Inhibitory effects of 3'-methyl-3-hydroxy-chalcone on proliferation of human malignant tumor cells and on skin carcinogenesis

Natural and Synthetic Chalcones: Potential Impact on Breast Cancer

Chalcones are small molecules, naturally found in fruits and vegetables, and exhibit diverse pharmacological activities. They also possess anticancer activity against different tumors. They can be converted into numerous derivatives by modifying hydrogen moieties, enabling the exploration of their diverse anticancer potentials. The main aims are to provide valuable insights into the recent progress made in utilizing chalcones and their derivatives as agents against breast cancer while delivering their underlying molecular mechanisms of action. This review presents anticancer molecular mechanisms and signaling pathways modulated by chalcones. Furthermore, it helps in the understating of the precise mechanisms of action and specific molecular targets of chalcones and their synthetic derivatives for breast cancer treatment.

Synthesis, spectroscopic (FT-IR, FT-Raman, NMR & UV-Vis), reactive (ELF, LOL, Fukui), drug likeness and molecular docking insights on novel 4-[3-(3-methoxy-phenyl)-3-oxo-propenyl]-benzonitrile by experimental and computational methods

The spectroscopic analysis such as FT-IR, FT-Raman, UV-Vis and NMR are conducted for the synthesized molecule by both experimental and theoretical approach. The theoretical computations were achieved by DFT method with B3LYP functional and 6-311 ++ G (d, P) basis set. Firstly the geometrical parameters obtained by DFT are compared with the related experimental parameters. Experimental FT-IR and FT-Raman spectra of the title molecule have been acquired. The vibrational analysis is conducted and the assignments concerned to the observed bands are mentioned through the potential energy distribution (PED). The GIAO method was employed for theoretical NMR analysis and the results are compared with experimental chemical shifts. In accumulation to these analyses NLO, NBO, FMO and MEP analysis have been conducted to understand the nature of the molecule. ELF and LOL were performed. The drug likeness and molecular docking studies also conducted. The potency of inhibition of molecule against MPRO and PLPRO receptors has been performed using molecular docking studies.

Synthesis and evaluation of modified chalcone based p53 stabilizing agents

Tumor suppressor protein p53 induces cell cycle arrest and apoptotic cell death in response to various cellular stresses thereby preventing cancer development. Activation and stabilization of p53 through small organic molecules is, therefore, an attractive approach for the treatment of cancers retaining wild-type p53. In this context, a series of nineteen chalcones with various substitution patterns of functional groups including chloro, fluoro, methoxy, nitro, benzyloxy, 4-methyl benzyloxy was prepared using Claisen-Schmidt condensation. The compounds were characterized using NMR, HRMS, IR and melting points. Evaluation of synthesized compounds against human colorectal (HCT116) and breast (CAL-51) cancer cell lines revealed potent antiproliferative activities. Nine compounds displayed GI₅₀ values in the low micromolar to submicromolar range; for example (E)-1-phenyl-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one (SSE14108) showed GI₅₀ of 0.473±0.043µM against HCT116 cells. Further analysis of these compounds revealed that (E)-3-(4-chlorophenyl)-1-phenylprop-2-en-1-one (SSE14105) and (E)-3-(4-methoxyphenyl)-1-phenylprop-2-en-1-one (SSE14106) caused rapid (4 and 8-h post-treatment) accumulation of p53 in HCT116 cells similar to its induction by positive control, Nutlin-3. Such activities were absent in 3-(4-methoxyphenyl)propiophenone (SSE14106H2) demonstrating the importance of conjugated ketone for antiproliferative and p53 stabilizing activity of the chalcones. We further evaluated p53 levels in the presence of cycloheximide (CHX) and the results showed that the p53 stabilization was regulated at post-translational level through blockage of its degradation. These chalcones can, therefore, act as fragment leads for further structure optimization to obtain more potent p53 stabilizing agents with enhanced anti-proliferative activities.

Syntheses and in Vitro Antiplasmodial Activity of Aminoalkylated Chalcones and Analogues

A series of readily synthesized and inexpensive aminoalkylated chalcones and diarylpropane analogues (1-55) were synthesized and tested against chloroquinone-sensitive (D10 and NF54) and -resistant (Dd2 and K1) strains of Plasmodium falciparum. Hydrogenation of the enone to a diarylpropane moiety increased antiplasmodial bioactivity significantly. The influence of the structure of the amine moiety, A-ring substituents, propyl vs ethyl linker, and chloride salt formation on further enhancing antiplasmodial activity was investigated. Several compounds have IC₅₀ values similar to or better than chloroquine (CQ). The most active compound (26) had an IC₅₀ value of 0.01 μM. No signs of resistance were detected, as can be expected from compounds with structures unrelated to CQ and other currently used antimalarial drugs. Toxicity tests (in vitro CHO cell assay) gave high SI indices.

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.

Anti-cancer chalcones: Structural and molecular target perspectives

Chalcone or (E)-1,3-diphenyl-2-propene-1-one scaffold remained a fascination among researchers in the 21st century due to its simple chemistry, ease of synthesis and a wide variety of promising biological activities. Several natural and (semi) synthetic chalcones have shown anti-cancer activity due to their inhibitory potential against various targets namely ABCG2/P-gp/BCRP, 5α-reductase, aromatase, 17-β-hydroxysteroid dehydrogenase, HDAC/Situin-1, proteasome, VEGF, VEGFR-2 kinase, MMP-2/9, JAK/STAT signaling pathways, CDC25B, tubulin, cathepsin-K, topoisomerase-II, Wnt, NF-κB, B-Raf and mTOR etc. In this review, a comprehensive study on molecular targets/pathways involved in carcinogenesis, mechanism of actions (MOAs), structure activity relationships (SARs) and patents granted have been highlighted. With the knowledge of molecular targets, structural insights and SARs, this review may be helpful for (medicinal) chemists to design more potent, safe, selective and cost effective anti-cancer chalcones.

Chemical constituents from the rhizomes of Smilax glabra and their antimicrobial activity

Six new phenolic compounds, named smiglabrone A (1), smiglabrone B (2), smilachromanone (3), smiglastilbene (4), smiglactone (5), smiglabrol (6), together with fifty-seven known ones 7–63were isolated from the rhizomes of Smilax glabra. Their structures were elucidated on the basis of extensive spectroscopic analyses, as well as by comparison with literature data. Twenty-seven of these compounds were obtained from and identified in the genus Smilax for the first time. The absolute configuration of (2S)-1,2-O-di-trans-p-coumaroylglycerol (43) was determined for the first time using the exciton-coupled circular dichroism (ECCD) method. Thirty isolated compounds were evaluated for their antimicrobial activity against three Gram-negative bacteria, three Gram-positive bacteria and one fungus, and the corresponding structure-activity relationships were also discussed. Eighteen compounds were found to be antimicrobial against the microorganisms tested and the minimum inhibitory concentrations (MIC) were in the range of 0.0794–3.09 mM. Among them, compound 1 showed antimicrobial activity against Canidia albicans with MIC value of 0.146 mM, which was stronger than cinchonain Ia with an MIC of 0.332 mM. Compounds 3 and 4 exhibited inhibitory activity against Staphylococcus aureus with MIC values of 0.303 and 0.205 mM, respectively. The results indicated that these antimicrobial constituents of this crude drug might be responsible for its clinical antimicrobial effect.

Synthesis of (±)-Pisonivanone and Other Analogs as Potent Antituberculosis Agents

A new class of alkylated chalcones and flavanones was synthesised and screened for antituberculosis, antixoidant, and cytotoxic activities. The desired compounds were synthesised using methyl substituted 2-hydroxyacetophenone as a key intermediate. The acetophenone derivative having methyl substitution was prepared in turn from methtylated phloroglucinol by formylation (by Vilsmeier-Haack reaction), followed by reduction with Wolf-Kishnner approach, and finally acetylation was involved. Among 17 compounds, compound5and compound4ainhibitedM. tuberculosisat minimum inhibitory concentration (MIC) in the range between 25 μg/mL and 50 μg/mL. The remaining other 15 compounds also potently inhibitedM. tuberculosisat MIC in range between 50 μg/mL and 100 μg/mL. Some of these compounds also showed moderate antioxidant and cytotoxic activities.

Induction of apoptosis and cell cycle arrest in L-1210 murine lymphoblastic leukaemia cells by (2E)-3-(2-naphthyl)-1-(3'-methoxy-4'-hydroxy-phenyl)-2-propen-1-one

OBJECTIVES

New compounds with biological targets and less cytotoxicity to normal cells are necessary for cancer therapy. In this work ten synthetic chalcones derived from 2-naphtaldehyde were evaluated for their cytotoxic effect in murine acute lymphoblastic leukemia cells L-1210.

METHODS

A series of ten chalcones derived from 2-naphtaldehyde and corresponding acetophenones were prepared by aldolic condensation, using methanol as solvent under basic conditions, at room temperature for 24 h. The cell viability was determined by MTT colorimeter method. The cell cycle phase analysis was carried out by flow cytometry after propidium iodide staining. The apoptosis induction was assessed by exposure to phosphatidylserine (ANNEXIN V-FITC). Cytometric analysis was performed to evaluate the expression of p53, Bcl-2 and Bax protein. The caspase-3 expression was studied by immunoblotting analysis.

KEY FINDINGS

A preliminary screening of a series of ten chalcones derived from 2-naphtaldehyde showed that chalcone 8, (2E)-3-(2-naphtyl)-1-(3'-methoxy-4'-hydroxy-phenyl)-2-propen-1-one, had the highest cytotoxic effect (IC50 of 54 microM), but not in normal human lymphocytes. To better understand the cytotoxic mechanism of chalcone 8, its effect on cell cycle and apoptosis was assessed. Our results showed that chalcone 8 caused cell cycle arrest in the G2/M phase and a significant increase in the proportion of cells in the subG0/G1 phase. Our results also demonstrated that chalcone 8 promoted a modification in Bax:Bcl-2 ratio and increased p53 expression and caspase-3 activation.

CONCLUSIONS

The studied chalcone 8 has cytotoxic effect against L-1210 lymphoblastic leukaemic cells, and this effect is associated with increase of p-53 and Bax expression.

Antioxidant and anticancer activity of 3‘-formyl-4’, 6‘-dihydroxy-2’-methoxy-5‘-methylchalcone and (2S)-8-formyl-5-hydroxy-7-methoxy-6-methylflavanone

Two new flavonoids - 3′-formyl-4′,6′-dihydroxy-2′-methoxy-5′-methylchalcone (FMC) and (2S)-8-formyl-5-hydroxy-7-methoxy-6-methylflavanone (FMF) - isolated from the buds of Cleistocalyx operculatus, were investigated for their antioxidant and anticancer activity. Total antioxidant activity and reducing ability were measured. 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and superoxide anion radical scavenging assays were carried out to evaluate the antioxidant potential of the two compounds. The antioxidant activity of the two compounds increased in a concentration-dependent manner. FMC and FMF at a concentration of 500 μM inhibited lipid peroxidation by 64.3 ± 2.5% and 60.3 ± 2.3%, respectively, an antioxidant activity approximately similar to that of 500 μM α-tocopherol (66.3 ± 2.5%). Similarly, the effect of FMC and FMF on reducing power increased in a concentration-dependent manner. In DPPH radical scavenging assays, the IC50 values of FMC and FMF were 50.2 ± 2.8 μM and 75.8 ± 2.5 μM, respectively. Moreover, FMC and FMF scavenged the superoxide generated by the phenazine methosulfate (PMS)/reduced β-nicotinamide adenine dinucleotide (NADH) nitroblue tetrazolium (NBT) system, with IC50 values of 56.3 ± 2.3 μM and 317.5 ± 2.9 μM, respectively. The anticancer activity of the two compounds were determined in five human cancer cell lines, SMMC-7721 (liver cancer), 8898 (pancreatic cancer), K562 (chronic leukaemia), HeLa (tumour of cervix uteri) and 95-D (high metastic lung carcinoma). FMC and FMF showed broad-spectrum anticancer activity against all the human cancer cell lines tested. The results obtained in the current study indicate that the two flavonoids could be a potential source of natural antioxidant and anticancer agents. To our knowledge, this is the first report on bioactivity of FMC and FMF.

Emerging role of Garcinol, the antioxidant chalcone from Garcinia indica Choisy and its synthetic analogs

Garcinol, harvested from Garcinia indica, has traditionally been used in tropical regions and appreciated for centuries; however its biological properties are only beginning to be elucidated. There is ample data to suggest potent antioxidant properties of this compound which have been used to explain most of its observed biological activities. However, emerging evidence suggests that garcinol could be useful as an anti-cancer agent, and it is increasingly being realized that garcinol is a pleiotropic agent capable of modulating key regulatory cell signaling pathways. Here we have summarized the progress of our current research knowledge on garcinol and its observed biological activities. We have also provided an explanation of observed properties based on its chemical structure and provided an insight into the structure and properties of chalcones, the precursors of garcinol. The available data is promising but more detailed investigations into the various properties of this compound, particularly its anti-cancer activity are urgently needed, and it is our hope that this review will stimulate further research for elucidating and appreciating the value of this nature's wonder agent.

Targeting protein-protein interactions: lessons from p53/MDM2

The tremendous challenge of inhibiting therapeutically important protein-protein interactions has created the opportunity to extend traditional medicinal chemistry to a new class of targets and to explore nontraditional strategies. Here we review a widely studied system, the interaction between tumor suppressor p53 and its natural antagonist MDM2, for which both traditional and nontraditional approaches have been reported. This system has been a testing ground for novel proteomimetic scaffold-based strategies, i.e., for attempts to mimic the recognition surface displayed by a folded protein with unnatural oligomers. Retroinverso peptides, peptoids, terphenyls, beta-hairpins, p-oligobenzamides, beta-peptides, and miniproteins have all been explored as inhibitors of the p53/MDM2 interaction, and we focus on these oligomer-based efforts. Traditional approaches have been successful as well, and we briefly review small molecule inhibitors along with other strategies for reactivation of the p53 pathway, for comparison with oligomer- based approaches. We close with comments on an emerging dichotomy among protein-protein interaction targets.

Highly active anticancer curcumin analogues

Curcumin, a compound in the human food supply, represents a near-perfect starting point for drug discovery. Consequently, a number of research groups have taken the natural product as a starting point to prepare and biologically evaluate a wide variety of curcumin analogues. One widely used structural modification truncates the central conjugated beta-diketone in curcumin to the monocarbonyl dienone. A diverse array of the latter compounds exhibit cytotoxicities against an equally diverse set of cancer-related cell lines. Importantly, these compounds still retain toxicity profiles in rodents comparable to the parent natural product, whereas some analogues (e.g., EF-24, 41) exhibit good oral bioavailability and good pharmacokinetics in mice. Thiol conjugates of EF-24 analogues have been prepared that address stability and solubility issues while demonstrating cellular activities similar to the unmodified dienones. In parallel experiments, the factor VIIa-tissue factor complex (fVIIa-TF) has been exploited to develop a targeting strategy for the analogues. In particular, the EF24-FFRck-fVIIa protein conjugate is not only somewhat more effective relative to the drug alone against breast cancer and melanocyte cells. Both simple curcumin analogues and the protein conjugate evidence antiangiogenic activity in cell culture. The implication is that the fVIIa-TF targeting process, like the dienone drugs, permits a double-pronged attack with the potential to destroy a tumor directly by apoptosis.

Cytostatic activity of novel 4′-aminochalcone-based imides

A series of nine 1-(4-((E)-3-arylacryloyl)phenyl)-1H-pyrrole-2,5-diones 3a-i (4'-aminochalcone-based maleimides) was synthesized as candidate cytotoxic agents. The efficacy of these potential cytotoxics were evaluated against three representative cell lines and more than half of the drug candidates proved to exhibit significant cytostatic activity in vitro. QSAR studies using statistical analyses on several physicochemical parameters and IC50 values resulted in a few very important correlations which will aid in later the amplification of the project. Representative test compounds were well tolerated by mice in in vivo survival and toxicity studies.

A boronic-chalcone derivative exhibits potent anticancer activity through inhibition of the proteasome

Chalcones and their derivatives have been shown to have potent anticancer activity. However, the exact mechanisms of cytotoxic activity remain to be established. In this study, we have evaluated a series of boronic chalcones for their anticancer activity and mechanisms of action. Among the eight chalcone derivatives tested, 3,5-bis-(4-boronic acid-benzylidene)-1-methyl-piperidin-4-one (AM114) exhibited most potent growth inhibitory activity with IC50 values of 1.5 and 0.6 microM in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and colony formation assay, respectively. The cytotoxic activity of AM114 was shown to be associated with the accumulation of p53 and p21 proteins and induction of apoptosis. Mechanistic studies showed that AM114 treatment inhibited the chymotrypsin-like activity of the 20S proteasome in vitro, leading to a significant accumulation of ubiquitinated p53 and other cellular proteins in whole cells. In vitro studies showed that AM114 did not significantly disrupt the interaction of p53 and murine double minute 2 protein. It is noteworthy that AM114 as a single agent was preferentially toxic to cells with wild-type p53 expression, whereas combination of this compound with ionizing radiation (IR) significantly enhanced the cell-killing activity of IR in both wild-type p53 and p53-null cells. Together, these results indicate that the boronic chalcone derivative AM114 induces significant cytotoxic effect in cancer cells through the inhibition of the cellular proteasome and provide a rationale for the further development of this class of compounds as novel cancer chemotherapeutic agents.

Synthesis and biological evaluation of chalcones and their derived pyrazoles as potential cytotoxic agents

A series of substituted chalcones and their corresponding pyrazoles were synthesized and evaluated for in vitro cytotoxic activity against a panel of human cancer cell lines. Out of 93 compounds screened, 8 compounds, 1s, 3i,j,n, 4i,j,n and 4s, showed marked activity. Compounds 4j,n and 4s were found to be the most promising in this study. SAR is also discussed.

In vivo antitumor activity by 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone in a solid human carcinoma xenograft model

Previously we have shown that 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), which is isolated from the buds of Cleistocalyx operculatus, significantly inhibits the growth of human liver cancer SMMC-7721 cells and is able to induce apoptosis of SMMC-7721 cells in vitro. Here we report the antitumor effects of DMC in vivo, using a solid human tumor xenograft mouse model using human liver cancer SMMC-7721 cells. The average tumor weights in the control group and in mice injected with 150 mg/kg DMC were 1.42+/-0.11 g and 0.59+/-0.12 g, respectively. Flow cytometric analysis of the tumor cell population demonstrated an aneuploid peak (representing 33.60+/-0.80% of the total in mice injected with 150 mg/kg DMC). To our knowledge, this is the first time that chalcone compounds have been applied to a human tumor xenograft model.

Induction of apoptosis in K562 human leukemia cells by 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone

2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), isolated from the buds of Cleistocalyx operculatus, was investigated in its cytotoxicity and anti-proliferation on K562 cell line. Our results revealed that the IC50 was equal to 14.2+/-0.45 microM and the EC50 was 3.3+/-0.14 microM. Staining with Hoechst 33258 showed fragmentation and condensation of chromatin in the cells treated with 8 microM DMC for 48 h. Flow cytometric analysis was performed to determine hypodiploid cells. The results of flow cytometry assay indicated that the percentage of hypodiploid K562 cells was 76.15+/-3.22% after 48 h treatment with 16.0 microM DMC. The treatment resulted in the appearance of a hypodiploid peak (A0 region), probably due to the presence of apoptosing cells and/or apoptotic bodies with DNA content less than 2n. Western blot results illustrated that in the same dosage and incubation time, DMC could down-regulate the level of Bcl-2 protein and did not influence the expression of Bax protein. The resulting net effect could thus lead to a lower ratio of Bcl-2/Bax, which might be responsible for the DMC-induced apoptosis in K562 cells.

In vivo antitumor activity by 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone in a solid human carcinoma xenograft model

Previously, we showed that 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), isolated from the buds of Cleistocalyx operculatus, significantly inhibited the growth of human liver cancer SMMC-7721 cells and could induce SMMC-7721 cells apoptosis in vitro. Here, we report the antitumor effects of DMC in vivo, using a solid human tumor xenograft model with a human liver cancer SMMC-7721 cell line. Our results revealed that the average tumor weight in a control group and a 150-mg/kg DMC injection group was 1.42+/-0.11 g and 0.59+/-0.12 g, respectively. Flow cytometric analysis of the tumor cell population demonstrated the existence of an aneuploid peak (representing 33.60+/-0.80% of the total in the 150-mg/kg DMC injection group). To our knowledge, this is the first time that chalcone compounds were applied to a human tumor xenograft model.

In vitro anti-tumor activity of 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone against six established human cancer cell lines

2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), isolated from the buds of Cleistocalyx operculatus, was investigated in its cytotoxicity and its influence on six human cancer cell lines. Among SMMC-7721, 8898, HeLa, SPC-A-1, 95-D and GBC-SD cell lines, SMMC-7721 cells was the most sensitive one in these tested cell lines, with IC50 equal to 32.3 +/- 1.13 microM, EC50 equal to 9.00 +/- 0.36 microM and the therapeutic index equal to 3.59. Staining with Hoechst 33258 showed fragmentation and condensation of chromatin in the cells treated with 9 microM DMC for 48 h. Flow cytometric analysis was performed to determine hypodiploid cells. The results of flow cytometry assay indicated that the percentage of hypodiploid SMMC-7721 cells were 49.44 +/- 1.06% after 48 h treatment with 18.0 microM DMC. The treatment resulted in the appearance of a hypodiploid peak (A0 region), probably due to the presence of apoptosing cells and/or apoptotic bodies with DNA content less than 2n. To our knowledge, this is the first report on anti-tumor activity by DMC.

Molecular cytotoxic mechanisms of anticancer hydroxychalcones

Chalcones are being considered as anticancer agents as they are natural compounds that are particularly cytotoxic towards K562 leukemia or melanoma cells. In this study, we have investigated phloretin, isoliquiritigenin, and 10 other hydroxylated chalcones for their cytotoxic mechanisms towards isolated rat hepatocytes. All hydroxychalcones partly depleted hepatocyte GSH and oxidized GSH to GSSG. These chalcones also caused a collapse of mitochondrial membrane potential and increased oxygen uptake. Furthermore, glycolytic or citric acid cycle substrates prevented cytotoxicity and mitochondrial membrane potential collapse. The highest pKa chalcones were the most effective at collapsing the mitochondrial membrane potential which suggests that the cytotoxic activity of hydroxychalcones are likely because of their ability to uncouple mitochondria.

Antitumor agents. Part 202: novel 2'-amino chalcones: design, synthesis and biological evaluation

New 4',5',2,3,4-substituted 2'-amino chalcones were synthesized and evaluated for cytotoxicity against a panel of human tumor cell lines. Several compounds displayed significant cytotoxicity. The most promising lead molecule (10) also had high activity toward multi-drug resistant KB-VIN, and ovarian 1A9 cell lines. 2'-Amino chalcones demonstrated significantly increased antitumor activity compared with the corresponding chalcones, while, the epoxide derivatives generally showed greatly reduced activity.

Effects of Selaginella tamariscina on in vitro tumor cell growth, p53 expression, G1 arrest and in vivo gastric cell proliferation

Selaginella tamariscina, an oriental medicinal plant, was extracted using water and several organic solvents, and each fraction was assayed for its tumoricidal effects with 3-(4,5-dimethylthiazolyl)-2,5-diphenyltetrazolium bromide (MTT). Influences on expression of p53 tumor suppressor gene and induction of G1 arrest in the cell cycle were analyzed by Northern blotting and flow cytometry, respectively. The modifying effects of pulverized Selaginella tamariscina on cell turnover in the stomach were also investigated in rats given 150 mg/kg of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) by gavage and then fed a diet containing 5, 1 or 0% Selaginella tamariscina. Fractions I-V showed significant tumoricidal effects against cultured human leukemia cells whereas these fractions did not affect normal human lymphocytes. Among the effective fractions, the water-extracted fraction (V) efficiently increased p53 gene expression and induced G1 arrest. The 1% Selaginella tamariscina feeding caused a significant reduction (P < 0.05) in the proliferating cell nuclear antigen-(PCNA) labeling index of the glandular stomach epithelium as compared with the MNNG-alone group value although 5% Selaginella tamariscina feeding was only associated with a tendency for decrease. These results suggest that Selaginella tamariscina could be a candidate chemopreventive agent against gastric cancer.

Antiproliferative and cytotoxic effects of prenylated flavonoids from hops (Humulus lupulus) in human cancer cell lines

Six flavonoids [xanthohumol (XN), 2',4',6',4-tetrahydroxy-3'-prenylchalcone (TP); 2',4',6',4-tetrahydroxy-3'-geranylchalcone (TG); dehydrocycloxanthohumol (DX); dehydrocycloxanthohumol hydrate (DH); and isoxanthohumol (IX)] from hops (Humulus lupulus) were tested for their antiproliferative activity in human breast cancer (MCF-7), colon cancer (HT-29) and ovarian cancer (A-2780) cells in vitro. XN, DX and IX caused a dose-dependent (0.1 to 100 microM) decrease in growth of all cancer cells. After a 2-day treatment, the concentrations at which the growth of MCF-7 cells was inhibited by 50% (IC50) were 13.3, 15.7 and 15.3 microM for XN, DX and IX, respectively. After a 4-day treatment, the IC50 for XN, DX and IX were 3.47, 6.87 and 4.69 microM, respectively. HT-29 cells were more resistant than MCF-7 cells to these flavonoids. In A-2780 cells, XN was highly antiproliferative with IC50 values of 0.52 and 5.2 microM after 2 and 4 days of exposure, respectively. At 100 microM, all the hop flavonoids were cytotoxic in the three cell lines. Growth inhibition of XN- and IX-treated MCF-7 cells was confirmed by cell counting. XN and IX inhibited DNA synthesis in MCF-7 cells. As antiproliferative agents, XN (chalcone) and IX (flavanone isomer of XN) may have potential chemopreventive activity against breast and ovarian cancer in humans.

Cytotoxic activities of Mannich bases of chalcones and related compounds

Various Mannich bases of chalcones and related compounds displayed significant cytotoxicity toward murine P388 and L1210 leukemia cells as well as a number of human tumor cell lines. The most promising lead molecule was 21 that had the highest activity toward L1210 and human tumor cells. In addition, 21 exerted preferential toxicity to human tumor lines compared to transformed human T-lymphocytes. Other compounds of interest were 38, with a huge differential in cytotoxicity between P388 and L1210 cells, and 42, with a high therapeutic index when cytotoxicity to P388 cells and Molt 4/C8 T-lymphocytes were compared. In general, the Mannich bases were more cytotoxic than the corresponding chalcones toward L1210 but not P388 cells. A ClusCor analysis of the data obtained from the in vitro human tumor screen revealed that the mode of action of certain groups of compounds was similar. For some groups of compounds, cytotoxicity was correlated with the sigma, pi, or molar refractivity constants in the aryl ring attached to the olefinic group. In addition, the IC50 values in all three screens correlated with the redox potentials of a number of Mannich bases. X-ray crystallography and molecular modeling of representative compounds revealed various structural features which were considered to contribute to cytotoxicity. While a representative compound 15 was stable and unreactive toward glutathione (GSH) in buffer, the Mannich bases 15, 18, and 21 reacted with GSH in the presence of the pi isozyme of glutathione S-transferase, suggesting that thiol alkylation may be one mechanism by which cytotoxicity was exerted in vitro. Representative compounds were shown to be nonmutagenic in an intrachromosomal recombination assay in yeast, devoid of antimicrobial properties and possessing anticonvulsant and neurotoxic properties. Thus Mannich bases of chalcones represent a new group of cytotoxic agents of which 21 in particular serves as an useful prototypic molecule.

Chalcones, myo-inositol and other novel inhibitors of pulmonary carcinogenesis

The objective of the studies reported here has been to find novel chemopreventive agents effective against carcinogenesis of the lung. In particular, identification of suppressing agents, i.e., compounds preventing the evolution of the neoplastic process, has been sought. For this purpose, inhibition of pulmonary neoplasia in female A/J mice given the test agent starting one week after the last administration of three doses of benzo[a]pyrene has been employed as the experimental model. Under these conditions, chalcone, 4'-methoxychalcone,myo-inositol, dexamethasone, and "terpeneless" orange oil added to the diet suppressed pulmonary adenoma formation. Chalcone and 4'-methoxychalcone are open chain flavonoids, neither of these compounds occurs naturally, and their mechanism of action is not known. myo-Inositol is a naturally occurring compound of particular interest because of its exceedingly low toxicity. Dexamethasone is a potent glucocorticoid. Amongst its biological properties is the capacity to induce maturation of Type 2 alveolar cells and to stimulate production of surfactant by these cells. "Terpeneless" orange oil is a fraction of orange oil consisting predominantly of compounds with carbonyl or hydroxyl groups. The constituent or constituents responsible for the inhibitory effects observed is not known. The above studies are in an early phase of development and their ramifications remain to be determined.

Inhibition of carcinogen-induced pulmonary and mammary carcinogenesis by chalcone administered subsequent to carcinogen exposure

A study of the capacity of chalcone to inhibit benzo[alpha]pyrene(BP)-induced carcinogenesis of the lungs and forestomach in female A/J mice and N-methyl-N-nitrosourea (MNU)-induced mammary carcinogenesis in female Sprague-Dawley rats has been carried out. Chalcone, 5 mg/g of diet, had a inhibitory effect on pulmonary adenoma formation (29%) and on mammary tumor formation (49%) when the compound was fed starting one week after final carcinogen administration. Chalcone did not inhibit forestomach tumor formation. In an additional study, chalcone started 4 weeks after MNU and fed for 3-week courses alternating with 3-week courses of control diet for the duration of the protocol also inhibited mammary tumor formation by 49%. The data showing that chalcone has inhibitory effects against both pulmonary and mammary carcinogenesis when given after carcinogen administration provides the basis for further investigations of this and possibly other chalcones as chemopreventive suppressing agents.

Anti-tumorigenic chalcones

On the basis of our recent findings that licochalcone A isolated from Xin-jiang licorice showed anti-inflammatory and anti-tumorigenic activities, we synthesized more than 40 chalcone derivatives to examine their anti-tumorigenic activities. In vitro inhibitory activity against phosphorylation of phospholipids promoted by tetradecanoylphorbol-13-acetate (TPA) in HeLa cells was adopted as a screening test for anti-tumor-promoting effect. In vivo experimental mouse skin tumors initiated by dimethylbenz[a]-anthracene (DMBA) and promoted by TPA were used to test the anti-tumor-promoting effect of chalcones. In the results, 3'- and 4'-methyl-3-hydroxychalcone showed the highest potency in inhibiting tumorigenesis. They also showed a remarkable inhibitory effect on the proliferation of HGC-27 cells derived from human gastric cancer. We discuss the structure-activity relationship, including stereo-chemical phototransformation, of some chalcone derivatives with reference to their ultraviolet (UV) and nuclear magnetic resonance (NMR) spectroscopic data.