Podophyllotoxin derivatives: drug discovery and development

Exploring the mechanism of enterotoxicity mediated by the microbiome-butyrate-PPAR axis in podophyllotoxin through the toxicological evidence chain (TEC) concept

Podophyllotoxin (PPT) is a lignan derived from the roots and stems of the Podophyllum plant. However, its enterotoxicity restricts its clinical application. The underlying mechanisms by which PPT exerts its action remain largely elusive. This study aimed to evaluate the molecular mechanisms underlying PPT-induced enterotoxicity utilizing the concept of toxicological evidence chain. Changes in body weight, behavior, and histopathological and biochemical markers in rats were observed. Additionally, microbiome, metabolome, and transcriptome analyses were integrated to identify potential microorganisms, metabolic markers, and major pathways using a co-occurrence network. Our findings suggested that PPT induced pathological changes in rats, including weight loss, diarrhea, and inflammation accompanied by increased levels of IFN-γ, IL-5, IL-6, GRO/KC, and IL-12p70. The decrease in butyrate levels in the PPT group may be related to the enrichment of Firmicutes. The reduction of butyrate levels may impair the expression of PPARγ, subsequently promoting Escherichia-Shigella proliferation. Additionally, the suppression of PPARs pathway may result in the increased production of inflammatory factors, contributing to enterotoxicity. This study offers a novel understanding of the molecular mechanisms underlying PPT-induced enterotoxicity, making a significant contribution to developing strategies to mitigate PPT toxicity and prevent associated diseases.

Design, synthesis, and biological evaluation of novel 2,3-Di-O-Aryl/Alkyl sulfonate derivatives of l-ascorbic acid: Efficient access to novel anticancer agents via in vitro screening, tubulin polymerization inhibition, molecular docking study and ADME predictions

A series of novel l-ascorbic acid derivatives bearing aryl and alkyl sulfonate substituents were synthesized and characterized. In vitro anticancer evaluation against MCF-7 (breast) and A-549 (lung) cancer cell lines revealed potent activity for most of the compounds, with 2b being equipotent to the standard drug colchicine against MCF-7 (IC50 = 0.04 μM). Notably, compound 2b displayed 89-fold selectivity for MCF-7 breast cancer over MCF-10A normal breast cells. Derivatives with two sulfonate groups (2a-g, 3a-g) exhibited superior potency over those with one sulfonate (4a-c,5g, 6b). Compounds 2b and 2c potently inhibited tubulin polymerization in A-549 cancer cells (73.12 % and 62.09 % inhibition, respectively), substantiating their anticancer potential through microtubule disruption. Molecular docking studies showed higher binding scores and affinities for these compounds at the colchicine-binding site of α, β-tubulin compared to colchicine itself. In-silico ADMET predictions indicated favourable drug-like properties, with 2b exhibiting the highest binding affinity. These sulfonate derivatives of l-ascorbic acid represents promising lead scaffolds for anticancer drug development.

Natural-Product-Inspired Discovery of Trimethoxyphenyl-1,2,4-triazolosulfonamides as Potent Tubulin Polymerization Inhibitors

An approach of natural product-inspired strategy and incorporation of an NP-privileged motif has been investigated for the discovery of new tubulin polymerization inhibitors. Two series, N-Arylsulfonyl-3-arylamino-5-amino-1,2,4-triazole derivatives, and their isomers were considered. The compounds were synthesized by construction of the N-aryl-1,2,4-triazole-3,5-diamine motif and sulfonylation. Although the chemo- and regioselectivity in sulfonylation were challenging due to multiple ring-tautomerizable-NH and exocyclic NH2 functionalities present in the molecular motifs, the developed synthetic method enabled the preparation of designed molecular skeletons with biologically important motifs. The approach also led to explore interesting molecular regio- and stereochemical aspects valuable for activity. The X-ray crystallography study indicated that the hydrogen bonding between the arylamine-NH and the arylsulfonyl-"O" unit and appropriate molecular-functionality topology allowed the cis-locking of two aryls, which is important for tubulin-binding and antiproliferative properties. All synthesized compounds majorly showed characteristic antiproliferative effects in breast cancer cells (MCF-7), and four compounds exhibited potent antiproliferative activity. One compound potently bound to tubulin at the colchicine site and inhibited tubulin polymerization in vitro. The compound significantly depolymerized microtubules in MCF-7 cells, arrested the cells at the G2/M phase, and induced cell death. This study represents the importance of the design strategy in medicinal chemistry and the molecular structural features relevant to anticancer anti-tubulin properties. The explored molecules have the potential for further development.

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.

A recent antitumor story of podophyllotoxin derivatives targeting tubulin: an update (2017-2022)

So far, numerous tubulin-targeted podophyllotoxin congeners were designed and synthesized to overcome the poor water-solubility and improve the pharmaceutical characteristics. However, few studies are dedicated to exploring the interaction of tubulin with the downstream signal transduction pathways, which is important for gaining insight into the role of tubulin in the anticancer action of podophyllotoxin-based conjugates. In this review, we described a detailed account of all the advances on tubulin targeting-podophyllotoxin derivatives from 2017 and 2022 with in depth knowledge about their antitumor action and potential molecular signaling pathways directly involved in tubulin depolymerization, aiming to help researchers design and develop better anticancer drugs derived from podophyllotoxin. Moreover, we also discussed the associated challenges and future opportunities in this field. Short teaser Recent reviews summarized podophyllotoxin-based analogues, with interaction between tubulin and signal pathways being rarely involved. This review comprehensively sum up how podophyllotoxin derivatives targeting tubulin exert their antitumor action via potential molecular signaling pathways.

Aryltetralin lignans from Hyptis brachiata inhibiting T lymphocyte proliferation

Increased activation and proliferation of T lymphocytes plays an essential role in the development of chronic inflammation and autoimmune diseases. Currently used immunosuppressive drugs often do not provide long-lasting relief of symptoms and show a gradual loss of efficacy over time, and are accompanied by various side effects. Therefore, novel immunosuppressive lead substances are needed. For this purpose, an in-house library consisting of 600 extracts of plants from Panama was screened for inhibition of human T lymphocyte proliferation. As one of the hits, an ethyl acetate extract from the aerial parts of Hyptis brachiata (Lamiaceae) exhibited strong inhibitory effects. Subsequent investigation resulted in the isolation of seven aryltetralin lignans, five arylnaphthalene lignans, two flavonoids, three triterpenes, and cinnamyl cinnamate. Aryltetralin lignans inhibited T lymphocyte proliferation in a concentration-dependent manner without induction of apoptosis. No relevant inhibition was observed for the arylnaphthalene lignans, flavonoids, and triterpenes. Additional cell cycle arrest investigations revealed that isolated aryltetralin lignans potently inhibited cell division in G2/M phase similarly to podophyllotoxin. Multifluorescence panel analyses of the extract also showed weak suppressive effects on the production of IL-2 and TNF-α. Therefore, preparations made out of H. brachiata could be further explored as an interesting herbal alternative in the treatment of autoimmune diseases.

Design, synthesis and biological evaluation of novel tubulin inhibitors targeting colchicine sites

Tubulin, a potential target for antitumor drug discovery, contains three main binding sites for clinical inhibitors: colchicine, vinblastine, and paclitaxel. CA-4 has been reported to be a classic tubulin inhibitor targeting the colchicine site. Herein, based on the structural modification of CA-4, 48 novel compounds were designed and synthesized by selecting structural fragments with various biological activities to replace the cis double bond of CA-4. Among these compounds, compound 8p was the most effective tubulin inhibitor (IC₅₀ = 65 nM aganist HepG2 cells). Immunofluorescence experiment confirmed the anti-tumor effect of 8p by destroying the network structure of microtubules. Further studies showed that 8p induced tumor cell apoptosis, arrested cell cycle, inhibited tumor cell migration and invasion.

Podophyllotoxin and its derivatives: Potential anticancer agents of natural origin in cancer chemotherapy

The use of plant secondary metabolites has gained considerable attention among clinicians in the prevention and treatment of cancer. A secondary metabolite isolated mainly from the roots and rhizomes of Podophyllum species (Berberidaceae) is aryltetralin lignan - podophyllotoxin (PTOX). The purpose of this review is to discuss the therapeutic properties of PTOX as an important anticancer compound of natural origin. The relevant information regarding the antitumor mechanisms of podophyllotoxin and its derivatives were collected and analyzed from scientific databases. The results of the analysis showed PTOX exhibits potent cytotoxic activity; however, it cannot be used in its pure form due to its toxicity and generation of many side effects. Therefore, it practically remains clinically unusable. Currently, high effort is focused on attempts to synthesize analogs of PTOX that have better properties for therapeutic use e.g. etoposide (VP-16), teniposide, etopophos. PTOX derivatives are used as anticancer drugs which are showing additional immunosuppressive, antiviral, antioxidant, hypolipemic, and anti-inflammatory effects. In this review, attention is paid to the high potential of the usefulness of in vitro cultures of P. peltatum which can be a valuable source of lignans, including PTOX. In conclusion, the preclinical pharmacological studies in vitro and in vivo confirm the anticancer and chemotherapeutic potential of PTOX and its derivatives. In the future, clinical studies on human subjects are needed to certify the antitumor effects and the anticancer mechanisms to be certified and analyzed in more detail and to validate the experimental pharmacological preclinical studies.

Stereoselective Total Synthesis of Formosanol, Tsugacetal, and Methyl β-Conidendral

The first enantioselective total synthesis of aryltetralin lignan acetals, (-)-formosanol, (+)-tsugacetal, (+)-methyl β-conidendral, and their enantiomers have been accomplished on the basis of the Pd-catalyzed asymmetric allylic cycloaddition as a key step. Six stereoisomers of the lignan acetals have been synthesized via a 7-8 step sequence in up to 14% overall yield. The in vitro cytotoxicity against several cancer cells has preliminarily been examined for the obtained six stereoisomers of lignan acetals.

Design, Synthesis, Molecular Docking, and Biological Evaluation of Pyrazole Hybrid Chalcone Conjugates as Potential Anticancer Agents and Tubulin Polymerization Inhibitors

Some (E)-3-(3-(4-(benzyloxy)phenyl)-1-phenyl-1H-pyrazol-4-yl)-1-phenylprop-2-en-1-one conjugates 5a–r were designed; synthesized; characterized by ¹H, ¹³C NMR, and ESI-MS; and evaluated for tubulin polymerization inhibitory activity and in vitro cytotoxicity against breast (MCF-7), cervical (SiHa), and prostate (PC-3) cancer cell lines, as well as a normal cell line (HEK-293T). The compounds were also tested to determine their binding modes at the colchicine-binding site of tubulin protein (PDB ID-3E22), for in silico ADME prediction, for bioactivity study, and for PASS prediction studies. Among all the synthesized conjugates, compound 5o exhibited excellent cytotoxicity with an IC₅₀ value of 2.13 ± 0.80 µM (MCF-7), 4.34 ± 0.98 µM (SiHa), and 4.46 ± 0.53 µM (PC-3) against cancer cell lines. The compound did not exhibit significant toxicity to the HEK cells. Results of the in silico prediction revealed that the majority of the conjugates possessed drug-like properties.

Podophyllotoxin: History, Recent Advances and Future Prospects

Podophyllotoxin, along with its various derivatives and congeners are widely recognized as broad-spectrum pharmacologically active compounds. Etoposide, for instance, is the frontline chemotherapeutic drug used against various cancers due to its superior anticancer activity. It has recently been redeveloped for the purpose of treating cytokine storm in COVID-19 patients. Podophyllotoxin and its naturally occurring congeners have low bioavailability and almost all these initially discovered compounds cause systemic toxicity and development of drug resistance. Moreover, the production of synthetic derivatives that could suffice for the clinical limitations of these naturally occurring compounds is not economically feasible. These challenges demanded continuous devotions towards improving the druggability of these drugs and continue to seek structure-optimization strategies. The discovery of renewable sources including microbial origin for podophyllotoxin is another possible approach. This review focuses on the exigency of innovation and research required in the global R&D and pharmaceutical industry for podophyllotoxin and related compounds based on recent scientific findings and market predictions.

Identification of new 3-phenyl-1H-indole-2-carbohydrazide derivatives and their structure-activity relationships as potent tubulin inhibitors and anticancer agents: A combined in silico, in vitro and synthetic study

Virtual screening of commercially available molecular entities by using CDRUG, structure-based virtual screening, and similarity identified eight new derivatives of 3-phenyl-1H-indole-2-carbohydrazide with anti-proliferative activities. The molecules were tested experimentally for inhibition of tubulin polymerisation, which revealed furan-3-ylmethylene-3-phenyl-1H-indole-2-carbohydrazide (27a) as the most potent candidate. Molecule 27a was able to induce G2/M phase arrest in A549 cell line, similar to other tubulin inhibitors. Synthetic modifications of 27a were focussed on small substitutions on the furan ring, halogenation at R₁ position and alteration of furyl connectivity. Derivatives 27b, 27d and 27i exhibited the strongest tubulin inhibition activities and were comparable to 27a. Bromine substitution at R₁ position showed most prominent anticancer activities; derivatives 27b-27d displayed the strongest activities against HuCCA-1 cell line and were more potent than doxorubicin and the parent molecule 27a with IC₅₀ values <0.5 μM. Notably, 27b with a 5-methoxy substitution on furan displayed the strongest activity against HepG2 cell line (IC₅₀ = 0.34 µM), while 27d displayed stronger activity against A549 cell line (IC₅₀ = 0.43 µM) compared to doxorubicin and 27a. Fluorine substitutions at the R₁ position tended to show more modest anti-tubulin and anticancer activities, and change of 2-furyl to 3-furyl was tolerable. The new derivatives, thiophenyl 26, displayed the strongest activity against A549 cell line (IC₅₀ = 0.19 µM), while 1-phenylethylidene 21b and 21c exhibited more modest anticancer activities with unclear mechanisms of action; 26 and 21c demonstrated G2/M phase arrest, but showed weak tubulin inhibitory properties. Molecular docking suggests the series inhibit tubulin at the colchicine site, in agreement with the experimental findings. The calculated molecular descriptors indicated that the molecules obey Lipinski's rule which suggests the molecules are drug-like structures.

Novel Hybrids of Podophyllotoxin and Coumarin Inhibit the Growth and Migration of Human Oral Squamous Carcinoma Cells

Oral squamous cell carcinoma is the most common malignancy of oral tumor. In this study, two novel hybrids of podophyllotoxin and coumarin were designed using molecular hybridization strategy and synthesized. Pharmacological evaluation showed that the potent compound 12b inhibited the proliferation of three human oral squamous carcinoma cell lines with nanomolar IC₅₀ values, as well as displayed less toxicity on normal cells. Mechanistic studies indicated that 12b triggered HSC-2 cell apoptosis, induced cell cycle arrest, and inhibited cell migration. Moreover, 12b could disturb the microtubule network via binding into the tubulin. It was noteworthy that induction of autophagy by 12b was associated with the upregulation of Beclin1, as well as LC3-II. Furthermore, 12b significantly stimulated the AMPK pathway and restrained the AKT/mTOR pathway in HSC-2 cells. These results indicated that compound 12b was a promising candidate for further investigation.

Novel Aza-podophyllotoxin derivative induces oxidative phosphorylation and cell death via AMPK activation in triple-negative breast cancer

BACKGROUND

To circumvent Warburg effect, several clinical trials for different cancers are utilising a combinatorial approach using metabolic reprogramming and chemotherapeutic agents including metformin. The majority of these metabolic interventions work via indirectly activating AMP-activated protein kinase (AMPK) to alter cellular metabolism in favour of oxidative phosphorylation over aerobic glycolysis. The effect of these drugs is dependent on glycaemic and insulin conditions.  Therefore, development of small molecules, which can activate AMPK, irrespective of the energy state, may be a better approach for triple-negative breast cancer (TNBC) treatment.

METHODS

Therapeutic effect of SU212 on TNBC cells was examined using in vitro and in vivo models.

RESULTS

We developed and characterised the efficacy of novel AMPK activator (SU212) that selectively induces oxidative phosphorylation and decreases glycolysis in TNBC cells, while not affecting these pathways in normal cells.   SU212 accomplished this metabolic reprogramming by activating AMPK independent of energy stress and irrespective of the glycaemic/insulin state. This leads to mitotic phase arrest and apoptosis in TNBC cells. In vivo, SU212 inhibits tumour growth, cancer progression and metastasis.

CONCLUSIONS

SU212 directly activates AMPK in TNBC cells, but does not hamper glucose metabolism in normal cells. Our study provides compelling preclinical data for further development of SU212 for the treatment of TNBC.

Sequential Treatment of Bioresponsive Nanoparticles Elicits Antiangiogenesis and Apoptosis and Synergizes with a CD40 Agonist for Antitumor Immunity

The combination of antiangiogenesis and chemotherapy regimens with cancer immunotherapy has the potential to synergistically boost antitumor immunity. Herein, we report the construction of two bioresponsive nanoparticles, namely, Podo-NP and CbP-NP, comprising prodrugs of podophyllotoxin (Podo) and carboplatin, respectively. Sequential treatment with esterase-responsive Podo-NP, redox-sensitive CbP-NP, and a CD40 agonist promotes antitumor T cell response. Podo-NP suppresses angiogenesis by preventing proliferation and migration of endothelial cells, sprouting of neovessels, formation of tubules, and stabilization of newly formed vessels. Vascular endothelial growth factor blockade and endostatin stimulation normalize tortuous tumor vasculatures to allow efficient infiltration of effector immune cells. Subsequent treatment with CbP-NP arrests the cell-division cycle and elicits the apoptosis of tumor cells. CD40 agonist activates antigen-presenting cells to process the released tumor-associated antigens from dying tumor cells, thus reversing immunosuppressive tumor microenvironments. Sequential delivery of antiangiogenic and chemotherapeutic agents with bioresponsive NPs activates tumor microenvironments and synergizes with CD40 agonist to regress transplanted tumors and inhibit disseminated tumors in a lung cancer mouse model.

Highly loaded deoxypodophyllotoxin nano-formulation delivered by methoxy polyethylene glycol-block-poly (D,L-lactide) micelles for efficient cancer therapy

Cancer is a kind of malignant diseases that threatens human health and the research application of anti-tumor drug therapeutics is growingly always been focused on. Many new compounds with great anticancer activity were synthesized but cannot be hard to be developed into clinical use due to its poor water solubility. Deoxypodophyllotoxin (DPT) is just an example. We develop lyophilized Deoxypodophyllotoxin (DPT) loaded polymeric micelles using methoxy polyethylene glycol-block-Poly (D, L-lactide) (mPEG-PLA). DPT-PM freeze-dried powder was successfully prepared using optimized formulation. mPEG-PLA was added to hydration media before hydrating as cryoprotectants. The freeze-dried powder exhibited white pie-solid without collapsing, and the particle size of DPT-PM reconstituted with water was about 20-35 nm. The entrapment efficiency of the reconstituted solution was 98%, which shows no differences with the micelles before lyophilization. In-vitro cytotoxicity and cellular uptake studies showed that DPT-PM has a higher degree of cytotoxicity comparing with DPT and mPEG-PLA micelles and uptake of mPEG-PLA was concentration and time-dependent. In vivo characterization of DPT-PM was done for pharmacokinetics behaviors, antitumor activity and safety. The obtained results showed significant improvement in plasma clearance bioavailability (p <0.05) and prolonged blood circulation time comparing with DPT-HP-β-CD. Moreover, mPEG-PLA micelles had a better degree of anti-tumor efficacy, this was due to better accumulation of mPEG-PLA in tumor cell via enhanced permeability and retention (EPR) effect. Therefore, DPT-PM has great clinical value, and can be expected to be a novel antitumor preparation.

The Effect of a Newly Synthesized Ferrocene Derivative against MCF-7 Breast Cancer Cells and Spheroid Stem Cells through ROS Production and Inhibition of JAK2/STAT3 Signaling Pathway

Background:

Breast Cancer Stem Cells (BCSCs) possess the ability of self-renewal and cellular heterogeneity, and therefore, play a key role in the initiation, propagation and clinical outcome of breast cancer. It has been shown that ferrocene complexes have remarkable potential as anticancer drugs.

Objective:

The present study was conducted to investigate the effects of a novel ferrocene complex, 1- ferrocenyl-3-(4-methylsulfonylphenyl)propen-1-one (FMSP) on MCF-7 breast cancer cell line and its derived mammospheres with cancer stem cell properties.

Methods:

Mammospheres were developed from MCF-7 cells and validated by the evaluation of CD44 and CD24 cell surface markers by flow cytometry as well as of the expression of genes that are associated with stem cell properties by real-time PCR. Cells viability was assessed by a soluble tetrazolium salt (MTS) after the treatment of cells with various concentrations of FMSP. Apoptosis was evaluated by flow cytometry analysis of annexin V and PI labeling of cells. Reactive Oxygen Species (ROS) production was measured using a cellpermeable, oxidant-sensitive fluorescence probe (carboxy-H2DCFDA). The involvement of the JAK2/STAT3 pathway was also investigated by western blotting.

Results:

FMSP could successfully prevent mammosphere formation from differentiated MCF-7 cells and significantly down-regulated the expression of genes involved in the production of the stem cell properties including Wnt1, Notch1, β -catenin, SOX2, CXCR4 and ALDH1A1. FMSP decreased cell viability in both MCF-7 cells and spheroid cells, although MCF-10A cells were unaffected by this compound. Apoptosis was also dramatically induced by FMSP, via ROS production but independent of CD95 activation. Phosphorylation levels of JAK2 and STAT3 were also found to be significantly attenuated even in the presence of IL-6, the putative activator of the JAK/STAT pathway.

Conclusion:

FMSP can effectively target BCSCs via ROS production and modulation of major signaling pathways that contribute to the stemness of breast cancer cells, and therefore, might be considered a promising anticancer agent after in vivo studies.

Tubulin inhibitors: Discovery of a new scaffold targeting extra-binding residues within the colchicine site through anchoring substituents properly adapted to their pocket by a semi-flexible linker

Bis-hydrazides 13a-h were designed and synthesized as potential tubulin inhibitors selectively targeting the colchicine site between α- and β-tubulin subunits. The newly designed ring-B substituents were assisted at their ends by 'anchor groups' which are expected to exert binding interaction(s) with new additional amino acid residues in the colchicine site (beyond those amino acids previously reported to interact with reference inhibitors as CA-4 and colchicine). Conformational flexibility of bis-hydrazide linker assisted these 'extra-binding' properties through reliving ligands' strains in the final ligand-receptor complexes. Compound 13f displayed the most promising computational and biological study results in the series: MM/GBSA binding energy of -62.362 kcal/mol (extra-binding to Arg α:221, Thr β:353 & Lys β:254); 34% NCI-H522 cells' death (at 10 µM), IC₅₀ = 0.073 µM (MTT assay); significant cell cycle arrest at G2/M phase; 11.6% preG1 apoptosis induction and 83.1% in vitro tubulin inhibition (at concentration = IC₅₀). Future researchers in bis-hydrazide tubulin inhibitors are advised to consider the 2-chloro-N-(4-substituted-phenyl)acetamide derivatives as compound 13f due to extra-binding properties of their ring B.

Radiosensitization of Head and Neck Squamous Cell Carcinoma (HNSCC) by a Podophyllotoxin

Surgical resection and radiotherapy are an effective treatment in many head and neck squamous cell carcinomas (HNSCC), but in others, the development of radiotherapy resistance limits treatment efficacy and permits disease progression. We developed a novel multiwell radiation dosing method to increase the throughput of our investigation of the activity of a novel podophyllotoxin SU093 in acting as a radiosensitizer in the HNSCC models FaDu and SCC-25. These in vitro studies showed that combining SU093 with 5 Grays ionizing radiation acted synergistically to increase HNSCC apoptosis and decrease its proliferation via inhibition of Nuclear factor, erythroid 2 like 2 (Nrf2), a key effector of the DNA damage response induced by ionizing radiation. Combined treatment reduced in vitro migration in a simulated wounding model while also promoting cell cycle arrest at the G2/M phase. These findings validate the potential of SU093 as a synergistic radiosensitizing agent for use in combination with localized radiotherapy in treatment resistant HNSCC.

Combined In Vitro Studies and in Silico Target Fishing for the Evaluation of the Biological Activities of Diphylleia cymosa and Podophyllum hexandrum

This paper reports the in silico prediction of biological activities of lignans from Diphylleia cymosa and Podophyllum hexandrum combined with an in vitro bioassays. The extracts from the leaves, roots and rhizomes of both species were evaluated for their antibacterial, anticholinesterasic, antioxidant and cytotoxic activities. A group of 27 lignans was selected for biological activities prediction using the Active-IT system with 1987 ligand-based bioactivity models. The in silico approach was properly validated and several ethnopharmacological uses and known biological activities were confirmed, whilst others should be investigated for new drugs with potential clinical use. The extracts from roots of D. cymosa and from rhizomes and roots of P. hexandrum were very effective against Bacillus cereus and Staphylococcus aureus, while podophyllotoxin inhibited the growth of Staphylococcus aureus and Escherichia coli. D. cymosa leaves and roots showed anticholinesterasic and antioxidant activities, respectively. The evaluated extracts showed to be moderately toxic to THP-1 cells. The chromatographic characterization indicated that podophyllotoxin was the major constituent of P. hexandrum extract while kaempferol and its hexoside were the main constituents of D. cymosa leaves and roots, respectively. These results suggest that the podophyllotoxin could be the major antibacterial lignan, while flavonoids could be responsible for the antioxidant activity.

Dangerous plants in dermatology: Legal and controlled

The plant and mushroom kingdoms have species used for intoxication, inebriation, or recreation. Some of these species are toxic. Given that many of these plants or substances are illegal and have histories of abuse, much of the research regarding therapeutic application is based on basic science, animal studies, and traditional use. This review examines Cannabis, Euphorbia, Ricinus, Podophyllum, Veratrum, mushrooms, and nightshades, along with resveratrol and cocaine as they relate to dermatology.

Catalytic Enantioselective Synthesis of (-)-Podophyllotoxin

The first catalytic enantioselective total synthesis of (-)-podophyllotoxin is accomplished by a challenging organocatalytic cross-aldol Heck cyclization and distal stereocontrolled transfer hydrogenation in five steps from three aldehydes. Reversal of selectivity in hydrogenation led to the syntheses of other stereoisomers from the common precursor.

Synthesis and Antiproliferative Activity of Novel All-Trans-Retinoic Acid-Podophyllotoxin Conjugate towards Human Gastric Cancer Cells

With the purpose of creating a multifunctional drug for gastric cancer treatment, a novel all-trans-retinoic acid (ATRA) conjugate with podophyllotoxin (PPT) was designed and synthesized, and its in vitro antiproliferative activity was evaluated against human gastric cancer cell lines using CCK-8 assay. The conjugate, P-A, exhibited significant anticancer activity against MKN-45 and BGC-823 cells with IC₅₀ values of 0.419 ± 0.032 and 0.202 ± 0.055 μM, respectively. Moreover, P-A efficiently triggered cell cycle arrest and induced apoptosis in MKN-45 and BGC-823 cells due to modulation of cell cycle arrest- (CDK1, CDK2, CyclinA and CyclinB1) and apoptosis- (cleaved caspase-3, -8 and -9) related proteins, respectively. Further mechanism studies revealed that P-A could increase the expression levels of RARα and RARβ, and decrease the level of RARγ in MKN-45 and BGC-823 cells. Finally, P-A inhibited the ERK1/2 and AKT signaling in the above two cancer cell lines. More importantly, the underlying mechanisms of P-A were similar to those of precursor PPT but different with the other precursor ATRA. Together, the conjugate P-A was a promising candidate for the potential treatment of human gastric cancer.

Assembled liposomes of dual podophyllotoxin phospholipid: preparation, characterization and in vivo anticancer activity

Aim: A novel amphiphilic prodrug dual podophyllotoxin (PPT) succinate glycerophosphorylcholine (Di-PPT-GPC) assembled liposomes was developed to improve efficiency of PPT. Materials & methods: Di-PPT-GPC liposomes were prepared by thin film technique and characterized by dynamic light scattering and cryo-electron microscopy. Results: In vitro release studies showed that Di-PPT-GPC liposomes could significantly release PPT in weakly acidic environment but had good stability under biological conditions. Methyl tetrazolium assay data revealed that the liposomes have comparable cytotoxicities to free PPT against MCF-7, HeLa and U87 cells. More importantly, in vivo antitumor evaluation indicated that Di-PPT-GPC liposomes exhibited favorable tumor growth inhibition without side effects. Conclusion: Di-PPT-GPC liposomes might have potential to promote the therapeutic effect of PPT for cancer therapy.

Recent Advances in the Chemistry and Biology of Podophyllotoxins

Podophyllotoxin and its related aryltetralin cyclolignans belong to a family of important products that exhibit various biological properties (e.g., cytotoxic, insecticidal, antifungal, antiviral, anti-inflammatory, neurotoxic, immunosuppressive, antirheumatic, antioxidative, antispasmogenic, and hypolipidemic activities). This Review provides a survey of podophyllotoxin and its analogues isolated from plants. In particular, recent developments in the elegant total chemical synthesis, structural modifications, biosynthesis, and biotransformation of podophyllotoxin and its analogues are summarized. Moreover, a deoxypodophyllotoxin-based chemosensor for selective detection of mercury ion is described. In addition to the most active podophyllotoxin derivatives in each series against human cancer cell lines and insect pests listed in the tables, the structure-activity relationships of podophyllotoxin derivatives as cytotoxic and insecticidal agents are also outlined. Future prospects and further developments in this area are covered at the end of the Review. We believe that this Review will provide necessary information for synthetic, medicinal, and pesticidal chemistry researchers who are interested in the chemistry and biology of podophyllotoxins.

Podophyllotoxin–pterostilbene fused conjugates as potential multifunctional antineoplastic agents against human uveal melanoma cells

Conjugate B1 showed potential multifunctional antineoplastic activity against human uveal melanoma cells.

Targeting Different Transthyretin Binding Sites with Unusual Natural Compounds

Misfolding and aggregation of the transthyretin (TTR) protein leads to certain forms of amyloidosis. Some nutraceuticals, such as flavonoids and natural polyphenols, have recently been investigated as modulators of the self-assembly process of TTR, but they generally suffer from limited bioavailability. To discover innovative and more bioavailable natural compounds able to inhibit TTR amyloid formation, a docking study was performed using the crystallographic structure of TTR. This computational strategy was projected as an ad hoc inspection of the possible relationship between binding site location and modulation of the assembly process; interactions with the as-yet-unexplored epigallocatechin gallate (EGCG) sites and with the thyroxine (T4) pocket were simultaneously analyzed. All the compounds studied seem to prefer the traditional T4 binding site, but some interesting results emerged from the screening of an in-house database, used for validating the computational protocol, and of the Herbal Ingredients Targets (HIT) catalogue available on the ZINC database.

Potential anti-MDR agents based on the podophyllotoxin scaffold: synthesis and antiproliferative activity evaluation against chronic myeloid leukemia cells by activating MAPK signaling pathways

Compound 9k exhibited excellent cytotoxicity, induced apoptosis and G2/M cell cycle arrest, downregulated Pgp expression and up-regulated the expression of p-ERK1/2, p-JNK and p-p38 in K562/ADR cells.

Novel cis-selective and non-epimerisable C3 hydroxy azapodophyllotoxins targeting microtubules in cancer cells

Podophyllotoxin (PT) and its clinically used analogues are known to be powerful antitumour agents. These compounds contain a trans fused strained γ-lactone system, a feature that correlates to the process of epimerisation, whereby the trans γ-lactone system of ring D opens and converts to the more thermodynamically stable cis epimer. Since these cis epimers are known to be either less active or lacking antitumour activity, epimerisation is an undesirable feature from a chemotherapeutic point of view. To circumvent this problem, considerable efforts have been reported, amongst which is the synthesis of azapodophyllotoxins where the stereocentres at C2 and C3 are removed in order to preclude epimerisation. Herein we report the identification of a novel C3 hydroxy, cis-selective γ-lactone configuration of ring C in the azapodophyllotoxin scaffold, through an efficient stereoselective multicomponent reaction (MCR) involving fluorinated and non-fluorinated aldehydes. This configuration releases the highly strained trans γ-lactone system in podophyllotoxin analogues into the more thermodynamically stable cis γ-lactone motif and yet retains significantly potent activity. These compounds were evaluated against the human cancer lines MCF-7 and 22Rv1 in vitro. Fourteen out of the seventeen tested compounds exhibited sub-micromolar activity with IC50 values in the range of 0.11-0.91 μM, which is comparable and in some cases better than the activity profile of etoposide in this assay. Interestingly, we obtained strong evidence from spectroscopic and X-ray data analyses that the previously reported structure of similar analogues is not accurate. Molecular modelling performed using the podophyllotoxin binding site on β tubulin revealed a novel binding mode of these analogues. Furthermore, sub-cellular study of our compounds using immunolabelling and confocal microscopy analyses showed strong microtubule disruptive activity, particularly in dividing cells.

Podophyllotoxin derivatives: a patent review (2012 - 2014)

INTRODUCTION

Podophyllotoxin (PPT) is a naturally occurring antimitotic agent and an interesting lead in the development of anticancer agents. Its optimization led to the development of etoposide and teniposide used in combination chemotherapy with other anticancer drugs; unlike PPT these drugs act by inhibiting topoisomerases. Clinical success and toxicity issues at later stages of etoposide usage inclined researchers to develop structurally modified PPT derivatives. Some of the compounds obtained are under clinical investigations and are anticipated to reach the market.

AREAS COVERED

The present review summarizes the attempts made by researchers across the globe to find out newer anticancer agents based on the PPT structure. It brings out the outline of the inventions filed in the form of patents during the years 2012 - 2014.

EXPERT OPINION

After the successful development of etoposide and teniposide there has been considerable interest in the PPT skeleton to develop newer chemotherapeutic agents. In this regard, several PPT derivatives such as TOP53, GL331, NK611, F11782, and so on, have been developed and are undergoing clinical trials. However, its low natural abundance is a major problem in carrying out research on PPT skeleton. This issue is expected to be addressed with the development of newer synthetic strategies to access structurally modified PPTs.

Progress Toward the Development of Noscapine and Derivatives as Anticancer Agents

Many nitrogen-moiety containing alkaloids derived from plant origins are bioactive and play a significant role in human health and emerging medicine. Noscapine, a phthalideisoquinoline alkaloid derived from Papaver somniferum, has been used as a cough suppressant since the mid 1950s, illustrating a good safety profile. Noscapine has since been discovered to arrest cells at mitosis, albeit with moderately weak activity. Immunofluorescence staining of microtubules after 24 h of noscapine exposure at 20 μM elucidated chromosomal abnormalities and the inability of chromosomes to complete congression to the equatorial plane for proper mitotic separation ( Proc. Natl. Acad. Sci. U. S. A. 1998 , 95 , 1601 - 1606 ). A number of noscapine analogues possessing various modifications have been described within the literature and have shown significantly improved antiprolific profiles for a large variety of cancer cell lines. Several semisynthetic antimitotic alkaloids are emerging as possible candidates as novel anticancer therapies. This perspective discusses the advancing understanding of noscapine and related analogues in the fight against malignant disease.

Design, synthesis, and cytotoxicity of perbutyrylated glycosides of 4β-triazolopodophyllotoxin derivatives

A series of novel perbutyrylated glycosides of 4β-triazolopodophyllotoxin derivatives were synthesized by utilizing the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. Evaluation of cytotoxicity against a panel of five human cancer cell lines (HL-60, SMMC-7721, A-549, MCF-7, SW480) using the MTT assay shows that some of these glycosylated derivatives have good anticancer activity. Among the synthesized compounds, compound 21a shows the highest activity, with IC₅₀ values ranging from 0.49 to 6.70 μM, which is more potent than the control drugs etoposide and cisplatin. Compound 21a is characterized by a perbutyrylated α-D(+)-galactosyl residue, the absence of an additional linking spacer between the sugar residue and the triazole ring, as well as a 4'-OH group on the E ring of the podophyllotoxin scaffold.

Design, synthesis, and biological and docking studies of novel epipodophyllotoxin–chalcone hybrids as potential anticancer agents

Click-chemistry based design and efficient synthesis of podophyllotoxin–chalcone conjugates as potential topoisomerase-II inhibitors towards the development of better anticancer leads.

Catalytic one-pot microwave assisted synthesis of 4-azapodophyllotoxin derivatives and rational design of experiment

A catalytic one-pot microwave assisted synthesis of 4-azapodophyllotoxin has been described. Rational design of experiment has been used to obtain the reaction yield.

Recent progress on C-4-modified podophyllotoxin analogs as potent antitumor agents

Podophyllotoxin (PPT), as well as its congeners and derivatives, exhibits pronounced biological activities, especially antineoplastic effects. Its strong inhibitory effect on tumor cell growth led to the development of three of the most highly prescribed anticancer drugs in the world, etoposide, teniposide, and the water-soluble prodrug etoposide phosphate. Their clinical success as well as intriguing mechanism of action stimulated great interest in further modification of PPT for better antitumor activity. The C-4 position has been a major target for structural derivatization aimed at either producing more potent compounds or overcoming drug resistance. Accordingly, numerous PPT derivatives have been prepared via hemisynthesis and important structure-activity relationship (SAR) correlations have been identified. Several resulting compounds, including GL-331, TOP-53, and NK611, reached clinical trials. Some excellent reviews on the distribution, sources, applications, synthesis, and SAR of PPT have been published. This review focuses on a second generation of new etoposide-related drugs and provides detailed coverage of the current status and recent development of C-4-modified PPT analogs as anticancer clinical trial candidates.

Novel isatin derivatives of podophyllotoxin: synthesis and cytotoxic evaluation against human leukaemia cancer cells as potent anti-MDR agents

Compound8cexhibited cytotoxicity at nanomolar range; induced G2/M cell cycle arrest accompanied by apoptosis and down-regulated the levels of Pgp, MRP-1 and GST-π.