2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone, from buds of Cleistocalyx operculatus, induces apoptosis in human hepatoma SMMC-7721 cells through a reactive oxygen species-dependent mechanism

Discovery of amino acid-conjugated dimethylcardamonin analogues as potent anti-cervical cancer agents on SiHa cells targeting p53 signalling pathway

DMC (1) is a phytochemical found in the seeds of Syzygium nervosum, exhibiting anticancer activity in various cells through multiple pathways. Herein, the bioactivity of DMC (1) was enhanced by chemical modification through esterification, attaching fatty acid and amino acid moieties to yield 27 semi-synthetic derivatives. These compounds were evaluated for their in vitro cytotoxicity against three main types of cervical cancer cells, including SiHa, HeLa, and C-33A. As a result, the amino acid DMC derivative, 4´-(L-tyrosinyloxy)-DMC (7j), exhibited potent cytotoxicity against SiHa cells, which was approximately two-fold greater than that of 1. Further investigation into the mechanism of action of 7j was conducted, revealing its ability to induce cell cycle arrest and apoptosis. Gene expression analysis showed the downregulation of CDK2 and upregulation of the BAX/BCL2 ratio. Atomistic insight was studied on HPV 16 E6 via molecular dynamics simulation, revealing key interactions between tyrosinyl portion and C51 residue.

NRF2 Modulators of Plant Origin and Their Ability to Overcome Multidrug Resistance in Cancers

Cancer is one of the most common causes of death in the world. Despite the fact that there are many types of therapies available, cancer treatment remains a major challenge. The main reason for the ineffectiveness of chemotherapy is the acquisition of multidrug resistance (MDR) by cancer cells. One of the factors responsible for the acquisition of MDR is the NRF2 transcription factor, which regulates the expression of proteins such as HO-1, NQO1, MRP1, MRP2, and GST. In normal cells, NRF2 is the first line of defense against oxidative stress, thereby preventing carcinogenesis. Still, its hyperactivation in cancer cells causes them to acquire MDR, which significantly reduces or eliminates the effectiveness of chemotherapy. Considering the important role NRF2 plays in the acquisition of MDR, its modulators and, above all, inhibitors are being sought after, including among compounds of plant origin. NRF2 inhibition may prove to be a key element of anticancer therapy. This review summarizes the current state of knowledge about plant NRF2 inhibitors and presents the effects of their use in overcoming MDR in cancer.

Synthesis and biological evaluation of imidazolium conjugated with dimethylcardamonin (DMC) as a novel potential agent against MDA-MB-231 triple-negative breast cancer cells

A new imidazolium ionic liquid (IL) halide conjugated with dimethylcardamonin (DMC, 1), namely [Bbim]Br-DMC (3), was synthesised to improve the biological activity of the natural chalcone. DMC was isolated from seeds of Syzygium nervosum A. Cunn. ex DC. which was an effective anti-breast cancer agent. The compound 1 and 3 showed anticancer activity in MDA-MB-231 cells with IC50 values of 14.54 ± 0.99 μM and 7.40 ± 0.15 μM, respectively. MTT assay showed that compound 3 had cytotoxic effect at least two-fold greater than compound 1 but was low toxic to normal cells of Hs 578Bst. After 48 h, compound 3 at concentration of IC50 value inhibited the proliferation and induced morphological changes of MDA-MB-231 cells in a time-dependent manner. The cell cycle profile also showed that compound 3 exerted anti-proliferation activity with the cell cycle arrest at G0/G1 phase and compound 3 also induced apoptosis and reduced mitochondrial membrane potential in MDA-MB-231 cells in a dose-dependent manner. In gene expression assay, compound 3 up-regulated pro-apoptotic genes such as Bax and p53 and suppressed anti-apoptotic Bcl-2 whereas there was no effect on DNA repair gene such as PARP1. The Bax/Bcl-2 ratio was significantly increased after treated with compound 3. In the molecular docking study, the interactions between compound 3 and B-DNA structure in the minor groove region via hydrogen bonds was reported. In conclusion, [Bbim]Br-DMC or compound 3 is a potential candidate to induce apoptosis and inhibits proliferation via cell cycle arrest and decreases mitochondrial membrane of triple-negative breast cancer MDA-MB-231 cells.

Cancer Chemopreventive Effect of 2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone on Diethylnitrosamine-Induced Early Stages of Hepatocarcinogenesis in Rats

2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC) is a major compound in Cleistocalyx nervosum seed extract (CSE), which has been reported to have various biological activities, including anti-cancer activity. Therefore, this study attempted to evaluate whether DMC is a chemopreventive compound in CSE. Moreover, the preventive mechanisms of CSE and DMC in the DEN-induced early stages of hepatocarcinogenesis in rats were investigated. Male Wistar rats were intraperitoneally injected with DEN 50 mg/kg bw once a week for 8 weeks. Rats received CSE and DMC orally throughout the experiment. The number of glutathione S-transferase placental form (GST-P)-positive foci in the liver was measured. Furthermore, the preventive mechanisms of CSE and DMC on DEN-induced HCC, including cell proliferation and apoptosis, were investigated. Administering CSE at a dosage of 400 mg/kg bw and DMC at a dosage of 10 mg/kg bw significantly decreased the number and size of GST-P-positive foci and GST-P expression. In addition, DMC inhibited the development of preneoplastic lesions by decreasing cell proliferation and causing cell apoptosis; however, CSE inhibited the development of preneoplastic lesions by inducing cell apoptosis. In conclusion, DMC exhibited a cancer chemopreventive effect on the early stages of hepatocarcinogenesis by increasing cell apoptosis and reducing cell proliferation.

2',4'-Dihydroxy-6'‑methoxy-3',5'-dimethylchalcone and its amino acid-conjugated derivatives induce G0/G1 cell cycle arrest and apoptosis via BAX/BCL2 ratio upregulation and in silico insight in SiHa cell lines

We modified the chemical structure of 2',4'-dihydroxy-6'‑methoxy-3',5'-dimethylchalcone (DMC, 1), a phytochemical found in the seed of Syzygium nervosum A.Cunn. ex DC., by conjugation with the amino acid L-alanine (compound 3a) or L-valine (compound 3b) to enhance anticancer activity and water solubility. Compounds 3a and 3b had antiproliferative activity in human cervical cancer cell lines (C-33A, SiHa and HeLa), with half-maximal inhibitory concentrations (IC₅₀) of 7.56 ± 0.27 and 8.24 ± 0.14 µM, respectively in SiHa cells; these values were approximately two-fold greater than DMC. We investigated the biological activities of compounds 3a and 3b based on a wound healing assay, a cell cycle assay and messenger RNA (mRNA) expression analysis to determine the possible mechanism of anticancer activity. Compounds 3a and 3b inhibited SiHa cell migration in the wound healing assay. After treatment with compounds 3a and 3b, there was an increase in SiHa cells in the G1 phase, indicative of cell cycle arrest. Moreover, compound 3a showed potential anticancer activity by upregulating TP53 and CDKN1A that resulted in upregulation of BAX and downregulation of CDK2 and BCL2, leading to apoptosis and cell cycle arrest. The BAX/BCL2 expression ratio was increased after treatment with compound 3avia the intrinsic apoptotic pathway. In silico molecular dynamics simulation and binding free energy calculation shed light on how these DMC derivatives interact with the HPV16 E6 protein, a viral oncoprotein associated with cervical cancer. Our findings suggest that compound 3a is a potential candidate for anti-cervical cancer drug development.

Dimethyl Cardamonin from Fruits of Campomanesia reitziana D. Legrand Promotes Gastroprotection and Gastric Healing Effects in Rodents

Campomanesia reitziana D. Legrand (Myrtaceae) displays antiulcer properties when given to rodents. The major active chemical components of C. reitziana are chalcones, including 4',6'-dihydroxy-2'-methoxy-3',5'-dimethylchalcone or dimethyl cardamonin (DMC); therefore, we hypothesized that this compound could have antiulcer effects and the present study aimed to evaluate its gastroprotective and gastric healing properties. DMC was isolated from the fruits of C. reitziana, and its gastroprotective effect was evaluated by ethanol and indomethacin-induced gastric ulcer models in mice (0.1 mg/kg, i.p. and 1 and 3 mg/kg, p.o.). Oxidative stress and inflammatory parameters were analyzed in the gastric tissue. Moreover, its gastric healing effect was evaluated in rats. In addition, the compound's mode of action was evaluated in vivo and in vitro by measuring H⁺ -K⁺ -ATPase activity. Finally, the cytotoxic potential of DMC was tested in fibroblasts and human gastric adenocarcinoma cells. The DMC reduced the ethanol-induced gastric ulcer in mice by 77 %, increased the adhered mucus, and reduced lipoperoxides levels. The block of nonprotein sulfhydryls (NP-SH) compounds by pretreatment with N-ethylmaleimide (NEM), the inhibition of nitric oxide synthase with Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME), or the antagonism of α₂ receptor using yohimbine reversed the gastroprotective effects of DMC. Furthermore, DMC reduced the acidity of gastric content in pylorus-ligated rats but did not change H⁺ , K⁺ -ATPase (isolated from rabbit) activity in vitro. DMC reduced the lesion area in acetic acid-induced ulcers and decreased myeloperoxidase activity. DMC did not change the viability of fibroblast cells (L929) but reduced the viability of human gastric adenocarcinoma cells (AGS). The results confirmed that DMC could significantly enhance the gastric healing process and prevent ulcers due to improving protective factors on the gastric mucosa and reducing gastric acid secretion.

Effects of 2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone from Syzygium nervosum Seeds on Antiproliferative, DNA Damage, Cell Cycle Arrest, and Apoptosis in Human Cervical Cancer Cell Lines

2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), a natural product derived from Syzygium nervosum A. Cunn. ex DC., was investigated for its inhibitory activities against various cancer cell lines. In this work, we investigated the effects of DMC and available anticervical cancer drugs (5-fluorouracil, cisplatin, and doxorubicin) on three human cervical cancer cell lines (C-33A, HeLa, and SiHa). DMC displayed antiproliferative cervical cancer activity in C-33A, HeLa, and SiHa cells, with IC50 values of 15.76 ± 1.49, 10.05 ± 0.22, and 18.31 ± 3.10 µM, respectively. DMC presented higher antiproliferative cancer activity in HeLa cells; therefore, we further investigated DMC-induced apoptosis in this cell line, including DNA damage, cell cycle arrest, and apoptosis assays. As a potential anticancer agent, DMC treatment increased DNA damage in cancer cells, observed through fluorescence inverted microscopy and a comet assay. The cell cycle assay showed an increased number of cells in the G0/G1 phase following DMC treatment. Furthermore, DMC treatment-induced apoptosis cell death was approximately three- to four-fold higher compared to the untreated group. Here, DMC represented a compound-induced apoptosis for cell death in the HeLa cervical cancer cell line. Our findings suggest that DMC, a phytochemical agent, is a potential candidate for antiproliferative cervical cancer drug development.

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.

Low-polar extract from seed of Cleistocalyx nervosum var. paniala modulates initiation and promotion stages of chemically-induced carcinogenesis in rats

BACKGROUND

Cleistocalyx nervosum var. paniala is a local fruit mainly cultivated in the north of Thailand. Our previous study has reported that the methanol extract of C. nervosum seed presented antimutagenicity in a Salmonella mutation assay. The present study focused on the effect of a low-polar extract of C. nervosum seed on the early stages of diethylnitrosamine (DEN)- and dimethylhydrazine (DMH)-induced carcinogenesis in rats.

METHODS

Dried C. nervosum seed powder was extracted using dichloromethane. To study its effect on the initiation stage of carcinogenesis of rats, they were fed with various doses of C. nervosum seed extract (CSE) for 21 days. DEN injection was used to initiate hepatocarcinogenesis and partial hepatectomy was performed to amplify mutated hepatocytes resulting in micronucleated hepatocyte formation. To study the role of CSE on the promotion stage, rats were injected with DEN and DMH to induce preneoplastic lesions and the numbers of glutathione S-transferase placental form (GST-P) positive foci in the liver and aberrant crypt foci (ACF) in the colon were measured. This was followed by CSE administration for 10 weeks. The inhibitory mechanisms of CSE on initiation and promotion stages, including xenobiotic metabolism, cell proliferation and apoptosis, were investigated.

RESULTS

The total phenolic content in CSE was 80.34 ± 2.29 mg gallic acid equivalents (GAE) per g of extract and 2,4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone was found to be a major flavonoid. The main terpenoids in CSE were β-selinene, α-selinene, γ-selinene and o-cymene while 24(Z)-methyl-25-homocholesterol was a major phytosterol. CSE significantly decreased the number of micronucleated hepatocytes in DEN-initiated rats and enhanced the activities of hepatic glutathione S-transferase and UDP-glucuronyltransferase. Furthermore, the formation of preneoplastic lesions in the liver and colon was statistically reduced by CSE. CSE also diminished cell proliferation in the liver and colon indicated by the number of PCNA positive cells. However, CSE did not alter the numbers of apoptotic hepatocytes and colonocytes in DEN- and DMH-initiated rats.

CONCLUSIONS

The dichloromethane extract of C. nervosum seed demonstrated chemopreventive effects on chemically-induced carcinogenesis in both initiation and promotion stages in rats. The inhibitory mechanism might be involved in the modulation of hepatic detoxifying enzymes and suppression of hepatocyte and colonocyte proliferation.

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.

The Effects of 2',4'-Dihydroxy-6'-methoxy-3',5'- dimethylchalcone from Cleistocalyx operculatus Buds on Human Pancreatic Cancer Cell Lines

2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), a principal natural chalcone of Cleistocalyx operculatus buds, suppresses the growth of many types of cancer cells. However, the effects of this compound on pancreatic cancer cells have not been evaluated. In our experiments, we explored the effects of this chalcone on two human pancreatic cancer cell lines. A cell proliferation assay revealed that DMC exhibited concentration-dependent cytotoxicity against PANC-1 and MIA PACA2 cells, with IC₅₀ values of 10.5 ± 0.8 and 12.2 ± 0.9 µM, respectively. Treatment of DMC led to the apoptosis of PANC-1 by caspase-3 activation as revealed by annexin-V/propidium iodide double-staining. Western blotting indicated that DMC induced proteolytic activation of caspase-3 and -9, degradation of caspase-3 substrate proteins (including poly[ADP-ribose] polymerase [PARP]), augmented bak protein level, while attenuating the expression of bcl-2 in PANC-1 cells. Taken together, our results provide experimental evidence to support that DMC may serve as a useful chemotherapeutic agent for control of human pancreatic cancer cells.

Antiproliferative Activity of Extracts of Campomanesia adamantium (Cambess.) O. Berg and Isolated Compound Dimethylchalcone Against B16-F10 Murine Melanoma

Campomanesia adamantium, a native species of the Brazilian Cerrado, is characterized as a natural source of phenolic compounds and has known potential anticancer activities. This study aimed to evaluate the chemical profile of dichloromethane extracts of pulp (DEGPU) and peel (DEGPE) from the fruits of C. adamantium and to identify compounds with antiproliferative effects in vitro against melanoma cells by sulforhodamine B (SRB) assay, apoptosis induction assay, caspase-3 activation assay, nitric oxide (NO) release in coculture of B16-F10 cells and murine peritoneal macrophages. The chemical profiles of DEGPU and DEGPE were analyzed by high performance liquid chromatography coupled to diode array detector and mass spectrometer using the electrospray ionization interface (HPLC-DAD-ESI-MS/MS). Thirteen compounds were identified in both extracts and the chromatographic study of the most active extract in SRB assay DEGPU (GI₅₀ of 16.17 μg/mL) resulted in the isolation of seven compounds. The isolated compound dimethylchalcone (DMC) had the highest antiproliferative activity against B16-F10 with a GI₅₀ of 7.11 μg/mL. DEGPU extract activated caspase-3 in 29% of cells at 25 μg/mL and caused a 50% decrease in NO release in coculture. DEGPU can be characterized as a source of bioactive compounds such as DMC, as seen from its antiproliferative effect in vitro by inducing B16-F10 cells to undergo apoptosis, essential feature in the search for new anticancer drugs.