Design, synthesis, and tumor drug resistance reversal activity of novel hederagenin derivatives modified by nitrogen-containing heterocycles

Modular Assembly of Pyrrolo[3,4-c]isoquinolines through Rh-Catalyzed Cascade C-H Activation/Annulation of O-Methyl Aryloximes with Maleimides

An efficient and practical strategy for the construction of pyrrolo[3,4-c]isoquinolines via Rh(III)-catalyzed cascade C-H activation and subsequential annulation process from easily available O-methyl aryloximes and maleimides has been disclosed. This facile protocol does not require any inert atmosphere protection with good efficiency in a low loading of catalyst and exhibits good functional group tolerance and broad substrate scope. Notably, the as-prepared products show potential photophysical properties.

An updated review of the pharmacological effects and potential mechanisms of hederagenin and its derivatives

Hederagenin (HG) is a natural pentacyclic triterpenoid that can be isolated from various medicinal herbs. By modifying the structure of HG, multiple derivatives with superior biological activities and safety profiles have been designed and synthesized. Accumulating evidence has demonstrated that HG and its derivatives display multiple pharmacological activities against cancers, inflammatory diseases, infectious diseases, metabolic diseases, fibrotic diseases, cerebrovascular and neurodegenerative diseases, and depression. Previous studies have confirmed that HG and its derivatives combat cancer by exerting cytotoxicity, inhibiting proliferation, inducing apoptosis, modulating autophagy, and reversing chemotherapy resistance in cancer cells, and the action targets involved mainly include STAT3, Aurora B, KIF7, PI3K/AKT, NF-κB, Nrf2/ARE, Drp1, and P-gp. In addition, HG and its derivatives antagonize inflammation through inhibiting the production and release of pro-inflammatory cytokines and inflammatory mediators by regulating inflammation-related pathways and targets, such as NF-κB, MAPK, JAK2/STAT3, Keap1-Nrf2/HO-1, and LncRNA A33/Axin2/β-catenin. Moreover, anti-pathogen, anti-metabolic disorder, anti-fibrosis, neuroprotection, and anti-depression mechanisms of HG and its derivatives have been partially elucidated. The diverse pharmacological properties of HG and its derivatives hold significant implications for future research and development of new drugs derived from HG, which can lead to improved effectiveness and safety profiles.

Novel pyxinol amide derivatives bearing an aliphatic heterocycle as P-glycoprotein modulators for overcoming multidrug resistance

P-glycoprotein (Pgp) modulators are promising agents for overcoming multidrug resistance (MDR) in cancer chemotherapy. In this study, via structural optimization of our lead compound S54 (nonsubstrate allosteric inhibitor of Pgp), 29 novel pyxinol amide derivatives bearing an aliphatic heterocycle were designed, synthesized, and screened for MDR reversal activity in KBV cells. Unlike S54, these active derivatives were shown to transport substrates of Pgp. The most potent derivative 4c exhibited promising MDR reversal activity (IC50 of paclitaxel = 8.80 ± 0.56 nM, reversal fold = 211.8), which was slightly better than that of third-generation Pgp modulator tariquidar (IC50 of paclitaxel = 9.02 ± 0.35 nM, reversal fold = 206.6). Moreover, the cytotoxicity of this derivative was 8-fold lower than that of tariquidar in human normal HK-2 cells. Furthermore, 4c blocked the efflux function of Pgp and displayed high selectivity for Pgp but had no effect on its expression and distribution. Molecular docking revealed that 4c bound preferentially to the drug-binding domain of Pgp. Overall, 4c is a promising lead compound for developing Pgp modulators.

Discovery of new tricyclic spiroindole derivatives as potent P-glycoprotein inhibitors for reversing multidrug resistance enabled by a synthetic methodology-based library

The discovery of novel and highly effective P-gp inhibitors is considered to be an effective strategy for overcoming tumor drug resistance. In this paper, a phenotypic screening via a self-constructed synthetic methodology-based library identified a new class of tricyclic spiroindole derivatives with excellent tumor multidrug resistance reversal activity. A stereospecific compound OY-103-B with the best reversal activity was obtained based on a detailed structure-activity relationship study, metabolic stability optimization and chiral resolution. For the VCR-resistant Eca109 cell line (Eca109/VCR), co-administration of 5.0 μM OY-103-B resulted in a reversal fold of up to 727.2, superior to the typical third-generation P-gp inhibitor tariquidar. Moreover, the compound inhibited the proliferation of Eca109/VCR cells in a concentration-dependent manner in plate cloning and flow cytometry. Furthermore, fluorescence substrate accumulation assay and chemotherapeutic drug reversal activity tests demonstrated that OY-103-B reversed tumor drug resistance via P-gp inhibition. In conclusion, this study provides a novel skeleton that inspires the design of new P-gp inhibitors, laying the foundation for the treatment of drug-resistant tumors.

Discovery of novel ocotillol derivatives modulating glucocorticoid receptor/NF-κB signaling for the treatment of sepsis

Glucocorticoids (GCs) have been used in the treatment of sepsis because of their potent anti-inflammatory effects. However, their clinical efficacy against sepsis remains controversial because of glucocorticoid receptor (GR) downregulation and side effects. Herein, we designed and synthesized 30 ocotillol derivatives and evaluated their anti-inflammatory activities. Ocotillol 24(R/S) differential isomers were stereoselective in their pharmacological action. Specifically, 24(S) derivatives had better anti-inflammatory activity than their corresponding 24(R) derivatives. Compound 20 most effectively inhibited NO release (85.97% reduction), and it exerted dose-dependent inhibitory effects on interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) levels. Mechanistic studies revealed that compound 20 reduces the degradation of GR mRNA and GR protein. Meanwhile, compound 20 inhibited the activation of nuclear factor-κB (NF-κB) signaling, thereby inhibiting the nuclear translocation of p65 and attenuating the inflammatory response. In vivo studies revealed that compound 20 attenuated hepatic, pulmonary, and renal pathology damage in mice with sepsis and suppressed the production of inflammatory mediators. These results indicated that compound 20 is a promising lead compound for designing and developing anti-sepsis drugs.

Natural products for combating multidrug resistance in cancer

Cancer cells frequently develop resistance to chemotherapeutic therapies and targeted drugs, which has been a significant challenge in cancer management. With the growing advances in technologies in isolation and identification of natural products, the potential of natural products in combating cancer multidrug resistance has received substantial attention. Importantly, natural products can impact multiple targets, which can be valuable in overcoming drug resistance from different perspectives. In the current review, we will describe the well-established mechanisms underlying multidrug resistance, and introduce natural products that could target these multidrug resistant mechanisms. Specifically, we will discuss natural compounds such as curcumin, resveratrol, baicalein, chrysin and more, and their potential roles in combating multidrug resistance. This review article aims to provide a systematic summary of recent advances of natural products in combating cancer drug resistance, and will provide rationales for novel drug discovery.

Novel betulin derivatives as multidrug reversal agents targeting P-glycoprotein

Chemotherapy is a powerful means of cancer treatment but its efficacy is compromised by the emergence of multidrug resistance (MDR), mainly linked to the efflux transporter ABCB1/P-glycoprotein (P-gp). Based on the chemical structure of betulin, identified in our previous work as an effective modulator of the P-gp function, a series of analogs were designed, synthesized and evaluated as a source of novel inhibitors. Compounds 6g and 6i inhibited rhodamine 123 efflux in the P-gp overexpressed leukemia cells, K562/Dox, at concentrations of 0.19 µM and 0.39 µM, respectively, and increased the intracellular accumulation of doxorubicin at the submicromolar concentration of 0.098 µM. Compounds 6g and 6i were able to restore the sensitivity of K562/Dox to Dox at 0.024 µM and 0.19 µM, respectively. Structure-activity relationship analysis and molecular modeling revealed important information about the structural features conferring activity. All the active compounds fitted in a specific region involving mainly transmembrane helices (TMH) 4-6 from one homologous half and TMH 7 and 12 from the other, also showing close contacts with TMH 6 and 12. Compounds that bound preferentially to another region were inactive, regardless of their free energy of binding. It should be noted that compounds 6g and 6i were devoid of toxic effects against peripheral blood mononuclear normal cells and erythrocytes. The data obtained indicates that both compounds might be proposed as scaffolds for obtaining promising P-gp inhibitors for overcoming MDR.

Design, synthesis, and evaluation of n-butylphthalide and ligustrazine hybrids as potent neuroprotective agents for the treatment of ischemic stroke in vitro and in vivo

A series of novel NBP-TMP hybrids with neuroprotective effects were designed and synthesized for the treatment of ischemic stroke. The anti-cerebral ischemic activity of these compounds was screened by evaluating their neuroprotective effects on the oxygen glucose deprivation/reperfusion (OGD/R)-induced SH-SY5Y cell injury model in vitro. Nine compounds 7e, 7h-7i, 7k, 7m-7p and 7r showed better activities on cell viability and LDH levels compared to NBP at the concentration of 6.25 μM. Among them, compound 7m showed the best potency with a percentage of protection 90.2 % compared to NBP (69.2 %) and other compounds. Preliminary structure-activity analysis revealed that the introduction of iodine and N-methylpiperazine groups could significantly improve the neuroprotective effect. Further mechanism research showed that compound 7m could reduce the damage to neuronal mitochondria caused by OGD/R by reducing ROS and increasing mitochondrial membrane potential (MMP), and reduce the apoptosis and necrosis of neurons to play a neuroprotective role. In addition, 7m could regulate the levels of mitochondrial apoptosis pathway-related proteins Bcl-2, Bax, and caspase 3. Finally, in vivo experiments showed that the compound 7m significantly inhibited ischemia-reperfusion injury and cerebral blood flow in rats, and showed a more significant neuroprotective effect than the positive drug NBP at a dose concentration of 20 mg/kg. In conclusion, our results suggest that 7m may be used as a novel lead compound for the future development of anti-cerebral ischemic agents.

A Novel 3-meta-Pyridine-1,2,4-oxadiazole Derivative of Glycyrrhetinic Acid as a Safe and Promising Candidate for Overcoming P-Glycoprotein-Mediated Multidrug Resistance in Tumor Cells

Given the pharmacophore properties of the nitrogen-containing moiety in the molecular structure of P-glycoprotein (P-gp) inhibitors, we report the evaluation of the P-gp inhibitory and MDR reversal activities of 2g, a 3-meta-pyridin-1,2,4-oxadiazole derivative of 18βH-glycyrrhetinic acid. Through molecular docking, we have shown that 2g has the potential to directly interact with the transmembrane domain of P-gp with a low free binding energy (-10.2 kcal/mol). Using KB-8-5 human cervical carcinoma cells and RLS40 murine lymphosarcoma cells, both of which exhibit a multidrug-resistant (MDR) phenotype mediated by P-gp activation, we have shown that 2g, at nontoxic concentrations, effectively increased the intracellular accumulation of fluorescent P-gp substrates (rhodamine 123 or doxorubicin (DOX)), leading to a marked sensitization of the model cells to the cytotoxic effect of DOX. Considering the comparable activity of 2g with verapamil, a known P-gp inhibitor, 2g can be considered as a promising candidate for the development of agents capable of overcoming P-gp-mediated MDR in tumor cells.

Advances in the anti-tumor potential of hederagenin and its analogs

Hederagenin is a pentacyclic triterpenoid that is widely distributed as the main pharmaceutical ingredient in various medicinal plants. Similarly as other pentacyclic triterpenoids, hederagenin has various pharmacological effects such as anti-tumor, anti-inflammatory, anti-depressant, and anti-viral activities. In particular, the anti-tumor activity of hederagenin indicates its potential for development into highly effective chemotherapeutic agents. Studies revealed that hederagenin effectively suppresses the growth of various tumor cell lines in vitro and interacts with several molecular targets that play essential roles in various cellular signaling pathways. The compound suppresses transformation, inhibits proliferation, and induces apoptosis in tumor cells. In this review, we highlight research progress on the source, pharmacokinetics, pharmacological activity, and mechanism of action of hederagenin and the anti-tumor activity of its analogs by integrating and analyzing relevant domestic and international studies and providing a basis for their further development and application.

Natural Products-Pyrazine Hybrids: A Review of Developments in Medicinal Chemistry

Pyrazine is a six-membered heterocyclic ring containing nitrogen, and many of its derivatives are biologically active compounds. References have been downloaded through Web of Science, PubMed, Science Direct, and SciFinder Scholar. The structure, biological activity, and mechanism of natural product derivatives containing pyrazine fragments reported from 2000 to September 2023 were reviewed. Publications reporting only the chemistry of pyrazine derivatives are beyond the scope of this review and have not been included. The results of research work show that pyrazine-modified natural product derivatives have a wide range of biological activities, including anti-inflammatory, anticancer, antibacterial, antiparasitic, and antioxidant activities. Many of these derivatives exhibit stronger pharmacodynamic activity and less toxicity than their parent compounds. This review has a certain reference value for the development of heterocyclic compounds, especially pyrazine natural product derivatives.

Pharmacological overview of hederagenin and its derivatives

Hederagenin is a pentacyclic triterpenoid isolated from plants and widely distributed in a variety of medicinal plants. By integrating and analyzing external related literature reports, the latest research progress on the pharmacological effects and structural modification of hederagenin was reviewed. Hederagenin has a wide range of pharmacological activities, including antitumor, anti-inflammatory, antidepressant, anti-neurodegenerative, antihyperlipidemic, antidiabetic, anti-leishmaniasis, and antiviral activities. Among them, it shows high potential in the field of anti-tumor treatment. This paper also reviews the structural modifications of hederagenin, including carboxyl group modifications and two hydroxyl group modifications. Future research on hederagenin will focus on prolonging its half-life, improving its bioavailability and structural modification to enhance its pharmacological activity, accelerating the preclinical research stage of hederagenin for it to enter the clinical research stage as soon as possible.

Strategies to overcome cancer multidrug resistance (MDR) through targeting P-glycoprotein (ABCB1): An updated review

The emergence of multidrug resistance (MDR) in malignant tumors is one of the leading threats encountered currently in many chemotherapeutic agents. The overexpression of the ATP-binding cassette (ABC) transporters is involved in MDR. P-glycoprotein (P-gp)/ABCB1 is a member of the ABC transporter family that significantly increases the efflux of various anticancer drugs from tumor cells. Therefore, targeting P-gp with small molecule inhibitors is an effective therapeutic strategy to overcome MDR. Over the past four decades, diverse compounds with P-gp inhibitory activity have been identified to sensitize drug-resistant cells, but none of them has been proven clinically useful to date. Research efforts continue to discover an effective approach for circumventing MDR. This review has provided an overview of the most recent advances (last three years) in various strategies for circumventing MDR mediated by P-gp. It may be helpful for the scientists working in the field of drug discovery to further synthesize and discover new chemical entities/therapeutic modalities with less toxicity and more efficacies to overcome MDR in cancer chemotherapy.

Recent advances in access to overcome cancer drug resistance by nanocarrier drug delivery system

Cancer is currently one of the most intractable diseases causing human death. Although the prognosis of tumor patients has been improved to a certain extent through various modern treatment methods, multidrug resistance (MDR) of tumor cells is still a major problem leading to clinical treatment failure. Chemotherapy resistance refers to the resistance of tumor cells and/or tissues to a drug, usually inherent or developed during treatment. Therefore, an urgent need to research the ideal drug delivery system to overcome the shortcoming of traditional chemotherapy. The rapid development of nanotechnology has brought us new enlightenments to solve this problem. The novel nanocarrier provides a considerably effective treatment to overcome the limitations of chemotherapy or other drugs resulting from systemic side effects such as resistance, high toxicity, lack of targeting, and off-target. Herein, we introduce several tumor MDR mechanisms and discuss novel nanoparticle technology applied to surmount cancer drug resistance. Nanomaterials contain liposomes, polymer conjugates, micelles, dendrimers, carbon-based, metal nanoparticles, and nucleotides which can be used to deliver chemotherapeutic drugs, photosensitizers, and small interfering RNA (siRNA). This review aims to elucidate the advantages of nanomedicine in overcoming cancer drug resistance and discuss the latest developments.

Design, synthesis, and biological evaluation of ocotillol derivatives fused with 2-aminothiazole via A-ring as modulators of P-glycoprotein-mediated multidrug resistance

Overexpression of P-glycoprotein (P-gp) plays a key role in the development of multidrug resistance (MDR), the major reason for the failure of chemotherapy in clinics. Ocotillol and its derivatives had been reported with good P-gp-mediated tumor MDR reversal activity in vitro. Herein, a series of ocotillol derivatives fused with 2-aminothiazole (2-AT) via A-ring were designed and synthesized to further improve the tumor MDR reversal potency. These compounds were evaluated for their MDR reversal activity against the KBV cells by MTT assay. Among them, the most promising derivative against P-gp-mediated MDR was compound 12 with 2-AT and glycine in the A-ring. Rhodamine123 (Rh123) accumulation assay, Western blot assay, and P-gp-Glo™ assay showed that compound 12 efficiently inhibited the efflux function of P-gp by stimulating P-gp ATPase rather than downregulating its expression. Moreover, compound 12 sensitized KBV cells to paclitaxel arrested cells in the G₂/M phase and induced cell apoptosis. Importantly, compound 12 significantly inhibited the growth of KBV cell-derived xenograft tumors in nude mice by increasing the sensitivity of paclitaxel in vivo. Finally, the structure-activity relationships (SARs) of ocotillol derivatives were further investigated. In summary, compound 12 has the potential to overcome MDR in cancer caused by P-gp.

Novel Epoxides of Soloxolone Methyl: An Effect of the Formation of Oxirane Ring and Stereoisomerism on Cytotoxic Profile, Anti-Metastatic and Anti-Inflammatory Activities In Vitro and In Vivo

It is known that epoxide-bearing compounds display pronounced pharmacological activities, and the epoxidation of natural metabolites can be a promising strategy to improve their bioactivity. Here, we report the design, synthesis and evaluation of biological properties of αO-SM and βO-SM, novel epoxides of soloxolone methyl (SM), a cyanoenone-bearing derivative of 18βH-glycyrrhetinic acid. We demonstrated that the replacement of a double-bound within the cyanoenone pharmacophore group of SM with α- and β-epoxide moieties did not abrogate the high antitumor and anti-inflammatory potentials of the triterpenoid. It was found that novel SM epoxides induced the death of tumor cells at low micromolar concentrations (IC₅₀^(24h) = 0.7–4.1 µM) via the induction of mitochondrial-mediated apoptosis, reinforced intracellular accumulation of doxorubicin in B16 melanoma cells, probably by direct interaction with key drug efflux pumps (P-glycoprotein, MRP1, MXR1), and the suppressed pro-metastatic phenotype of B16 cells, effectively inhibiting their metastasis in a murine model. Moreover, αO-SM and βO-SM hampered macrophage functionality in vitro (motility, NO production) and significantly suppressed carrageenan-induced peritonitis in vivo. Furthermore, the effect of the stereoisomerism of SM epoxides on the mentioned bioactivities and toxic profiles of these compounds in vivo were evaluated. Considering the comparable antitumor and anti-inflammatory effects of SM epoxides with SM and reference drugs (dacarbazine, dexamethasone), αO-SM and βO-SM can be considered novel promising antitumor and anti-inflammatory drug candidates.

Natural Products in Preventing Tumor Drug Resistance and Related Signaling Pathways

Drug resistance is still an obstacle in cancer therapy, leading to the failure of tumor treatment. The emergence of tumor drug resistance has always been a main concern of oncologists. Therefore, overcoming tumor drug resistance and looking for new strategies for tumor treatment is a major focus in the field of tumor research. Natural products serve as effective substances against drug resistance because of their diverse chemical structures and pharmacological effects. We reviewed the signaling pathways involved in the development of tumor drug resistance, including Epidermal growth factor receptor (EGFR), Renin-angiotensin system (Ras), Phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt), Wnt, Notch, Transforming growth factor-beta (TGF-β), and their specific signaling pathway inhibitors derived from natural products. This can provide new ideas for the prevention of drug resistance in cancer therapy.