Differential effects of flavonoid compounds on tumor promoter-induced activation of the human CYP1A2 enhancer

Quercetin as one of the most abundant represented biological valuable plant components with remarkable chemoprotective effects - A review

As a consequence of environmental quality changes as well as changes in our population's lifestyle, there is rapidly increasing variability and many so-called lifestyle disorders, allergies, and food intolerances (also known as non-allergic food hypersensitivity). Unhealthy eating practices, an inappropriate food composition with an excessive energy intake, a high intake of saturated fats, simple sugars, and salt, as well as an inadequate intake of fibre, vitamins, and substances with preventive effects (such as antioxidants), are some of the factors causing this detrimental phenomenon. Enhanced consumption of plant foods rich in valuable secondary metabolites such as phenolic acids and flavonoids with the benefit on human health, food research focused on these components, and production of foods with declared higher content of biologically active and prophylactic substances are some ways how to change and improve this situation. A unique class of hydroxylated phenolic compounds with an aromatic ring structure are called flavonoids. One unique subclass of flavonoids is quercetin. This phytochemical naturally takes place in fruits, vegetables, herbs, and other plants. Quercetin and its several derivates are considered to be promising substances with significant antidiabetic, antibacterial, anti-inflammatory, and antioxidant effects, which could also act preventively against cardiovascular disease, cancer, or Alzheimer's disease.

Quercetin and 5-Fu Loaded Chitosan Nanoparticles Trigger Cell-Cycle Arrest and Induce Apoptosis in HCT116 Cells via Modulation of the p53/p21 Axis

Nanoparticles (NPs) are encapsulating agents that exist in the nanometer range. They can be classified into different classes based on their properties, shapes, or sizes. Metal NPs, fullerenes, polymeric NPs, ceramic NPs, and luminescent nanoporous hybrid materials are only a few examples. This study explored the anticancer potential of quercetin and 5-fluorouracil-encapsulated chitosan nanoparticles (CS-5-FU-QCT NPs). The nanoparticles were prepared by ionic gelation, and their efficacy and mechanism of action were examined. CS-5-FU-QCT NPs were characterized using dynamic light scattering (DLS), atomic force microscopy (AFM), UV-visible spectroscopy, and Fourier transform infrared spectroscopy (FTIR); cytotoxicity was analyzed using an MTT assay. Cells were treated with CS-5-FU-QCT NPs and incubated for 12, 24, and 36 h, and apoptosis analysis (using Annexin V/FITC), cell-cycle analysis, Western blotting, and confocal microscopic analysis were performed. Biophysical analysis revealed that the CS-5-FU-QCT NPs fall in the range of 300-400 nm with a near-spherical shape. The in vitro drug release profile indicates sustained release of drugs over a period of about 36 h. The cytotoxicity of CS-5-FU-QCT NPs was more prominent in HCT116 cells than in other cancer cells. This particular nanoformulation caused G0/G1 phase cell-cycle arrest in HCT116 cells and induced intracellular ROS generation, thereby causing apoptosis. It also downregulated Bcl2, cyclin D1, and Cdk4 and upregulated BAX, p53, and p21, causing cell-cycle arrest and apoptosis. In summary, CS-5-FU-QCT NPs hindered proliferation of HCT116 cells via ROS generation and altered the expression of key proteins in the p53/p21 axis and apoptotic machinery in a time-dependent manner.

Evidence-based capacity of natural cytochrome enzyme inhibitors to increase the effectivity of antineoplastic drugs

Cytochrome (CYP) enzymes catalyze the metabolism of numerous exogenous and endogenous substrates in cancer therapy leading to significant drug interactions due to their metabolizing effect. CYP enzymes play an important role in the metabolism of essential anticancer medications. They are shown to be overexpressed in tumor cells at numerous locations in the body. This overexpression could be a result of lifestyle factors, presence of hereditary variants of CYP (Bio individuality) and multi-drug resistance. This finding has sparked an interest in using CYP inhibitors to lower their metabolizing activity as a result facilitating anti-cancer medications to have a therapeutic impact. As a result of the cytotoxic nature of synthetic enzyme inhibitors and the increased prevalence of herbal medication, natural CYP inhibitors have been identified as an excellent way to inhibit overexpression sighting their tendency to show less cytotoxicity, lesser adverse drug reactions and enhanced bioavailability. Nonetheless, their effect of lowering the hindrance caused in chemotherapy due to CYP enzymes remains unexploited to its fullest. It has been observed that there is a substantial decrease in first pass metabolism and increase in intestinal absorption of chemotherapeutic drugs like paclitaxel when administered along with flavonoids which help suppress certain specific cytochrome enzymes which play a role in paclitaxel metabolism. This review elaborates on the role and scope of phytochemicals in primary, secondary and tertiary care and how targeted prevention of cancer could be a breakthrough in the field of chemotherapy and oncology. This opens up a whole new area of research for delivery of these natural inhibitors along with anticancer drugs with the help of liposomes, micelles, nanoparticles, the usage of liquid biopsy analysis, artificial intelligence in medicine, risk assessment tools, multi-omics and multi-parametric analysis. Further, the site of action, mechanisms, metabolites involved, experimental models, doses and observations of two natural compounds, quercetin & thymoquinone, and two plant extracts, liquorice & garlic on CYP enzymes have been summarized.

Quercetin Loaded Cationic Solid Lipid Nanoparticles in a Mucoadhesive In Situ Gel-A Novel Intravesical Therapy Tackling Bladder Cancer

The study aim was to develop an intravesical delivery system of quercetin for bladder cancer management in order to improve drug efficacy, attain a controlled release profile and extend the residence time inside the bladder. Either uncoated or chitosan coated quercetin-loaded solid lipid nanoparticles (SLNs) were prepared and evaluated in terms of colloidal, morphological and thermal characteristics. Drug encapsulation efficiency and its release behaviour were assessed. Furthermore, cytotoxicity of SLNs on T-24 cells was evaluated. Ex vivo studies were carried out using bovine bladder mucosa. Spherical SLNs (≈250 nm) ensured good entrapment efficiencies (EE > 97%) and sustained drug release up to 142 h. Cytotoxicity profile revealed concentration-dependent toxicity recording an IC50 in the range of 1.6−8.9 μg/mL quercetin. SLNs were further dispersed in in situ hydrogels comprising poloxamer 407 (20%) with mucoadhesive polymers. In situ gels exhibited acceptable gelation temperatures (around 25 °C) and long erosion time (24−27 h). SLNs loaded gels displayed remarkably enhanced retention on bladder tissues relative to SLNs dispersions. Coated SLNs exhibited better penetration abilities compared to uncoated ones, while coated SLNs dispersed in gel (G10C-St-QCT-SLNs-2) showed the highest penetration up to 350 μm. Hence, G10C-St-QCT-SLNs-2 could be considered as a platform for intravesical quercetin delivery.

A Comprehensive Analysis and Anti-Cancer Activities of Quercetin in ROS-Mediated Cancer and Cancer Stem Cells

Reactive oxygen species (ROS) induce carcinogenesis by causing genetic mutations, activating oncogenes, and increasing oxidative stress, all of which affect cell proliferation, survival, and apoptosis. When compared to normal cells, cancer cells have higher levels of ROS, and they are responsible for the maintenance of the cancer phenotype; this unique feature in cancer cells may, therefore, be exploited for targeted therapy. Quercetin (QC), a plant-derived bioflavonoid, is known for its ROS scavenging properties and was recently discovered to have various antitumor properties in a variety of solid tumors. Adaptive stress responses may be induced by persistent ROS stress, allowing cancer cells to survive with high levels of ROS while maintaining cellular viability. However, large amounts of ROS make cancer cells extremely susceptible to quercetin, one of the most available dietary flavonoids. Because of the molecular and metabolic distinctions between malignant and normal cells, targeting ROS metabolism might help overcome medication resistance and achieve therapeutic selectivity while having little or no effect on normal cells. The powerful bioactivity and modulatory role of quercetin has prompted extensive research into the chemical, which has identified a number of pathways that potentially work together to prevent cancer, alongside, QC has a great number of evidences to use as a therapeutic agent in cancer stem cells. This current study has broadly demonstrated the function-mechanistic relationship of quercetin and how it regulates ROS generation to kill cancer and cancer stem cells. Here, we have revealed the regulation and production of ROS in normal cells and cancer cells with a certain signaling mechanism. We demonstrated the specific molecular mechanisms of quercetin including MAPK/ERK1/2, p53, JAK/STAT and TRAIL, AMPKα1/ASK1/p38, RAGE/PI3K/AKT/mTOR axis, HMGB1 and NF-κB, Nrf2-induced signaling pathways and certain cell cycle arrest in cancer cell death, and how they regulate the specific cancer signaling pathways as long-searched cancer therapeutics.

Comparison for quantification of eight components in Alpinia officinarum Hance by using high-performance liquid chromatography coupled with diode array detector and charged aerosol detector with individual and substitute reference compound

An efficient HPLC-DAD-CAD method was developed and compared for simultaneous quantification of four flavonoids and four diarylheptanoids in Alpinia officinarum Hance (A. officinarum) using individual and substitute reference compound. All calibration curves for investigated analytes showed good linear regression (R²> 0.9991). The LODs of investigated compounds for DAD and CAD were 0.15-7.92 ng (0.03-1.58 μg/mL) and 2.91-3.95 ng (0.58-0.79 μg/mL), respectively, whereas the LOQs were 0.52-26.39 ng (0.10-5.28 μg/mL) for DAD, and 9.70-13.18 ng (1.94-2.64 μg/mL) for CAD. Recoveries of all analytes, which ranged from 96.58% to 100.06% for DAD, and from 96.29% to 99.61% for CAD, were acceptable. According to the quantitative results, the eight compounds in A. officinarum can be accurately quantified with individual calibration curves by two detectors. In addition, to overcome the bottleneck of shortage of reference standards, diphenylheptane A and galangin, respectively, were selected for direct or calibrated quantitative determination of other diarylheptanoids and flavonoids in A. officinarum. The results showed the contents of eight components in A. officinarum determined by these methods were similar, which suggested that substitute reference compound was suitable for quantification of its analogues.

Quercetin and Luteolin Improve the Anticancer Effects of 5-Fluorouracil in Human Colorectal Adenocarcinoma In Vitro Model: A Mechanistic Insight

The aim of this study was to investigate the antitumor effects of quercetin and luteolin combined with 5-Fluorouracil (5-FU) in HT-29 human colorectal cancer cells. Cell viability induced by quercetin, luteolin and combination of these compounds with 5-FU were determined by MTT assay, also Cell death detection Elisa assay and fluorescence microscopy were performed to investigate apoptotic effects. Hu-VEGF Elisa assay was employed to determine the effects of treatments on angiogenesis. Western blot and qRT-PCR analysis were performed to investigate effects on p53, Bax, Bcl-2, p38 MAPK, mTOR, PTEN, and Akt proteins and genes. The results indicated that quercetin, luteolin and combinations of these compounds with 5-FU inhibited the growth of HT 29 cells. Compared to the control, apoptosis were triggered 8.1 and 10.1 fold in HT-29 cells, that treated with quercetin + 5-FU and luteolin + 5-FU, respectively. VEGF amount significantly decreased by combined treatments. qRT-PCR and western blot results demonstrated that quercetin, luteolin and the combinations of these flavonoids with 5-FU, modulate the apoptotic pathways in HT-29 cells. The increase in p53, Bax, p38 MAPK, and PTEN gene expression levels compared to the control group was 1.71, 1.42, 3.26, and 3.29-fold with 5-FU + L treatment, respectively, while this increase was 8.43, 1.65, 3.55, and 3.54-fold with 5-FU + Q treatment, respectively. In addition, when the anti-apoptotic Bcl-2, mTOR, and Akt gene expression levels were normalized as 1 in the control group, they were 0.28, 0.41, and 0.22 with 5-FU + L treatment, and 0.32, 0.46, and 0.39, respectively, with 5-FU + Q treatment. These findings suggested that quercetin and luteolin synergistically enhanced the anticancer effect of 5-FU in HT 29 cells and may therefore minimize the toxic effects of 5-FU in the clinical treatment of colorectal cancer.

Synthesis and characterization of chitosan/polyvinylpyrrolidone coated nanoporous γ-Alumina as a pH-sensitive carrier for controlled release of quercetin

pH-sensitive drug delivery systems based on amphiphilic copolymers constitute a promising strategy to overcome some challenges to cancer treatment. In the present study, quercetin-loaded chitosan/polyvinylpyrrolidone/γ-Alumina nanocomposite was fabricated through a double oil in water emulsification method for the first time. γ-Alumina was incorporated to improve the drug loading efficiency and release behavior of polyvinylpyrrolidone and chitosan copolymeric hydrogel. γ-Alumina nanoparticles were obtained by the sol-gel method with a nanoporous structure, high surface area, and hydroxyl-rich surface. Quercetin, a natural anticancer agent, was loaded into the nanocomposite as a drug model. XRD and FTIR analyses confirmed the crystalline properties and chemical bonding of the prepared nanocomposite. The size of drug-loaded nanocomposites was 141 nm with monodisperse particle distribution, having a spherical shape approved by DLS analysis and FE-SEM, respectively. Incorporating γ-Alumina nanoparticles improved the encapsulation efficiency up to 95%. Besides, swelling study and the quercetin release profile demonstrated that γ-Alumina ameliorated pH sensitivity of nanocomposite and a targeted controlled release was obtained. Various release kinetic models were applied to the experimental release data to study the mechanism of drug release. Through MTT assay and flow cytometry, the quercetin-loaded nanocomposite showed significant cytotoxicity on MCF-7 breast cancer cells. Also, the enhanced apoptotic cell death confirmed the anticancer activity of γ-Alumina. These results suggest that the chitosan/polyvinylpyrrolidone/γ-Alumina nanocomposite is a novel pH-sensitive drug delivery system for anticancer applications.

Systematic insight into the active constituents and mechanism of Guiqi Baizhu for the treatment of gastric cancer

Traditional Chinese medicine treatment of diseases has been recognized, but the material basis and mechanisms are not clear. In this study, target prediction of the antigastric cancer (GC) effect of Guiqi Baizhu (GQBZP) and the analysis of potential key compounds, key targets, and key pathways for the therapeutic effects against GC were carried out based on the method of network analysis and Kyoto Encyclopedia of Genes and Genomes enrichment. There were 33 proteins shared between GQBZP and GC, and 131 compounds of GQBZP had a high correlation with these proteins, indicating that the PI3K‐AKT signaling pathway might play a key role in GC. From these studies, we selected human epidermal growth factor receptor 2 (HER2) and programmed cell death 1‐ligand 1 (PD‐L1) for docking; the results showed that 385 and 189 compounds had high docking scores with HER2 and PD‐L1, respectively. Six compounds were selected for microscale thermophoresis (MST). Daidzein/quercetin and isorhamnetin/formononetin had the highest binding affinity for HER2 and PD‐L1, with K_d values of 3.7 μmol/L and 490, 667, and 355 nmol/L, respectively. Molecular dynamics simulation studies based on the docking complex structures as the initial conformation yielded the binding free energy between daidzein/quercetin with HER2 and isorhamnetin/formononetin with PD‐L1, calculated by molecular mechanics Poisson‐Boltzmann surface area, of −26.55, −14.18, −19.41, and −11.86 kcal/mol, respectively, and were consistent with the MST results. In vitro experiments showed that quercetin, daidzein, and isorhamnetin had potential antiproliferative effects in MKN‐45 cells. Enzyme activity assays showed that quercetin could inhibit the activity of HER2 with an IC₅₀ of 570.07 nmol/L. Our study provides a systematic investigation to explain the material basis and molecular mechanism of traditional Chinese medicine in treating diseases.

Neuraminidase inhibitory diarylheptanoids from Alpinia officinarum: In vitro and molecular docking studies

Diarylheptanoids, known to be rich in the Zingiberaceae family, have been reported to have various pharmacological activities including neuraminidase (NA) inhibitory activity. In this study, to analyze the correlation between NA and diarylheptanoid, A. officinarum, belonging to the Zingiberaceae family, was selected as a natural resource. Four new compounds along with 26 known diarylheptanoids from the rhizomes of A. officinarum were isolated using various chromatographic techniques. The Structure-based virtual screening (SBVS) was performed to discover putative binding ligand and corresponding binding conformation of the isolated compounds. Among the isolated compounds, 10 compounds showed stable binding energy levels in NA. Five of these 10 potential hits showed the potent inhibitory activity through in vitro NA enzyme assay. Moreover, it can be deduced that hydrogen-bonding formation between carbonyl group of active diarylheptanoids and arginine 555 and arginine 615 of NA allowed for the most stable binding between the enzyme and docked compounds.

An in vitro study of the effect of carob (Ceratonia siliqua L.) leaf extracts on gilthead seabream (Sparus aurata L.) leucocyte activities. Antioxidant, cytotoxic and bactericidal properties

Carob leaves, the main residues of the carob tree, were investigated as a renewable and abundant source of bioactive compounds for fish aquaculture. Aqueous and ethanolic extracts obtained from carob leaves were characterized in terms of biochemical composition, antiradical and cytotoxic effects and immunostimulant and antibacterial activities. The ethanolic extract showed higher levels of total phenolics, flavonoids and condensed tannins and higher antioxidant activity than the aqueous extract. No significant immunostimulant effects were observed on gilthead seabream (Sparus aurata) head kidney leucocytes (viability, phagocytosis and respiratory burst activities and peroxidase content) after incubation for 24 h with different extracts. Furthermore, the ethanolic extracts used at 0.5, 0.75 and 1 mg mL^-1 and aqueous extracts at 1 g mL^-1 had a cytotoxic effect on PLHC-1 cells. When the bactericidal activity was tested against three fish pathogenic bacteria (Vibrio harveyi, Vibrio anguillarum and Photobacterium damselae) notable activity of the different extracts was detected against P. damselae at all three concentrations. A similar effect was demonstrated against V. haryeri when ethanolic extracts were used in the same range of concentrations. This work demonstrates interesting in vitro effects of carob leaf extracts and suggests it could be used as an alternative to chemical compounds with farmed fish. The concentration and nature of the extracts were very important in terms of any positive results.

Improvement of conventional anti-cancer drugs as new tools against multidrug resistant tumors

Multidrug resistance (MDR) is the dominant cause of the failure of cancer chemotherapy. The design of antitumor drugs that are able to evade MDR is rapidly evolving, showing that this area of biomedical research attracts great interest in the scientific community. The current review explores promising recent approaches that have been developed with the aim of circumventing or overcoming MDR. Encouraging results have been obtained in the investigation of the MDR-modulating properties of various classes of natural compounds and their analogues. Inhibition of P-gp or downregulation of its expression have proven to be the main mechanisms by which MDR can be surmounted. The use of hybrid molecules that are able to simultaneously interact with two or more cancer cell targets is currently being explored as a means to circumvent drug resistance. This strategy is based on the design of hybrid compounds that are obtained either by merging the structural features of separate drugs, or by conjugating two drugs or pharmacophores via cleavable/non-cleavable linkers. The approach is highly promising due to the pharmacokinetic and pharmacodynamic advantages that can be achieved over the independent administration of the two individual components. However, it should be stressed that the task of obtaining successful multivalent drugs is a very challenging one. The conjugation of anticancer agents with nitric oxide (NO) donors has recently been developed, creating a particular class of hybrid that can combat tumor drug resistance. Appropriate NO donors have been shown to reverse drug resistance via nitration of ABC transporters and by interfering with a number of metabolic enzymes and signaling pathways. In fact, hybrid compounds that are produced by covalently attaching NO-donors and antitumor drugs have been shown to elicit a synergistic cytotoxic effect in a variety of drug resistant cancer cell lines. Another strategy to circumvent MDR is based on nanocarrier-mediated transport and the controlled release of chemotherapeutic drugs and P-gp inhibitors. Their pharmacokinetics are governed by the nanoparticle or polymer carrier and make use of the enhanced permeation and retention (EPR) effect, which can increase selective delivery to cancer cells. These systems are usually internalized by cancer cells via endocytosis and accumulate in endosomes and lysosomes, thus preventing rapid efflux. Other modalities to combat MDR are described in this review, including the pharmaco-modulation of acridine, which is a well-known scaffold in the development of bioactive compounds, the use of natural compounds as means to reverse MDR, and the conjugation of anticancer drugs with carriers that target specific tumor-cell components. Finally, the outstanding potential of in silico structure-based methods as a means to evaluate the ability of antitumor drugs to interact with drug transporters is also highlighted in this review. Structure-based design methods, which utilize 3D structural data of proteins and their complexes with ligands, are the most effective of the in silico methods available, as they provide a prediction regarding the interaction between transport proteins and their substrates and inhibitors. The recently resolved X-ray structure of human P-gp can help predict the interaction sites of designed compounds, providing insight into their binding mode and directing possible rational modifications to prevent them from becoming P-gp drug substrates. In summary, although major efforts were invested in the search for new tools to combat drug resistant tumors, they all require further implementation and methodological development. Further investigation and progress in the abovementioned strategies will provide significant advances in the rational combat against cancer MDR.

Contemporary Formulations for Drug Delivery of Anticancer Bioactive Compounds

BACKGROUND

The immense development in the field of anticancer research has led to an increase in the research of bioactive compounds with anticancer potential. It has been known that many bioactive natural compounds have low solubility (and low bioavailability) as their main drawback when it comes to the formulation and drug delivery to specific sites.

OBJECTIVE

As many attempts have been made to overcome this issue, this review gives a summary of the current accomplishments regarding the development of new Drug Delivery Systems (DDSs) represented by nanoparticles (NPs) and exosomes.

METHODS

We analyzed the published data concerning selected compounds that present the most prominent plant secondary metabolites with anticancer potential, specifically flavone (quercetin), isoflavone (genistein and curcumin) and stilbene (resveratrol) groups that have been formulated as NPs and exosomes. In addition, we summarized the patent literature published from 2015-2018 that address these formulations.

RESULTS

Although the exact mechanism of action for the selected natural compounds still remains unclear, the anticancer effect is evident and the main research efforts are directed to finding the most suitable delivery systems. Recent patents in this field serve as evidence that these newly designed natural compound delivery systems could be powerful new anticancer agents in the very near future if the noted difficulties are overcome.

CONCLUSION

The focus of recent research is not only to clarify the exact mechanisms of action and therapeutic effects, but also to answer the issue of suitable delivery systems that can transport sufficient doses of bioactive compounds to the desired target.

Innovative approaches for cancer treatment: current perspectives and new challenges

Every year, cancer is responsible for millions of deaths worldwide and, even though much progress has been achieved in medicine, there are still many issues that must be addressed in order to improve cancer therapy. For this reason, oncological research is putting a lot of effort towards finding new and efficient therapies which can alleviate critical side effects caused by conventional treatments. Different technologies are currently under evaluation in clinical trials or have been already introduced into clinical practice. While nanomedicine is contributing to the development of biocompatible materials both for diagnostic and therapeutic purposes, bioengineering of extracellular vesicles and cells derived from patients has allowed designing ad hoc systems and univocal targeting strategies. In this review, we will provide an in-depth analysis of the most innovative advances in basic and applied cancer research.

Natural products as multidrug resistance modulators in cancer

Cancer is a prominent cause of death globally. Currently, many drugs that are in clinical practice are having a high prevalence of side effect and multidrug resistance. Risk of tumors acquiring resistance to chemotherapy (multidrug resistance) remains a significant hurdle to the successful treatment of various types of cancer. Membrane-embedded drug transporters, generally overexpressed in cancer, are the leading cause among multiple mechanisms of multidrug resistance (MDR). P-glycoprotein (P-gp) also MDR1/ABCB1, multidrug resistance associated protein 1 (MRP1/ABCC1), MRP2 and breast cancer resistance protein (BCRP/ABCG2) are considered to be a prime factor for induction of MDR. To date, several chemical substances have been tested in a number of clinical trials for their MDR modulatory activity which are not having devoid of any side effects that necessitates to find newer and safer way to tackle the current problem of multidrug resistance in cancer. The present study systematically discusses the various classes of natural products i.e flavonoids, alkaloids, terpenoids, coumarins (from plants, marine, and microorganisms) as potential MDR modulators and/or as a source of promising lead compounds. Recently a bisbenzyl isoquinoline alkaloid namely tetrandrine, isolated from Chinese herb Stephania tetrandra (Han-Fang-Chi) is in clinical trials for its MDR reversal activity.

The Flavonoid Quercetin Induces AP-1 Activation in FRTL-5 Thyroid Cells

Previous studies have shown that quercetin inhibits thyroid function both in vitro and in vivo. An attempt to evaluate the effect of quercetin at the promoter level of the thyroid-specific genes led to the observation that this compound induces the basal activity of the reporter vector. Therefore, the action of quercetin has been evaluated on the basal activity of several reporter vectors: The PGL3 basic, promoter and control vectors from Promega, and a pSV-based chloramphenicol acetyltransferase (CAT) reporter vector. In the Fisher Rat Thyroid cell Line FRTL-5 thyroid cells transiently transfected, quercetin 10 μM increased the basal activity of all the reporter vectors evaluated, although the degree of the effect was significantly different among them. The analysis of the difference among the regulatory regions of these vectors identified the activator protein 1 (AP-1) binding site as one of the potential sites involved in the quercetin effect. Electromobility shift assay experiments showed that the treatment with quercetin induced the binding of a protein complex to an oligonucleotide containing the AP-1 consensus binding site. This is the first study showing an effect of quercetin on AP-1 activity in thyroid cells. Further studies are in progress to understand the role of AP-1 activation in the effects of quercetin on thyroid function.

Synthesis and biological evaluation of quercetin and resveratrol peptidyl derivatives as potential anticancer and antioxidant agents

Quercetin and resveratrol are polyphenolic compounds, members of the flavonoid and the stilbene family, respectively, both medicinally important as dietary anticancer and antioxidant agents. They are present in a variety of foods-including fruits, vegetables, tea, wine, as well as other dietary supplements-and are responsible for various health benefits. Different quercetin and resveratrol esters of Leu/Met-enkephalin and tetrapeptide Leu-Ser-Lys-Leu (LSKL) were synthesized as model systems for monitoring the influence of the peptides on biological activity of resveratrol and quercetin. General formula of the main peptidyl-quercetin derivatives is 2-[3-(aa)_n-4-hydroxyphenyl]-3,5,7-tri-hydroxy-4H-1-benzopyran-4-on, and the general formula of the main peptidyl-resveratrol derivatives is (E)-5-[4-(aa)_n)styryl]benzene-1,3-diol. The antioxidant and anticancer activities of prepared compounds were investigated. Significant anticancer activity was obtained for the LSKL-based both quercetin and resveratrol derivatives. All prepared compounds exhibit antioxidant activity, in particular quercetin derivative containing Met-enkephalin.

Salvia fruticosa Modulates mRNA Expressions and Activity Levels of Xenobiotic Metabolizing CYP1A2, CYP2E1, NQO1, GPx, and GST Enzymes in Human Colorectal Adenocarcinoma HT-29 Cells

Natural products have gained considerable interests because of their use in some industrial areas including nutrition, cosmetic, pharmacy, and medicine. Salvia fruticosa M. (Lamiaceae) is known for its antioxidant, antimicrobial, and antiproliferative activities. Phase I xenobiotic metabolizing enzymes, CYP1A2 and CYP2E1, produce reactive metabolites which are eliminated by the action of phase II enzymes, NQO1, GPx, and glutathione S-transferases (GSTs). In this study, in vitro modulatory effects of S. fruticosa and its major phenolic compound rosmarinic acid (RA) on CYP1A2, CYP2E1, NQO1, GPx, and GSTm1 mRNA expressions and enzyme activities of GPx and GSTs were investigated in HT-29 cells. An mRNA expression analysis revealed that CYP1A2 and CYP2E1 levels were decreased while those of NQO1, GPx, and GSTm1 increased after S. fruticosa and RA treatments. In parallel to gene expressions, enzyme activities of GPx and GSTs by S. fruticosa increased 1.68- and 1.48-fold, respectively. Moreover, RA increased GPx and GSTs activities 1.67- and 1.94-fold, respectively. The results of this preliminary study show that metabolism of xenobiotics may be altered due to changes in the expression and activity of the investigated enzymes by S. fruticosa.

Molecular Targets Underlying the Anticancer Effects of Quercetin: An Update

Quercetin, a medicinally important member of the flavonoid family, is one of the most prominent dietary antioxidants. It is present in a variety of foods—including fruits, vegetables, tea, wine, as well as other dietary supplements—and is responsible for various health benefits. Numerous pharmacological effects of quercetin include protection against diseases, such as osteoporosis, certain forms of malignant tumors, and pulmonary and cardiovascular disorders. Quercetin has the special ability of scavenging highly reactive species, such as hydrogen peroxide, superoxide anion, and hydroxyl radicals. These oxygen radicals are called reactive oxygen species, which can cause oxidative damage to cellular components, such as proteins, lipids, and deoxyribonucleic acid. Various oxygen radicals play important roles in pathophysiological and degenerative processes, such as aging. Subsequently, several studies have been performed to evaluate possible advantageous health effects of quercetin and to collect scientific evidence for these beneficial health claims. These studies also gather data in order to evaluate the exact mechanism(s) of action and toxicological effects of quercetin. The purpose of this review is to present and critically analyze molecular pathways underlying the anticancer effects of quercetin. Current limitations and future directions of research on this bioactive dietary polyphenol are also critically discussed.

Anti Proliferative and Pro Apoptotic Effects of Flavonoid Quercetin Are Mediated by CB1 Receptor in Human Colon Cancer Cell Lines

Quercetin, the major constituent of flavonoid and widely present in fruits and vegetables, is an attractive compound for cancer prevention due to its beneficial anti proliferative effects, showing a crucial role in the regulation of apoptosis and cell cycle signaling. In vitro studies have demonstrated that quercetin specifically influences colon cancer cell proliferation. Our experiments, using human colon adenocarcinoma cells, confirmed the anti proliferative effect of quercetin and gave intriguing new insight in to the knowledge of the mechanisms involved. We observed a significant increase in the expression of the endocannabinoids receptor (CB1-R) after quercetin treatment. CB1-R can be considered an estrogen responsive receptor and quercetin, having a structure similar to that of the estrogens, can interact with CB1-R leading to the regulation of cell growth. In order to clarify the contribution of the CB1-R to the quercetin action, we investigated some of the principal molecular pathways that are inhibited or activated by this natural compound. In particular we detected the inhibition of the major survival signals like the PI3K/Akt/mTOR and an induction of the pro apoptotic JNK/JUN pathways. Interestingly, the metabolism of β-catenin was modified by flavonoid both directly and through activated CB1-R. In all the experiments done, the quercetin action has proven to be reinforced by anandamide (Met-F-AEA), a CB1-R agonist, and partially counteracted by SR141716, a CB1-R antagonist. These findings open new perspectives for anticancer therapeutic strategies.

Antimutagenic effect of dioscorea pentaphylla on genotoxic effect induced by methyl methanesulfonate in the Drosophila wing spot test

Objectives:

Plants as dietary sources are known to have several chemoprotective agents. Dioscorea pentaphylla is an important medicinal plant, which is often used as edible food. This study was undertaken to evaluate the antigenotoxic potential of D. pentaphylla extracts on the genotoxic effect induced by methyl methanesulfonate (MMS) in the Drosophila wing spot test.

Materials and Methods:

The somatic mutation and recombination test (SMART) was carried out in Drosophila melanogaster. In transheterogyous larvae, multiple wing hair (mwh 3-0.3) and flare (flr3-38.8) genes were used as markers of the extent of mutagenicity.

Results:

It was observed thatall the three extracts (petroleum ether, choloroform, and ethyl alcohol) in the combined treatment had significantly inhibited the effect of MMS-induced genotoxic effects. When compared to others, the ethanol extract showed a very significant antimutagenic activity.

Conclusion:

The compounds that are present in the extracts may directly interact with the methyl radical groups of MMS and inactivate them by chemical reaction. It is also possible that the compounds in the extract compete to interact with the nucleophilic sites in deoxyribonucleic acid (DNA), thus altering the binding of the mutagen to these sites. Although our results indicate that the compounds present in the extracts may directly interact with the methyl radical groups of MMS and inactivate them by chemical reaction, it may also be quite interesting to investigate through the other different mechanisms by which D. pentaphylla could interfere in vivo on the effect of genotoxic agents.

The use of endemic Iranian plant, Echium amoenum, against the ethyl methanesulfonate and the recovery of mutagenic effects

In this study, potential genotoxic effects of ethyl methanesulfonate (EMS) that caused mutagenicity in a variety of organisms were tried to resolve by the methanol and chloroform extract of Echium amoenum (EAmet and EAchl) Fisch. & C.A. Mey. from the family of Boraginaceae, which is an endemic plant, and is used as an alternative treatment among public in Iran. Somatic mutation and recombination test with Drosophila wing was used to determine the genotoxic and antigenotoxic effects in our investigations. For this purpose, 3-day-old transheterozygous larvae of mwh/flr3 genotype of Drosophila melanogaster were used in all our experiments. The larvae were fed chronically on the Drosophila instant medium (DIM) including 1 ppm EMS. However, in another application group, different concentrations (1, 2 and 4 ppm) of EAmet and EAchl were added to DIM including 1 ppm EMS (EMS + EAmet and EMS + EAchl). Then, for the matured individuals, wing preparates were prepared within the mediums that include control group that has only DIM, negative control group that contains dimethyl sulfoxide and application groups in different concentrations that contain EMS, EMS + EAmet and EMS + EAchl. Clone induction frequency for the normal wing phenotype of EMS application group was observed to be 2.00. In the EMS + EAmet application group, the value of 1 ppm EAmet is 1.49, value of 2 ppm EAmet is 1.08 and value of 4 ppm EAmet is 0.72; in the EMS + EAchl application group, the value of 1 ppm is EAchl 1.33, value of 2 ppm EAchl is 0.67 and value of 4 ppm EAchl is 0.56 were determined. This decrease observed between EMS and all application groups in terms of total induction frequency is statistically significant ( p < 0.05). These results concluded that chloroform extracts were more effective than the methanol extracts of E. amoenum.

Dose-dependent effect of galangin on fructose-mediated insulin resistance and oxidative events in rat kidney

Galangin is an antioxidant flavonol present in high concentrations in the rhizome of Alpinia galanga. We investigated the effect of galangin on whole-body insulin resistance and kidney oxidative stress in a fructose-induced rat model of metabolic syndrome. Male albino Wistar rats were divided into 6 groups containing six animals each. Groups I and VI received a starch-based control diet, while groups II, III, IV and V were fed a high fructose diet (60 g/100 g). Groups III, IV and V additionally received galangin (50, 100 and 200 μg/kg body weight, respectively) while group VI received 200 μg galangin/kg body weight. At the end of 60 days, fructose-fed rats exhibited insulin resistance, increased levels of peroxidation end products and diminished antioxidant status. galangin, dose-dependently normalized blood glucose and insulin levels. The minimum effective dose was 100 μg galangin/kg body weight. At this dose, galangin also prevented the development of insulin resistance and the exaggerated the response to oral glucose challenge. The oxidant-antioxidant balance was maintained by galangin. Micro-albuminuria and tubular and glomerular changes observed in fructose-treated rats were significantly prevented by galangin (100 μg/kg body weight). These findings imply that galangin potentiates insulin sensitivity and antioxidant capacity and reduces renal damage in this dietary model of metabolic syndrome.

Quercetin: a potential drug to reverse multidrug resistance

This review centers on recent findings with respect to modulating cancer multidrug resistance (MDR) with the well-known flavonoid quercetin. After a short introduction of quercetin, major in vitro and in vivo findings are summarized showing that quercetin is a MDR modulator and thus a potential chemosensitizer. Finally, we contemplate future prospects of modulating MDR in the clinic.

Free radical scavenging, antioxidant enzymes and wound healing activities of leaves extracts from Clerodendrum infortunatum L

Three successive extracts of Clerodendrum infortunatum L. leaves have been studied for their potential as antioxidants in 1,1-diphenyl-2-picrylhydrazyl (DPPH) model. The scavenging activity of ethanol extract was found to be high when compared to petroleum ether and chloroform extracts. Hence, it was selected to evaluate the beneficial properties using in vitro and in vivo models. The antioxidant and its protective effects against CCl(4) induced oxidative stress in rats were significantly high. Further, to validate the traditional therapeutic claim, wound healing activity of the plant extracts was also carried out. Among the three extracts tested the petroleum ether and ethanol extracts exhibited a significant response. The presence of high antioxidant and pharmacological properties correlates to the total phenolic contents in the plant Clerodendrum infortunatum L.

Myricetin, quercetin, (+)-catechin and (-)-epicatechin protect against N-nitrosamines-induced DNA damage in human hepatoma cells

The aim of this study was to investigate the protective effect of myricetin, quercetin, (+)-catechin and (-)-epicatechin, against N-nitrosodibutylamine (NDBA) and N-nitrosopiperidine (NPIP)-induced DNA damage in human hepatoma cells (HepG2). DNA damage (strand breaks and oxidized purines/pyrimidines) was evaluated by the alkaline single-cell gel electrophoresis or Comet assay. (+)-Catechin at the lowest concentration (10 microM) showed the maximum reduction of DNA strand breaks (23%), the formation of endonuclease III (Endo III, 19-21%) and formamidopyrimidine-DNA glycosylase (Fpg, 28-40%) sensitive sites induced by NDBA or NPIP. (-)-Epicatechin also decreased DNA strand breaks (10 microM, 20%) and the oxidized pyrimidines/purines (33-39%) induced by NDBA or NPIP, respectively. DNA strand breaks induced by NDBA or NPIP were weakly reduced by myricetin at the lowest concentration (0.1 microM, 10-19%, respectively). Myricetin also reduced the oxidized purines (0.1 microM, 17%) and pyrimidines (0.1 microM, 15%) induced by NDBA, but not the oxidized pyrimidines induced by NPIP. Quercetin did not protect against NDBA-induced DNA damage, but it reduced the formation of Endo III and Fpg sensitive sites induced by NPIP (0.1 microM, 17-20%, respectively). In conclusion, our results indicate that (+)-catechin and (-)-epicatechin at the concentrations tested protect human derived cells against oxidative DNA damage effects of NDBA and NPIP. However, myricetin at the concentrations tested only protects human cells against oxidative DNA damage induced by NDBA and quercetin against oxidative DNA damage induced by NPIP.

Antigenotoxic effects of Citrus aurentium L. fruit peel oil on mutagenicity of two alkylating agents and two metals in the Drosophila wing spot test

Antigenotoxic effects of Citrus aurentium L. (Rutaceae) fruit peel oil (CPO) in combination with mutagenic metals and alkylating agents were studied using the wing spot test of D. melanogaster. The four reference mutagens, potassium dichromate (K2Cr2O7), cobalt chloride (CoCl2), ethylmethanesulfonate (EMS), and N-ethyl-N-nitrosourea (ENU) were clearly genotoxic. CPO alone at doses from 0.1 to 0.5% in Tween 80 was not mutagenic and did not enhance the mutagenic effect of the reference mutagens. However, antigenotoxic effects of CPO were clearly demonstrated in chronic cotreatments with mutagens and oil, by a significant decrease in wing spots induced by all four mutagens. The D. melanogaster wing spot test was found to be a suitable assay for detecting antigenotoxic effects in vivo.

Regulation of polyphenols accumulation by combined overexpression/silencing key enzymes of phenylpropanoid pathway

There is a growing interest in the metabolic engineering of plant with increased desirable polyphenols such as chlorogenic acid (CGA) and rutin. In this study, the effects of overexpression of both phenylalanine ammonia lyase (AtPAL2), the first enzyme of the phenylpropanoid pathway, and hydroxycinnamoyl-CoA quinate:hydroxycinnamoyl transferase (NtHQT), the last enzyme of CGA biosynthesis, and the overexpression of AtPAL2 together with silencing of NtHQT were investigated in tobacco. Transgenic tobacco plants overexpressing AtPAL2 showed two and five times increases of CGA and rutin levels than the wild-type (WT) plants, respectively. Overexpression of NtHQT further increases the accumulation of CGA in the AtPAL2 plants to about three times than that of the WT level, while silencing of NtHQT in AtPAL2 plants results in about 12 times increase in rutin level than that of the WT plants. Simultaneous overexpression of phenylalanine ammonia lyase (PAL) and overexpression/silencing HQT could be used for the production of functional food with increased polyphenols.

Comparative QSAR studies of CYP1A2 inhibitor flavonoids using 2D and 3D descriptors

Comparative Quantitative Structure Activity Relationship (QSAR) analyses have been performed with 21 naturally occurring flavonoids for their inhibitory effects on cytochrome P450 1A2 enzyme using two-dimensional (topological, structural, and thermodynamic) and three-dimensional (spatial) descriptors. The chemometric tools used for the analyses are stepwise multiple linear regression, partial least squares, genetic function approximation, and genetic partial least squares. The data set was divided into a training set (n = 15) and test set (n = 6), based on K-means clustering technique applied on standardized two-dimensional descriptor matrix, and models were developed from the training set compounds. The best model (genetic partial least squares model using two-dimensional descriptors) was selected based on the highest external predictive R(2) (R(2)(pred)) value (0.840) and the lowest root mean square error of prediction value (0.351). The developed QSAR equations suggest the importance of the double bond present at 2 and 3 positions and requirement of absence of hydroxyl substituent or glycosidic linkage at 3 position of the 1,4-benzopyrone nucleus. Furthermore, the phenyl ring present at 2 position of the 1,4-benzopyrone ring should not be substituted with hydroxyl group. Moreover, hydroxyl groups present at 5 and 7 positions of the benzopyran nucleus should not be glycosylated for good cytochrome P450 1A2 enzyme inhibitory activity.

Metabolomics: a tool for personalizing medicine?

The concept of personalized medicine is based upon using personal genetic information to predict individual responses to drug therapy. However, environmental factors such as diet, energy status, gut microbiota, health status and age will influence the expression of one’s genetic potential. Metabolomics data from biofluid and tissue sample analysis hold information regarding a patient’s genotype and phenotype. Metabolomics data can be rapidly collected from biofluid samples over time, providing temporal metabolic analyses of patient samples. In addition to metabolic markers of a patient’s phenotype, metabolomics can provide markers of drug efficacy, toxicity and clearance.

Cancer phytotherapeutics: role for flavonoids at the cellular level

Dietary foods and fruits possess an array of flavonoids with unique chemical structure and diverse bioactivities relevant to cancer. Numerous epidemiological studies have validated the inverse relation between the consumption of flavonoids and the risk of cancer. Flavonoids possess cancer blocking and suppressing effects. Flavonoids modulate various CYPs involved in carcinogen activation and scavenging reactive species formed from carcinogens by CYP-mediated reactions. They induce biosynthesis of several CYPs. They are involved in the regulation of enzymes of phase-II responsible for xenobiotic biotransformation and colon microflora. Since cytochromes P450, P-gp and phase-II enzymes are involved in the metabolism of drugs and in the processes of chemical carcinogenesis, interactions of flavonoids with these systems hold great promise for their therapeutic potential. The role of flavonoids also includes the inhibition of activation of pro-carcinogens, inhibition of proliferation of cancer cells, selective death of cancer cells by apoptosis, inhibition of metastasis and angiogenesis, activation of immune response against cancer cells, modulation of the inflammatory cascade and the modulation of drug resistance. This has greatly extended the goal of cancer therapy from eradicating the affected cells to control of the cancer phenotype. Phytotherapy is being used in combination with other therapies as phytonutrients have been shown to work by nutrient synergy.

Multitargeted cancer prevention by quercetin

Quercetin is an anti-oxidative flavonoid widely distributed in the plant kingdom. Phenolic hydroxyl groups at the B-ring and the 3-position are responsible for its free radical-scavenging activity. Quercetin is commonly present as a glycoside and is converted to glucuronide/sulfate conjugates during intestinal absorption and only conjugated metabolites are therefore found in circulating blood. Although metabolic conversion attenuates its biological effects, active aglycone may be generated from the glucuronide conjugates by enhanced beta-glucuronidase activity during inflammation. With respect to its relationship with molecular targets relevant to cancer prevention, quercetin aglycone has been shown to interact with some receptors, particularly an aryl hydrocarbon receptor, which is involved in the development of cancers induced by certain chemicals. Quercetin aglycone has also been shown to modulate several signal transduction pathways involving MEK/ERK and Nrf2/keap1, which are associated with the processes of inflammation and carcinogenesis. Rodent studies have demonstrated that dietary administration of this flavonol prevents chemically induced carcinogenesis, especially in the colon, whilst epidemiological studies have indicated that an intake of quercetin may be associated with the prevention of lung cancer. Dietary quercetin is, therefore, a promising agent for cancer prevention and further research is warranted.

The Chemopreventive Effect of Taxifolin Is Exerted through ARE-Dependent Gene Regulation

Phase II detoxification enzymes are responsible for the detoxification and elimination of activated carcinogens, and thus act as important biomarkers for chemoprevention. In this study, we tested the chemopreventive activity of taxifolin, a flavanon compound purified from a mongolian medicinal plant, by measuring quinone reductase (QR) activity in HCT 116 cells. Taxifolin induced significant QR activity, but displayed relatively low cytotoxicity in cells (chemoprevention index=5.75). To identify the target genes regulated by taxifolin, DNA microarray was performed with a 3K human cancer chip containing 3096 human genes associated with carcinogenesis. Significant analysis of microarray (SAM) revealed 428 differentially expressed (DE) genes as statistically significant, with a false discovery rate (FDR) of 57.2% (delta=0.3366). Sixty-five genes, including a few detoxification enzymes (NQO1, GSTM1) and an antioxidant enzyme (TXNRD1), were up-regulated and 363 genes were down-regulated in the presence of 60 microM taxifolin. In view of the finding that selected genes of interest contained antioxidant response element (ARE), we hypothesize that taxifolin modulates chemopreventive genes through activation of the ARE. Transient transfection experiments using the ARE QR-CAT construct demonstrate that taxifolin significantly activates ARE, but not xenobiotic response element (XRE). In conclusion, taxifolin acts as a potential chemopreventive agent by regulating genes via an ARE-dependent mechanism.

Anti-adipogenic activity of rutin in 3T3-L1 cells and mice fed with high-fat diet

Polyphenolic compounds were examined for their effects on suppressing adipocyte differentiation in 3T3-L1 cells. Most polyphenolic compounds inhibited adipocyte development from 3T3-L1 cells to some extent. Among them, rutin was the most effective in suppressing adipocyte differentiation in a dosage dependant manner. Activity of glycerol-3-phosphate dehydrogenase (GPDH), which has a central position in lipogenesis in adipose cells, was also decreased by rutin addition at the induction stage. RT-PCR results demonstrated that mRNA expression of adipogenic transcription factors such as peroxisome proliferator-activated receptor-gamma (PPARgamma) and CCAAT/enhancer binding protein-alpha (C/EBPalpha) in 3T3-L1 cells were remarkably down regulated by rutin treatment. For further investigation on anti-adipogenic activities of rutin, it was orally administered (25 and 50 mg/kg b.w/daily) with high-fat diet (64.4% of total calories as fat) to C57BL/6 mice. Body weight gains were less in high-fat diet + rutin fed groups (HFR) than high-fat diet alone fed group (HF) after 4 weeks. Total cholesterol contents in blood were significantly lower in HFR groups. When mRNA expressions of PPARgamma and C/EBPalpha in hepatocytes were compared between the control HF and HFR groups, their expressions in hepatocytes of HFR groups were significantly suppressed. These results indicate that rutin inhibits adipogenic development in pre-adipocytes and hepatocytes by down regulating expressions of key adipogenic transcription factors.

Dietary flavonoids: effects on xenobiotic and carcinogen metabolism

Flavonoids are present in fruits, vegetables and beverages derived from plants (tea, red wine), and in many dietary supplements or herbal remedies including Ginkgo Biloba, Soy Isoflavones, and Milk Thistle. Flavonoids have been described as health-promoting, disease-preventing dietary supplements, and have activity as cancer preventive agents. Additionally, they are extremely safe and associated with low toxicity, making them excellent candidates for chemopreventive agents. The cancer protective effects of flavonoids have been attributed to a wide variety of mechanisms, including modulating enzyme activities resulting in the decreased carcinogenicity of xenobiotics. This review focuses on the flavonoid effects on cytochrome P450 (CYP) enzymes involved in the activation of procarcinogens and phase II enzymes, largely responsible for the detoxification of carcinogens. A number of naturally occurring flavonoids have been shown to modulate the CYP450 system, including the induction of specific CYP isozymes, and the activation or inhibition of these enzymes. Some flavonoids alter CYPs through binding to the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, acting as either AhR agonists or antagonists. Inhibition of CYP enzymes, including CYP 1A1, 1A2, 2E1 and 3A4 by competitive or mechanism-based mechanisms also occurs. Flavones (chrysin, baicalein, and galangin), flavanones (naringenin) and isoflavones (genistein, biochanin A) inhibit the activity of aromatase (CYP19), thus decreasing estrogen biosynthesis and producing antiestrogenic effects, important in breast and prostate cancers. Activation of phase II detoxifying enzymes, such as UDP-glucuronyl transferase, glutathione S-transferase, and quinone reductase by flavonoids results in the detoxification of carcinogens and represents one mechanism of their anticarcinogenic effects. A number of flavonoids including fisetin, galangin, quercetin, kaempferol, and genistein represent potent non-competitive inhibitors of sulfotransferase 1A1 (or P-PST); this may represent an important mechanism for the chemoprevention of sulfation-induced carcinogenesis. Importantly, the effects of flavonoids on enzymes are generally dependent on the concentrations of flavonoids present, and the different flavonoids ingested. Due to the low oral bioavailability of many flavonoids, the concentrations achieved in vivo following dietary administration tend to be low, and may not reflect the concentrations tested under in vitro conditions; however, this may not be true following the ingestion of herbal preparations when much higher plasma concentrations may be obtained. Effects will also vary with the tissue distribution of enzymes, and with the species used in testing since differences between species in enzyme activities also can be substantial. Additionally, in humans, marked interindividual variability in drug-metabolizing enzymes occurs as a result of genetic and environmental factors. This variability in xenobiotic metabolizing enzymes and the effect of flavonoid ingestion on enzyme expression and activity can contribute to the varying susceptibility different individuals have to diseases such as cancer. As well, flavonoids may also interact with chemotherapeutic drugs used in cancer treatment through the induction or inhibition of their metabolism.

The antimutagenic activity of Lavandula angustifolia (lavender) essential oil in the bacterial reverse mutation assay

Essential oils from Melaleuca alternifolia (tea-tree oil) and Lavandula angustifolia (lavender oil) are commonly used to treat minor health problems. Tea-tree oil possesses broad-spectrum antimicrobial activity, and is increasingly used for skin problems. Lavender oil, traditionally used as an antiseptic agent, is now predominantly used as a relaxant, carminative, and sedative in aromatherapy. Despite their growing use no data are available on their mutagenic potential. In this study, after determining the chemical composition of tea-tree oil and lavender oil, by gas-chromatography and mass spectrometry, we investigated their mutagenic and antimutagenic activities by the bacterial reverse mutation assay in Salmonella typhimurium TA98 and TA100 strains and in Escherichia coli WP2 uvrA strain, with and without an extrinsic metabolic activation system. Neither essential oil had mutagenic activity on the two tested Salmonella strains or on E. coli, with or without the metabolic activation system. Conversely, lavender oil exerted strong antimutagenic activity, reducing mutant colonies in the TA98 strain exposed to the direct mutagen 2-nitrofluorene. Antimutagenicity was concentration-dependent: the maximal concentration (0.80 mg/plate) reduced the number of histidine-independent revertant colonies by 66.4%. Lavender oil (0.80 mg/plate) also showed moderate antimutagenicity against the TA98 strain exposed to the direct mutagen 1-nitropyrene. Its antimutagenic property makes lavender oil a promising candidate for new applications in human healthcare.

Molecular cloning and sequence analysis of a novel chalcone synthase cDNA from Ginkgo biloba

A chalcone synthase (CHS) gene was cloned from Ginkgo biloba for the first time and it was also the first cloned gene involved in flavonoids metabolic pathway in G. biloba. The full-length cDNA of G. biloba CHS (designated as Gbchs) was 1608bp with poly(A) tailing and it contained a 1173bp open reading frame (ORF) encoding a 391 amino acid protein. Gbchs was found to have extensive homology with those of other plant chs genes via multiple alignments. The active sites of the CoA binding, coumaroyl pocket and cyclization pocket in CHS protein of Medicago sativa were also found in GbCHS. Molecular modeling of GbCHS indicated that the three-dimensional structure of GbCHS strongly resembled that of M. sativa (MsCHS2), implying GbCHS may have similar functions with MsCHS2. Phylogenetic tree analysis revealed that GbCHS had closer relationship with CHSs from gymnosperm plants than from other plants. Gbchs is a useful tool to study the regulation of flavonoids metabolism in G. biloba.

Suppression of CYP1A1 expression by naringenin in murine Hepa-1c1c7 cells

Naringenin, dietary flavonoid, is antioxidant constituents of many citrus fruits. In the present study, we investigated the effect of naringenin on 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-inducible CYP1A1 gene expression in mouse hepatoma Hepa-1c1c7 cells. Naringenin alone did not affect CYP1A1-specific 7-ethoxyresorufin O-deethylase (EROD) activity. In contrast, the TCDD-inducible EROD activities were markedly reduced upon concomitant treatment with TCDD and naringenin in a dose dependent manner. TCDD-induced CYP1A1 mRNA level was also markedly suppressed by naringenin. A transient transfection assay using dioxin-response element (DRE)-linked luciferase and electrophoretic mobility shift assay revealed that naringenin reduced transformation of the aryl hydrocarbons receptor(AhR) to a form capable of specifically binding to the DRE sequence in the promoter of the CYP1A1 gene. These results suggest the down regulation of the CYP1A1 gene expression by either naringenin in Hepa-1c1c7 cells might be antagonism of the DRE binding potential of nuclear AhR.

Lack of an inducible effect of dietary soy isoflavones on the mRNA abundance of hepatic cytochrome P-450 isozymes in rats

Modulation of the activity and content of cytochrome P-450 (CYP) in hepatic microsomes may be important to human health since these enzymes activate and inactivate a wide range of xenobiotics and food components. Regulation of the inducibility of most CYPs involves transcriptional regulation and post-transcriptional mRNA stabilization. We examined in the present study the effect of dietary soy isoflavone (0-300 mg of isoflavone/kg of diet) on the mRNA abundance of rat hepatic CYP1A1, CYP1A2, CYP2B1/2, CYP2C11, CYP2E1, CYP3A1, CYP3A2 and CYP4A1 by quantitative competitive RT-PCR and real-time monitored RT-PCR. A fermented soy extract containing 155 mg/g of genistein, 127 mg/g of daidzein, and other minor isoflavones was used as the isoflavone source. The dietary soy isoflavone had no affect on the hepatic mRNA abundance of these CYPs. The results by both methods were well matched and indicate that the dietary soy isoflavone did not cause the induction of CYPs by transcriptional step-up regulation or post-transcriptional mRNA stabilization.

Kinetic Comparisons of Anthocyanin Reactivities towards 2,2′-Azobis(2-amidinopropane) (AAPH) Radicals, Hydrogen Peroxide and tert-Buthylhydroperoxide by Capillary Zone Electrophoresis

Twelve major anthocyanins identified in bilberry extracts were studied in vitro using capillary zone electrophoresis (CZE) for their reactions towards 2,2'-azobis(2-amidinopropane) (AAPH) radicals, hydrogen peroxides (H(2)O(2)) and tert-buthylhydroperoxides (t-BuOOH). Reactivity towards AAPH radicals was primarily determined by the aglycon structure, not by the type of sugar moiety. Delphinidins carrying three-hydroxyl groups on the B ring were most reactive followed by cyanidins, with two-hydroxyl groups. Further, methylation of the hydroxyl groups reduced reactivity towards AAPH radicals. However, reactivity of anthocyanins towards H(2)O(2) was not significantly affected by aglycon structure or by the type of sugar moiety; there being no marked difference in reaction rates among the anthocyanins. Reactivity towards t-BuOOH was essentially the same as towards H(2)O(2), although the reaction rate was several times smaller. Also, the reaction rate of anthocyanin towards peroxide was relatively high compared to that of (+)-catechin (approximately 30 times larger) measured as a reference antioxidant, whereas the reactivities of anthocyanins and (+)-catechin towards AAPH radicals were similar.