Synthesis and estrogen receptor binding affinities of 7-hydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-ones containing a basic side chain

Isolation and identification of three new chromones from the leaves of Pimenta dioica with cytotoxic, oestrogenic and anti-oestrogenic effects

CONTEXT

Pimenta dioica (L.) Merr. (Myrtaceae) is used in Costa Rican traditional medicine for women's health. Our previous work showed that P. dioica extracts were oestrogenic.

OBJECTIVES

This work identifies phytochemicals from P. dioica that are responsible for the plant's oestrogen-like activities.

MATERIALS AND METHODS

P. dioica leaves were collected in Costa Rica in 2005. Fractions resulting from chromatographic separation of a methanol extract were tested at 50 μg/mL in a competitive oestrogen receptor-binding assay. Active compounds were isolated by HPLC and identified by NMR and MS. Pure compounds were tested at 1 μM in the oestrogen-responsive SEAP reporter gene assay. The effects on cell viability, cytotoxicity and apoptosis were investigated in breast cancer (MCF-7 and SK-BR3) and gastric cancer (AGS and NCI-N87) cell lines using the ApoTox-Glo and Caspase-Glo assays and qPCR.

RESULTS

Quercitrin and three new chromones, including a 2-phenoxychromone, 6,8-di-C-methylcapillarisin (1) were isolated and identified. Compound 1 caused a 6.2-fold increase in SEAP expression at 1 μM (p < 0.05). This activity was blocked by the ER antagonist ICI 182,780. Compound 2 caused a 6.0-fold increase in SEAP, inhibited the growth of MCF-7, AGS and NCI-N87 cells (IC50 54.27, 38.13 and 51.22 μg/mL, respectively), and induced apoptosis via caspase 8 and increased the Bax/Bcl-2 mRNA ratio in MCF-7 cells. Compound 3 was anti-oestrogenic in MCF-7 cells.

DISCUSSION AND CONCLUSIONS

Compounds from P. dioica have oestrogenic, anti-oestrogenic and cytotoxic effects that may explain the ethnomedical use of this plant.

Synthesis and biological activity of 3-N-substituted estrogen derivatives as breast cancer agents

3-N-substituted-estrogen derivatives were synthesized and characterized. Their antiproliferative activities against human ER (+) MCF-7 (Breast), ER (-) MDA-MB-231 (breast) and Ishikawa (endometrial) cancer cell lines were determined after 72 hours drug exposure employing CellTiter-Glo assay at concentrations ranging from (0.01-100,000 nM). The antiproliferative activities of these compounds were compared to tamoxifen (TAM), 4-hydroxytamoxifen (4-OHT, active metabolite of tamoxifen) and raloxifene (RAL). In vitro results indicated that compound 5 (IC50 = 12 µM) displayed comparable antiproliferative activity against MDA-MB 231 cell line; while compounds 6, 7 and 13 (IC50 = 12 µM) displayed higher activity against MCF-7 and Ishikawa cell lines, in comparison to TAM activity (19-33 µM).

2,6-Bis-arylmethyloxy-5-hydroxychromones with antiviral activity against both hepatitis C virus (HCV) and SARS-associated coronavirus (SCV)

In this study, as a bioisosteric alternative scaffold of the antiviral aryl diketoacids (ADKs), we used 5-hydroxychromone on which two arylmethyloxy substituents were installed. The 5-hydroxychromones (5b–5g) thus prepared showed anti-HCV activity and, depending on the aromatic substituents on the 2-arylmethyloxy moiety, some of the derivatives (5b–5f) were also active against SCV. In addition, unlike the ADKs which showed selective inhibition against the helicase activity of the SCV NTPase/helicase, the 5-hydroxychromones (5b–5f) were active against both NTPase and helicase activities of the target enzyme. Among those, 3-iodobenzyloxy-substituted derivative 5e showed the most potent activity against HCV (EC₅₀ = 4 μM) as well as SCV (IC₅₀ = 4 μM for ATPase activity, 11 μM for helicase activity) and this might be used as a platform structure for future development of the multi-target or broad-spectrum antivirals.

One step synthesis of 2-hydroxymethylisoflavone and their osteogenic activity

An efficient one step synthesis of new 2-hydroxymethylisoflavone is reported. A series of deoxybenzoin was subjected to cyclization with glyoxal in the presence of basic condition (KOH/EtOH) to afford the 2-hydroxymethyl isoflavone. The structures of compounds 5a-g were confirmed by NMR experiments including (1)H, (13)C, HMBC, HSQC and COSY. These compounds were assessed for stimulation of osteoblast function using primary culture of rat calvarial osteoblasts in vitro. Compounds 5a, 5d, 5f and 5g were potent in stimulating differentiation of osteoblasts as assessed by measuring alkaline phosphatase (ALP) activity. Besides, effect of these analogs was also seen on the transcript levels of osteogenic genes like Runx-2, osteocalcin and Bone morphogenetic protein-2 (BMP-2), involved in osteoblast differentiation and mineralization. Based on quantitative PCR data, compound 5f was found to be the potent followed by 5d. Compound 5f robustly increased the mRNA levels of Runx-2 (8.0 fold), BMP-2 (∼2 fold) and osteocalcin (∼2.0 fold) in osteoblasts. Collectively, we demonstrate osteogenic activity of the novel 2-hydroxymethyl isoflavones with 5f having the most potent activity.

In-vitro antiproliferative activity of benzopyranone derivatives in comparison with standard chemotherapeutic drugs

The cytotoxic activities of five new benzopyranone derivatives containing basic amino side chain are described. Their cytotoxicities against ER(+) MCF-7 and ER(-) MDA-MB-231 human breast cancer cell lines, and Ishikawa human endometrial cell line were determined after 72 h drug exposure employing CellTiter-Glo assay at concentrations ranging from 0.01-1.0 × 10(5) nM. The antiproliferative activities of these compounds were compared to tamoxifen (TAM), 4-hydroxytamoxifen (4-OHT, active metabolite of tamoxifen), and raloxifene (RAL). In-vitro results indicated that compounds 9, 10, 12, and 13 were more potent than TAM against the human breast cancer cell lines with IC(50)  < 20 µM. The in-silico structure-activity relationships of these compounds and their binding mode within the estrogen receptor (ER) binding site using AutoDock vina are discussed.

7-Hydroxy-benzopyran-4-one derivatives: a novel pharmacophore of peroxisome proliferator-activated receptor alpha and -gamma (PPARalpha and gamma) dual agonists

Design, synthesis, and in vitro bioevaluation of a new class of potential dual PPARalpha and gamma agonists discovered through a structure-driven design paradigm are described. The 7-hydroxy-benzopyran-4-one moiety (includes flavones, flavanones, and isoflavones) is the key pharmacophore of these novel molecules, exhibiting similarity to the core structure of both fibrates and thiazolidinediones. New lead PPAR ligands were identified from "natraceuticals" and synthetic analogues. In total, 77 molecules, including chalcones, flavones, flavanones, isoflavones, and pyrazole derivatives, were screened and structure-activity relationship studies of the dual agonists undertaken. Compounds 68, 70, 72, and 76 were identified as novel and potent dual PPARalpha and gamma agonists. These novel molecules may have the potential to be the future leads in PPAR-related disorders, including type II diabetes mellitus and metabolic syndrome.

Evaluation of synthetic isoflavones on cell proliferation, estrogen receptor binding affinity, and apoptosis in human breast cancer cells

Natural isoflavones have demonstrated numerous pharmacological activities in breast cancer cells, including antiproliferative activities and binding affinities for estrogen receptors (ERs). Chemical modifications on the isoflavone ring system have been prepared and explored for the development of new therapeutics for hormone-dependent breast cancer. The antiproliferative actions of the synthesized isoflavones on MCF-7 and MDA-MB-231 breast cancer cells were examined, as well as cytotoxicity, interaction with estrogen receptors, and proapoptotic activity. The compounds were screened in the absence and in the presence of estradiol to evaluate whether or not estradiol could rescue cell proliferation on MCF-7 cells. Several compounds were able to inhibit cell proliferation in a dose-dependent manner, and compounds containing the bulky 7-phenylmethoxy substituent resulted in cell toxicity not only in MCF-7 cells but also in MDA-MB-231 cells. Selected synthetic isoflavones were able to bind to estrogen receptor with low affinity. Apoptotic pathways were also activated by these compounds in breast cancer cells. The majority of the compounds can bind to both ERs with low affinity, and their effects on hormone-independent breast cancer cells suggest that their ability to inhibit cell growth in breast cancer cells is not exclusively mediated by ERs. Thus, the synthetic trisubstituted isoflavones act on multiple signaling pathways leading to activation of mechanisms of cell-death and ultimately affecting breast cancer cell survival.

Synthesis and characterization of azole isoflavone inhibitors of aromatase

The synthesis and biological evaluation of a series of 2-azole and 2-thioazole isoflavones as potential aromatase inhibitors are described. Differences in inhibitory activity of triazole and imidazole inhibitors are rationalized with density functional theory to expose a key difference in the electronic structure of these molecules. In addition, difference binding spectra of inhibitors to immunoaffinity-purified aromatase produces classical Type II spectra consistent with coordination of the nitrogen lone pair electrons to the aromatase P450 heme.

Estrogen receptor ligands. Part 1: The discovery of flavanoids with subtype selectivity

A class of flavanoids exhibiting a high degree of selectivity for ERalpha over ERbeta has been discovered. The most active analogue 6 was found to be 66-fold ERalpha-selective and demonstrated uterine estradiol antagonism.

4-(4-Alkylpiperazin-1-yl)phenyl group: A novel class of basic side chains for selective estrogen receptor modulators

In the structure-activity relationships of spiro[indene-1,1'-indane] series, the 4-(4-alkylpiperazin-1-yl)phenyl group was found to be functionally equipotent to the 4-(1-piperidinoethoxy)phenyl group, the most widely used basic side chain in selective estrogen receptor modulators.