bioisoster of carboxylic acid, and its derivatives demonstrated promising anticancer activity. Hybridization of tetrazole with other anticancer pharmacophores may provide novel candidates with anticancer potency. The present review described the anticancer activity of tetrazole hybrids, and the structure-activity relationship (SAR) is also discussed to provide an insight for rational designs of tetrazole anticancer candidates with higher efficiency.

Synthesis and Biological Evaluation of 4β-N-Acetylamino Substituted Podophyllotoxin Derivatives as Novel Anticancer Agents

A series of novel podophyllotoxin derivatives obtained by 4β-N-acetylamino substitution at C-4 position was designed, synthesized, and evaluated for in vitro cytotoxicity against four human cancer cell lines (EC-9706, HeLA, T-24 and H460) and a normal human epidermal cell line (HaCaT). The cytotoxicity test indicated that most of the derivatives displayed potent anticancer activities. In particular, compound 12h showed high activity with IC₅₀ values ranging from 1.2 to 22.8 μM, with much better cytotoxic activity than the control drug etoposide (IC₅₀: 8.4 to 78.2 μM). Compound 12j exhibited a promising cytotoxicity and selectivity profile against T24 and HaCaT cell lines with IC₅₀ values of 2.7 and 49.1 μM, respectively. Compound 12g displayed potent cytotoxicity against HeLA and T24 cells with low activity against HaCaT cells. According to the results of fluorescence-activated cell sorting (FACS) analysis, 12g induced cell cycle arrest in the G2/M phase accompanied by apoptosis in T24 and HeLA cells. Furthermore, the docking studies showed possible interactions between human DNA topoisomerase IIα and 12g. These results suggest that 12g merits further optimization and development as a new podophyllotoxin-derived lead compound.

What Has Come out from Phytomedicines and Herbal Edibles for the Treatment of Cancer?

Several modern treatment strategies have been adopted to combat cancer with the aim of minimizing toxicity. Medicinal plant-based compounds with the potential to treat cancer have been widely studied in preclinical research and have elicited many innovations in cutting-edge clinical research. In parallel, researchers have eagerly tried to decrease the toxicity of current chemotherapeutic agents either by combining them with herbals or in using herbals alone. The aim of this article is to present an update of medicinal plants and their bioactive compounds, or mere changes in the bioactive compounds, along with herbal edibles, which display efficacy against diverse cancer cells and in anticancer therapy. It describes the basic mechanism(s) of action of phytochemicals used either alone or in combination therapy with other phytochemicals or herbal edibles. This review also highlights the remarkable synergistic effects that arise between certain herbals and chemotherapeutic agents used in oncology. The anticancer phytochemicals used in clinical research are also described; furthermore, we discuss our own experience related to semisynthetic derivatives, which are developed based on phytochemicals. Overall, this compilation is intended to facilitate research and development projects on phytopharmaceuticals for successful anticancer drug discovery.

Design, synthesis and screening of 1, 2, 4-triazinone derivatives as potential antitumor agents with apoptosis inducing activity on MCF-7 breast cancer cell line

Some triazinone derivatives are designed and synthesized as potential antitumor agents. Triazinone derivatives 4c, 5e and 7c show potent anticancer activity over MCF-7 breast cancer cells higher than podophyllotoxin (podo) by approximate 6-fold. DNA flow cytometry analysis for the compounds 3c, 4c, 5e, 6c and 7c show a potent inhibitory activity of cell proliferation and cell cycle arrest at G₂/M phase. Compounds 4c, 5e and 7c exhibit low to moderate β-tubulin polymerization inhibition percentage. Meanwhile, compound 6c displayed excellent β-tubulin percentage of polymerization inhibition equivalent to that exhibited by podo. In addition, compounds 4c, 5e and 7c show strong topoisomerase (topo) II inhibitory activity in nano-molar concentration, compared to known topo inhibitor as etoposide. Finally, apoptotic inducing activity over MCF-7 of compounds 4c, 5e, 6c and 7c is due to up-regulation of p53, increased Bax/Bcl-2 ratio and caspase3/7 levels 2-fold higher than podo.

Podophyllotoxin derivatives as an excellent anticancer aspirant for future chemotherapy: A key current imminent needs

Cancer is one of the leading groups of threatened caused by abnormal state cell growth and second leading diseases involved in the major global death. To treat this, research looking for promising anticancer drugs from natural resource, or synthesized novel molecules by diverse group of scientists worldwide. Currently, drugs get into clinical practices and showing side effects with target actions which in turn leading to multidrug resistance unknowingly. Podophyllotoxin, a naturally occurring lignan and with hybrids have become one of the most attractive subjects due to their broad spectrum of pharmacological activities. Podophyllotoxin derivatives have been the centre of attention of extensive chemical amendment and pharmacological investigation in modern decades. Mainly, the innovation of the semi-synthetic anticancer drugs etoposide and teniposide has stimulated prolonged research interest in this structural phenotype. The present review focuses mainly onnew anticancer drugs from podophyllotoxin analogs, mechanism of action and their structure-activity relationships (SAR) as potential anticancer candidates for future discovery of suitable drug candidates.

Synthesis and evaluation of biological properties of ferrocenyl–podophyllotoxin conjugates

Ferrocenyl–podophyllotoxin conjugates have been synthesised and their antiproliferative activity, influence on cell cycle, and interactions with tubulin were evaluated.