Piperlongumine derived cyclic sulfonamides (sultams): Synthesis and in vitro exploration for therapeutic potential against HeLa cancer cell lines

Piperlongumine and its derivatives against cancer: A recent update and future prospective

Piperlongumine, or piplartine (PL), is a bioactive alkaloid isolated from Piper longum L. and a potent phytoconstituent in Indian Ayurveda and traditional Chinese medicine with a lot of therapeutic benefits. Apart from all of its biological activities, it demonstrates multimodal anticancer activity by targeting various cancer-associated pathways and being less toxic to normal cells. According to their structure-activity relationship (SAR), the trimethylphenyl ring (cinnamoyl core) and 5,6-dihydropyridin-2-(1H)-one (piperdine core) are responsible for the potent anticancer activity. However, it has poor intrinsic properties (low aqueous solubility, poor bioavailability, etc.). As a result, pharmaceutical researchers have been trying to optimise or modify the structure of PL to improve the drug-likeness profiles. The present review selected 26 eligible research articles on PL derivatives published between 2012 and 2023, followed by the preferred reporting items for systematic reviews and meta-analyses (PRISMA) format. We have thoroughly summarised the anticancer potency, mode of action, SAR and drug chemistry of the proposed PL-derivatives against different cancer cells. Overall, SAR analyses with respect to anticancer potency and drug-ability revealed that substitution of methoxy to hydroxyl, attachment of ligustrazine and 4-hydroxycoumarin heterocyclic rings in place of phenyl rings, and attachment of heterocyclic rings like indole at the C7-C8 olefin position in native PL can help to improve anticancer activity, aqueous solubility, cell permeability, and bioavailability, making them potential leads. Hopefully, the large-scale collection and critical drug-chemistry analyses will be helpful to pharmaceutical and academic researchers in developing potential, less-toxic and cost-effective PL-derivatives that can be used against different cancers.

Unveiling sultam in drug discovery: spotlight on the underexplored scaffold

Decades ago, the application of cyclic sulfonamide (sultam) and its derivatives primarily focused on their antibacterial properties. However, recent years have seen a shift in research attention towards exploring their potential as anticancer, anti-inflammatory, antidiabetic, and antiviral agents. Despite this broadening scope, only a few sultam drugs have made it to the commercial market, as much of the research on sultams remains in the discovery phase. This class of compounds holds significant promise and remains pertinent in pharmaceutical research. Due to sultam's relevance and growing importance in drug discovery, this review paper aims to consolidate and examine the biological activities of sultam derivatives ranging from 4 to 8-membered ring structures.

Design, Synthesis, and Cytotoxic Activity of Novel Natural Arylsulfonamide-Inspired Molecules

Primary arylsulfonamide functional groups feature prominently in diverse pharmaceuticals. However, natural arylsulfonamides are relatively infrequent. In this work, two novel arylsulfonamide natural products were first synthesized, and then a series of novel molecules derived from natural arylsulfonamides were designed and synthesized, and their in vitro cytotoxic activities against A875, HepG2, and MARC145 cell lines were systematically evaluated. The results indicate that some of these arylsulfonamide derivatives exhibit significantly good cytotoxic activity against the tested cell lines compared with the control 5-fluorouracil (5-FU), such as compounds 10l, 10p, 10q, and 10r. In particular, the potential molecule 10q, containing a carbazole moiety, exhibited the highest inhibitory activity against all tested cell lines, with IC50 values of 4.19 ± 0.78, 3.55 ± 0.63, and 2.95 ± 0.78 μg/mL, respectively. This will offer the potential to discover novel drug-like compounds from the sparsely populated area of natural products that can lead to effective anticancer agents.

The promising potential of piperlongumine as an emerging therapeutics for cancer

In spite of the immense advancement in the diagnostic and treatment modalities, cancer continues to be one of the leading causes of mortality across the globe, responsible for the death of around 10 million patients every year. The foremost challenges faced in the treatment of this disease are chemoresistance, adverse effects of the drugs, and the high cost of treatment. Though scientific studies over the past few decades have foreseen and are focusing on the cancer-preventive and therapeutic potential of natural products and their underlying mechanism of action, many more of these agents are not still explored. Piperlongumine (PL), or piplartine, is one such alkaloid isolated from Piper longum Linn. which is shown to be safe and has significant potential in the prevention and therapy of cancer. Numerous shreds of evidence have established the ability of this alkaloid and its analogs and nanoformulations in modulating various complex molecular pathways such as phosphatidylinositol-3-kinase/protein kinase B /mammalian target of rapamycin, nuclear factor kappa-B, Janus kinases/signal transducer and activator of transcription 3, etc. and inhibit different hallmarks of cancer such as cell survival, proliferation, invasion, angiogenesis, epithelial-mesenchymal-transition, metastases, etc. In addition, PL was also shown to inhibit radioresistance and chemoresistance and sensitize the cancer cells to the standard chemotherapeutic agents. Therefore, this compound has high potential as a drug candidate for the prevention and treatment of different cancers. The current review briefly reiterates the anti-cancer properties of PL against different types of cancer, which permits further investigation by conducting clinical studies.

Overview of piperlongumine analogues and their therapeutic potential

Natural products have long been an important source for discovery of new drugs to treat human diseases. Piperlongumine (PL) is an amide alkaloid isolated from Piper longum L. (long piper) and other piper plants and has received widespread attention because of its diverse biological activities. A large number of PL derivatives have been designed, synthesized and assessed in many pharmacological functions, including antiplatelet aggregation, neuroprotective activities, anti-diabetic activities, anti-inflammatory activities, anti-senolytic activities, immune activities, and antitumor activities. Among them, the anti-tumor effects and application of PL and its derivatives are most extensively studied. We herein summarize the development of PL derivatives, the structure and activity relationships (SARs), and their therapeutic potential on the treatments of various diseases, especially against cancer. We also discussed the challenges and future directions associated with PL and its derivatives in these indications.

Piperlongumine inhibits the growth of non-small cell lung cancer cells via the miR-34b-3p/TGFBR1 pathway

BACKGROUND

Non-small cell lung cancer is a common type of lung cancer. Piperlongumine (PL), which is extracted from the roots of piperaceae plant, long pepper, and peppercorn, is an alkaloid amide that inhibits tumor growth and metastasis. However, whether it affects lung cancer cells remains unclear.

METHODS

We assessed the effects of PL on the proliferation and apoptosis of A549 and H1299 NSCLC cell lines.

RESULTS

PL was mildly toxic to normal human bronchial epithelial cells and significantly suppressed growth and facilitated apoptosis of A549 and H1299 cells. It also upregulated microRNA (miR)-34b-3p and downregulated the transforming growth factor beta type I receptor (TGFBR1). The dual-luciferase reporter assay showed that TGFBR1 is a target gene of miR-34b-3p. Silencing of miR-34b-3p or overexpression of TGFBR1 partially attenuated the effects of PL on A549 and H1299 cells.

CONCLUSIONS

PL inhibits proliferation and induces apoptosis of A549 and H1299 cells by upregulating miR-34b-3p and modulating TGFBR1 signaling pathway.

Novel Phenylmethylenecyclohexenone Derivatives as Potent TrxR Inhibitors Display High Antiproliferative Activity and Induce ROS, Apoptosis, and DNA Damage

The natural product piperlonguminine (PL) has been shown to exert potential anticancer activity against several types of cancer via elevation of reactive oxidative species (ROS). However, the application of PL has been limited due to its poor water solubility and moderate activity. To improve PL's potency, we designed and synthesized a series of 17 novel phenylmethylenecyclohexenone derivatives and evaluated their pharmacological properties. Most of them exerted antiproliferative activities against four cancer cell lines with IC₅₀ values lower than PL. Among these, compound 10 e not only showed good water solubility and exerted the most potent antiproliferative activity against HGC27 cells (IC₅₀ =0.76 μM), which was 10-fold lower than PL (IC₅₀ =7.53 μM), but also exhibited lower cytotoxicity in human normal gastric epithelial cells GES-1 compared with HGC27 cells. Mechanistically, compound 10 e inhibited thioredoxin reductase (TrxR) activity, increased ROS levels, and diminished mitochondrial transmembrane potential (MTP) in HGC27 cells. Furthermore, 10 e also induced G₂ /M cell-cycle arrest, and triggered cancer cell apoptosis through the regulation of apoptotic proteins. Finally, 10 e promoted DNA damage in HGC27 cells via the activation of the H2AX(S139ph) and p53 signaling. In conclusion, 10 e, with prominent tumor selectivity and water solubility, could be a promising candidate for the treatment of cancer and, as such, warrants further investigation.

Efficacy of novel methylenecyclohexenone derivatives as TrxR inhibitors in suppressing the proliferation and metastasis of human cancer cells

A series of mono- and di-methylenecyclohexenone derivatives, 3a-f and 4a-f, respectively, were designed and synthesized from piperlongumine (PL) and their in vitro and in vivo pharmacological properties were evaluated. A majority of the compounds exhibited a potent antiproliferative effect on five human cancer cell lines, especially those causing breast cancer. Compound 4f showed the highest antiproliferative potency among all of the compounds, almost a 10-fold higher inhibitory potency against thioredoxin reductase (TrxR) compared with PL in cells causing breast cancer. In addition, 4f was found to increase the levels of reactive oxygen species (ROS), thus leading to more potent antiproliferative effects. More importantly, the suppression assays of migration and invasion revealed that compound 4f could reverse the epithelial-mesenchymal transition induced by the transforming growth factor β1, and exhibit prominent anti-metastasis effects. Compound 4f also showed strong inhibition potency toward solid tumors of breast cancer in vivo. Our findings show that compound 4f is a promising therapeutic candidate in the treatment of breast cancer, which, however, needs further research to be proved.

Medicinally Privileged Sultams: Synthesis and Mechanism of Action

To date, more than a thousand research articles have been published detailing various regio-, stereo-, chemo-, and enantioselective specific synthesis of the cyclic sulfonamides (sultams). Although enormous synthetic efforts were made, but bioactivities of sultams have not been widely investigated. Sultams are the sulfur analogs of lactams (cyclic amides) which demonstrate a broad range of medicinal activities and several lactam drugs are commercially available. In contrast, only a few sultam drugs are commercially available, while the presence of two oxygens on sulfur in sultam motifs can serve as a better H-bond acceptor than lactam scaffolds. One of the major objectives of this minireview is to draw appropriate attention from the medicinal/pharmaceutical chemists to conduct indepth research on sultam derivatives targeted to the development of new drugs. This article gives a brief account of the synthesis, potential bioactivity, and mechanisms of therapeutic action of four to seven-membered sultam derivatives. Based on the available literature, this is the first effort to consolidate only the medicinally privileged sultam molecules and drugs under the same umbrella. While every effort was taken to comprise all the relevant reports related to bioactive sultams, any oversight is truly unintentional.

A Route to Triazole-Fused Sultams via Metal-Free Base-Mediated Cyclization of Sulfonamide-Tethered 5-Iodotriazoles

An efficient direct approach to triazole-fused sultams has been developed. The key step of the proposed strategy is base-mediated cyclization of sulfonamide-tethered 5-iodo-1,2,3-triazoles which are readily available via an improved protocol for Cu-catalyzed 1,3-dipolar cycloaddition. The annulation of the sultam fragment to the triazole ring proceeds smoothly under transition-metal-free conditions in the presence of Cs₂CO₃ in dioxane at 100 °C and affords fused heterocycles in high yields up to 99%. The favorability of an S_NAr-like mechanism for the cyclization was supported by DFT calculations. The applicability of the developed procedure to modification of natural compounds was demonstrated by preparation of a deoxycholic acid derivative.

New Zampanolide Mimics: Design, Synthesis, and Antiproliferative Evaluation

Zampanolide is a promising microtubule-stabilizing agent (MSA) with a unique chemical structure. It is superior to the current clinically used MSAs due to the covalent nature of its binding to β-tubulin and high cytotoxic potency toward multidrug-resistant cancer cells. However, its further development as a viable drug candidate is hindered by its limited availability. More importantly, conversion of its chemically fragile side chain into a stabilized bioisostere is envisioned to enable zampanolide to possess more drug-like properties. As part of our ongoing project aiming to develop its mimics with a stable side chain using straightforward synthetic approaches, 2-fluorobenzyl alcohol was designed as a bioisosteric surrogate for the side chain based on its binding conformation as confirmed by the X-ray structure of tubulin complexed with zampanolide. Two new zampanolide mimics with the newly designed side chain have been successfully synthesized through a 25-step chemical transformation for each. Yamaguchi esterification and intramolecular Horner–Wadsworth–Emmons condensation were used as key reactions to construct the lactone core. The chiral centers at C17 and C18 were introduced by the Sharpless asymmetric dihydroxylation. Our WST-1 cell proliferation assay data in both docetaxel-resistant and docetaxel-naive prostate cancer cell lines revealed that compound 6 is the optimal mimic and the newly designed side chain can serve as a bioisostere for the chemically fragile N-acetyl hemiaminal side chain in zampanolide.

Cu(i) catalysed annulation of isothiocyanates/isocyanates with 2-iodo-sulfonamides: synthesis of benzodithiazines, benzothiadiazinones, benzothiazinylidene-anilines and benzothiazolylidene-anilines

An efficient Cu(i)-catalysed cyclisation reaction of 2-iodobenzene sulfonamides with aryl-isothiocyanates and isocyanates that affords functionalised benzodithiazines and benzothiadiazinones, respectively, has been developed. Thus, in the reaction with aryl isothiocyanates (Ar-N[double bond, length as m-dash]C[double bond, length as m-dash]S), the C[double bond, length as m-dash]S moiety participates in the cyclisation leading to a dithiazine. By contrast, in the case of aryl isocyanates (Ar-N[double bond, length as m-dash]C[double bond, length as m-dash]O), the N[double bond, length as m-dash]C part is involved in the cyclisation and a thiadiazinone is obtained. Analogous reactions of isothiocyanates with N-tosyl-2-iodo-anilines and 2-iodo-benzyl sulfonamides afford (benzothiazin-2-ylidene)anilines and (benzothiazol-2-ylidene)anilines, respectively. Probable mechanistic pathways are briefly discussed.

Synthesis of Sultams and Cyclic N-Sulfonyl Ketimines via Iron-Catalyzed Intramolecular Aliphatic C-H Amidation

Cyclic sulfonamides (sultams) play a unique role in drug discovery and synthetic chemistry. A direct synthesis of sultams by an intramolecular C(sp³)-H amidation reaction using an iron complex in situ derived from Fe(ClO₄)₂ and aminopyridine ligand is reported. This strategy features a readily available catalyst and tolerates a broad variety of substrates as demonstrated by 22 examples (up to 89% yield). A one-pot iron-catalyzed amidation/oxidation procedure for the synthesis of cyclic N-sulfonyl ketimines is also realized with up to 92% yield (eight examples). The synthetic utility of the method is validated by a gram-scale reaction and derivatization of the products to ring-fused sultams.

Senolytic activity of piperlongumine analogues: Synthesis and biological evaluation

Selective clearance of senescent cells (SCs) has emerged as a potential therapeutic approach for age-related diseases, as well as chemotherapy- and radiotherapy-induced adverse effects. Through a cell-based phenotypic screening approach, we recently identified piperlongumine (PL), a dietary natural product, as a novel senolytic agent, referring to small molecules that can selectively kill SCs over normal or non-senescent cells. In an effort to establish the structure-senolytic activity relationships of PL analogues, we performed a series of structural modifications on the trimethoxyphenyl and the α,β-unsaturated δ-valerolactam rings of PL. We show that modifications on the trimethoxyphenyl ring are well tolerated, while the Michael acceptor on the lactam ring is critical for the senolytic activity. Replacing the endocyclic C2-C3 olefin with an exocyclic methylene at C2 render PL analogues 47-49 with increased senolytic activity. These α-methylene containing analogues are also more potent than PL in inducing ROS production in WI-38 SCs. Similar to PL, 47-49 reduce the protein levels of oxidation resistance 1 (OXR1), an important oxidative stress response protein that regulates the expression of a variety of antioxidant enzymes, in cells. This study represents a useful starting point toward the discovery of senolytic agents for therapeutic uses.

Piperlongumine (piplartine) as a lead compound for anticancer agents - Synthesis and properties of analogues: A mini-review

Piperlongumine, also known as piplartine, is an amide alkaloid of Piper longum L. (long piper), a medical plant known from Ayurvedic medicine. Although was discovered well over fifty years ago, its pharmacological properties have been uncovered in the past decade. In particular, piperlongumine has been most extensively studied as a potential anticancer agent. Piperlongumine has exhibited cytotoxicity against a broad spectrum of human cancer cell lines, as well as demonstrated antitumor activity in rodents. Piperlongumine has also been found to be a proapoptotic, anti-invasive, antiangiogenic agent and synergize with modern chemotherapeutic agents. Because of its clinical potential, several studies were undertaken to obtain piperlongumine analogues, which have exhibited more potent activity or more appropriate drug-like parameters. In this review, the synthesis of piperlongumine analogues and piperlongumine-based hybrid compounds, as well as their anticancer properties and the molecular basis for their activity are explored. General structure-activity relationship conclusions are drawn and directions for the future research are indicated.