Synthesis and bioevaluation of novel arylnaphthalene lignans as anticancer agents

Bioactivities and Mechanisms of Action of Diphyllin and Its Derivatives: A Comprehensive Systematic Review

Natural products are treasure houses for modern drug discovery. Diphyllin is a natural arylnaphthalene lignan lactone isolated from the leaf of Astilboides tabularis. Studies have found that it possesses plenty of bioactivity characteristics. In this paper, we reviewed the structure, bioactivity, and mechanism of action of diphyllin and its derivatives. The references were obtained from PubMed, Web of Science, and Science Direct databases up to August 2023. Papers without a bio-evaluation were excluded. Diphyllin and its derivatives have demonstrated V-ATPase inhibition, anti-tumor, anti-virus, anti-biofilm, anti-inflammatory, and anti-oxidant activities. The most studied activities of diphyllin and its derivatives are V-ATPase inhibition, anti-tumor activities, and anti-virus activities. Furthermore, V-ATPase inhibition activity is the mechanism of many bioactivities, including anti-tumor, anti-virus, and anti-inflammatory activities. We also found that the galactosylated modification of diphyllin is a common phenomenon in plants, and therefore, galactosylated modification is applied by researchers in the laboratory to obtain more excellent diphyllin derivatives. This review will provide useful information for the development of diphyllin-based anti-tumor and anti-virus compounds.

New Products Generated from the Transformations of Ferulic Acid Dilactone

Various ferulic acid (FA) dimers occurring in plant cell walls, such as 8-5-, 8-O-4-, 5-5-, and 8-8- coupled dimers, are effective antioxidants and potential antimicrobials. It is necessary to access these diferulates as reference compounds to validate those isolated from plants. 3,6-bis(4-hydroxy-3-methoxyphenyl)-tetrahydrofuro-[3,4-c]furan-1,4-dione, a 8-8-coupled FA dilactone generated from ferulic acid via radical coupling, has been used to synthesize 8-8-coupled FA dimers although few reports investigated the distribution of products and mechanisms involved in the transformation of FA dilactone. In this work, the FA dilactone, obtained from FA by a peroxidase-catalyzed radical coupling, was reacted under various base/acid conditions. Effects of reaction conditions and workup procedures on the distribution of products were investigated by GC-MS. The isolated products from such treatments of FA dilactone were characterized by NMR. New derivatives of FA dimer including 2-(4-hydroxy-3-methoxybenzylidene)-3-(hydroxyl-(4-hydroxy-3-methoxyphenyl)methyl)succinic acid and 2-(bis(4-hydroxy-3-methoxyphenyl)-methyl)-succinic acid were produced from NaOH treatment. Another novel 8-8-coupled cyclic FA dimer, diethyl 6-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-7-methoxy-1,2-dihydronaphthalene-2,3-dicarboxylate was identified in products from FA dilactone treated by dry HCl in absolute ethanol. Mechanisms involved in such transformations were proposed.

Design, Synthesis, and Biological Evaluation of Novel Thiazolyl Substituted Bis-pyrazole Oxime Derivatives with Potent Antitumor Activities by Selectively Inducing Apoptosis and ROS in Cancer Cells

BACKGROUND

A large number of pyrazole derivatives have different biological activities such as anticancer, antimicrobial, anti-inflammatory, analgesic and antiepileptic activity. Among them, pyrazole oximes have attracted much attention due to their potential pharmacological activities, particularly anticancer activities.

OBJECTIVE

Our goal is to synthesize novel thiazolyl substituted bis-pyrazole oxime derivatives with potent antitumor activities by selectively inducing apoptosis and Reactive Oxygen Species (ROS) accumulation in cancer cells.

METHODS

Eighteen bis-pyrazole oximes were synthesized by conjugating thiazolyl substituted pyrazoles with pyrazoxime. The target compounds were characterized by 1HNMR, 13C NMR, and HRMS, and screened for their antiproliferative activity against four cancer cells in MTT assay. The most potent compound was examined for its inhibitory effect and ROS accumulation in both cancer cells HCT116 and normal intestinal epithelial cells CCD841. Finally, the most potent compound was further evaluated for its apoptotic induction by flow cytometry analysis and immunoblot analysis of apoptosis-related proteins and DNA damage proteins.

RESULTS

Most compounds displayed potent antiproliferative activity against four cancer cell lines in vitro, displaying potencies superior to 5-FU. In particular, the most potent compound 13l selectively inhibited proliferation of colorectal cancer HCT116 cells but not normal colon CCD841 cells. Furthermore, compound 13l also selectively promoted intracellular ROS accumulation in HCT116 which was involved in 13l inhibition of cancer cell proliferation and induction of cell apoptosis. Finally, compound 13l also dose-dependently induced cancer cell apoptosis by regulating apoptotic and DNA damage related proteins expressions.

CONCLUSION

Our synthetic bis-pyrazole oxime derivatives possess potent antitumor activities by selectively inducing apoptosis and ROS accumulation in cancer cells, which may hold great promise as therapeutic agents for the treatment of human cancers.

Hydroxamic Acid Derivatives of β-Carboline/Hydroxycinnamic Acid Hybrids Inducing Apoptosis and Autophagy through the PI3K/Akt/mTOR Pathways

Naturally occurring β-carbolines are known to have antitumor activities but with limited effectiveness. In order to improve their efficacy, a series of new hydroxamic-acid-containing β-carbolines connected via a hydroxycinnamic acid moitey (12a-f) were developed to incorporate histone deacetylase (HDAC) inhibition for possible synergistic effects. When evaluated in in vitro assays, most of the analogues showed significant antitumor activities against four human cancer cells. In particular, 12b showed the highest cytotoxic potency of the series, including drug-resistant Bel7402 cells, but had minimal effect on normal hepatic LO2 cells. These compounds also showed excellent inhibitory effects against HDAC1/6, which appear to contribute greatly to their antiproliferative properties. Compound 12b enhanced the acetylation levels of histone H3 and α-tubulin and induced greater cancer cell apoptosis than the FDA-approved HDAC inhibitor SAHA by regulating expression of apoptotic proteins Bax, Bcl-2, and caspase 3. Importantly, 12b also induced a significant amount of autophagic flux activity in Bel7402 cells by increasing the expression of Beclin-1 and LC3-II proteins and decreasing that of LC3-I and p62. Finally, 12b significantly inhibited PI3K/Akt/mTOR signaling, an important cell-growth-promoting pathway aberrantly activated in many cancers. Together, the results suggest that these hydroxamic-acid-containing β-carboline derivatives may be new leads for the discovery of agents for the treatment of human carcinoma cancers.

Anti-virus reagents targeting the capsid protein assembly

The capsid protein is a promising target for the development of therapeutic anti-virus agents.

Development of novel amino-quinoline-5,8-dione derivatives as NAD(P)H:quinone oxidoreductase 1 (NQO1) inhibitors with potent antiproliferative activities

Fourteen novel amino-quinoline-5,8-dione derivatives (6a-h and 7a-h) were designed and synthesized by coupling different alkyl- or aryl-amino fragments at the C6- or C7-position of quinoline-5,8-dione. All target compounds showed antiproliferative potency in the low micromolar range in both drug sensitive HeLaS3 and multidrug resistant KB-vin cell lines. Compounds 6h, 6d, 7a, and 7d exhibited more potent antiproliferative effects than the other compounds. Especially, compounds 6d and 7d displayed NQO1-dependent cytotoxicity and competitive NQO1 inhibitory effects in both drug sensitive HeLaS3 and multidrug resistant KB-vin cell lines. Furthermore, compounds 6h, 6d, 7a, and 7d induced a dose-dependent lethal mitochondrial dysfunction in both drug sensitive HeLaS3 and multidrug resistant KB-vin cells by increasing intracellular reactive oxygen species (ROS) levels. Notably, compound 7d selectively inhibited cancer cells, but not non-tumor liver cell proliferation in vitro, and significantly triggered HeLaS3 cell apoptosis by regulating apoptotic proteins of Bcl-2, Bax, and cleaved caspase-3 in a dose-dependent manner. Our findings suggest that these novel C6- or C7-substituted amino-quinoline-5,8-dione derivatives, such as 7d, could be further developed in the future as potent and selective antitumor agents to potentially circumvent multi-drug resistance (MDR).

Cancer with low cathepsin D levels is susceptible to vacuolar (H+ )-ATPase inhibition

Vacuolar (H⁺)‐ATPases (V‐ATPases) have important roles in the supply of nutrients to tumors by mediating autophagy and the endocytic uptake of extracellular fluids. Accordingly, V‐ATPases are attractive therapeutic targets for cancer. However, the clinical use of V‐ATPase inhibitors as anticancer drugs has not been realized, possibly owing to their high toxicity in humans. Inhibition of V‐ATPase may be an appropriate strategy in highly susceptible cancers. In this study, we explored markers of V‐ATPase inhibitor sensitivity. V‐ATPase inhibitors led to pH impairment in acidic intracellular compartments, suppression of macropinocytosis, and decreased intracellular amino acid levels. The sensitivity of cells to V‐ATPase inhibitors was correlated with low cathepsin D expression, and cancer cells showed increased sensitivity to V‐ATPase inhibitors after pretreatment with a cathepsin D inhibitor and siRNA targeting the cathepsin D gene (CTSD). In addition, V‐ATPase inhibitor treatment led to the induction of the amino acid starvation response, upregulation of endoplasmic reticulum stress markers, and suppression of mammalian target of rapamycin (mTOR) signaling in cells expressing low levels of cathepsin D. Some colorectal cancer patients showed the downregulation of cathepsin D in tumor tissues compared with matched normal tissues. These findings indicate that V‐ATPase inhibitors are promising therapeutic options for cancers with downregulated cathepsin D.

Development of novel β-carboline-based hydroxamate derivatives as HDAC inhibitors with DNA damage and apoptosis inducing abilities

A series of novel β-carboline-based hydroxamate derivatives (8a-n) as HDAC inhibitors have been designed and synthesized. Most of these compounds displayed potent histone deacetylase inhibitory effects and good antiproliferative activity with IC₅₀s in the low micromolar range. One of the most potent compounds (8k) showed the strongest inhibition of the proliferation of human hepatocellular carcinoma (HCC) cells in vitro, with IC₅₀ values lower than that of the currently approved HDAC inhibitor SAHA. Compound 8k also increased acetylation of histone H3 and α-tubulin, consistent with its potent HDAC inhibition. Importantly, 8k induced hypochromism by electrostatic interactions with CT-DNA, suggesting potential induction of DNA damage. Finally, 8k significantly induced HepG2 cell apoptosis by regulating apoptotic relative proteins expression. Together, our findings suggest that these novel β-carboline-based hydroxamate derivatives may provide a new framework for the discovery of novel antitumor agents for the intervention of human carcinoma cells.

A regioselective facile synthesis of furo[3,4-b]carbazolones: application to the total synthesis of mafaicheenamine E and claulansine D

1-Hydroxycarbazole-2,3-dicarboxylates have been shown to undergo chemoselective reductive cyclization to furo[3,4-b]carbazolones with LiAlH₄.