Studies on the anti-tumor activities of the soy isoflavone daidzein on murine neuroblastoma cells

Diversity and regioselectivity of O-methyltransferases catalyzing the formation of O-methylated flavonoids

Flavonoids and their methylated derivatives have immense market potential in the food and biomedical industries due to their multiple beneficial effects, such as antimicrobial, anti-inflammatory, and anticancer activities. The biological synthesis of flavonoids and their derivatives is often accomplished via the use of genetically modified microorganisms to ensure large-scale production. Therefore, it is pivotal to understand the properties of O-methyltransferases (OMTs) that mediate the methylation of flavonoids. However, the properties of these OMTs are governed by their: sources, substrate specificity, amino acid residues in the active sites, and the intricate mechanism. In order to obtain a clue for the selection of suitable OMTs for the biosynthesis of a target methylated flavonoid, we made a comprehensive review of the currently reported results, with a particular focus on their comparative regioselectivity for different flavonoid substrates. Additionally, the possible mechanisms for the diversity of this class of enzymes were explored using molecular simulation technology. Finally, major gaps in our understanding and areas for future studies were discussed. The findings of this study may be useful in selecting genes that encode OMTs and designing enzyme-based processes for synthesizing O-methylated flavonoids.

Identification and characterization of two Isatis indigotica O-methyltransferases methylating C-glycosylflavonoids

Isatis indigotica accumulates several active substances, including C-glycosylflavonoids, which have important pharmacological activities and health benefits. However, enzymes catalyzing the methylation step of C-glycosylflavonoids in I. indigotica remain unknown. In this study, three O-methyltransferases (OMTs) were identified from I. indigotica that have the capacity for O-methylation of the C-glycosylflavonoid isoorientin. The Type II OMTs IiOMT1 and IiOMT2 efficiently catalyze isoorientin to form isoscoparin, and decorate one of the aromatic vicinal hydroxyl groups on flavones and methylate the C6, C8, and 3'-hydroxyl positions to form oroxylin A, wogonin, and chrysoeriol, respectively. However, the Type I OMT IiOMT3 exhibited broader substrate promiscuity and methylated the C7 and 3'-hydroxyl positions of flavonoids. Further site-directed mutagenesis studies demonstrated that five amino acids of IiOMT1/IiOMT2 (D121/D100, D173/D149, A174/A150R, N200/N176, and D248/D233) were critical residues for their catalytic activity. Additionally, only transient overexpression of Type II OMTs IiOMT1 and IiOMT2 in Nicotiana benthamiana significantly increased isoscoparin accumulation, indicating that the Type II OMTs IiOMT1 and IiOMT2 could catalyze the methylation step of C-glycosylflavonoid, isoorientin at the 3'-hydroxyl position. This study provides insights into the biosynthesis of methylated C-glycosylflavonoids, and IiOMTs could be promising catalysts in the synthesis of bioactive compounds.

Investigation of inhibition effect of daidzein on osteosarcoma cells based on experimental validation and systematic pharmacology analysis

Objective

This study aims to explore the effect of daidzein, which is a natural isoflavone compound mainly extracted from soybeans, on osteosarcoma and the potential molecular mechanism.

Material and Methods

143B and U2OS osteosarcoma cells were treated with gradient concentrations of daidzein, and MTT assay was used to determine the cell proliferation capacity and IC₅₀. Hoechst 33342 staining and Annexin V-FITC/PI detection were used to determine apoptosis. Cell cycle was analyzed by flow cytometry, and migration ability were detected by transwell assays and scratch wound assay. An osteosarcoma xenograft mice model was applied to investigate the effect of daidzein on osteosarcoma in vivo. Systematic pharmacology and molecular modeling analysis were applied to predict the target of daidzein to osteosarcoma, and the target Src was verified by western blotting. We also observed the effect of daidzein on cell proliferation and apoptosis of Src-overexpressing osteosarcoma cells.

Results

In vitro, daidzein significantly inhibited 143B and U2OS osteosarcoma cell proliferation and migration, and induced cell cycle arrest. In vivo, daidzein exerts antitumor effects in osteosarcoma xenograft mice. After systematic screening and analysis, Src-MAPK signaling pathway was predicted as the highest-ranked pathway. Western blot demonstrated that daidzein inhibited phosphorylation of the Src-ERK pathway in osteosarcoma cells. Also, overexpression of Src could partially reverse the inhibitory effects of daidzein on osteosarcoma cell proliferation.

Conclusion

Daidzein exerts an antitumor effect on osteosarcoma, and the mechanism may be through the Src-ERK pathway.

Therapeutic Potential of Isoflavones with an Emphasis on Daidzein

Daidzein is a phytoestrogen isoflavone found in soybeans and other legumes. The chemical composition of daidzein is analogous to mammalian estrogens, and it could be useful with a dual-directional purpose by substituting/hindering with estrogen and estrogen receptor (ER) complex. Hence, daidzein puts forth shielding effects against a great number of diseases, especially those associated with the control of estrogen, such as breast cancer, diabetes, osteoporosis, and cardiovascular disease. However, daidzein also has other ER-independent biological activities, such as oxidative damage reduction acting as an antioxidant, immune regulator as an anti-inflammatory agent, and apoptosis regulation, directly linked to its potential anticancer effects. In this sense, the present review is aimed at providing a deepen analysis of daidzein pharmacodynamics and its implications in human health, from its best-known effects alleviating postmenopausal symptoms to its potential anticancer and antiaging properties.

Phytochemical profiling and cytotoxic evaluation of Premna serratifolia L. against human liver cancer cell line

Premna serratifolia L. (Lamiaceae) is a medicinal plant, widely distributed in the tropical and subtropical regions and commonly used in traditional medicine. The current study was focused to evaluate the cytotoxic potential of aqueous extract of root of P. serratifolia (AEPS) against human hepatoblastoma cancer cell line (Hep G2).The yield of the dried extract was 5.8% and used for further studies.Cytotoxic potential of AEPS was analyzed by MTT assay, which exhibits IC50 value 1000 µg/mL after 48 h incubation. Hoechst and AO/EtBr staining, ROS measurement, mitochondrial membrane potential, clonogenic and wound healing assays also confirmed the cytotoxic efficacy of AEPS in dose and time-dependent manner. UPLC-Q-TOF-MS/MS analysis of AEPS confirmed the presence of 12polyphenolic compounds, namely 4-hydroxy-3-methoxycinnamic acid, linarin, peonidin-3,5-O-di-beta-glucopyranoside, diosmin, trans-cinnamic acid, daidzein, saponarin, homoorietin, acacetin, sarsasapogenin, phytol and sissotrin. The cytotoxic potential of AEPS might due to presence of biologically active polyphenolic compounds.

Analysis of Flavonoid Metabolites in Chaenomeles Petals Using UPLC-ESI-MS/MS

Chaenomeles species are used for both ornamental decoration and medicinal purposes. In order to have a better understanding of the flavonoid profile of Chaenomeles, the petals of four Chaenomeles species, including Chaenomeles japonica (RB), Chaenomeles speciose (ZP), Chaenomeles sinensis (GP), and Chaenomeles cathayensis (MY), were selected as experimental material. The total flavonoid content of GP was found to be the highest, followed by MY, ZP, and RB. In total, 179 flavonoid metabolites (including 49 flavonols, 46 flavonoids, 19 flavone C-glycosides, 17 procyanidins, 15 anthocyanins, 10 flavanols, 10 dihydroflavonoids, 6 isoflavones, 5 dihydroflavonols, and 2 chalcones) were identified by Ultra-Performance Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometry. Screening of differential flavonoid metabolites showed that GP had higher levels of metabolites when compared with the other three Chaenomeles species. Annotation and enrichment analysis of flavonoid metabolites revealed that cyanidin 3,5-diglucoside and pelargonidin-3,5-diglucoside anthocyanins are likely responsible for the color differences of the four Chaenomeles petals. Additionally, a large number of flavonoids, flavonols, and isoflavones were enriched in the petals of GP. This study provides new insights into the development and utilization of Chaenomeles petals and provides a basis for future investigations into their utilization.

Daidzein cocrystals: An opportunity to improve its biopharmaceutical parameters

The present study involves the contribution of cocrystallization towards the modification of the biopharmaceutical parameters of poorly watersoluble plant-originated isoflavone, daidzein (DAID). The cocrystals were prepared with GRAS status coformers i.e., isonicotinamide, theobromine and cytosine using mechanochemical grinding and characterized by various analytical techniques (DSC, FT-IR, PXRD and solid-state NMR). Crystal structures were obtained from PXRD data using BIOVIA Materials Studio software and compared in terms of supramolecular motifs. An additional qualitative and quantitative insight into interactions between both components of the cocrystal illustrated the presence of OH⋯N and OH⋯O=C heterosynthons and revealed a stabilizing role of hydrogen bonding. The cocrystals were further evaluated for their solubility, intrinsic dissolution and in vivo profile. Solubility and dissolution studies of pure daidzein and its cocrystals, namely daidzein-isonicotinamide (DIS), daidzein-cytosine (DCYT) and daidzein-theobromine (DTB) exhibited an almost 2-fold improvement. Evaluation of maximum concentration (Cmax) of cocrystals reveals that the DIS cocrystal shows the highest Cmax of 1848.7 ng/ml followed by DCYT cocrystal (1614.9 ng/ml) and DTB cocrystal (1326.0 ng/ml) in comparison to DAID which has a Cmax 870.5 ng/ml. Each of these cocrystals showed significant enhancement in in vivo and in vitro activities in comparison to daidzein. Thus, this report suggests cocrystallization as a viable approach to resolve the solubility and bioavailability issues that circumvent the use of a therapeutically potential isoflavone, daidzein.

In Vitro Anti-Neuroblastoma Activity of Thymoquinone Against Neuro-2a Cells via Cell-cycle Arrest

We have recently shown that thymoquinone (TQ) has a potent cytotoxic effect and induces apoptosis via caspase-3 activation with down-regulation of XIAP in mouse neuroblastoma (Neuro-2a) cells. Interestingly, our results showed that TQ was significantly more cytotoxic towards Neuro-2a cells when compared with primary normal neuronal cells. In this study, the effects of TQ on cell-cycle regulation and the mechanisms that contribute to this effect were investigated using Neuro-2a cells. Cell-cycle analysis performed by flow cytometry revealed cell-cycle arrest at G2/M phase and a significant increase in the accumulation of TQ-treated cells at sub-G1 phase, indicating induction of apoptosis by the compound. Moreover, TQ increased the expression of p53, p21 mRNA and protein levels, whereas it decreased the protein expression of PCNA, cyclin B1 and Cdc2 in a dose- dependent manner. Our finding suggests that TQ could suppress cell growth and cell survival via arresting the cell-cycle in the G2/M phase and inducing apoptosis of neuroblastoma cells.

Endophytic Streptomyces sp. AC35, a producer of bioactive isoflavone aglycones and antimycins

In this research, a microbial endophytic strain obtained from the rhizosphere of the conifer Taxus baccata and designated as Streptomyces sp. AC35 (FJ001754.1 Streptomyces, GenBank) was investigated. High 16S rDNA gene sequence similarity suggests that this strain is closely related to S. odorifer. The major fatty acid profile of intracellular lipids was also carried out to further identify this strain. Atomic force microscopy and scanning acoustic microscopy were used to image our strain. Its major excreted substances were extracted, evaluated for antimicrobial activity, purified, and identified by ultraviolet-visible spectroscopy (UV-vis), liquid chromatography-mass spectrometry (LC-MS/MS) and nuclear magnetic resonance as the bioactive isoflavone aglycones-daidzein, glycitein and genistein. Batch cultivation, performed under different pH conditions, revealed enhanced production of antimycin components when the pH was stable at 7.0. Antimycins were detected by HPLC and identified by UV-vis and LC-MS/MS combined with the multiple reaction monitoring. Our results demonstrate that Streptomyces sp. AC35 might be used as a potential source of effective, pharmaceutically active compounds.

Methylation of flavonoids: Chemical structures, bioactivities, progress and perspectives for biotechnological production

Among the natural products, flavonoids have been particularly attractive, highly studied and become one of the most important promising agent to treat cancer, oxidant stress, pathogenic bacteria, inflammations, cardio-vascular dysfunctions, etc. Despite many promising roles of flavonoids, expectations have not been fulfilled when studies were extended to the in vivo condition, particularly in humans. Instability and very low oral bioavailability of dietary flavonoids are the reasons behind this. Researches have demonstrated that the methylation of these flavonoids could increase their promise as pharmaceutical agents leading to novel applications. Methylation of the flavonoids via theirs free hydroxyl groups or C atom dramatically increases their metabolic stability and enhances the membrane transport, leading to facilitated absorption and highly increased oral bioavailability. In this paper, we concentrated on analysis of flavonoid methoxides including O- and C-methoxide derivatives in aspect of structure, bioactivities and description of almost all up-to-date O- and C-methyltransferases' enzymatic characteristics. Furthermore, modern biological approaches for synthesis and production of flavonoid methoxides using metabolic engineering and synthetic biology have been focused and updated up to 2015. This review will give a handful information regarding the methylation of flavonoids, methyltransferases and biotechnological synthesis of the same.

A novel and effective chromatographic approach to the separation of isoflavone derivatives from Pueraria lobata

A novel and effective chromatographic approach to the separation and purification of isoflavone compounds from Pueraria lobata is described. The method is based on flash chromatography (FC), coupled to preparative high performance liquid chromatography (prep-HPLC) via a six-way valve. The FC step comprised tandem reversed phase columns, pre-packed with MCI gel (Mitsubishi Chemical Corp., Tokyo, Japan) and C18 (Fuji Silysia Chemical Ltd, Osaka, Japan) resin, respectively, and was designed to separate a crude Pueraria lobata extract into several preliminary fractions. Fractions containing the target compounds were then directly injected via the six-way valve into prep-HPLC columns, without further treatment, for final isolation and purification. Nine isoflavonoids were successfully isolated, three through an online mode and the other six through an offline mode. The purities of all compounds exceeded 95.0%, as determined by HPLC with an UV-vis photodiode array detector. The convenience, low solvent consumption, and time-saving advantages of this method offer an attractive and promising approach to the isolation of natural products.

Quantitative trait loci analysis of individual and total isoflavone contents in soybean seeds

Soybean isoflavones play diverse roles in human health, including cancers, osteoporosis, heart disease, menopausal symptoms and pabulums. The objective of this study was to identify the quantitative trait loci (QTL) associated with the isoflavones daidzein (DC), genistein (GeC), glycitein (GlC) and total isoflavone contents (TIC) in soybean seeds. A population of 184 F2:10 recombinant inbred lines derived from a 'Xiaoheidou' x 'GR8836' cross was planted in pot and field conditions to evaluate soybean isoflavones. Twenty-one QTL were detected by composite interval mapping. Several QTL were associated with the traits for DC, GeC, GlC and TIC only. QDGeGlTIC4_1 and QDGlTIC12_1 are reported first in this study and were associated with the DC, GeC, GlC and TIC traits simultaneously. The QTL identified have potential value for marker-assisted selection to develop soybean varieties with desirable isoflavone content.

Synthesis and anticancer evaluation of 3-substituted quinolin-4-ones and 2,3-dihydroquinolin-4-ones

A series of 3-aryl-5,7-dimethoxyquinolin-4-ones 8 and 3-aryl-5,7-dimethoxy-2,3-dihydroquinolin-4-ones 13 were synthesized in good yields. Demethylation under a range of conditions afforded the corresponding 5-hydroxy and 5,7-dihydroxy derivatives. Biological evaluation against a range of cancer cells lines showed that the quinolin-4-one scaffold was more cytotoxic than the reduced 2,3-dihydroquinolin-4-one scaffold. The most active monohydroxy compound 15f demonstrated 85.9-99% reduction in cell viability against the cell lines tested.

Genistein inhibits estradiol- and environmental endocrine disruptor-induced growth effects on neuroblastoma cells in vitro

The aim of this study was to examine the effect of genistein on human neuroblastoma cell proliferation induced by two common environmental endocrine disruptors, bisphenol A (BPA) and Di-2-ethylhexyl phthalate (DEHP), and to investigate its underlying mechanism. SK-N-SH human neuroblastoma cells were treated with E₂ (1 ng/ml), BPA (2 μg/ml) or DEHP (100 μM), with or without genistein (12.5 μM) in vitro. The number of viable cells was detected with an absorbance reader after 0, 24, 48 or 72 h treatment. The percentage of cells in different phases, and expression of Akt and its phosphorylation levels were also assessed by flow cytometry and western blot analysis at 72 h, respectively. The BPA and DEHP groups had a 30% higher number of viable cells compared to the non-treated group at 48 h (P<0.001). However, the cell numbers did not increase significantly in the groups with additional treatment with genistein (P>0.05 vs. control) and the same trend was observed at 72 h. The expression of phospho-Akt protein was increased in the groups treated with BPA or DEHP compared to the control group at 72 h (P<0.05), while no significant elevation in the expression of phospho-Akt was observed (P>0.05) in genistein-treated groups. Cells were arrested at the G₂/M phase by genistein. Similar effects were observed in the E₂ group with or without genistein treatment. Akt protein expression had no significant change among all the groups (P>0.05). In conclusion, estradiol- or environmental endocrine disruptor-induced proliferation of human neuroblastoma cells is effectively abolished by genistein, likely in a cell cycle- and Akt pathway-dependent manner.

A potential daidzein derivative enhances cytotoxicity of epirubicin on human colon adenocarcinoma Caco-2 cells

In this study, we evaluated the effects of 8-hydroxydaidzein (8HD), an isoflavone isolated from fermented soy germ koji, and epirubicin (Epi), an antineoplastic agent, on the production of reactive oxygen species (ROS). We subsequently correlated the ROS levels to the anticancer mechanisms of Epi and 8HD in human colon adenocarcinoma Caco-2 cells. 8HD enhanced cytotoxicity of Epi and generated a synergistic effect. Epi and/or 8HD treatments increased the hydrogen peroxide and superoxide levels. Combined treatment markedly decreased mRNA expression levels of multidrug resistance protein 1 (MDR1), MDR-associated protein (MRP) 1, and MRP2. 8HD significantly intensified Epi intracellular accumulation in Caco-2 cells. 8HD and/or Epi-induced apoptosis, as indicated by the reduced mitochondrial membrane potential and increased sub-G1 phase in cell cycle. Moreover, 8HD and Epi significantly enhanced the mRNA expressions of Bax, p53, caspases-3, -8, and -9. To our best knowledge, this study verifies for the first time that 8HD effectively circumvents MDR in Caco-2 cells through the ROS-dependent inhibition of efflux transporters and p53-mediated activation of both death receptor and mitochondrial pathways of apoptosis. Our findings of 8HD shed light on the future search for potential biotransformed isoflavones to intensify the cytotoxicity of anticancer drugs through simultaneous reversal of pump and nonpump resistance.

Indirubin-3'-oxime induces mitochondrial dysfunction and triggers growth inhibition and cell cycle arrest in human neuroblastoma cells

Neuroblastoma is the most common extracranial solid tumor found in infancy and childhood. Current multimodal therapies such as surgery, chemotherapy, radiotherapy and stem cell transplantation often cause inevitable severe side-effects, therefore, it is necessary to develop novel drugs with higher efficacy on neuroblastoma cells and minimal side-effects on normal cells. Indirubin-3'-oxime (I3M), an indigo alkaloid, was found to exhibit potent antitumor activities on various types of cancer cells. However, its modulatory effects on human neuroblastoma and the underlying mechanisms remain poorly understood. As mitochondrial biogenesis and function play critical roles in cell growth and survival, in the present study the effects of I3M on mitochondrial functions and their correlation to the anticancer effect of I3M on human neuroblastoma cells were investigated. I3M was found to inhibit the growth of the human neuroblastoma LA-N-1, SH-SY5Y and SK-N-DZ cells in a dose- and time-dependent manner, but exhibited little, if any, direct cytotoxicity on normal cells. Mechanistic studies showed that I3M specifically decreased the expression of the mitochondrial regulators ERRγ and PGC-1β and resulted in decreased mitochondrial mass and altered mitochondrial function characterized by a reduction in mitochondrial membrane potential and elevation of reactive oxygen species levels in LA-N-1 cells. I3M also increased the level of CDK inhibitor p27Kip1 and reduced the levels of CDK2 and cyclin E in LA-N-1 cells, leading to cell cycle arrest at the G0/G1 phase. Collectively, these results suggest that mitochondrial dysfunction might be an important mechanism underlying the I3M-induced cell cycle arrest.

Current knowledge and future direction of research on soy isoflavones as a therapeutic agents

Isoflavones, the most abundant phytoestrogens in Soy beans, are structurally similar to 17beta-estradiol. The antioxidant property of the soy isoflavones, namely, genistein and daidzein is well established in different experimental models and also in clinical studies. The compounds have been found effective in the management of diabetes by acting on peroxisome proliferator-activated receptors. It reduces the risk of coronary heart disease by reducing the level of low-density lipoprotein and triglycerides. Soy isoflavones have the potential in the treatment of osteoporosis to act on osteoclasts further to inhibit tyrosine kinase. Among the soy isoflavones, genistein is the potential compound found effective in the treatment of cancer by acting on androgen receptor further to inhibit tyrosine kinases. In this article, various aspects of the diverse biological activities of soy isoflavones and their potential clinical implications with mechanism of action, especially in the treatment and prevention of diabetes, cardiovascular diseases, cancer, osteoporosis, neuroprotection, and also future area of research on soy isoflavones are reviewed and discussed.

Optimisation of ultrasound-assisted extraction of puerarin and total isoflavones from Puerariae Lobatae Radix (Pueraria lobata (Wild.) Ohwi) with response surface methodology

INTRODUCTION

Isoflavones, particularly puerarin, are a group of important components from Puerariae Lobatae Radix (PLR) which show diverse pharmacological activities, therefore giving rise to the development of various extraction methods. Ultrasound-assisted extraction (UAE) has been explored for isoflavone extraction from PLR as it provides higher extraction efficiency compared with traditional methods.

OBJECTIVE

To optimise the UAE conditions for puerarin and total isoflavone extraction from PLR using response surface methodology (RSM).

METHODOLOGY

Samples were prepared by use of ultrasound-assisted extraction, and then subjected to HPLC analysis. Box-Behnken Design (BBD), a widely used form of RSM, was used for the optimisation of the UAE process.

RESULTS

The effects of ethanol concentration, extraction time and the solvent-to-material ratio on the yields of puerarin and total isoflavones were investigated. The Box-Behnken experimental results demonstrate that optimal extraction was obtained with an ethanol concentration of 71.35%, an extraction time of 49.08 min and a solvent-to-material ratio of 21.72 for puerarin, and an ethanol concentration of 80.00%, an extraction time of 55.00 min and a solvent-to-material ratio of 12.81 for total isoflavones. The yields of puerarin and total isoflavones were 41 ± 0.63 mg/g and 128 ± 0.82 mg/g, respectively, under the optimised extraction conditions, which are in agreement with the values predicted by the RSM.

CONCLUSION

The RSM allows for optimising the extraction parameters such that maximum extraction of puerarin and total isoflavones was achieved experimentally.

A self-assembled nanodelivery system enhances the oral bioavailability of daidzein: in vitro characteristics and in vivo performance

AIM

A self-assembled nano-based delivery system was designed and developed to increase the oral bioavailability of poor hydrophilic and lipophilic daidzein.

METHODS

Daidzein was firstly combined with lecithin to form the daidzein-lecithin complex, then self-assembled into micelles (DLMs) with lecithin and sodium bile. The physiochemical properties and intestinal absorption of DLMs were characterized, and the pharmacokinetic behavior was evaluated in rats.

RESULTS

DLMs exhibited nanometer-sized particles. DLMs were mainly distributed in the stomach and proximal intestine after oral administration. The intestinal absorption of DLMs was significantly improved, and DLMs could be absorbed via both endocytosis and passive transport. The AUC(0-t) value of daidzein in rats treated with DLMs was ninefold greater than that of free daidzein suspension.

CONCLUSION

The presented delivery system could provide a new promising strategy for enhancing the oral bioavailability of drugs with poor hydrophilicity and lipophilicity.

The comparison of different daidzein-PLGA nanoparticles in increasing its oral bioavailability

The aim of this research was to increase the oral bioavailability of daidzein by the formulations of poly(lactic-co-glycolic) acid (PLGA) nanoparticles loaded with daidzein. Amongst the various traditional and novel techniques of preparing daidzein-loaded PLGA nanoparticles, daidzein-loaded phospholipid complexes PLGA nanoparticles and daidzein-loaded cyclodextrin inclusion complexes PLGA nanoparticles were selected. The average drug entrapment efficiency, particle size, and zeta potential of daidzein-loaded phospholipid complexes PLGA nanoparticles and daidzein-loaded cyclodextrin inclusion complexes PLGA nanoparticles were 81.9% ± 5%, 309.2 ± 14.0 nm, -32.14 ± 2.53 mV and 83.2% ± 7.2%, 323.2 ± 4.8 nm, -18.73 ± 1.68 mV, respectively. The morphological characterization of nanoparticles was observed with scanning electron microscopy by stereological method and the physicochemical state of nanoparticles was valued by differential scanning calorimetry. The in vitro drug-release profile of both nanoparticle formulations fitted the Weibull dynamic equation. Pharmacokinetic studies demonstrated that after oral administration of daidzein-loaded phospholipid complexes PLGA nanoparticles and daidzein-loaded cyclodextrin inclusion complexes PLGA nanoparticles to rats at a dose of 10 mg/kg, relative bioavailability was enhanced about 5.57- and 8.85-fold, respectively, compared to daidzein suspension as control. These results describe an effective strategy for oral delivery of daidzein-loaded PLGA nanoparticles and might provide a fresh approach to enhancing the bioavailability of drugs with poor lipophilic and poor hydrophilic properties.

Soy isoflavones sensitize cancer cells to radiotherapy

Soy isoflavones are dietary compounds isolated from soybeans, which are safe for human use and have mild anti-cancer properties. Soy isoflavones inhibit the activity of transcription factors and genes essential for tumor cell proliferation, invasion, and neovascularization, and it appears that soy isoflavones may enhance the effectiveness of conventional therapies against cancer. Soy isoflavones could be an effective complementary treatment given that they inhibit the survival signaling pathways of various cancer cells through altered activation of APE1/Ref-1, NF-κB, and HIF-1α, which are genes essential for tumor cell survival, tumor growth, and angiogenesis, thus making such cells more sensitive to radiotherapy. Studies in which soy isoflavones were given in conjunction with radiotherapy to prostate cancer patients suggest that soy isoflavones might also mitigate the adverse effects of radiation on normal tissues, probably by acting as antioxidants. These observations open new avenues for exploiting soy isoflavones as supplements to conventional therapies.

Risks and benefits of dietary isoflavones for cancer

A high intake of fruits and vegetables is associated with a lower risk of cancer. In this context, considerable attention is paid to Asian populations who consume high amounts of soy and soy-derived isoflavones, and have a lower risk for several cancer types such as breast and prostate cancers than populations in Western countries. Hence, interest focuses on soyfoods, soy products, and soy ingredients such as isoflavones with regard to their possible beneficial effects that were observed in numerous experiments and studies. The outcomes of the studies are not always conclusive, are often contradictory depending on the experimental conditions, and are, therefore, difficult to interpret. Isoflavone research revealed not only beneficial but also adverse effects, for instance, on the reproductive system. This is also the case with tumor-promoting effects on, for example, breast tissue. Isoflavone extracts and supplements are often used for the treatment of menopausal symptoms and for the prevention of age-associated conditions such as cardiovascular diseases and osteoporosis in postmenopausal women. In relation to this, questions about the effectiveness and safety of isoflavones have to be clarified. Moreover, there are concerns about the maternal consumption of isoflavones due to the development of leukemia in infants. In contrast, men may benefit from the intake of isoflavones with regard to reducing the risk of prostate cancer. Therefore, this review examines the risks but also the benefits of isoflavones with regard to various kinds of cancer, which can be derived from animal and human studies as well as from in vitro experiments.

Effects of 7-O substitutions on estrogenic and anti-estrogenic activities of daidzein analogues in MCF-7 breast cancer cells

Daidzein (1) is a natural estrogenic isoflavone. We report here that 1 can be transformed into anti-estrogenic ligands by simple alkyl substitutions of the 7-hydroxyl hydrogen. To test the effect of such structural modifications on the hormonal activities of the resulting compounds, a series of daidzein analogues have been designed and synthesized. When MCF-7 cells were treated with the analogues, those resulting from hydrogen substitution by isopropyl (3d), isobutyl (3f), cyclopentyl (3g), and pyrano- (2) inhibited cell proliferation, estrogen-induced transcriptional activity, and estrogen receptor (ER) regulated progesterone receptor (PgR) gene expression. However, methyl (3a) and ethyl (3b) substitutions of the hydroxyl proton only led to moderate reduction of the estrogenic activities. These results demonstrated the structural requirements for the transformation of daidzein from an ER agonist to an antagonist. The most effective analogue, 2, was found to reduce in vivo estrogen stimulated MCF-7 cell tumorigenesis using a xenograft mouse model.

Daidzein regulates secretion, production and gene expression of mucin from airway epithelial cells stimulated by proinflammatory factor and growth factor

In this study, we investigated whether daidzein significantly affects secretion, production and gene expression of mucin from cultured airway epithelial cells. Confluent primary rat tracheal surface epithelial (RTSE) cells were pretreated with adenosine triphosphate (ATP) for 5 min and then chased for 30 min in the presence of daidzein to assess the effect on mucin secretion using ELISA. At the same time, confluent NCI-H292 cells were pretreated with daidzein for 30 min and then stimulated with EGF and PMA for 24 h, respectively. The MUC5AC mucin gene expression and mucin protein production were measured by RT-PCR and ELISA. The results were as follows: (1) daidzein significantly decreased ATP-induced mucin secretion from cultured RTSE cells; (2) daidzein inhibited the production of MUC5AC mucin protein induced by EGF or PMA from NCI-H292 cells; (3) daidzein also inhibited the expression of MUC5AC mucin gene induced by EGF or PMA from NCI-H292 cells. This result suggests that daidzein can regulate secretion, production and gene expression of mucin, by directly acting on airway epithelial cells.

Daidzein effect on hormone refractory prostate cancer in vitro and in vivo compared to genistein and soy extract: potentiation of radiotherapy

PURPOSE

Genistein, the major bioactive isoflavone of soybeans, acts as a radiosensitizer for prostate cancer (PCa) both in vitro and in vivo. However, pure genistein promoted increased metastasis to lymph nodes. A mixture of soy isoflavones (genistein, daidzein, glycitein) did not cause increased metastasis, but potentiated radiotherapy. We tested whether daidzein could negate genistein-induced metastasis.

METHODS

Mice bearing PC-3 prostate tumors were treated with daidzein, genistein or both, and with tumor irradiation. Primary tumors and metastases were evaluated. The effects of each isoflavone and soy were compared in vitro using PC-3 (AR-) and C4-2B (AR+) androgen-independent PCa cell lines.

RESULTS

Daidzein did not increase metastasis to lymph nodes and acted as a radiosensitizer for prostate tumors. Daidzein inhibited cell growth and enhanced radiation in vitro but at doses higher than genistein or soy. Daidzein caused milder effects on inhibition of expression and/or activities of APE1/Ref-1, HIF-1alpha and NF-kappaB in PC-3 and C4-2B cells.

CONCLUSIONS

Daidzein could be the component of soy that protects against genistein-induced metastasis. Daidzein inhibited cell growth and synergized with radiation, affecting APE1/Ref-1, NF-kappaB and HIF-1alpha, but at lower levels than genistein and soy, in AR+ and AR- PCa cells, suggesting it is an AR-independent mechanism.

Protective effects of resveratrol and quercetin against MPP+ -induced oxidative stress act by modulating markers of apoptotic death in dopaminergic neurons

Reactive oxygen species produced by oxidative stress may participate in the apoptotic death of dopamine neurons distinctive of Parkinson's disease. Resveratrol, a red wine extract, and quercetin, found mainly in green tea, are two natural polyphenols, presenting antioxidant properties in a variety of cellular paradigms. The aim of this study was to evaluate the effect of resveratrol and quercetin on the apoptotic cascade induced by the administration of 1-methyl-4-phenylpyridinium ion (MPP(+)), a Parkinsonian toxin, provoking the selective degeneration of dopaminergic neurons. Our results show that a pre-treatment for 3 h with resveratrol or quercetin before MPP(+) administration could greatly reduce apoptotic neuronal PC12 death induced by MPP(+). We also demonstrated that resveratrol or quercetin modulates mRNA levels and protein expression of Bax, a pro-apoptotic gene, and Bcl-2, an anti-apoptotic gene. We then evaluated the release of cytochrome c and the nuclear translocation of the apoptosis-inducing factor (AIF). Altogether, our results indicate that resveratrol and quercetin diminish apoptotic neuronal cell death by acting on the expression of pro- and anti-apoptotic genes. These findings support the role of these natural polyphenols in preventive and/or complementary therapies for several human neurodegenerative diseases caused by oxidative stress and apoptosis.

Prostatic soy isoflavone concentrations exceed serum levels after dietary supplementation

BACKGROUND

The effects of soy isoflavones on prostate cancer may be concentration-dependent. The impact of soy supplementation on isoflavone concentrations in prostate tissues and serum remain unclear.

OBJECTIVE

To assess and compare concentrations of soy isoflavones in prostate tissue and serum among 19 men with prostate cancer who had elected to undergo radical prostatectomy.

METHODS

Participants were randomized to receive either daily soy supplements (82 mg/day aglycone equivalents) or placebos for 2 weeks (14 days) prior to surgery. Serum samples were obtained at the time of the surgery. Isoflavone concentrations were measured by HPLC/ESI-MS-MS.

RESULTS

The median (25th, 75th percentile) total isoflavone concentration in the isoflavone-supplemented group was 2.3 micromol/L (1.2, 6.9) in the prostate tissue and 0.7 micromol/L (0.2, 1.2) in the serum. Total isoflavone concentrations in this group were an average of approximately 6-fold higher in prostate tissue compared to serum; the tissue versus serum ratio was significantly lower for genistein than daidzein, 4-fold versus 10-fold, P = 0.003. Tissue and serum levels of isoflavones among the placebo group were negligible with a few exceptions.

CONCLUSIONS

The findings from the present study suggest that prostate tissue may have the ability to concentrate dietary soy isoflavones to potentially anti-carcinogenic levels.

Radiation-induced HIF-1alpha cell survival pathway is inhibited by soy isoflavones in prostate cancer cells

We previously showed that treatment of prostate cancer cells with soy isoflavones and radiation resulted in greater cell killing in vitro, and caused downregulation of NF-kappaB and APE1/Ref-1. APE1/Ref-1 functions as a redox activator of transcription factors, including NF-kappaB and HIF-1alpha. These molecules are upregulated by radiation and implicated in radioresistance of cancer cells. We extended our studies to investigate the role of HIF-1alpha survival pathway and its upstream Src and STAT3 molecules in isoflavones and radiation interaction. Radiation induced phosphorylation of Src and STAT3 leading to induction of HIF-1alpha. Genistein, daidzein or a mixture of soy isoflavones did not activate this pathway. These data were observed both in PC-3 (AR-) and C4-2B (AR+) androgen-independent cell lines. Pretreatment with isoflavones inhibited Src/STAT3/HIF-1alpha activation by radiation and nuclear translocation of HIF-1alpha. These findings correlated with decreased expression of APE1/Ref-1 and DNA binding activity of HIF-1alpha and NF-kappaB. In APE1/Ref-1 cDNA transfected cells, radiation caused a greater increase in HIF-1alpha and NF-kappaB activities but this effect was inhibited by pretreatment with soy prior to radiation. Transfection experiments indicate that APE1/Ref-1 inhibition by isoflavones impairs the radiation-induced transcription activity of NF-kappaB and HIF-1alpha. This mechanism could result in the inhibition of genes essential for tumor growth and angiogenesis, as demonstrated by inhibition of VEGF production and HUVECs tube formation. Our novel findings suggest that the increased responsiveness to radiation mediated by soy isoflavones could be due to pleiotropic effects of isoflavones blocking cell survival pathways induced by radiation including Src/STAT3/HIF-1alpha, APE1/Ref-1 and NF-kappaB.

Prevention of chemically induced mammary tumorigenesis by daidzein in pre-pubertal rats: the role of peroxidative damage and antioxidative enzymes

Isoflavones are biologically active plant derived compounds that have several health promoting effects. In the present study hitherto unknown effects of one of the well known isoflavonoids, daidzein, has been evaluated on its chemo-preventive action against breast cancers in pre-pubertal rats. Either daidzein (500 mug/g bwt) or vehicle, dimethyl sulphoxide (DMSO), was administered at 16th, 18th, and 20th day post-partum and the chemopreventive efficacy was evaluated in dimethylbenz[a]nthracene (DMBA) induced Sprague-Dawley rats, at 50th day. To elucidate the mechanism of action, the antioxidative status was also examined in the liver and mammary gland of prebubertal rats using two different doses of daidzein (0.5 mg/kg bwt and 50 mg/kg bwt, p.o.) for 10 days. The specific activity of antioxidant enzymes as well as reduced glutathione (GSH) level and peroxidative damage were evaluated spectrophotometrically, both in liver as well as in mammary gland. Animals treated with daidzein pre-pubertally, showed a significant reduction in the tumorigenesis of mammary gland up to 37.4% as compared to animals induced for tumors with DMBA. In animals treated with 50 mg/kg of daidzein, a significant increase in the specific activities of the antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione transferase (GST), DT-diaphorase (DTD), and in GSH content were observed in both liver and mammary gland. Expectedly, the specific activity of lactate dehydrogenase (LDH) and level of peroxidative damage was decreased, as compared to that of control group of animals. Our results suggest that, daidzein can be considered as a potent chemopreventive agent against mammary carcinogenesis in pre-pubertal animals, with modulation of antioxidant enzymes being one of its mechanisms of actions.

Prospective cohort study of soy food intake and colorectal cancer risk in women

BACKGROUND

Soy and some of its constituents, such as isoflavones, have been shown to have cancer-inhibitory activities in experimental studies. Data from epidemiologic studies linking usual soy food intake with colorectal cancer are limited and inconsistent.

OBJECTIVE

The objective was to investigate whether soy food intake is associated with colorectal cancer risk.

DESIGN

We prospectively examined 68,412 women aged 40-70 y and free of cancer and diabetes at enrollment. Usual soy food intake was assessed at baseline (1997-2000) and reassessed during the first follow-up (2000-2002) through in-person interviews with a validated food-frequency questionnaire. We excluded the first year of observation to minimize lifestyle changes related to preclinical disease.

RESULTS

During a mean follow-up of 6.4 y, 321 incident colorectal cancer cases were identified. After adjustment for potential confounding factors, total soy food intake was inversely associated with colorectal cancer risk. Each 5-g/d increment in intake of soy foods as assessed by dry weight [equivalent to approximately 1 oz (28.35 g) tofu/d] was associated with an 8% reduction in risk (95% CI: 3%, 14%). Women in the highest tertile of intake had a multivariate relative risk of 0.67 (95% CI: 0.49, 0.90) compared with those in the lowest tertile (P for trend = 0.008). This inverse association was primarily confined to postmenopausal women. Similar results were also found for intakes of soy protein and isoflavones.

CONCLUSION

This prospective study suggests that consumption of soy foods may reduce the risk of colorectal cancer in postmenopausal women.