Synthesis and biological evaluation of new selective cytotoxic cyclolignans derived from podophyllotoxin

Podophyllic Aldehyde, a Podophyllotoxin Derivate, Elicits Different Cell Cycle Profiles Depending on the Tumor Cell Line: A Systematic Proteomic Analysis

When new antitumor therapy drugs are discovered, it is essential to address new target molecules from the point of view of chemical structure and to carry out efficient and systematic evaluation. In the case of natural products and derived compounds, it is of special importance to investigate chemomodulation to further explore antitumoral pharmacological activities. In this work, the compound podophyllic aldehyde, a cyclolignan derived from the chemomodulation of the natural product podophyllotoxin, has been evaluated for its viability, influence on the cell cycle, and effects on intracellular signaling. We used functional proteomics characterization for the evaluation. Compared with the FDA-approved drug etoposide (another podophyllotoxin derivative), we found interesting results regarding the cytotoxicity of podophyllic aldehyde. In addition, we were able to observe the effect of mitotic arrest in the treated cells. The use of podophyllic aldehyde resulted in increased cytotoxicity in solid tumor cell lines, compared to etoposide, and blocked the cycle more successfully than etoposide. High-throughput analysis of the deregulated proteins revealed a selective antimitotic mechanism of action of podophyllic aldehyde in the HT-29 cell line, in contrast with other solid and hematological tumor lines. Also, the apoptotic profile of podophyllic aldehyde was deciphered. The cell death mechanism is activated independently of the cell cycle profile. The results of these targeted analyses have also shown a significant response to the signaling of kinases, key proteins involved in signaling cascades for cell proliferation or metastasis. Thanks to this comprehensive analysis of podophyllic aldehyde, remarkable cytotoxic, antimitotic, and other antitumoral features have been discovered that will repurpose this compound for further chemical transformations and antitumoral analysis.

Cytotoxic Cyclolignans Obtained by the Enlargement of the Cyclolignan Skeleton of Podophyllic Aldehyde, a Selective Podophyllotoxin-Derived Cyclolignan

Podophyllotoxin, a cyclolignan natural product, has been the object of extensive chemomodulation to obtain better chemotherapeutic agents. Among the obtained podophyllotoxin derivatives, podophyllic aldehyde showed very interesting potency and selectivity against several tumoral cell lines, so it became our lead compound for further modifications, as described in this work, oriented toward the enlargement of the cyclolignan skeleton. Thus, modifications performed at the aldehyde function included nucleophilic addition reactions and the incorporation of the aldehyde carbon into several five-membered rings, such as thiazolidinones and benzo-fused azoles. The synthesized derivatives were evaluated against several types of cancer cells, and although some compounds were cytotoxic at the nanomolar range, most of them were less potent and less selective than the parent compound podophyllic aldehyde, with the most potent being those having the lactone ring of podophyllotoxin. In silico ADME evaluation predicted good druggability for most of them. The results indicate that the γ-lactone ring is important for potency, while the α,β-unsaturated aldehyde is necessary to induce selectivity in these cyclolignans.

Podophyllotoxin: Recent Advances in the Development of Hybridization Strategies to Enhance Its Antitumoral Profile

Podophyllotoxin is a naturally occurring cyclolignan isolated from rhizomes of Podophyllum sp. In the clinic, it is used mainly as an antiviral; however, its antitumor activity is even more interesting. While podophyllotoxin possesses severe side effects that limit its development as an anticancer agent, nevertheless, it has become a good lead compound for the synthesis of derivatives with fewer side effects and better selectivity. Several examples, such as etoposide, highlight the potential of this natural product for chemomodulation in the search for new antitumor agents. This review focuses on the recent chemical modifications (2017-mid-2023) of the podophyllotoxin skeleton performed mainly at the C-ring (but also at the lactone D-ring and at the trimethoxyphenyl E-ring) together with their biological properties. Special emphasis is placed on hybrids or conjugates with other natural products (either primary or secondary metabolites) and other molecules (heterocycles, benzoheterocycles, synthetic drugs, and other moieties) that contribute to improved podophyllotoxin bioactivity. In fact, hybridization has been a good strategy to design podophyllotoxin derivatives with enhanced bioactivity. The way in which the two components are joined (directly or through spacers) was also considered for the organization of this review. This comprehensive perspective is presented with the aim of guiding the medicinal chemistry community in the design of new podophyllotoxin-based drugs with improved anticancer properties.

Improving Properties of Podophyllic Aldehyde-Derived Cyclolignans: Design, Synthesis and Evaluation of Novel Lignohydroquinones, Dual-Selective Hybrids against Colorectal Cancer Cells

New lignohydroquinone conjugates (L-HQs) were designed and synthesized using the hybridization strategy, and evaluated as cytotoxics against several cancer cell lines. The L-HQs were obtained from the natural product podophyllotoxin and some semisynthetic terpenylnaphthohydroquinones, prepared from natural terpenoids. Both entities of the conjugates were connected through different aliphatic or aromatic linkers. Among the evaluated hybrids, the L-HQ with the aromatic spacer clearly displayed the in vitro dual cytotoxic effect derived from each starting component, retaining the selectivity and showing a high cytotoxicity at short (24 h) and long (72 h) incubation times (4.12 and 0.0450 µM, respectively) against colorectal cancer cells. In addition, the cell cycle blockade observed by flow cytometry studies, molecular dynamics, and tubulin interaction studies demonstrated the interest of this kind of hybrids, which docked adequately into the colchicine binding site of tubulin despite their large size. These results prove the validity of the hybridization strategy and encourage further research on non-lactonic cyclolignans.

In Vitro and In Silico Biological Studies of 4-Phenyl-2-quinolone (4-PQ) Derivatives as Anticancer Agents

Our previous study found that 2-phenyl-4-quinolone (2-PQ) derivatives are antimitotic agents, and we adopted the drug design concept of scaffold hopping to replace the 2-aromatic ring of 2-PQs with a 4-aromatic ring, representing 4-phenyl-2-quinolones (4-PQs). The 4-PQ compounds, whose structural backbones also mimic analogs of podophyllotoxin (PPT), maybe a new class of anticancer drugs with simplified PPT structures. In addition, 4-PQs are a new generation of anticancer lead compounds as apoptosis stimulators. On the other hand, previous studies showed that 4-arylcoumarin derivatives with 5-, 6-, and 7-methoxy substitutions displayed remarkable anticancer activities. Therefore, we further synthesized a series of 5-, 6-, and 7-methoxy-substituted 4-PQ derivatives (19-32) by Knorr quinoline cyclization, and examined their anticancer effectiveness. Among these 4-PQs, compound 22 demonstrated excellent antiproliferative activities against the COLO205 cell line (50% inhibitory concentration (IC₅₀) = 0.32 μM) and H460 cell line (IC₅₀ = 0.89 μM). Furthermore, we utilized molecular docking studies to explain the possible anticancer mechanisms of these 4-PQs by the docking mode in the colchicine-binding pocket of the tubulin receptor. Consequently, we selected the candidate compounds 19, 20, 21, 22, 25, 27, and 28 to predict their absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiles. Pharmacokinetics (PKs) indicated that these 4-PQs displayed good drug-likeness and bioavailability, and had no cardiotoxic side effects or carcinogenicity, but we detected risks of drug-drug interactions and AMES toxicity (mutagenic). However, structural modifications of these 4-PQs could improve their PK properties and reduce their side effects, and their promising anticancer activities attracted our attention for further studies.

Chemistry and Biological Activities of Naturally Occurring and Structurally Modified Podophyllotoxins

Plants containing podophyllotoxin and its analogues have been used as folk medicines for centuries. The characteristic chemical structures and strong biological activities of this class of compounds attracted attention worldwide. Currently, more than ninety natural podophyllotoxins were isolated, and structure modifications of these molecules were performed to afford a variety of derivatives, which offered optimized anti-tumor activity. This review summarized up to date reports on natural occurring podophyllotoxins and their sources, structural modification and biological activities. Special attention was paid to both structural modification and optimized antitumor activity. It was noteworthy that etoposide, a derivative of podophyllotoxin, could prevent cytokine storm caused by the recent SARS-CoV-2 viral infection.

2, 4, 5-Trideoxyhexopyranosides Derivatives of 4'- Demethylepipodophyllotoxin: De novo Synthesis and Anticancer Activity

BACKGROUND

Podophyllotoxin is a natural lignan which possesses anticancer and antiviral activities. Etoposide and teniposide are semisynthetic glycoside derivatives of podophyllotoxin and are increasingly used in cancer medicine.

OBJECTIVE

The present work was aimed to design and synthesize a series of 2, 4, 5-trideoxyhexopyranosides derivatives of 4'-demethylepipodophyllotoxin as novel anticancer agents.

METHODS

A divergent de novo synthesis of 2, 4, 5-trideoxyhexopyranosides derivatives of 4'-demethylepipodophyllotoxin has been established via palladium-catalyzed glycosylation. The abilities of synthesized glycosides to inhibit the growth of A549, HepG2, SH-SY5Y, KB/VCR and HeLa cancer cells were investigated by MTT assay. Flow cytometric analysis of cell cycle with propidium iodide DNA staining was employed to observe the effect of compound 5b on cancer cell cycle.

RESULTS

Twelve D and L monosaccharides derivatives 5a-5l have been efficiently synthesized in three steps from various pyranone building blocks employing de novo glycosylation strategy. D-monosaccharide 5b showed highest cytotoxicity on five cancer cell lines with the IC50 values from 0.9 to 6.7 mM. It caused HepG2 cycle arrest at G2/M phase in a concentration-dependent manner.

CONCLUSION

The present work leads to the development of novel 2, 4, 5-trideoxyhexopyranosides derivatives of 4'- demethylepipodophyllotoxin. The biological results suggested that the replacement of the glucosyl moiety of etoposide with 2, 4, 5-trideoxyhexopyranosyl is favorable to their cytotoxicity. D-monosaccharide 5b caused HepG2 cycle arrest at G2/M phase in a concentration-dependent manner.

A Novel Cytotoxic Conjugate Derived from the Natural Product Podophyllotoxin as a Direct-Target Protein Dual Inhibitor

Natural products are the ideal basis for the design of novel efficient molecular entities. Podophyllotoxin, a naturally occurring cyclolignan, is an example of natural product which displays a high versatility from a biological activity point of view. Based on its unique chemical structure, different derivatives have been synthesized presenting the original antitumoral properties associated with the compound, i.e., the tubulin polymerization inhibition and arising anti-topoisomerase II activity from structural modifications on the cyclolignan skeleton. In this report, we present a novel conjugate or hybrid which chemically combines both biological activities in one single molecule. Chemical design has been planned based in our lead compound, podophyllic aldehyde, as an inhibitor of tubulin polymerization, and in etoposide, an approved antitumoral drug targeting topoisomerase II. The cytotoxicity and selectivity of the novel synthetized hybrid has been evaluated in several cell lines of different solid tumors. In addition, these dual functional effects of the novel compound have been also evaluated by molecular docking approaches.

Divergent de novo synthesis of 2,4,5-trideoxyhexopyranosides derivatives of podophyllotoxin as anticancer agents

Aim: Identification of new anticancer glycosidic derivatives of podophyllotoxin. Methods: 14 podophyllotoxin D- and L-monosaccharides have been synthesized in three steps employing de novo glycosylation strategy, and their abilities to inhibit the growth of HeLa, HepG2, MCF-7, A549 and MDA-MB-231 cancer cells were investigated by MTT assay. Molecular docking study of compound 5j with tubulin was performed. Immunofluorescence was applied for detecting the inhibitory effect of 5j on tubulin polymerization. Results & conclusion: Most of synthesized compounds showed strong cytotoxicity activity against five cancer cell lines. Compound 5j possessed the highest cytotoxicity with the IC50 values from 41.6 to 95.2 nM, and could concentration-dependently inhibit polymerization of the microtubule cytoskeleton of MCF-7 cells. Molecular docking disclosed that sugar moiety-dedicated hydrogen bond endowed 5j a higher binding affinity for tubulin.

New Hybrids Derived from Podophyllic Aldehyde and Diterpenylhydroquinones with Selectivity toward Osteosarcoma Cells

A new family of molecular hybrids, between cyclolignans related to podophyllic aldehyde and several diterpenylnaphthohydroquinones (DNHQ), was prepared and its biological activity evaluated in several human solid tumor cell lines, which are representative of the most prevalent solid tumors in the Western world. Both cyclolignan and quinone fragments were linked through aliphatic or aromatic spacers. The new hybrid family was evaluated for its cytotoxicity, and it was found that the hybrids were several times more potent against the osteosarcoma cell line MG-63 than against MCF-7 and HT-29 cell lines. The presence of an aromatic ring in the linker gave the most potent and selective agent, improving the cytotoxicity of the parent compounds. Cell cycle studies demonstrated that this hybrid induces a strong and rapid apoptotic effect and arrests cells at the G2/M phase of the cell cycle, in the same way that the parent compound podophyllic aldehyde does.

Antileishmanial activity and tubulin polymerization inhibition of podophyllotoxin derivatives on Leishmania infantum

Leishmania microtubules play an important role not only in cell division, but also in keeping the shape of the parasite and motility of its free-living stages. Microtubules result from the self-assembly of alpha and beta tubulins, two phylogenetically conserved and very abundant eukaryotic proteins in kinetoplastids. The colchicine binding domain has inspired the discovery and development of several drugs currently in clinical use against parasites. However, this domain is less conserved in kinetoplastids and may be selectively targeted by new compounds. This report shows the antileishmanial effect of several series of compounds (53), derived from podophyllotoxin (a natural cyclolignan isolated from rhizomes of Podophyllum spp.) and podophyllic aldehyde, on a transgenic, fluorescence-emitting strain of Leishmania infantum. These compounds were tested on both promastigotes and amastigote-infected mouse splenocytes, and in mammalian – mouse non-infected splenocytes and liver HepG2 cells – in order to determine selective indexes of the drugs. Results obtained with podophyllotoxin derivatives showed that the hydroxyl group at position C-7α was a structural requisite to kill the parasites. On regards podophyllic aldehyde, derivatives with C9-aldehyde group integrated into a bicyclic heterostructure displayed more potent antileishmanial effects and were relatively safe for host cells. Docking studies of podophyllotoxin and podophyllic aldehyde derivatives showed that these compounds share a similar pattern of interaction at the colchicine site of Leishmania tubulin, thus pointing to a common mechanism of action. However, the results obtained suggested that despite tubulin is a remarkable target against leishmaniasis, there is a poor correlation between inhibition of tubulin polymerization and antileishmanial effect of many of the compounds tested, fact that points to alternative pathways to kill the parasites.

Antigiardial Activity of Podophyllotoxin-Type Lignans from Bursera fagaroides var. fagaroides

Giardiasis, a diarrheal disease, is highly prevalent in developing countries. Several drugs are available for the treatment of this parasitosis; unfortunately, all of them have variable efficacies and adverse effects. Bursera fagaroides has been known for its anti-inflammatory and antidiarrheal properties in Mexican traditional medicine. We investigated the in vitro anti-giardial activities of four podophyllotoxin-type lignans from Bursera fagaroides var. fagaroides, namely, 5'-desmethoxy-β-peltatin-A-methylether (5-DES), acetylpodophyllotoxin (APOD), burseranin (BUR), and podophyllotoxin (POD). All lignans affected the Giardia adhesion and electron microscopy images revealed morphological alterations in the caudal region, ventral disk, membrane, and flagella, to different extents. Only 5-DES, APOD, and POD caused growth inhibition. Using the Caco-2 human cell line as a model of the intestinal epithelium, we demonstrated that APOD displayed direct antigiardial killing activity and low toxicity on Caco-2 cells. This finding makes it an attractive potential starting point for new antigiardial drugs.

Cytotoxic activity of a synthetic deoxypodophyllotoxin derivative with an opened D-ring

Podophyllotoxin and its synthetic derivatives are valuable medicinal agents that have antitumor, insecticidal, and antifungal properties. We previously synthesized a deoxypodophyllotoxin derivative with an opened D-ring (DPD) exhibiting potent insecticidal activity. This article was firstly performed to identify the cytotoxicity of DPD toward human cancer cell lines (SGC7901, HeLa, and A549) and normal cell line (HEK293T) using MTT assay. DPD showed potent cytotoxicity against human cancer lines (HeLa and A549) and less cytotoxicity against normal cell lines HEK293T. DPD could also induce the cell cycle arrest at G2/M phase in HeLa cells and significantly increase the phosphorylation (Tyr 15) of CDC2 leading to inactivation of CDC2. The effects of DPD on cellular microtubule networks were detected using immunofluorescence technique in HeLa cells. The immunofluorescence results showed DPD influenced the arrangement and organization of cellular microtubule networks in HeLa cells. Microtubules are long, hollow cylinders made up of polymerized tubulin dimers. Total microtubules were separated after DPD treatment. Western blot results showed that the free polymerized tubulin dimers were obviously increased after DPD treatment. DPD may be a good drug candidate with the therapeutic potential to human cancer by affecting microtubule polymerization.

Iron-catalyzed trifluoromethylation of vinylcyclopropanes: facile synthesis of CF3–containing dihydronaphthalene derivatives

FeCl₂-catalyzed trifluoromethylation of vinylcyclopropanes to generate a series of CF₃-containing dihydronaphthalene derivatives in moderate to high yields (up to 96%) under mild reaction conditions was successfully developed.

Tetracyclic dihydronaphthalene derivatives via gold-catalyzed aminative homodimerization of ortho-alkynylbenzaldehydes

o-Alkynylbenzaldehydes undergo gold-catalyzed aminative homodimerization via a domino 6-endo-dig/hydroamination/[4+2] cycloaddition reaction sequence, furnishing tetracyclic products that incorporate medicinally relevant moieties.

Synthesis and biological evaluation of podophyllotoxin congeners as tubulin polymerization inhibitors

A series of new podophyllotoxin derivatives containing structural modifications at C-7, C-8, and C-9 were synthesized and evaluated for their cytotoxic activity against three human cancer cell lines. All the synthesized compounds showed significant growth inhibition with GI50 values in micromolar levels while some of the compounds were several times more potent against MCF-7 and HeLa cell lines than MIAPACA cell line. Three compounds (12a, 12d and 12e) emerged as potent compounds with broad spectrum of cytotoxic activity against all the tested cell lines with GI50 values in the range of 0.01-2.1 μM. These compounds induce microtubule depolymerization and arrests cells at the G2/M phase of the cell cycle. Moreover, compounds 12d and 12e disrupted microtubule network and accumulated tubulin in the soluble fraction in a similar manner to their parent podophyllotoxin scaffold. In addition, structure activity relationship studies within the series were also discussed. Molecular docking studies of these compounds into the colchicine-binding site of tubulin, revealed possible mode of inhibition by these compounds.

Rational approaches, design strategies, structure activity relationship and mechanistic insights for anticancer hybrids

A Hybrid drug which comprises the incorporation of two drug pharmacophores in one single molecule are basically designed to interact with multiple targets or to amplify its effect through action on another bio target as one single molecule or to counterbalance the known side effects associated with the other hybrid part(.) The present review article offers a detailed account of the design strategies employed for the synthesis of anticancer agents via molecular hybridization techniques. Over the years, the researchers have employed this technique to discover some promising chemical architectures displaying significant anticancer profiles. Molecular hybridization as a tool has been particularly utilized for targeting tubulin protein as exemplified through the number of research papers. The microtubule inhibitors such as taxol, colchicine, chalcones, combretasatin, phenstatins and vinca alkaloids have been utilized as one of the functionality of the hybrids and promising results have been obtained in most of the cases with some of the tubulin based hybrids exhibiting anticancer activity at nanomolar level. Linkage with steroids as biological carrier vector for anticancer drugs and the inclusion of pyrrolo [2,1-c] [1,4]benzodiazepines (PBDs), a family of DNA interactive antitumor antibiotics derived from Streptomyces species in hybrid structure based drug design has also emerged as a potential strategy. Various heteroaryl based hybrids in particular isatin and coumarins have also been designed and reported to posses' remarkable inhibitory potential. Apart from presenting the design strategies, the article also highlights the structure activity relationship along with mechanistic insights revealed during the biological evaluation of the hybrids.

Design and synthesis of 6,7-methylenedioxy-4-substituted phenylquinolin-2(1H)-one derivatives as novel anticancer agents that induce apoptosis with cell cycle arrest at G2/M phase

Novel 6,7-methylenedioxy-4-substituted phenylquinolin-2(1H)-one derivatives 12a-n were designed and prepared through an intramolecular cyclization reaction and evaluated for in vitro anticancer activity. Among the synthesized compounds, 6,7-methylenedioxy-4-(2,4-dimethoxyphenyl)quinolin-2(1H)-one (12e) displayed potent cytotoxicity against several different tumor cell lines at a sub-micromolar level. Furthermore, results of fluorescence-activated cell sorting (FACS) analysis suggested that 12e induced cell cycle arrest in the G2/M phase accompanied by apoptosis in HL-60 and H460 cells. This action was confirmed by Hoechst staining and caspase-3 activation. Due to their easy synthesis and remarkable biological activities, 4-phenylquinolin-2(1H)-one analogs (4-PQs) are promising new anticancer leads based on the quinoline scaffold. Accordingly, compound 12e was identified as a new lead compound that merits further optimization and development as an anticancer candidate.

Synthesis and biological evaluation of a series of podophyllotoxins derivatives as a class of potent antitubulin agents

A series of eight novel podophyllotoxin derivatives were designed, synthesized and evaluated for biological activities. The antiproliferative activities were tested against a panel of human cancer cell lines (K562, SGC, Hela and HepG) and the inhibition of tubulin polymerization was also evaluated. Compound 8e displayed significant antiproliferative activities for all four cell lines and strong levels of tubulin polymerization inhibition effect. Combined with cell apoptosis and cell cycle analysis, it demonstrated that compound 3e that effectively interfere with tubulin dynamics prevent mitosis in cancer cells, leading to cell cycle arrest and, eventually dose dependent apoptosis. All experimental measurements were also supported by molecular docking simulations of colchicine binding site, which revealed the governing forces for the binding behavior and a good relationship with anti-tubulin activity and antiproliferative activities. The synthesis and biological studies provided an interesting new class of antitubulin agents for development of lead compounds and also a direction for further structure modification to obtain more potent anti-cancer drugs.

N-hydroxyethyl-4-aza-didehydropodophyllotoxin derivatives as potential antitumor agents

Three different series of N-hydroxyethyl aza-podophyllotoxin derivatives containing (i) a five-membered methylenedioxy ring (7a-f), (ii) a five-membered ring with no heteroatom (8a-f) or (iii) a six membered ethylenedioxy ring (9a-f) as ring A were synthesized using a convenient one-pot multi-component reaction. Further variation on ring E was done by decorating it with methoxy and hydroxy groups at different positions. Calculation of logP values of these compounds indicates them to be better soluble than corresponding non-hydroxy derivatives. These novel aza-podophyllotoxin derivatives were screened for their cytostatic and cytotoxic activities on National Cancer Institute's 60 human tumor cell lines to study the structure activity relationship. The overall anticancer activity of these compounds was in the order of 8a-f>9a-f>7a-f. Furthermore, the compounds having 3'-methoxy and 3',4',5'-trimethoxy substitution at ring E were the most active within the series. The cytotoxicity of all the active compounds was low, while their antiproliferative (or cytostatic) activity was high, providing a wide therapeutic window for their potential application as anticancer drugs.

Antiproliferation and cell apoptosis inducing bioactivities of constituents from Dysosma versipellis in PC3 and Bcap-37 cell lines

BACKGROUND

Recently, interest in phytochemicals from traditional Chinese medicinal herbs with the capability to inhibit cancer cells growth and proliferation has been growing rapidly due to their nontoxic nature. Dysosma versipellis as Bereridaceae plants is an endemic species in China, which has been proved to be an important Chinese herbal medicine because of its biological activity. However, systematic and comprehensive studies on the phytochemicals from Dysosma versipellis and their bioactivity are limited.

RESULTS

Fifteen compounds were isolated and characterized from the roots of Dysosma versipellis, among which six compounds were isolated from this plant for the first time. The inhibitory activities of these compounds were investigated on tumor cells PC3, Bcap-37 and BGC-823 in vitro by MTT method, and the results showed that podophyllotoxone (PTO) and 4'-demethyldeoxypodophyllotoxin (DDPT) had potent inhibitory activities against the growth of human carcinoma cell lines. Subsequent fluorescence staining and flow cytometry analysis indicated that these two compounds could induce apoptosis in PC3 and Bcap-37 cells, and the apoptosis ratios reached the peak (12.0% and 14.1%) after 72 h of treatment at 20 μM, respectively.

CONCLUSIONS

This study suggests that most of the compounds from the roots of D. versipellis could inhibit the growth of human carcinoma cells. In addition, PTO and DDPT could induce apoptosis of tumor cells.

Synthesis and antitumor activity of novel aroylthiourea derivatives of podophyllotoxin

A novel series of 4β-[(4-substituted) aroylthiourea] derivatives of podophyllotoxin were synthesized and their abilities to inhibit the growth of cancer cells were investigated by MTT assay. Compound 4a possessed the highest cytotoxicity on HepG2, A549 and HCT-116 cancer cell lines with the IC(50) values of 0.1 μM. Apoptosis in HCT-116 cells induced by compound 4a was observed by Hoechst33342-Propidium iodide (PI) and acridine orange (AO)-ethidium bromide (EB) double staining assays. DNA flow cytometric analysis revealed that 4a induced cell cycle arrest at G2/M phase and kDNA decatenation assay indicated that 4a inhibited topoisomerase IIα-mediated kDNA decatenation. Our results indicated that compound 4a possessed promising antitumor activity, which need to be studied further.

[Interest of lignans in prevention and treatment of cancers]

Lignans are diphenolic compounds widely distributed in the plant kingdom. They are mainly localised in lignified tissues, seeds and roots. These molecules are involved in plant defence mechanisms, but are also interesting for human health. Flax lignans belonging to the phytoestrogens are metabolised after ingestion into enterolignans that may offer a protection against the onset and development of hormono-dependant cancers. In vitro studies based on mammalian cellular models tend to confirm their beneficial effects observed during epidemiological studies and give us insights about their mechanisms of action. The most studied lignan, podophyllotoxin, and its semi-synthetic derivatives (etoposide, teniposide, etoposide phosphate), are particularly interesting at a curative level due to their cytotoxic properties. These semi-synthetic derivatives are used in chemotherapy of lung cancer for example. However, the extensive use of these anticancer drugs will lead to the problem of podophyllotoxin supply. This molecule is currently extracted from the rhizomes and roots of an Indian species Podophyllum hexandrum which has subsequently become endangered. Strategies are investigated to obtain economically viable alternative sources of Podophyllotoxin from plants and in vitro cultures of several species. Among them, north american Podophyllum peltatum, Linum wild species, Hyptis, Anthriscus, Juniperus or Dysosma species which accumulate Podophyllotoxin or closely related derivatives, are good candidates. double dagger.

Natural products as leads to anticancer drugs

Throughout history, natural products have afforded a rich source of compounds that have found many applications in the fields of medicine, pharmacy and biology. Within the sphere of cancer, a number of important new commercialised drugs have been obtained from natural sources, by structural modification of natural compounds, or by the synthesis of new compounds, designed following a natural compound as model. The search for improved cytotoxic agents continues to be an important line in the discovery of modern anticancer drugs. The huge structural diversity of natural compounds and their bioactivity potential have meant that several products isolated from plants, marine flora and microorganisms can serve as "lead" compounds for improvement of their therapeutic potential by molecular modification. Additionally, semisynthesis processes of new compounds, obtained by molecular modification of the functional groups of lead compounds, are able to generate structural analogues with greater pharmacological activity and with fewer side effects. These processes, complemented with high-throughput screening protocols, combinatorial chemistry, computational chemistry and bioinformatics are able to afford compounds that are far more efficient than those currently used in clinical practice. Combinatorial biosynthesis is also applied for the modification of natural microbial products. Likewise, advances in genomics and the advent of biotechnology have improved both the discovery and production of new natural compounds.

A new and efficient strategy for the synthesis of podophyllotoxin and its analogues

[structure: see text]. An efficient and stereoselective strategy for the total synthesis of podophyllotoxin was developed. This route leads to podophyllotoxin 1 in only 12 steps with 29% overall yield. A notable feature of this synthetic strategy is the use of the cascade addition-alkylation to ensure the key C1-C2 stereochemistry that is pivotal for the synthesis of podophyllotoxin.

Synthesis and cytotoxic evaluation of C-9 oxidized podophyllotoxin derivatives

A series of podophyllotoxin and podophyllic aldehyde derivatives, lacking the lactone ring and oxidized at C-9 position, has been prepared. The functionalities considered at C-9 were carboxylic acids and several derivatives such as esters, amides, nitriles or anhydrides. The synthesized compounds were cytotoxic at the micromolar level, though less potent and selective than the parent compounds, revealing the influence of the C-9 electrophilic character on the potency and selectivity of these cyclolignans.

Synthesis and biological evaluation of new 4beta-5-Fu-substituted 4'-demethylepipodophyllotoxin derivatives

A series of new 4beta-5-Fu-substituted 4'-demethylepipodophyllotoxin derivatives were synthesized and evaluated, together with some previously prepared ones, for their cytotoxic activities against four tumor cell lines (HL60, P388, A549 and BEL7402). Three of these compounds exhibited superior in vitro anticancer activity against P388 and A549 than the reference compound etoposide. In addition, the partition coefficients (P) of all the new and previously synthesized derivatives were determined.

Synthesis and biological evaluation of new spin-labeled derivatives of podophyllotoxin

In order to find compounds with superior bioactivity and less toxicity, a series of spin-labeled podophyllotoxin derivatives were synthesized and tested for the partition coefficients and cytotoxicity against P-388 and A-549. Furthermore, we also determined antioxidant activities of target molecular in tissues of SD rats by the TBA method. Results revealed that most synthesized compounds showed more significant cytotoxicity against P-388 and A-549 in vitro than VP-16. Among them, 9d exhibited most potent cytotoxicity against P-388 and A-549 cells (IC50 is <0.01 and 0.13 microM, respectively). Also, the antioxidative activities showed that the modified compounds of 4'-demethylepipodophyllotoxin (9a-d and 10a-c) are higher than those of podophyllotoxin series (8a-d). The relationship between the cytotoxicity and antioxidative activity discussed.

Synthesis and cytotoxic activity of novel derivatives of 4'-demethylepipodophyllotoxin

Nine novel 4beta-N-substituted-5-FU-4'-demethylepipodophyllotoxin derivatives were synthesized and evaluated as potential antitumor agents. All of the target compounds showed more significant cytotoxic activity against HL-60 and A-549 in vitro than VP-16 and 5-FU. Among them, 4beta-N-substituted-phenylalanine 5-Fu pentyl ester-4'-demethylepipodophyllotoxin (9 g) was found to exhibit most potent cytotoxic activity against HL-60 and A-549 cell (IC50 is 0.04 and <0.01 microM, respectively).