In VitroandIn VivoReversal of Cancer Cell Multidrug Resistance by 2',4'-Dihydroxy-6'-methoxy-3',5'- dimethylchalcone

Recent developments of P-glycoprotein inhibitors and its structure-activity relationship (SAR) studies

P-glycoprotein (P-gp) over-expression is a key factor in multi-drug resistance (MDR), which is a major factor in the failure of cancer treatment. P-gp inhibitors have been demonstrated to have powerful pharmacological properties and may be used as a therapeutic approach to overcome the MDR in cancer cells. Combining clinical investigations with biochemical and computational research may potentially lead to a clearer understanding of the pharmacological properties and the mechanisms of action of these P-gp inhibitors. The task of turning these discoveries into effective therapeutic candidates for a variety of malignancies, including resistant and metastatic kinds, falls on medicinal chemists. A variety of P-gp inhibitors with great potency, high selectivity, and minimal toxicity have been identified in recent years. The latest advances in drug design, characterization, structure-activity relationship (SAR) research, and modes of action of newly synthesized, powerful small molecules P-gp inhibitors over the previous ten years are highlighted in this review. P-gp transporter over-expression has been linked to MDR, therefore the development of P-gp inhibitors will expand our understanding of the processes and functions of P-gp-mediated drug efflux, which will be helpful for drug discovery and clinical cancer therapies.

Anticancer Therapeutic Effects of Green Tea Catechins (GTCs) When Integrated with Antioxidant Natural Components

After decades of research and development concerning cancer treatment, cancer is still at large and very much a threat to the global human population. Cancer remedies have been sought from all possible directions, including chemicals, irradiation, nanomaterials, natural compounds, and the like. In this current review, we surveyed the milestones achieved by green tea catechins and what has been accomplished in cancer therapy. Specifically, we have assessed the synergistic anticarcinogenic effects when green tea catechins (GTCs) are combined with other antioxidant-rich natural compounds. Living in an age of inadequacies, combinatorial approaches are gaining momentum, and GTCs have progressed much, yet there are insufficiencies that can be improvised when combined with natural antioxidant compounds. This review highlights that there are not many reports in this specific area and encourages and recommends research attention in this direction. The antioxidant/prooxidant mechanisms of GTCs have also been highlighted. The current scenario and the future of such combinatorial approaches have been addressed, and the lacunae in this aspect have been discussed.

Synthesis, cytotoxicity evaluation and molecular docking studies on 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone derivatives

2′,4′-Dihydroxy-6′-methoxy-3′,5′-dimethylchalcone (DMC, 1) was isolated from seeds of Syzygium nervosum A.Cunn. ex DC. exhibiting intriguing biological activities. Herein, thirty three DMC derivatives including 4′-O-monosubstituted-DMC (2), 7-O-acylated-4-hydroxycoumarin derivatives (3), stilbene–coumarin derivatives (4), 2′,4′-disubstituted-DMC (5), and flavanone derivatives (6), were synthesised through acylation, alkylations, and sulfonylation. These semi-synthetic DMC derivatives were evaluated for in vitro cytotoxicity against six carcinoma cell lines. It was found that most derivatives exhibited higher cytotoxicity than DMC. In particular, 4′-O-caproylated-DMC (2b) and 4′-O-methylated-DMC (2g) displayed the strongest cytotoxicity against SH-SY5Y with IC₅₀ values of 5.20 and 7.52 μM, respectively. Additionally, 4′-O-benzylated-DMC (2h) demonstrated the strongest cytotoxicity against A-549 and FaDu with IC₅₀ values of 9.99 and 13.98 μM, respectively. Our structure–activity relationship (SAR) highlights the importance of 2′-OH and the derivatisation pattern of 4′-OH. Furthermore, molecular docking simulation studies shed further light on how these bioactive compounds interact with cyclin-dependent kinase 2 (CDK2).

Semi-synthetic DMC derivatives were synthesised and displayed biological potency against various cancer cell lines.

Inhibition of the NRF2/KEAP1 Axis: A Promising Therapeutic Strategy to Alter Redox Balance of Cancer Cells

Significance: The nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1 (NRF2/KEAP1) pathway is a crucial and highly conserved defensive system that is required to maintain or restore the intracellular homeostasis in response to oxidative, electrophilic, and other types of stress conditions. The tight control of NRF2 function is maintained by a complex network of biological interactions between positive and negative regulators that ultimately ensure context-specific activation, culminating in the NRF2-driven transcription of cytoprotective genes. Recent Advances: Recent studies indicate that deregulated NRF2 activation is a frequent event in malignant tumors, wherein it is associated with metabolic reprogramming, increased antioxidant capacity, chemoresistance, and poor clinical outcome. On the other hand, the growing interest in the modulation of the cancer cells' redox balance identified NRF2 as an ideal therapeutic target. Critical Issues: For this reason, many efforts have been made to identify potent and selective NRF2 inhibitors that might be used as single agents or adjuvants of anticancer drugs with redox disrupting properties. Despite the lack of specific NRF2 inhibitors still represents a major clinical hurdle, the researchers have exploited alternative strategies to disrupt NRF2 signaling at different levels of its biological activation. Future Directions: Given its dualistic role in tumor initiation and progression, the identification of the appropriate biological context of NRF2 activation and the specific clinicopathological features of patients cohorts wherein its inactivation is expected to have clinical benefits, will represent a major goal in the field of cancer research. In this review, we will briefly describe the structure and function of the NRF2/ KEAP1 system and some of the most promising NRF2 inhibitors, with a particular emphasis on natural compounds and drug repurposing. Antioxid. Redox Signal. 34, 1428-1483.

Mechanistic insights into dimethyl cardamonin-mediated pharmacological effects: A double control of the AMPK-HMGB1 signaling axis

Dimethyl cardamonin (DMC) has been isolated from diverse plants, notably from Cleistocalyx operculatus. We have reviewed the pharmacological properties of this natural product which displays anti-inflammatory, anti-hyperglycemic and anti-cancer properties. The pharmacological activities essentially derive from the capacity of DMC to interact with the protein targets HMGB1 and AMPK. Upon binding to HMGB1, DMC inhibits the nucleocytoplasmic transfer of the protein and its extracellular secretion, thereby blocking its alarmin function. DMC also binds to the AMP site of AMPK to activate phospho-AMPK and then to trigger downstream signals leading to the anti-inflammatory and anti-hyperglycemic effects. AMPK activation by DMC reinforces inhibition of HMGB1, to further reduce the release of the alarmin protein, likely contributing to the anticancer effects. The characterization of a tight control of DMC over the AMPK-HMGB1 axis not only helps to explain the known activities of DMC but also suggests opportunities to use this chalcone to treat other pathological conditions such as the acute respiratory distress syndrome (which affects patients with COVID-19). DMC structural analogues are also evoked.

Ethnopharmacology, Phytochemistry, and Pharmacology of Syzygium nervosum

Syzygium nervosum, which belongs to the Myrtaceae plant family, is widely distributed and cultivated in South East Asian countries. The decoction of S. nervosum leaves and flower buds has been consumed regularly as a beverage among the Vietnamese and Chinese communities. In addition, it has also been used in traditional medicine for a variety of purposes, notably for influenza, skin diseases, and digestive conditions. To date, there has been a considerable number of publications on chemical profiling and pharmacological activities of S. nervosum crude extract and pure isolated compounds. Our analysis indicated the characteristic chemical scaffolds and potential bioactivities on cancer, diabetes, and inflammatory diseases of this plant. The review aims to summarize up-to-date past study results and suggest future research direction on this species, in order to promote clinical applications of S. nervosum.

Design, Synthesis and Biological Evaluation of Dimethyl Cardamonin (DMC) Derivatives as P-glycoprotein-mediated Multidrug Resistance Reversal Agents

Background:

P-glycoprotein (P-gp) has been regarded as an important factor in the multidrug resistance (MDR) of tumor cells within the last decade, which can be solved by inhibiting Pgp to reverse MDR. Thus, it is an effective strategy to develop inhibitor of P-gp.

Objective:

In this study, the synthesis of a series of derivatives had been carried out by bioisosterism design on the basis of Dimethyl Cardamonin (DMC). Subsequently, we evaluated their reversal activities as potential P-glycoprotein (P-gp)-mediated Multidrug Resistance (MDR) agents.

Methods:

Dimethyl cardamonin derivatives were synthesized from acetophenones and the corresponding benzaldehydes in the presence of 40% KOH by Claisen-Schmidt reaction. Their cytotoxicity and reversal activities in vitro were assessed with MTT. Moreover, the compound B4 was evaluated by Doxorubicin (DOX) accumulation, Western blot and wound-healing assays deeply.

Results and Conclusion:

The results showed that compounds B2, B4 and B6 had the potency of MDR reversers with little intrinsic cytotoxicity. Meanwhile, these compounds also demonstrated the capability to inhibit MCF-7 and MCF-7/DOX cells migration. Besides, the most compound B4 was selected for further study, which promoted the accumulation of DOX in MCF-7/DOX cells and inhibited the expressionof P-gp at protein levels.

Conclusion:

The above findings may provide new insights for the research and development of Pgp- mediated MDR reversal agents.

Medicinal chemistry strategies to discover P-glycoprotein inhibitors: An update

The presence of multidrug resistance (MDR) in malignant tumors is one of the primary causes of treatment failure in cancer chemotherapy. The overexpression of the ATP binding cassette (ABC) transporter, P-glycoprotein (P-gp), which significantly increases the efflux of certain anticancer drugs from tumor cells, produces MDR. Therefore, inhibition of P-gp may represent a viable therapeutic strategy to overcome cancer MDR. Over the past 4 decades, many compounds with P-gp inhibitory efficacy (referred to as first- and second-generation P-gp inhibitors) have been identified or synthesized. However, these compounds were not successful in clinical trials due to a lack of efficacy and/or untoward toxicity. Subsequently, third- and fourth-generation P-gp inhibitors were developed but dedicated clinical trials did not indicate a significant therapeutic effect. In recent years, an extraordinary array of highly potent, selective, and low-toxicity P-gp inhibitors have been reported. Herein, we provide a comprehensive review of the synthetic and natural products that have specific inhibitory activity on P-gp drug efflux as well as promising chemosensitizing efficacy in MDR cancer cells. The present review focuses primarily on the structural features, design strategies, and structure-activity relationships (SAR) of these compounds.

Design, synthesis and biological evaluation of chalcones as reversers of P-glycoprotein-mediated multidrug resistance

Overexpression of P-glycoprotein (P-gp) is one of the major causes for multidrug resistance (MDR), which has become a major obstacle in cancer therapy. One hopeful approach to reverse the MDR is to develop inhibitors of P-gp in expression and/or function. Here, we designed and synthesized a series of chalcone derivatives as P-gp inhibitors and evaluated their potential reversal activities against MDR. Among them, the most active compound MY3 had little intrinsic cytotoxicity and showed the highest activity (RF = 50.19) in reversing DOX resistance in MCF-7/DOX cells. Further studies demonstrated that MY3 could increase intracellular accumulation of DOX and inhibit expression of P-gp at mRNA and protein levels. More importantly, MY3 significantly enhanced the efficacy of DOX against the tumor xenografts bearing MCF-7/DOX cells with the precondition of unchanged body weight. Therefore, MY3 might represent a promising lead to develop MDR reversal agents for cancer chemotherapy.

VB1 Promoted Green Synthesis of Chalcones and its Neuroprotection Potency Evaluation

For the first time, thiamine hydrochloride (VB1) has been employed as a catalyst for the synthesis of chalcones by metal-free Claisen–Schmidt condensation. Such an environmentally benign approach has several advantages such as a wide range of functional groups tolerance, a high yield of products, and the recoverability of this catalyst. Moreover, this unprecedented methodology enables the synthesis of the pharmaceutically important molecule 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone (3f) and its derivatives. Moreover, 3f and its derivatives were screened for their preliminary in vitro neuroprotective activity against oxygen-glucose deprivation/reoxygenation (OGD/R)-induced apoptosis in SH-SY5Y cell lines. Most of the compounds exhibited the neuroprotective activity, and one of the prepared chalcones (3s), which incorporates prenyl moiety, showed the most potency by decreasing the expression of cleaved caspase-3, cleaved caspase-9, Bax, and p53 protein.

Synthesis, cytotoxic activity and drug combination study of tertiary amine derivatives of 2′,4′-dihydroxyl-6′-methoxyl-3′,5′-dimethylchalcone

Tertiary amine derivative of DMC (2b) exhibited broad spectrum of cytotoxicity and strong synergism with Taxol® against HeLa/Tax cells.

Synthesis, Antiproliferative, and Multidrug Resistance Reversal Activities of Heterocyclic α,β-Unsaturated Carbonyl Compounds

A series of heterocyclic α,β-unsaturated carbonyl compounds (1a-1d, 2a-2d, 3a-3d, 4a-3d, and 5a-5d) with 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore were synthesized for the development of anticancer and multidrug resistance reverting agents. The antiproliferative activities were tested against nine human cancer cell lines. Approximately 73% of the IC50 values were below 5 μm, while 35% of these figures were submicromolar, and compounds 3a-3d with 4-trifluoro methyl in the arylidene benzene rings were the most potent, since their IC50 values are between 0.06 and 3.09 μm against all cancer cell lines employed. Meanwhile, their multidrug resistance reversal properties and cellular uptake were further examined. The data displayed that all of these compounds could reverse multidrug resistance, particularly, compounds 3a and 4a demonstrated both potent multidrug resistance reverting properties and strong antiproliferative activities, which can be taken as leading molecules for further research of dual effect agents in tumor chemotherapy.

Molecular targeted approaches to cancer therapy and prevention using chalcones

There is an emerging paradigm shift in oncology that seeks to emphasize molecularly targeted approaches for cancer prevention and therapy. Chalcones (1,3-diphenyl-2-propen-1-ones), naturally-occurring compounds with widespread distribution in spices, tea, beer, fruits and vegetables, consist of open-chain flavonoids in which the two aromatic rings are joined by a three-carbon α, β-unsaturated carbonyl system. Due to their structural diversity, relative ease of chemical manipulation and reaction of α, β-unsaturated carbonyl moiety with cysteine residues in proteins, some lead chalcones from both natural products and synthesis have been identified in a variety of screening assays for modulating important pathways or molecular targets in cancers. These pathways and targets that are affected by chalcones include MDM2/p53, tubulin, proteasome, NF-kappa B, TRIAL/death receptors and mitochondria mediated apoptotic pathways, cell cycle, STAT3, AP-1, NRF2, AR, ER, PPAR-γ and β-catenin/Wnt. Compared to current cancer targeted therapeutic drugs, chalcones have the advantages of being inexpensive, easily available and less toxic; the ease of synthesis of chalcones from substituted benzaldehydes and acetophenones also makes them an attractive drug scaffold. Therefore, this review is focused on molecular targets of chalcones and their potential implications in cancer prevention and therapy.

Dual role of 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone in inhibiting high-mobility group box 1 secretion and blocking its pro-inflammatory activity in hepatic inflammation

A previous study reported that 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC) had a potential hepatoprotective effect through preventing acute liver injury in mice. This study further evaluated the preventive effects of DMC on lipopolysaccharide (LPS)-stimulated hepatic inflammation and the underlying mechanism in liver macrophage. DMC significantly suppressed LPS-stimulated secretion and nucleocytoplasmic translocation of high-mobility group box 1 (HMGB1). DMC could dose-dependently reduce the phosphorylation of phosphatidylinositol 3-kinase (PI3K), protein kinase C alpha (PKCα), and phosphoinositide-dependent kinase 1 (PDK1). Furthermore, HMGB1 phosphorylation, the interaction between PKC and HMGB1, and the expression of HMGB1-dependent inflammation-related molecules were dose-dependently inhibited by DMC. Finally, DMC could target binding to the B box of HMGB1 by molecular modeling studies. All of these results indicated that DMC exhibited a potential protective effect against hepatitis probably via inhibiting HMGB1 secretion and blocking HMGB1 pro-inflammatory activity.

2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone promoted glucose uptake and imposed a paradoxical effect on adipocyte differentiation in 3T3-L1 cells

2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), one of the flavonoids isolated and purified from the dried flower buds of Cleistocalyx operculatus, was explored for its function in glucose uptake/glycogen synthesis in insulin-sensitive tissue cells and its effect and mechanism on 3T3-L1 preadipocyte differentiation. DMC (10 μM) treatment remarkably promoted glucose uptake in differentiated 3T3-L1 adipocytes (P < 0.05 vs control group), whereas the glucose uptake in L6 myoblasts and glycogen synthesis in HepG2 hepatocytes were not affected by the treatment. DMC had paradoxical effects on lipid accumulation in 3T3-L1 cells compared with differentiation control. High concentrations of DMC (10 and 20 μM) markedly diminished lipid accumulation; however, a low concentration of DMC (2.5 μM) enhanced lipid storage in 3T3-L1 cells (P < 0.01 vs differentiation control group), and 5 μM DMC did not impose a significant effect. It was demonstrated that the effect of DMC in lipid accumulation was controlled by the expression of PPAR-γ.

2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone protects the impaired insulin secretion induced by glucotoxicity in pancreatic β-cells

2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), which is isolated and purified from the dried flower buds of Cleistocalyx operculatus (Roxb.) Merr. et Perry (Myrtaceae), was investigated for its insulinotropic benefits against glucotoxicity using in vitro methods. When exposed to high glucose at the cytotoxicity level for 48 h, RIN-5F β-cells experienced a significant viability loss and impaired insulin secretion function, whereas cotreating with DMC could protect β-cells against glucotoxicity-induced decrease in glucose-stimulated insulin secretion in a dose-dependent manner without affecting basal insulin secretion. It was demonstrated that DMC increased insulin secretion against glucotoxicity by simulating the effect of GLP-1 and enhancing the expression of GLP-1R, followed by activating the signal pathway of PDX-1, PRE-INS, and GLUT2-GCK. Another mechanism was that DMC avoided the pancreatic islet dysfunction resulting from cellular damage by suppressing the production of nitric oxide (NO) by iNOS, and the expression of MCP-1. The results indicated the potential application of DMC in the intervention against glucotoxicity-induced hyperglycemia.

In vitro investigation of 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone for glycemic control

2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), a compound isolated and purified from the dried flower buds of Cleistocalyx operculatus (Roxb.) Merr. et Perry (Myrtaceae), was investigated for its glucose control benefits using in vitro methods. DMC showed strong noncompetitive (IC(50) of 43 μM) inhibition of pancreatic α-amylase; it was, however, ineffective against intestinal α-glucosidase. In addition, DMC exhibited remarkable glucose transport inhibition effects in both simulated fasting and fed states in Caco-2 cell monolayers (P < 0.05). Besides, exposure of MIN6 cells to 250 μM H(2)O(2) for 1 h caused a significant viability loss and insulin secretion reduction. Pretreatment of MIN6 cells with DMC for 2 h protected against the H(2)O(2)-induced decrease in glucose-stimulated insulin secretion in a dose-dependent manner and also enhanced the impaired basal insulin secretion. Such effects highlight the therapeutic potential of DMC in the management of hyperglycemia.

Protective effect against oxygen reactive species and skin fibroblast stimulation of Couroupita guianensis leaf extracts

In this study, hydroalcoholic leaf extracts of Couroupita guianensis were examined for antioxidant activity, phytochemical and total phenolic composition, stimulation of human skin fibroblast (HSF) proliferation and UV-absorption. The radical scavenging capacity, reducing power and protection against joint oxidation of linoleic acid and β-carotene bleaching oxidation in emulsion were used to evaluate the antioxidant activity. The results of this study strongly indicate in vitro antioxidant activity, which may be due to the presence of a high total phenolic content. In order to identify active principles, the extracts were submitted to fractionation and the compounds isolated were the flavonoids 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (1), 7-hydroxy-5-methoxy-6,8-dimethylflavanone (2) and the phenolic acid 4-hydroxybenzoic acid (3). In addition, a high level of stimulation of HSF proliferation and significant absorption of UV radiation were also observed. The results suggest that the hydroalcoholic leaf extracts of C. guianensis have promising skin care properties.