Podophyllotoxin Analogues Research Articles

C-4 analogues of podophyllotoxin as tubulin inhibitors: synthesis, biological evaluation, and structure-activity relationship

The diversity of lignan small molecules derived from podophyllotoxin, a non-covalent tubulin inhibitor isolated from the Podophyllum family, has led to the clinical development of FDA-approved anticancer agents etoposide and teniposide. While these two compounds share the same tetracyclic core as podophyllotoxin, two subtle structural changes—4’ demethylation on the aromatic ring and stereospecific glycosylation at the C-4 hydroxyl—result in an alternate biological mechanism. Given the immense pharmacological importance of altering the C-4 position, we synthesised and evaluated a systematic library of diversified esters to establish a structure-activity relationship regarding modification at C-4 on the properties of podophyllotoxin. We determined the biological activity of these esters through cell viability assays, computer docking models, tubulin polymerisation assays, and cell cycle analysis. Altogether, we demonstrate that increasing steric hindrance at C-4 leads to a loss in potency against human cancer cells but has a significantly lesser impact on cell-free tubulin inhibition.

Ultrasound-Assisted, BF3·OEt2-Promoted, Multicomponent Synthesis of Chromene-Based Podophyllotoxin Analogues

AbstractA novel method was developed to synthesise chromene-lactone analogues of podophyllotoxin using an ultrasound-assisted multicomponent reaction (MCR). The MCR involved tetronic acid, phenols, and aromatic aldehydes and was promoted by BF3·OEt2, resulting in the production of ten derivatives with different substituents on the aromatic rings in yields ranging from 32% to 93%. These compounds are of interest due to their reported activity against tumour cells. Their ease of synthesis through the MCR may allow for more in-depth studies on anticancer activity, as well as investigations of other biological targets. The synthesised derivatives contain important pharmacophoric groups for potential applications in medicinal chemistry.

Chemistry and Biology of Podophyllotoxins: An Update.

Podophyllotoxin is an aryltetralin lignan lactone derived from different plants of Podophyllum. It consists of five rings with four chiral centers, one trans-lactone and one aryl tetrahydronaphthalene skeleton with multiple modification sites. Moreover, podophyllotoxin and its derivatives showed lots of bioactivities, including anticancer, anti-inflammatory, antiviral, and insecticidal properties. The demand for podophyllotoxin and its derivatives is rising as a result of their high efficacy. As a continuation of our previous review (Chem. Eur. J., 2017, 23, 4467-4526), herein, total synthesis, biotransformation, structural modifications, bioactivities, and structure-activity relationships of podophyllotoxin and its derivatives from 2017 to 2022 are summarized. Meanwhile, a piece of update information on the origin of new podophyllotoxin analogues from plants from 2014 to 2022 was compiled. We hope that this review will provide a reference for future high value-added applications of podophyllotoxin and its analogues in the pharmaceutical and agricultural fields.

Myricetin: a potential plant-derived anticancer bioactive compound-an updated overview.

The globe is currently confronting a global fight against the deadliest cancer sickness. Chemotherapy, hormonal therapy, surgery, and radiation therapy are among cancer treatment options. Still, these treatments can induce patient side effects, including recurrence, multidrug resistance, fever, and weakness. As a result, the scientific community is always working on natural phytochemical substances. Numerous phytochemical compounds, including taxol analogues, vinca alkaloids such as vincristine and vinblastine, and podophyllotoxin analogues, are currently undergoing testing and have shown promising results against a number of the deadliest diseases, as well as considerable advantages due to their safety and low cost. According to research, secondary plant metabolites such as myricetin, a flavonoid in berries, herbs, and walnuts, have emerged as valuable bio-agents for cancer prevention. Myricetin and its derivatives have antiinflammatory, anticancer, apoptosis-inducing, and anticarcinogenic properties and can prevent cancer cell proliferation. Multiple studies have found that myricetin has anticancer characteristics in various malignancies, including colon, breast, prostate, bladder, and pancreatic cancers. Current knowledge of the anticancer effects of myricetin reveals its promise as a potentially bioactive chemical produced from plants for the prevention and treatment of cancer. This review aimed to study the numerous bioactivities, mode of action, and modification of several cellular processes that myricetin possesses to impede the spread of cancer cells. This review also addresses the challenges and future prospects of using myricetin as a anticancer drug.

Synthetic analogues of podophillotoxin and their antimitotic activities

Podophyllotoxin finds a lot of scopes in pharmaceutical field as it show wide biological activities. Several analogues of podophyllotoxin were reported variety of biological activities such as cathartic, cytotoxic, antimitotic, anticancer, antitropical skin disease, antimalarial, virucidal, fungicidal etc. Experiment was carried out to synthesize 6, 6a-dihydro-2, 3-dimethoxy-9-methyl-11bH benzo [c] fluoren - 5, 7 dione and Synthesis of 6, 6a-dihydro-3-methoxy-2, 9-dimethyl-11 bH benzo [c] fluoren - 5, 7 dione. The products were re-crystallized in ethanol and characterized by spectrometric methods, IR, NMR and Mass spectroscopy. A yield of 82.72 and 83.6 percent were recorded respectively. The anti-mitotic activities of the synthesized analogues were examined by the onion root tip method with reference to b- apopicropodophyllin and Podophyllotoxin. In the present work, the synthetic analogues D and E have shown increased anti-mitotic activities with ID50 of 2.005 x 10-6 M and 2.260 x 10-6M respectively with reference to standard and control

"Preclinical Research to Clinical Practice: A Review of Phytochemicals in Cancer Treatment"

Cancer is a serious health issue that remains a top cause of mortality across the globe. Anticancer medications have been developed as we have understood the molecular mechanism that leads to cancer genesis has grown. Chemically produced medications, on the other hand, have had little impact on overall survival rates during the last several decades. As a result, to improve the efficacy of conventional therapies of cancer, new approaches and revolutionary chemoprevention drugs are necessary. Phytochemicals are those molecules that occur naturally in plants, are important resources for developing new medicines and may also be used to treat cancer. Only a few example include taxol analogues, vinca alkaloids such as vinblastine vincristine and, and podophyllotoxin analogues. These phytochemical generally work by interfering with molecular pathways connected to cancer formation and progress. Some of the distinct approaches include increased antioxidants status, carcinogen inactivation, reducing its rapid growth, promotion of cell cycle arrest and death, and immune system regulation. The main goal of this study is to summarise what we now know about natural product active chemicals, including their pharmacology and molecular or particular targets. The most recent advancements and limitations in the development of phytochemical-based anticancer therapies are also discussed. The author wants to boost phytochemicals research not just for its scientific worth, but also for its medicine development potential. As a result, anticancer phytochemicals that have been studied in preclinical and clinical settings have gotten a lot of attention.

Synthetic development of sugar amino acid oligomers towards novel podophyllotoxin analogues

In this work, we have developed an approach for the synthesis of sugar amino acid oligomers based on the glucosamine scaffold. We found that the solid-phase approach was unsuccessful for the preparation of sugar amino acid oligomers and the limitation of the liquid-phase approach revolved around the low solubility of larger oligomers. Nevertheless, this strategy allowed the coupling of alkynylated carbohydrate amino acids with podophyllotoxin-bearing an azide functional group yielding novel podophyllotoxin analogues. Due to their low solubility, the antiproliferative study revealed no anticancer activity of these newly synthesized analogues.

Natural podophyllotoxin analog 4DPG attenuates EMT and colorectal cancer progression via activation of checkpoint kinase 2

Epithelial–mesenchymal transition (EMT) is critical for the metastatic dissemination of cancer cells and contributes to drug resistance. In this study, we observed that epithelial colorectal cancer (CRC) cells transiently exposed to 5-fluorouracil (5-FU) (a chemotherapeutic drug for CRC) as well as 5-FU-resistant cells (5-FU-R) develop EMT characters as evidenced by activation of Vimentin and augmented invasive properties. On the other hand, 4DPG (4′-demethyl-deoxypodophyllotoxin glucoside), a natural podophyllotoxin analog attenuates EMT and invadopodia formation abilities of HCT-116/5-FU-R and SW-620/5-FU-R cells. Treatment with 4DPG restrains Vimentin phosphorylation (Ser38) in 5-FU-R cells, along with downregulation of mesenchymal markers Twist1 and MMP-2 while augmenting the expression of epithelial markers E-cadherin and TIMP-1. Moreover, 4DPG boosts the tumor-suppressor protein, checkpoint kinase 2 (Chk2) via phosphorylation at Thr68 in a dose-dependent manner in 5-FU-R cells. Mechanistically, SiRNA-mediated silencing of Chk2, as well as treatment with Chk2-specific small-molecule inhibitor (PV1019), divulges that 4DPG represses Vimentin activation in a Chk2-dependent manner. Furthermore, immunoprecipitation analysis unveiled that 4DPG prevents complex formation between Vimentin and p53 resulting in the rescue of p53 and its nuclear localization in aggressive 5-FU-R cells. In addition, 4DPG confers suitable pharmacokinetic properties and strongly abrogates tumor growth, polyps formation, and lung metastasis in an orthotopic rat colorectal carcinoma model. In conclusion, our findings demonstrate 4DPG as a targeted antitumor/anti-metastatic pharmacological lead compound to circumvent EMT-associated drug resistance and suggest its clinical benefits for the treatment of aggressive cancers.

Synthesis and evaluation of etoposide and podophyllotoxin analogs against topoisomerase IIα and HCT-116 cells

Etoposide is a widely-used anticancer agent that targets human type II topoisomerases. Evidence suggests that metabolism of etoposide in myeloid progenitor cells is associated with translocations involved in leukemia development. Previous studies suggest halogenation at the C-2′ position of etoposide reduces metabolism. Halogens were introduced into the C-2′ position by electrophilic aromatic halogenation onto etoposide (ETOP, 1), podophyllotoxin (PPT, 2), and 4-dimethylepipodophyllotoxin (DMEP, 3), and to bridge the gap of knowledge regarding the activity of these metabolically stable analogs. Five halogenated analogs (6–10) were synthesized. Analogs 8–10 displayed variable ability to inhibit DNA relaxation. Analog 9 was the only analog to show concentration-dependent enhancement of Top2-mediated DNA cleavage. Dose response assay results indicated that 8 and 10 were most effective at decreasing the viability of HCT-116 and A549 cancer cell lines in culture. Flow cytometry with 8 and 10 in HCT-116 cells provide evidence of sub-G1 cell populations indicative of apoptosis. Taken together, these results indicate C-2′ halogenation of etoposide and its precursors, although metabolically stable, decreases overall activity relative to etoposide.

Management of Glioblastoma Multiforme by Phytochemicals: Applications of Nanoparticle-Based Targeted Drug Delivery System.

The Glioblastoma Multiforme (GBM; grade IV astrocytoma) exhorts tumors of star-shaped glial cells in the brain. It is a fast-growing tumor that spreads to nearby brain regions specifically to cerebral hemispheres in frontal and temporal lobes. The etiology of GBM is unknown, but major risk factors are genetic disorders like neurofibromatosis and schwannomatosis, which develop the tumor in the nervous system. The management of GBM with chemo-radiotherapy leads to resistance, and current drug regimen like Temozolomide (TMZ) is less efficacious. The reasons behind the failure of drugs are due to DNA alkylation in the cell cycle by enzyme DNA guanidase and mitochondrial dysfunction. Naturally occurring bioactive compounds from plants referred as phytochemicals, serve as vital sources for anti-cancer drugs. Some prototypical examples include taxol analogs, vinca alkaloids (vincristine, vinblastine), podophyllotoxin analogs, camptothecin, curcumin, aloe-emodin, quercetin, berberine etc. These phytochemicals often regulate diverse molecular pathways, which are implicated in the growth and progression of cancers. However, the challenges posed by the presence of BBB/BBTB to restrict the passage of these phytochemicals, culminates in their low bioavailability and relative toxicity. In this review, we integrated nanotech as a novel drug delivery system to deliver phytochemicals from traditional medicine to the specific site within the brain for the management of GBM.

Non-food renewable and bioactive forest products for pest management: Valuation of agricultural properties of podophyllotoxin analogs derived from Podophyllum hexandrum as botanical pesticides

Due to appearance of pests resistance and negative effects on ecological environment, it is high desirable to explore candidate pesticides from non-food bioactive products. Here a series of succinic acid derivatives of podophyllotoxin derived from the renewable Sinopodophyllum hexandrum, were semisynthesized for pest management. The spatial configurations of three derivatives were determined by X-ray crystallography. Compounds IIIc and IIId (> 2-fold of podophyllotoxin) exhibited the most pronounced insecticidal activity. Compounds 5, IIIa and IIIb displayed > 11-fold promising acaricidal activity of podophyllotoxin. Especially compound IIIb showed the pronounced insecticidal and acaricidal activities. It will pave the way for further structural modifications and application of podophyllotoxins as potentially renewable botanical pesticidal agents in crop protection.

Phytochemicals in Cancer Treatment: From Preclinical Studies to Clinical Practice.

Cancer is a severe health problem that continues to be a leading cause of death worldwide. Increasing knowledge of the molecular mechanisms underlying cancer progression has led to the development of a vast number of anticancer drugs. However, the use of chemically synthesized drugs has not significantly improved the overall survival rate over the past few decades. As a result, new strategies and novel chemoprevention agents are needed to complement current cancer therapies to improve efficiency. Naturally occurring compounds from plants known as phytochemicals, serve as vital resources for novel drugs and are also sources for cancer therapy. Some typical examples include taxol analogs, vinca alkaloids such as vincristine, vinblastine, and podophyllotoxin analogs. These phytochemicals often act via regulating molecular pathways which are implicated in growth and progression of cancer. The specific mechanisms include increasing antioxidant status, carcinogen inactivation, inhibiting proliferation, induction of cell cycle arrest and apoptosis; and regulation of the immune system. The primary objective of this review is to describe what we know to date of the active compounds in the natural products, along with their pharmacologic action and molecular or specific targets. Recent trends and gaps in phytochemical based anticancer drug discovery are also explored. The authors wish to expand the phytochemical research area not only for their scientific soundness but also for their potential druggability. Hence, the emphasis is given to information about anticancer phytochemicals which are evaluated at preclinical and clinical level.

Screening of Insecticidal Activity of Podophyllotoxin Analogues against Athetis dissimilis

As our ongoing work on research of natural-product-based insecticidal agents, eighteen podophyllotoxin analogues with diverse chemical structures were evaluated for their insecticidal activities against the pre-fourth-instar larvae of Athetis dissimilis Hampson in vivo at the concentration of 1 mg/mL. Among all the reported analogues, compounds 6, 8, 12, 13, 15 and 17 showed more potent insecticidal activities than matrine, quinine and toosendanin, three commercial plant secondary metabolites. 2′,6′-Dichloropodophyllotoxin (8) and 2′,6′-dichloroepipodophyllotoxin (13) exhibited the most pronounced and promising insecticidal activity with the final corrected mortality rates of greatly 60%. This suggested that variation of chemical structures in the podophyllotoxin skeleton conspicuously has effect on the insecticidal activity profiles of podophyllotoxin analogues. Moreover, SAR revealed that the substituents and configuration were critical for their insecticidal activities. The results may be useful in guiding further design and structural modification of podophyllotoxins in the development of potential novel insecticidal agents.

Plant-Derived Anticancer Agents: Lessons from the Pharmacology of Geniposide and Its Aglycone, Genipin.

For centuries, plants have been exploited by mankind as sources of numerous cancer chemotherapeutic agents. Good examples of anticancer compounds of clinical significance today include the taxanes (e.g., taxol), vincristine, vinblastine, and the podophyllotoxin analogues that all trace their origin to higher plants. While all these drugs, along with the various other available therapeutic options, brought some relief in cancer management, a real breakthrough or cure has not yet been achieved. This critical review is a reflection on the lessons learnt from decades of research on the iridoid glycoside geniposide and its aglycone, genipin, which are currently used as gold standard reference compounds in cancer studies. Their effects on tumour development (carcinogenesis), cancer cell survival, and death, with particular emphasis on their mechanisms of actions, are discussed. Particular attention is also given to mechanisms related to the dual pro-oxidant and antioxidant effects of these compounds, the mitochondrial mechanism of cancer cell killing through reactive oxygen species (ROS), including that generated through the uncoupling protein-2 (UCP-2), the inflammatory mechanism, and cell cycle regulation. The implications of various studies for the evaluation of glycosidic and aglycone forms of natural products in vitro and in vivo through pharmacokinetic scrutiny are also addressed.

Inhibition of Twist1-mediated invasion by Chk2 promotes premature senescence in p53-defective cancer cells.

Twist1, a basic helix-loop-helix transcription factor is implicated as a key mediator of epithelial-mesenchymal transition (EMT) and metastatic dissemination in p53-deficient cancer cells. On the other hand, checkpoint kinase 2 (Chk2), a major cell cycle regulatory protein provides a barrier to tumorigenesis due to DNA damage response by preserving genomic stability of the cells. Here we demonstrate that Chk2 induction proficiently abrogates invasion, cell scattering and invadopodia formation ability of p53-mutated invasive cells by suppressing Twist1, indicating Chk2 confers vital role in metastasis prevention. In addition, ectopic Chk2, as well as its (Chk2) induction by natural podophyllotoxin analog, 4'-demethyl-deoxypodophyllotoxin glucoside (4DPG), strongly restrain Twist1 activity along with other mesenchymal markers, for example, ZEB-1, vimentin and Snail1, whereas the epithelial markers such as E-cadherin and TIMP-1 expression augmented robustly. However, downregulation of endogenous Chk2 by siRNA as well as Chk2 selective inhibitor PV1019 implies that 4DPG-mediated inhibition of Twist1 is Chk2-dependent. Further, mechanistic studies unveil that Chk2 negatively regulates Twist1 promoter activity and it (Chk2) interacts steadily with Snail1 protein to curb EMT. Strikingly, Chk2 overexpression triggers premature senescence in these cells with distinctive increase in senescence-associated β-galactosidase (SA-β-gal) activity, G2/M cell cycle arrest and induction of senescence-specific marker p21waf1/Cip1. Importantly, stable knockdown of Twist1 by shRNA markedly augments p21 expression, its nuclear accumulation, senescence-associated heterochromatin foci (SAHF) and amplifies the number of SA-β-gal-positive cells. Moreover, our in vivo studies also validate that 4DPG treatment significantly abrogates tumor growth as well as metastatic lung nodules formation by elevating the level of phospho-Chk2, Chk2 and suppressing Twist1 activity in mouse mammary carcinoma model. In a nutshell, this report conceives a novel strategy of Twist1 suppression through Chk2 induction, which prevents metastatic dissemination and promotes premature senescence in p53-defective invasive cancer cells.

Approach to ferrocenyl-podophyllotoxin analogs and their evaluation as anti-tumor agents

Podophyllotoxin is a natural product endowed of a high antimitotic activity and a high affinity for tubulin. Its action results in the cessation of cell division, inducing cell death. However, its high toxicity restrains its use as drug. To overcome this drawback, several chemical modifications of the native podophyllotoxin have been made. However, to date, no reports have so far been directed toward incorporation of a metallocene moiety. The search for new organometallic drugs is a central field in drug discovery, including the domain of cancer therapy. In particular, metallocenyl moieties are known to increase or decrease, depending on the degree of conjugation in the organometallic motif, the selectivity of drugs toward cancer cells. The conjugate organometallic compound reduces the damage of healthy tissues, yet permitting the selective desired antimitotic and cytotoxic effects of the active principle. We report here the synthesis of ferrocene-containing podophyllotoxin analogs and preliminary antiproliferative tests.

Synthesis and Cytotoxicity of Novel Analogues of Podophyllotoxin

We have synthesized four novel derivatives of podophyllotoxin, the chalcone derivatives namely 2-benzylidene-6,7-dimethoxy-4-phenyl-3,4-dihydro-2H-naphthalen-1-one (4a), 2-benzylidene-5,7-dichloro-6-hydroxy-4-phenyl-3,4-dihydro-2H-naphthalen-1-one(4b), and the amino-thiazolyl derivatives namely7,8-dimethoxy-5-phenyl-4,5-dihydro-naphtha[1,2-d] thiazol-2-yl amine (5a) and 2-amino-6,8-dichloro-5-phenyl-4,5-dihydro-naphtho[1,2-d] thiazol-7-ol (5b). The aryl tetralin ring system in these compounds were attached to a fused aminothiazolyl ring or a chalcone ring. Synthesis of the tetralin ring in these podophyllotoxin derivatives was accomplished by the cyclization of the γ-hydroxyketones. These derivatives were evaluated for the induction of cytotoxicity in mouse mammary carcinoma cells in vitro. All the four compounds exhibited time dependent cytotoxicity at a concentration of 100μM when assessed by Trypan blue dye exclusion assay on Ehrlich Ascites Tumor (EAT) cells in vitro.

Structural and Biochemical Characterization of the Interaction of Tubulin with Potent Natural Analogues of Podophyllotoxin.

Four natural analogues of podophyllotoxin obtained from the Mexican medicinal plant Bursera fagaroides, namely, acetyl podophyllotoxin (2), 5'-desmethoxy-β-peltatin A methyl ether (3), 7',8'-dehydro acetyl podophyllotoxin (4), and burseranin (5), have been characterized, and their interactions with tubulin have been investigated. Cytotoxic activity measurements, followed by immunofluorescence microscopy and flow cytometry studies, demonstrated that these compounds disrupt microtubule networks in cells and cause cell cycle arrest in the G2/M phase in the A549 cell line. A tubulin binding assay showed that compounds 1-4 were potent assembly inhibitors, displaying binding to the colchicine site with Kb values ranging from 11.75 to 185.0 × 10(5) M(-1). In contrast, burseranin (5) was not able to inhibit tubulin assembly. From the structural perspective, the ligand-binding epitopes of compounds 1-3 have been mapped using STD-NMR, showing that B and E rings are the major points for interaction with the protein. The obtained results indicate that the inhibition of tubulin assembly of this family of compounds is more effective when there are at least two methoxyl groups at the E ring, along with a trans configuration of the lactone ring in the aryltetralin lignan core.

English

Podophyllum hexandrum Royle, a rhizomatous perennial herb from the Berberidaceae family, is a highly reputed medicinal plant known for its lignan, podophyllotoxin. Podophyllotoxin and its semisynthetic derivativatives are potent anticancer agents. The semisynthetic analogues of podophyllotoxin are also used in the treatment of lung cancer, testicular cancer, neuroblastoma, hepatoma and other tumor diseases. While Podophyllotoxin acts as an inhibitor of the microtubule assembly, the cytotoxic action of its derevatives is based on the inhibition of topoisomerase. Owing to the ever-increasing demand of Podophyllum hexandrum for podophyllotoxin, it has been subjected to heavy collection from the wild. The anti-cancer lignan derivative podophyllotoxin is biosynthesized at very low quantities in intact Podophyllum hexandrum plant and the whole plant is harvested to isolate the bioactive lignan adding to the threats that the plant is currently facing. Therefore, biotechnological production of podophyllotoxin has been considered essential. The present review gives a brief introduction about the phytochemistry, pharmacology and biosynthesis of podophyllotoxin and also discusses the potential of biotechnology for production of podophyllotoxin to meet the increasing demand of this highly valued plant metabolite.

Synthesis and characterization of tetralones as intermediates for podophyllotoxin analogues

Podophyllotoxin has captured the attention of chemists all over the world for its biological activity. It was isolated from many plants of Podophyllum species such as Podophyllum emodi , Podophyllum peltatum and others. It mainly exhibits anticancer, antimitotic, antimalarial, anti-aids and other activities. Its use is restricted due to its toxicity and unfavourable solubility. It was aimed to synthesize some new heterocyclic analogues of podophyllotoxin by changing the substituents by changing lactone ring with pyrazoline ring and substituents in ring C with hydrogen and methoxy group. Chalcones were prepared by Claisen-Schmidt reaction of 1,3-methylene dioxyacetophenone with benzaldehyde and p -anisaldehyde. The reaction of chalcone with trimethylsulphoxonium iodide in presence of sodium hydride gave cyclopropyl ketone. Intramolecular cyclization reaction of cyclopropyl ketone gave tetralone intermediates of podophyllotoxin. They are obtained in good yields. The structure of all the products was confirmed by spectral data.