Design, Synthesis and Cytotoxicity of Novel Podophyllotoxin Derivatives

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.

Interactions between artemisinin derivatives and P-glycoprotein

BACKGROUND

Artemisinin was isolated and identified in 1972, which was the starting point for a new era in antimalarial drug therapy. Furthermore, numerous studies have demonstrated that artemisinin and its derivatives exhibit considerable anticancer activity both in vitro, in vivo, and even in clinical Phase I/II trials. P-glycoprotein (P-gp) mediated multi-drug resistance (MDR) is one of the most serious causes of chemotherapy failure in cancer treatment. Interestingly, many artemisinin derivatives exhibit excellent ability to overcome P-gp mediated MDR and even show collateral sensitivity against MDR cancer cells. Furthermore, some artemisinin derivatives show P-gp-mediated MDR reversal activity. Therefore, the interaction between P-gp and artemisinin derivatives is important to develop novel combination treatment protocols with artemisinin derivatives and established anticancer drugs that are P-gp substrates.

PURPOSE

This systematic review provides an updated overview on the interaction between artemisinin derivatives and P-gp and the effect of artemisinin derivatives on the P-gp expression level.

RESULTS

Artemisinin derivatives exhibit multi-specific interactions with P-gp. The currently used artemisinin derivatives are not transported by P-gp. However, some of novel synthetized artemisinin derivatives exhibit P-gp substrate properties. Furthermore, many artemisinin derivatives act as P-gp inhibitors, which exhibit the potential to reverse MDR towards clinically used anticancer drugs.

CONCLUSION

Therefore, studies on the interaction between artemisinin derivatives and P-gp provide important information for the development of novel anti-cancer artemisinin derivatives to reverse P-gp mediated MDR and for the design of rational artemisinin-based combination therapies against cancer.

A comprehensive review of topoisomerase inhibitors as anticancer agents in the past decade

The topoisomerase enzymes play an important role in DNA metabolism, and searching for enzyme inhibitors is an important target in the search for new anticancer drugs. Discovery of new anticancer chemotherapeutical capable of inhibiting topoisomerase enzymes is highlighted in anticancer research. Therefore, biologists, organic chemists and medicinal chemists all around the world have been identifying, designing, synthesizing and evaluating a variety of novel bioactive molecules targeting topoisomerase. This review summarizes types of topoisomerase inhibitors in the past decade, and divides them into nine classes by structural characteristics, including N-heterocycles compounds, quinone derivatives, flavonoids derivatives, coumarin derivatives, lignan derivatives, polyphenol derivatives, diterpenes derivatives, fatty acids derivatives, and metal complexes. Then we discussed the application prospect and development of these anticancer compounds, as well as concluded parts of their structural-activity relationships. We believe this review would be invaluable in helping to further search potential topoisomerase inhibition as antitumor agent in clinical usage.

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.

Biotechnological interventions for harnessing podophyllotoxin from plant and fungal species: current status, challenges, and opportunities for its commercialization

Podophyllotoxin is an aryltetralin lignan synthesized in several plant species, which is used in chemotherapies for cancers and tumor treatment. More potent semisynthetic derivatives of podophyllotoxin such as etoposide and teniposide are being developed and evaluated for their efficacy. To meet the ever increasing pharmaceutical needs, species having podophyllotoxin are uprooted extensively leading to the endangered status of selective species mainly Sinopodophyllum hexandrum. This has necessitated bioprospection of podophyllotoxin from different plant species to escalate the strain on this endangered species. The conventional and non-conventional mode of propagation and bioprospection with the integration of biotechnological interventions could contribute to sustainable supply of podophyllotoxin from the available plant resources. This review article is focused on the understanding of different means of propagation, development of genomic information, and its implications for elucidating podophyllotoxin biosynthesis and metabolic engineering of pathways. In addition, various strategies for sustainable production of this valuable metabolite are also discussed, besides a critical evaluation of future challenges and opportunities for the commercialization of podophyllotoxin.

Direct reductive coupling of indoles to nitrostyrenes en route to (indol-3-yl)acetamides

A highly efficient one-pot method for the reductive coupling of indoles to nitrostyrenes in PPA doped with PCl₃ was developed. This method allows direct access to primary (indol-3-yl)acetamides, interesting as anti-cancer drug candidates.

Photochemical synthesis and anticancer activity of barbituric acid, thiobarbituric acid, thiosemicarbazide, and isoniazid linked to 2-phenyl indole derivatives

2-Phenyl-1H-indole-3-carbaldehyde-based barbituric acid, thiobarbituric acid, thiosemicarbazide, isoniazid, and malononitrile derivatives were synthesized under photochemical conditions. The antitumor activities of the synthesized compounds were evaluated on three different human cancer cell lines representing prostate cancer cell line DU145, Dwivedi (DWD) cancer cell lines, and breast cancer cell line MCF7. All the screened compounds possessed moderate anticancer activity, and out of all the screened compounds, 5-{1[2-(4-chloro-phenyl)2-oxo-ethyl]-2-phenyl-1H-indole-3-ylmethylene}-2-thioxo-dihydro-pyrimidine-4,6-dione (2b) and 5-{1[2-(4-methoxy-phenyl)2-oxo-ethyl]-2-phenyl-1H-indole-3-ylmethylene}-2-thioxo-dihydro-pyrimidine-4,6-dione (2d) exhibited marked antitumor activity against used cell lines. Additionally, barbituric acid derivatives were selective to inhibit cell line DWD and breast cancer cell lines.

Arylidene pyruvic acids motif in the synthesis of new thiopyrano[2,3-d]thiazoles as potential biologically active compounds

Novel

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.

Microwave irradiation: synthesis and characterization of α-ketoamide and bis (α-ketoamide) derivatives via the ring opening of N-acetylisatin

Background

The carbonyl group at position 2 of N-acetylisatin behaves as an amide which is more susceptible to nucleophilic attack via ring-opening in the presence of nucleophiles. Because of this behavior, in the present work we describe the microwave synthesis of a series of α-ketoamide and bis-(α-ketoamide) derivatives via the facile ring-opening of N-acylisatin with different amines and diamines. The microwave irradiation afforded the product in less reaction time, higher yield and purity. Reaction of N-acylisatin with methanol under microwave irradiation afforded the α-phenylglyoxyl methyl ester derivatives with excellent yields and purities. Aminolysis of the ester derivatives with piperidine and morpholine afforded the same α-ketoamide derivatives obtained from direct aminolysis of N-acylisatin. The structures of the synthesized compounds were confirmed by FT-IR, NMR, X-ray and elemental analysis.

Results

Reaction of N-acetylisatin and N-propoionylsatin with different amines and diamines afforded a series of α-ketoamide and bis-(α-ketoamide) derivatives respectively via the ring opening of N-acylisatins. The reaction was performed under conventional condition as well as microwave irradiation. The microwave irradiation afforded the product in less reaction time, higher yield and purity. Reaction of N-acylisatin with methanol under microwave irradiation afforded the α-phenylglyoxyl methyl ester derivatives in excellent yields and purities as observed from their spectral data. A plausible mechanism involves nucleophilic attack by methanol at C2 carbonyl carbon of N-acetylisatin and subsequent ring opening to generate the α-ketoester. Aminolysis of α-ketoester with amine afforded the same α-ketoamide which is obtained by direct aminolysis of N-acylisatin. The IR, NMR spectra, microanalyses, and single crystal X-ray diffraction confirmed the structures of the synthesized compounds.

Conclusions

In conclusion, we have demonstrated that microwave irradiation could be employed efficiently for the synthesis of biologically important α-ketoamide and bis-(α-ketoamide) derivatives. The microwave irradiation has more advantageous over the classical method with regard to reaction time, solvent quantity, and product yield. Reaction of N-acylisatin with methanol under microwave irradiation afforded the α-phenylglyoxyl methyl ester derivatives with excellent yields and purities. Aminolysis of the methyl ester derivatives with amine under microwave irradiation afford the same α-ketoamide derivatives as obtained from direct aminolysis of N-acylisatins.

OxymaPure/DIC: an efficient reagent for the synthesis of a novel series of 4-[2-(2-acetylaminophenyl)-2-oxo-acetylamino] benzoyl amino acid ester derivatives

OxymaPure (ethyl 2-cyano-2-(hydroxyimino)acetate) was tested as an additive for use in the carbodiimide (DIC) approach for the synthesis of a novel series of α-ketoamide derivatives (4-[2-(2-acetylaminophenyl)-2-oxo-acetylamino]benzoyl amino acid ester derivatives). OxymaPure showed clear superiority to HOBt/DIC or carbodiimide alone in terms of purity and yield. The title compounds were synthesized via the ring opening of N-acylisatin. First, N-acetylisatin was reacted with 4-aminobenzoic acid under conventional heating as well as microwave irradiation to afford 4-(2-(2-acetamidophenyl)-2-oxoacetamido)benzoic acid. This α-ketoamide was coupled to different amino acid esters using OxymaPure/DIC as a coupling reagent to afford 4-[2-(2-acetylaminophenyl)-2-oxo-acetylamino]benzoyl amino acid ester derivatives in excellent yield and purity. The synthesized compounds were characterized using FT-IR, NMR, and elemental analysis.

Design, synthesis, and antitumor activity of novel podophyllotoxin derivatives as potent anticancer agents

In order to find novel synthetic compounds with superior antitumor activity and overcome multidrug resistance, a series of novel 4β-N-substituted podophyllotoxin derivatives were synthesized under mild conditions with satisfactory yield. Nine novel podophyllotoxin derivatives were synthesized by linking 4β-amino-podophyllotoxin with aldehydes via the formation of a Schiff's base, and imines were reducted to secondary amines. These novel derivatives have been evaluated for cytotoxicity against human cancer cell lines Hela, K562, and K562/AO2. The results indicated that these compounds possess superior bioactivity (IC50 values were found at the range of 10(- 6)-10(- 8) mol/l) and weak multidrug resistance.

An Efficient and Mild Method for the Synthesis and Hydrazinolysis ofN-Glyoxylamino Acid Esters

N-Glyoxylamino acid ester derivatives were synthesized via the ring opening ofN-acetylisatin using moderate conditions. During the hydrazinolysis ofN-glyoxylamino acid ester derivatives with hydrazine hydrate (80%) in methanol, unexpected reduction of theα-keto group occurred to affordN-acylamino acid hydrazide derivatives in good yield (80–90%) (Wolff-Kishner type reaction). All the synthesized compounds were characterized by1H NMR,13C NMR, and elemental microanalysis.

9-[(Furan-2-ylmeth-yl)amino]-5-(3,4,5-trimeth-oxy-phen-yl)-5,5a,8a,9-tetra-hydro-furo[3',4':6,7]naphtho-[2,3-d][1,3]dioxol-6(8H)-one

In title compound, C₂₇H₂₇NO₈, the dihydrofuran-2(3H)-one ring and the six-membered ring fused to it both display envelope conformations. The dihedral angle between the benzene ring of the benzo[d][1,3]dioxole group and the other benzene ring is 60.59 (2)°. In the crystal, weak inter­molecular C—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional network. The furan ring is disordered over two sets of sites with occupancies of 0.722 (7) and 0.278 (7)

9-{[4-(Dimethyl-amino)-benz-yl]amino}-5-(3,4,5-trimeth-oxy-phen-yl)-5,5a,8a,9-tetra-hydro-furo[3',4':6,7]naphtho-[2,3-d][1,3]dioxol-6(8H)-one

In the title compound, C₃₁H₃₄N₂O₇, the fused tetra­hydro­furan and six-membered rings each display an envelope conformation. The dihedral angles between the benzene ring of the benzo[d][1,3]dioxole and the other two benzene rings are 89.68 (3) and 63.38 (2)°. In the crystal, weak inter­molecular C—H⋯O hydrogen bonds link the mol­ecules.

Synthesis and antitumor activity of novel podophyllotoxin derivatives against multidrug-resistant cancer cells

Seven novel 4β-N-substituted podophyllotoxin derivatives with indole rings were prepared and evaluated for cytotoxicity against human cancer cell lines HeLa, KB, KBV, K562, and K562/AO2. Most of them demonstrated improved antitumor activity and weak multidrug resistance compared to the drugs currently available.

Aplysinopsin analogs: Synthesis and anti-proliferative activity of substituted (Z)-5-(N-benzylindol-3-ylmethylene)imidazolidine-2,4-diones

A series of substituted (Z)-5-(N-benzylindol-3-ylmethylene)imidazolidine-2,4-dione (3) analogs structurally related to aplysinopsin, and that incorporate a variety of substituents in both the indole and N-benzyl moieties have been synthesized under microwave irradiation and conventional heating methods These analogs were evaluated for their anti-proliferative activity against MCF-7 and MDA-231 breast cancer cell lines, and A549 and H460 lung cancer cell lines. Two analogs, 3f and 3j had IC(50) values of 4.4 and 5.2microM, respectively, compared to 5-fluorouracil (IC(50)=15.2microM) against MCF-7 cells.

4-Des-oxy-4β-(4-methoxy-carbonyl-1,2,3-triazol-1-yl)podophyllotoxin dichloro-methane solvate

In the title compound {systematic name: methyl 1-[12-oxo-10-(3,4,5-trimethoxy-phen-yl)-4,6,13-trioxa-tetra-cyclo-[7.7.0.0(3,7).0(11,15)]hexa-deca-1,3(7),8-trien-16-yl]-1H-1,2,3-triazole-4-carboxyl-ate dichloro-methane solvate}, C(26)H(25)N(3)O(9)·CH(2)Cl(2), the tetra-hydro-furan ring and the six-membered ring fused to it both display envelope conformations.

Synthesis and structure-activity relationships of N-aryl(indol-3-yl)glyoxamides as antitumor agents

The synthesis and study of the structure-activity relationships of cytotoxic compounds based on N-pyridinyl or N-aryl-2-(1-benzylindol-3-yl)glyoxamide skeleton, represented by the lead structures D-24241 and D-24851, are described. The presence of N-(pyridin-4-yl) moiety was crucial for activity and 2-[1-(4-chloro-3-nitrobenzyl)-1H-indol-3-yl]-2-oxo-N-(pyridin-4-yl)acetamide (55), the most potent derivative, showed IC(50)=39 nM, 51 nM and 11 nM against HeLa/KB (human cervix carcinoma), L1210 (murine leukemia) and SKOV3 (human ovarian carcinoma) cell lines proliferation assay, respectively, as active as the lead compounds.

4-Des-oxy-4β-[(5-meth-oxy-1H-indol-3-yl)oxalylamino]podophyllotoxin methanol solvate

The main mol-ecule of the title solvate, C(33)H(30)N(2)O(10)·CH(3)OH, is a new anti-tumor agent, which shows cytotoxicity against MDR cancer cell lines. It has been synthesized by coupling 4β-amino-podophyllotoxin with (5-meth-oxy-1H-indol-3-yl)glyoxyl chloride and structurally characterized. There are two crystallographically independent mol-ecules in the asymmetric unit, which differ in the dihedral angles between the aromatic rings. The dihedral angles between the benzene ring of the benzo[d][1,3]dioxole and the benzene ring of the 5-meth-oxy-1H-indole are 85.08 (3) and 76.88 (3)° and reflect the main conformational difference between the two independent mol-ecules. The asymmetric unit is completed with two methanol solvent mol-ecules, one of which is disordered over two positions, with occupancies close to 0.5.