Screening Method for the Discovery of Potential Cancer Chemoprevention Agents Based on Mass Spectrometric Detection of Alkylated Keap1

Keap1-Nrf2 pathway: a key mechanism in the occurrence and development of cancer

The Keap1-Nrf2 signaling pathway is a major regulator of the cytoprotective response, participating in endogenous and exogenous stress caused by ROS (reactive oxygen species). Nrf2 is the core of this pathway. We summarized the literature on Keap1-Nrf2 signaling pathway and summarized the following three aspects: structure, function pathway, and cancer and clinical application status. This signaling pathway is similar to a double-edged sword: on the one hand, Nrf2 activity can protect cells from oxidative and electrophilic stress; on the other hand, increasing Nrf2 activity can enhance the survival and proliferation of cancer cells. Notably, oxidative stress is also considered a marker of cancer in humans. Keap1-Nrf2 signaling pathway, as a typical antioxidant stress pathway, is abnormal in a variety of human malignant tumor diseases (such as lung cancer, liver cancer, and thyroid cancer). In recent years, research on the Keap1-Nrf2 signaling pathway has become increasingly in-depth and detailed. Therefore, it is of great significance for cancer prevention and treatment to explore the molecular mechanism of the occurrence and development of this pathway.

Chlorogenic acid as an indispensible partner of caffeic acid in coffee via selective regulation of prooxidative actions of caffeic acid

Chlorogenic acid (CGA) and caffeic acid (CA) are two major phenolic acids in coffee. Though the International Agency for Research on Cancer has classified CA as a Group2B carcinogen, coffee consumption seems generally safe within the usual levels of intake and is more likely to benefit health than to harm it. We thus speculated that CGA may effectively suppress the carcinogenic potential of CA. In a molar ratio achievable in vivo, this study shows that CGA can inhibit (i) copper reduction caused by CA, (ii) CA oxidation caused by copper, (iii) the formation of hydroxyl radicals by CA and copper, and (iv) DNA damage induced by CA, quercetin or (-)-epigallocatechin-3-gallate in the presence of copper. CA tends to undergo autoxidation to produce hydrogen peroxide and quinone, which further reacts with proteins to form quinoproteins. This autoxidation at a tolerable level normally induces beneficial adaptive responses. This study shows that CGA is less efficient than CA in producing hydrogen peroxide and quinoprotein; however, together they synergistically produce hydrogen peroxide and quinoprotein in vitro at a molar ratio achievable in vivo. In conclusion, CGA can selectively regulate the prooxidant activities of CA depending on whether copper is involved or not. CGA could be viewed as an indispensable partner of CA in coffee, given its dual role in suppressing the carcinogenic potential of CA and boosting CA autoxidation which is beneficial for disease prevention.

Progress of isolation, chemical synthesis and biological activities of natural chalcones bearing 2-hydroxy-3-methyl-3-butenyl group

Chalcones have a three-carbon α,β-unsaturated carbonyl system composed of two phenolic rings. Many chalcones have shown broad spectrum of biological activities with clinical potentials against various diseases. They are usually abundant in seeds, fruit skin, bark and flowers of most edible plants. Among them, chalcones bearing 2-hydroxy-3-methyl-3-butenyl (HMB) group have been reported several times in the past few decades due to their novel scaffolds and numerous interesting biological activities. In this paper, we reviewed the isolation of twelve natural chalcones and a natural chalcone-type compound bearing 2-hydroxy-3-methyl-3-butenyl group discovered so far, and reviewed their synthesis methods and biological activities reported in the literature. We anticipate that this review will inspire further research of natural chalcones.

Dracaenone, a novel type of homoisoflavone: Natural source, biological activity and chemical synthesis

Abstract:

The discovery and synthesis of natural products, especially those possessing novel scaffolds, are crucial to the development of new drugs. Dracaenones are part of homoisoflavone natural products, owning a complex spiro-bridged polycyclic structures bearing benzylic quaternary carbon centers, and some of them reveal considerable biological activity. There have been continuous studies on these compounds due to the rare structure and the important biological properties. However, a systematic summary and analysis for dracaenone is lacking. This review aims to generally summarize the natural source, synthetic strategies and biological activities of dracaenones, moreover, the limitations, challenges, and future prospects were discussed, wishing to provide references for the follow-up study of compounds with similar skeleton.

Dietary prenylated flavonoid xanthohumol alleviates oxidative damage and accelerates diabetic wound healing via Nrf2 activation

Diabetic skin ulcer is one of the most common complications in patients suffering diabetes mellitus. Xanthohumol (XN), a hop-derived prenylated dietary flavonoid, has multiple health beneficial bioactivities. In the present study, we reported XN alleviates oxidative damage and accelerates diabetic wound healing via Nrf2 activation. In vitro, XN attenuated hydrogen peroxide (H₂O₂)-induced cytotoxicity, ROS production, cell apoptosis, as well as high glucose-induced cell damage. Mechanistic studies further demonstrated that XN could stabilize nuclear factor erythroid 2-related factor 2 (Nrf2) and promote its nuclear translocation, which was associated with AMPKα activation and covalent modification of Keap1 by XN. In vivo, XN increased Nrf2 expression and accelerated diabetic wound healing. Our study revealed a novel function of XN in diabetic wound healing as well as the underlying molecular mechanisms, suggesting XN is a promising lead compound and a potential food and/or drug candidate for the treatment of diabetic skin ulcers.

Protein Adducts and Protein Oxidation as Molecular Mechanisms of Flavonoid Bioactivity

There are tens of thousands of scientific papers about flavonoids and their impacts on human health. However, despite the vast amount of energy that has been put toward studying these compounds, a unified molecular mechanism that explains their bioactivity remains elusive. One contributing factor to the absence of a general mechanistic explanation of their bioactivity is the complexity of flavonoid chemistry in aqueous solutions at neutral pH. Flavonoids have acidic protons, are redox active, and frequently auto-oxidize to produce an array of degradation products including electrophilic quinones. Flavonoids are also known to interact with specificity and high affinity with a variety of proteins, and there is evidence that some of these interactions may be covalent. This review summarizes the mechanisms of flavonoid oxidation in aqueous solutions at neutral pH and proposes the formation of protein-flavonoid adducts or flavonoid-induced protein oxidation as putative mechanisms of flavonoid bioactivity in cells. Nucleophilic residues in proteins may be able to form covalent bonds with flavonoid quinones; alternatively, specific amino acid residues such as cysteine, methionine, or tyrosine in proteins could be oxidized by flavonoids. In either case, these protein-flavonoid interactions would likely occur at specific binding sites and the formation of these types of products could effectively explain how flavonoids modify proteins in cells to induce downstream biochemical and cellular changes.

Chemical labeling strategies for small molecule natural product detection and isolation

Covering: Up to 2020.It is widely accepted that small molecule natural products (NPs) evolved to carry out a particular ecological function and that these finely-tuned molecules can sometimes be appropriated for the treatment of disease in humans. Unfortunately, for the natural products chemist, NPs did not evolve to possess favorable physicochemical properties needed for HPLC-MS analysis. The process known as derivatization, whereby an NP in a complex mixture is decorated with a nonnatural moiety using a derivatizing agent (DA), arose from this sad state of affairs. Here, NPs are freed from the limitations of natural functionality and endowed, usually with some degree of chemoselectivity, with additional structural features that make HPLC-MS analysis more informative. DAs that selectively label amines, carboxylic acids, alcohols, phenols, thiols, ketones, and aldehydes, terminal alkynes, electrophiles, conjugated alkenes, and isocyanides have been developed and will be discussed here in detail. Although usually employed for targeted metabolomics, chemical labeling strategies have been effectively applied to uncharacterized NP extracts and may play an increasing role in the detection and isolation of certain classes of NPs in the future.

The Multiple Biological Targets of Hops and Bioactive Compounds

Botanical dietary supplements for women's health are increasingly popular. Older women tend to take botanical supplements such as hops as natural alternatives to traditional hormone therapy to relieve menopausal symptoms. Especially extracts from spent hops, the plant material remaining after beer brewing, are enriched in bioactive prenylated flavonoids that correlate with the health benefits of the plant. The chalcone xanthohumol (XH) is the major prenylated flavonoid in spent hops. Other less abundant but important bioactive prenylated flavonoids are isoxanthohumol (IX), 8-prenylnaringenin (8-PN), and 6-prenylnaringenin (6-PN). Pharmacokinetic studies revealed that these flavonoids are conjugated rapidly with glucuronic acid. XH also undergoes phase I metabolism in vivo to form IX, 8-PN, and 6-PN. Several hop constituents are responsible for distinct effects linked to multiple biological targets, including hormonal, metabolic, inflammatory, and epigenetic pathways. 8-PN is one of the most potent phytoestrogens and is responsible for hops' estrogenic activities. Hops also inhibit aromatase activity, which is linked to 8-PN. The weak electrophile, XH, can activate the Keap1-Nrf2 pathway and turn on the synthesis of detoxification enzymes such as NAD(P)H-quinone oxidoreductase 1 and glutathione S-transferase. XH also alkylates IKK and NF-κB, resulting in anti-inflammatory activity. Antiobesity activities have been described for XH and XH-rich hop extracts likely through activation of AMP-activated protein kinase signaling pathways. Hop extracts modulate the estrogen chemical carcinogenesis pathway by enhancing P450 1A1 detoxification. The mechanism appears to involve activation of the aryl hydrocarbon receptor (AhR) by the AhR agonist, 6-PN, leading to degradation of the estrogen receptor. Finally, prenylated phenols from hops are known inhibitors of P450 1A1/2; P450 1B1; and P450 2C8, 2C9, and 2C19. Understanding the biological targets of hop dietary supplements and their phytoconstituents will ultimately lead to standardized botanical products with higher efficacy, safety, and chemopreventive properties.

Activation of Nrf2 signaling by natural products-can it alleviate diabetes?

Type 2 diabetes mellitus (DM) has reached pandemic proportions and effective prevention strategies are wanted. Its onset is accompanied by cellular distress, the nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor boosting cytoprotective responses, and many phytochemicals activate Nrf2 signaling. Thus, Nrf2 activation by natural products could presumably alleviate DM. We summarize function, regulation and exogenous activation of Nrf2, as well as diabetes-linked and Nrf2-susceptible forms of cellular stress. The reported amelioration of insulin resistance, β-cell dysfunction and diabetic complications by activated Nrf2 as well as the status quo of Nrf2 in precision medicine for DM are reviewed.

Ligand Fishing: A Remarkable Strategy for Discovering Bioactive Compounds from Complex Mixture of Natural Products

Identification of active compounds from natural products is a critical and challenging task in drug discovery pipelines. Besides commonly used bio-guided screening approaches, affinity selection strategy coupled with liquid chromatography or mass spectrometry, known as ligand fishing, has been gaining increasing interest from researchers. In this review, we summarized this emerging strategy and categorized those methods as off-line or on-line mode according to their features. The separation principles of ligand fishing were introduced based on distinct analytical techniques, including biochromatography, capillary electrophoresis, ultrafiltration, equilibrium dialysis, microdialysis, and magnetic beads. The applications of ligand fishing approaches in the discovery of lead compounds were reviewed. Most of ligand fishing methods display specificity, high efficiency, and require less sample pretreatment, which makes them especially suitable for screening active compounds from complex mixtures of natural products. We also summarized the applications of ligand fishing in the modernization of Traditional Chinese Medicine (TCM), and propose some perspectives of this remarkable technique.

Botanicals and Their Bioactive Phytochemicals for Women's Health

Botanical dietary supplements are increasingly popular for women's health, particularly for older women. The specific botanicals women take vary as a function of age. Younger women will use botanicals for urinary tract infections, especially Vaccinium macrocarpon (cranberry), where there is evidence for efficacy. Botanical dietary supplements for premenstrual syndrome (PMS) are less commonly used, and rigorous clinical trials have not been done. Some examples include Vitex agnus-castus (chasteberry), Angelica sinensis (dong quai), Viburnum opulus/prunifolium (cramp bark and black haw), and Zingiber officinale (ginger). Pregnant women have also used ginger for relief from nausea. Natural galactagogues for lactating women include Trigonella foenum-graecum (fenugreek) and Silybum marianum (milk thistle); however, rigorous safety and efficacy studies are lacking. Older women suffering menopausal symptoms are increasingly likely to use botanicals, especially since the Women's Health Initiative showed an increased risk for breast cancer associated with traditional hormone therapy. Serotonergic mechanisms similar to antidepressants have been proposed for Actaea/Cimicifuga racemosa (black cohosh) and Valeriana officinalis (valerian). Plant extracts with estrogenic activities for menopausal symptom relief include Glycine max (soy), Trifolium pratense (red clover), Pueraria lobata (kudzu), Humulus lupulus (hops), Glycyrrhiza species (licorice), Rheum rhaponticum (rhubarb), Vitex agnus-castus (chasteberry), Linum usitatissimum (flaxseed), Epimedium species (herba Epimedii, horny goat weed), and Medicago sativa (alfalfa). Some of the estrogenic botanicals have also been shown to have protective effects against osteoporosis. Several of these botanicals could have additional breast cancer preventive effects linked to hormonal, chemical, inflammatory, and/or epigenetic pathways. Finally, although botanicals are perceived as natural safe remedies, it is important for women and their healthcare providers to realize that they have not been rigorously tested for potential toxic effects and/or drug/botanical interactions. Understanding the mechanism of action of these supplements used for women's health will ultimately lead to standardized botanical products with higher efficacy, safety, and chemopreventive properties.

Induction of NAD(P)H:Quinone Oxidoreductase 1 (NQO1) by Glycyrrhiza Species Used for Women's Health: Differential Effects of the Michael Acceptors Isoliquiritigenin and Licochalcone A

For the alleviation of menopausal symptoms, women frequently turn to botanical dietary supplements, such as licorice and hops. In addition to estrogenic properties, these botanicals could also have chemopreventive effects. We have previously shown that hops and its Michael acceptor xanthohumol (XH) induced the chemoprevention enzyme,

NAD(P)H

quinone oxidoreductase 1 (NQO1), in vitro and in vivo. Licorice species could also induce NQO1, as they contain the Michael acceptors isoliquiritigenin (LigC) found in Glycyrrhiza glabra (GG), G. uralensis (GU), G. inflata (GI), and licochalcone A (LicA) which is only found in GI. These licorice species and hops induced NQO1 activity in murine hepatoma (Hepa1c1c7) cells; hops ≫ GI > GG ≅ GU. Similar to the known chemopreventive compounds curcumin (turmeric), sulforaphane (broccoli), and XH, LigC and LicA were active dose-dependently; sulforaphane ≫ XH > LigC > LicA ≅ curcumin ≫ liquiritigenin (LigF). Induction of the antioxidant response element luciferase in human hepatoma (HepG2-ARE-C8) cells suggested involvement of the Keap1-Nrf2 pathway. GG, GU, and LigC also induced NQO1 in nontumorigenic breast epithelial MCF-10A cells. In female Sprague-Dawley rats treated with GG and GU, LigC and LigF were detected in the liver and mammary gland. GG weakly enhanced NQO1 activity in the mammary tissue but not in the liver. Treatment with LigC alone did not induce NQO1 in vivo most likely due to its conversion to LigF, extensive metabolism, and its low bioavailability in vivo. These data show the chemopreventive potential of licorice species in vitro could be due to LigC and LicA and emphasize the importance of chemical and biological standardization of botanicals used as dietary supplements. Although the in vivo effects in the rat model after four-day treatment are minimal, it must be emphasized that menopausal women take these supplements for extended periods of time and long-term beneficial effects are quite possible.

Xanthohumol, a prenylated chalcone from beer hops, acts as an α-glucosidase inhibitor in vitro

Xanthohumol (XN) is a unique prenylated flavonoid in hops (Humulus lupulus L.) and beer. XN alleviates hyperglycemia and has potential usage in the treatment of type 2 diabetes. In the present study, a series of in vitro experiments were performed to investigate whether XN was an effective inhibitor of α-glucosidase. The results showed that XN inhibited α-glucosidase in a reversible and noncompetitive manner, with an IC50 value of 8.8 μM and that XN inhibited the release of glucose from the maltose in the apical side of the Caco-2 cell monolayer. Fluorescence and circular dichroism spectra results indicated that XN directly bound to α-glucosidase and induced minor conformational changes of the enzyme. These results demonstrated that XN is a promising α-glucosidase inhibitor, which therefore could be used as functional food to alleviate postprandial hyperglycemia and as a potential candidate for the development of an antidiabetic agent.

Biological and chemical standardization of a hop (Humulus lupulus) botanical dietary supplement

Concerned about the safety of conventional estrogen replacement therapy, women are using botanical dietary supplements as alternatives for the management of menopausal symptoms such as hot flashes. Before botanical dietary supplements can be evaluated clinically for safety and efficacy, botanically authenticated and standardized forms are required. To address the demand for a standardized, estrogenic botanical dietary supplement, an extract of hops (Humulus lupulus L.) was developed. Although valued in the brewing of beer, hop extracts are used as anxiolytics and hypnotics and have well-established estrogenic constituents. Starting with a hop cultivar used in the brewing industry, spent hops (the residue remaining after extraction of bitter acids) were formulated into a botanical dietary supplement that was then chemically and biologically standardized. Biological standardization utilized the estrogen-dependent induction of alkaline phosphatase in the Ishikawa cell line. Chemical standardization was based on the prenylated phenols in hops that included estrogenic 8-prenylnaringenin, its isomer 6-prenylnaringenin, and pro-estrogenic isoxanthohumol and its isomeric chalcone xanthohumol, all of which were measured using high-performance liquid chromatography-tandem mass spectrometry. The product of this process was a reproducible botanical extract suitable for subsequent investigations of safety and efficacy.

Differential regulation of detoxification enzymes in hepatic and mammary tissue by hops (Humulus lupulus) in vitro and in vivo

SCOPE

Hops contain the phytoestrogen, 8-prenylnaringenin, and the cytoprotective compound, xanthohumol (XH). XH induces the detoxification enzyme, NAD(P)H-quinone oxidoreductase (NQO1) in vitro; however, the tissue distribution of XH and 8-prenylnaringenin and their tissue-specific activity have not been analyzed.

METHODS AND RESULTS

An orally administered hop extract and subcutaneously injected XH were administered to Sprague-Dawley rats over 4 days. LC-MS-MS analysis of plasma, liver, and mammary gland revealed that XH accumulated in liver and mammary glands. Compared with the low level in the original extract, 8-prenylnaringenin was enriched in the tissues. Hops and XH-induced NQO1 in the liver, while only hops reduced NQO1 activity in the mammary gland. Mechanistic studies revealed that hops modulated NQO1 through three mechanisms. In liver cells, (i) XH modified Kelch-like ECH-associated protein leading to nuclear factor (erythroid-derived 2)-like 2 (Nrf2) translocation and antioxidant response element (ARE) activation; (ii) hop-mediated ARE induction was partially mediated through phosphorylation of Nrf2 by PKC; (iii) in breast cells, 8-prenylnaringenin reduced NQO1 likely through binding to estrogen receptorα, recruiting Nrf2, and downregulating ARE-regulated genes.

CONCLUSION

XH and 8-prenylnaringenin in dietary hops are bioavailable to the target tissues. While hops and XH might be cytoprotective in the liver, 8-prenylnaringenin seems responsible for hop-mediated NQO1 reduction in the mammary gland.

The Keap1-Nrf2 cell defense pathway--a promising therapeutic target?

By regulating the basal and inducible expression of an abundance of detoxification enzymes, antioxidant proteins, xenobiotic transporters and other stress response proteins, the Keap1-Nrf2 pathway plays a crucial role in determining the sensitivity of mammalian cells to chemical and oxidative insults that have the capacity to provoke cellular harm. This review highlights historical and recent advances in our understanding of the molecular mechanisms that regulate the activity of the Keap1-Nrf2 pathway. The important role of Nrf2 in protecting against the onset of specific diseases and drug-induced toxicities is also examined, alongside the emerging role of Nrf2 in promoting oncogenesis and chemotherapeutic drug resistance. A particular emphasis is placed on the potential for translation of this mechanistic understanding into clinical strategies that can improve human health, with consideration of the potential applications of targeting Nrf2 therapeutically.

Xanthohumol uptake and intracellular kinetics in hepatocytes, hepatic stellate cells, and intestinal cells

Xanthohumol (XN) is the major prenylated chalcone of hops and hence an ingredient of beer. Despite many advances in understanding of the pharmacology of XN, one largely unresolved issue is its low bioavailability in the human organism. Also, not much is known about its actual concentrations and pharmacokinetics in liver and intestinal cells. Therefore, the uptake, intracellular distribution, and kinetics of XN were studied in various cell types, namely, hepatocellular carcinoma cells (HuH-7), hepatic stellate cells (HSC), primary cultured hepatocytes, and colorectal adenocarcinoma cells (Caco-2). Fluorescent microscopy allowed for the first time visualization and tracing of the uptake and intracellular distribution of XN. A rapid accumulation of XN concentrations that were up to >60-fold higher than the concentration present in the ambient culture medium was observed. Fluorescence recovery after photobleaching experiments revealed that most XN molecules are bound to cellular proteins, which may alter properties of cellular factors.

Screening for natural chemoprevention agents that modify human Keap1

Upregulation of cytoprotective enzymes by therapeutic agents to prevent damage by reactive oxygen species and xenobiotic electrophiles is a strategy for cancer chemoprevention. The Kelch-like ECH-associated protein 1 (Keap1) and its binding partner, transcription factor NF-E2-related factor-2 (NRF2), are chemoprevention targets because of their role in regulating the antioxidant response element (ARE) in response to oxidative stress and exposure to electrophiles. Modification of the sensor protein Keap1 by electrophiles such as the isothiocyanate sulforaphane can direct Nrf2 accumulation in the nucleus and subsequent ARE activation. Since our previous matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS)-based screening method to discover natural products that modify Keap1 does not detect covalent modification of Keap1 by some highly reversible agents such as sulforaphane, a more sensitive screening assay was developed. In this new assay, electrophiles that have reversibly modified Keap1 can be released, trapped, and detected as β-mercaptoethanol adducts by mass spectrometry. Isoliquiritigenin and sulforaphane, known ARE activators that target Keap1, were used to validate the assay. To determine the ability of the assay to identify electrophiles in complex matrixes that modify Keap1, sulforaphane was spiked into a cocoa extract, and LC-MS/MS using high resolution mass spectrometry with accurate mass measurement was used to identify β-mercaptoethanol adducts of sulforaphane that had been released from Keap1. This screening assay permits identification of potential chemoprevention agents in complex natural product mixtures that reversibly modify Keap1 but cannot be detected using MALDI-TOF MS.

Improving the NQO1-inducing activities of phenolic acids from radix Salvia miltiorrhiza: a methylation strategy

NAD(P)H: quinone oxidoreductase1 (NQO1) is an important detoxification enzyme that can protect mammalian cells against toxic quinones and reduce the risk of tumorigenesis. In this study, it was found that salvianolic acid B (SaB), lithospermic acid (LA), and rosmarinic acid (RA), three main hydrophilic constituents in Danshen, conjugated with glutathione (GSH) easily in vitro but exhibited no NQO1-inducing activities in Hepa 1c1c7 cells, which might attribute to their poor absorptions. After a simple methylation strategy that aimed at improving the liposolubility, both the NQO1-inducing activities and the absorptions in cells of the phenolic acids improved obviously, without losing the GSH-conjugating abilities. The concentration to double the specific activity of NQ01 values of methylated products of lithospermic acid and rosmarinic acid were 17.86 ± 2.34 μg/mL and 11.97 ± 0.60 μg/mL, respectively. The findings indicated that methylation is an effective strategy to improve the NQO1-inducing activities of phenolic acids in Danshen.

A deuterium-labelling mass spectrometry-tandem diode-array detector screening method for rapid discovery of naturally occurring electrophiles

Because electrophiles regulate many signalling pathways in cells, by modifying cysteine residues in proteins, they have a wide range of biological activity. In this study, a deuterium-labelling mass spectrometry-tandem diode-array detector (MS-DAD) screening method was established for rapid discovery of naturally occurring electrophiles. Glutathione (GSH) was used as a probe and incubated with natural product extracts. To distinguish different types of electrophile, incubation was performed in two reaction solvents, H(2)O and D(2)O. Ten types of naturally occurring electrophile were chosen, on the basis of their properties, to undergo the screening assay. By using this screening method, we successfully discovered the bioactive electrophile 4-hydroxyderricin in an ethanol extract of Angelica keiskei. This electrophile had potent NAD(P)H:quinone oxidoreductase 1 (NQO1)-inducing activity at a concentration of 20 μmol L(-1).

Progress in nanotechnology based approaches to enhance the potential of chemopreventive agents

Cancer chemoprevention is defined as the use of natural agents to suppress, reverse or prevent the carcinogenic process from turning into aggressive cancer. Over the last two decades, multiple natural dietary compounds with diverse chemical structures such flavonoids, tannins, curcumins and polyphenols have been proposed as chemopreventive agents. These agents have proven excellent anticancer potential in the laboratory setting, however, the observed effects in vitro do not translate in clinic where they fail to live up to their expectations. Among the various reasons for this discrepancy include inefficient systemic delivery and robust bioavailability. To overcome this barrier, researchers have focused towards coupling these agents with nano based encapsulation technology that in principle will enhance bioavailability and ultimately benefit clinical outcome. The last decade has witnessed rapid advancement in the development of nanochemopreventive technology with emergence of many nano encapsulated formulations of different dietary anticancer agents. This review summarizes the most up-to-date knowledge on the studies performed in nanochemoprevention, their proposed use in the clinic and future directions in which this field is heading. As the knowledge of the dynamics of nano encapsulation evolves, it is expected that researchers will bring forward newer and far more superior nanochemopreventive agents that may become standard drugs for different cancers.

Screening natural products for inhibitors of quinone reductase-2 using ultrafiltration LC-MS

Inhibitors of quinone reductase-2 (NQO2; QR-2) can have antimalarial activity and antitumor activities or can function as chemoprevention agents by preventing the metabolic activation of toxic quinones such as menadione. To expedite the search for new natural product inhibitors of QR-2, we developed a screening assay based on ultrafiltration liquid chromatography-mass spectrometry that is compatible with complex samples such as bacterial or botanical extracts. Human QR-2 was prepared recombinantly, and the known QR-2 inhibitor, resveratrol, was used as a positive control and as a competitive ligand to eliminate false positives. Ultrafiltration LC-MS screening of extracts of marine sediment bacteria resulted in the discovery of tetrangulol methyl ether as an inhibitor of QR-2. When applied to the screening of hop extracts from the botanical, Humulus lupulus L., xanthohumol and xanthohumol D were identified as ligands of QR-2. Inhibition of QR-2 by these ligands was confirmed using a functional enzyme assay. Furthermore, binding of xanthohumol and xanthohumol D to the active site of QR-2 was confirmed using X-ray crystallography. Ultrafiltration LC-MS was shown to be a useful assay for the discovery of inhibitors of QR-2 in complex matrixes such as extracts of bacteria and botanicals.

The role of chalcones in suppression of NF-κB-mediated inflammation and cancer

Although consumption of fruits, vegetables, spices, cereals and pulses has been associated with lower incidence of cancer and other chronic diseases, how these dietary agents and their active ingredients minimize these diseases, is not fully understood. Whether it is oranges, kawa, hops, water-lilly, locorice, wax apple or mulberry, they are all connected by a group of aromatic ketones, called chalcones (1,3-diaryl-2-propen-1-ones). Some of the most significant chalcones identified from these plants include flavokawin, butein, xanthoangelol, 4-hydroxyderricin, cardamonin, 2',4'-dihydroxychalcone, isoliquiritigenin, isosalipurposide, and naringenin chalcone. These chalcones have been linked with immunomodulation, antibacterial, antifungal, antiviral, anti-inflammatory, antioxidant, anticancer, and antidiabetic activities. The current review, however, deals with the role of various chalcones in inflammation that controls both the immune system and tumorigenesis. Inflammatory pathways have been shown to mediate the survival, proliferation, invasion, angiogenesis and metastasis of tumors. How these chalcones modulate inflammatory pathways, tumorigenesis and immune system is the focus of this review.

Xanthohumol, a prenylated chalcone from hops, modulates hepatic expression of genes involved in thyroid hormone distribution and metabolism

In the present study, we analyzed the influence of xanthohumol (XN) on thyroid hormone (TH) distribution and metabolism in rats. A potent and selective competition of XN for thyroxine (T4) binding to transthyretin (IC(50)=1 microM at 1.7 nM [(125)I]T4) was found in human and rat sera in vitro. Female rats treated orally with XN showed increased hepatic expression of T4-binding globulin and decreased transthyretin and albumin. Thyrotropin levels and hepatic type 1 deiodinase activity were moderately increased. Northern blot analysis revealed diminished expression of liver sulfotransferase (Sult1a1) and uridine-diphosphate glucuronosyltransferase (Ugt1a1) after XN treatment. The transcript levels of constitutive androstane receptor (CAR), known to be involved in regulation of enzymes metabolizing hormones, drugs and xenobiotics, was lower in rats treated with >10 mg XN/kg body weight per day. Immunoblot analysis indicates reduced amounts of CAR protein. The phenobarbital-inducible cytochrome P450 mRNA level was decreased in rats treated with >10 mg XN/kg/day, in agreement with reduced CAR protein. Although only moderate changes in TH serum levels were observed, the XN-dependent altered expression of components involved in TH homeostasis might be important not only for hormone metabolism, but also for hepatic phase I and II elimination of drug metabolites and xenobiotics.

Biological reactive intermediates (BRIs) formed from botanical dietary supplements

The use of botanical dietary supplements is increasingly popular, due to their natural origin and the perceived assumption that they are safer than prescription drugs. While most botanical dietary supplements can be considered safe, a few contain compounds, which can be converted to biological reactive intermediates (BRIs) causing toxicity. For example, sassafras oil contains safrole, which can be converted to a reactive carbocation forming genotoxic DNA adducts. Alternatively, some botanical dietary supplements contain stable BRIs such as simple Michael acceptors that react with chemosensor proteins such as Keap1 resulting in induction of protective detoxification enzymes. Examples include curcumin from turmeric, xanthohumol from hops, and Z-ligustilide from dang gui. Quinones (sassafras, kava, black cohosh), quinone methides (sassafras), and epoxides (pennyroyal oil) represent BRIs of intermediate reactivity, which could generate both genotoxic and/or chemopreventive effects. The biological targets of BRIs formed from botanical dietary supplements and their resulting toxic and/or chemopreventive effects are closely linked to the reactivity of BRIs as well as dose and time of exposure.

The keap1-nrf2 cellular defense pathway: mechanisms of regulation and role in protection against drug-induced toxicity

Adverse drug reactions pose a significant public health problem. In some cases, the process of drug metabolism can contribute to the onset of toxicity through the bioactivation of a parent molecule to a chemically reactive intermediate. In order to maintain a favorable balance between bioactivation and detoxification, mammalian cells have evolved an inducible cell defense system known as the antioxidant response pathway. The activity of this cytoprotective pathway is largely regulated by the transcription factor Nrf2, which governs the expression of many phase II detoxification and antioxidant enzymes. In turn, the activity of Nrf2 is regulated by the cysteine-rich cytosolic inhibitor Keap1, which acts as a "sensor" for chemical/oxidative stress. This article summarizes our current understanding of the molecular mechanisms that regulate the function of the Keap1-Nrf2 pathway and highlights the importance of Nrf2 in the protection against drug-induced toxicity.

Toward an "omic" physiopathology of reactive chemicals: thirty years of mass spectrometric study of the protein adducts with endogenous and xenobiotic compounds

Cancer and degenerative diseases are major causes of morbidity and death, derived from the permanent modification of key biopolymers such as DNA and regulatory proteins by usually smaller, reactive molecules, present in the environment or generated from endogenous and xenobiotic components by the body's own biochemical mechanisms (molecular adducts). In particular, protein adducts with organic electrophiles have been studied for more than 30 [see, e.g., Calleman et al., 1978] years essentially for three purposes: (a) as passive monitors of the mean level of individual exposure to specific chemicals, either endogenously present in the human body or to which the subject is exposed through food or environmental contamination; (b) as quantitative indicators of the mean extent of the individual metabolic processing which converts a non-reactive chemical substance into its toxic products able to damage DNA (en route to cancer induction through genotoxic mechanisms) or key proteins (as in the case of several drugs, pesticides or otherwise biologically active substances); (c) to relate the extent of protein modification to that of biological function impairment (such as enzyme inhibition) finally causing the specific health damage. This review describes the role that contemporary mass spectrometry-based approaches employed in the qualitative and quantitative study of protein-electrophile adducts play in the discovery of the (bio)chemical mechanisms of toxic substances and highlights the future directions of research in this field. A particular emphasis is given to the measurement of often high levels of the protein adducts of several industrial and environmental pollutants in unexposed human populations, a phenomenon which highlights the possibility that a number of small organic molecules are generated in the human organism through minor metabolic processes, the imbalance of which may be the cause of "spontaneous" cases of cancer and of other degenerative diseases of still uncharacterized etiology. With all this in mind, it is foreseen that a holistic description of cellular functions will take advantage of new analytical methods based on time-integrated metabolomic measurements of a new biological compartment, the "adductome," aimed at better understanding integrated organism response to environmental and endogenous stressors.

Characterization of tanshinones with quinone reductase induction activity from Radix Salvia miltiorrhiza by liquid chromatography/tandem mass spectrometry

Quinone reductase (QR) induction is a reliable biomarker of phase II enzyme induction. In this study, glutathione (GSH) was employed and a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was introduced to reveal the chemical constituents with QR activity from the ethyl acetate extract of roots Salvia miltiorrhiza ('Danshen') and nine tanshinones (9, 13, 17-19, 21, 24-26), which could conjugate with GSH, were characterized by LC/MS/MS and considered to have QR activities. Then, thirteen tanshinones, including six compounds (17, 18, 21, 24-26) of the above nine tanshinones, were isolated to conduct QR induction evaluation, and it was found that miltirone and its derivatives (18, 20, 24, 26) exhibited significant activities. The GSH conjugate abilities of the isolated tanshinones were also examined; this showed that compounds 18, 20, 24 and 26 had good conjugating abilities with GSH. Compared with the in vitro bioactivity screening results, this proved that conjugate ability is related with QR activity, so an LC/MS/MS method can be applied to find more active compounds.

Research highlights from the UIC/NIH Center for Botanical Dietary Supplements Research for Women's Health: Black cohosh from the field to the clinic

In 1999, the Department of Medicinal Chemistry and Pharmacognosy at the College of Pharmacy, University of Illinois (UIC) at Chicago was funded to establish a Botanical Dietary Supplements Research Center from the National Institutes of Health (NIH). The emphasis of the UIC/NIH Center for Botanical Dietary Supplements Research (CBDSR) is botanical dietary supplements (BDS) for women's health. Center's research has focused on BDS that may improve women's health and quality of life, specifically in the areas of menopause, premenstrual syndrome, and persistent urinary tract infections. Center investigators have overcome many challenges associated with botanical dietary supplements research, including acquiring and identifying plant species for investigation, isolating and identifying active constituents, elucidating the mechanisms of action of these botanicals, and conducting phase I and phase II clinical studies. Black cohosh [Actaea racemosa L. (Ranunculaceae)] has been used as a model to illustrate the steps involved in taking a botanical dietary supplement from the field, all the way to clinical trials. Bioassays are described that were necessary to elucidate the pertinent biological studies of plant extracts and their mechanisms of action. The Center has used an innovative multidisciplinary approach to this type of research, and thus has been very successful in fulfilling its specific aims.

Neuroprotective effects of the triterpenoid, CDDO methyl amide, a potent inducer of Nrf2-mediated transcription

The NF-E2-related factor-2 (Nrf2)/antioxidant response element (ARE) signaling pathway regulates phase 2 detoxification genes, including a variety of antioxidative enzymes. We tested neuroprotective effects of the synthetic triterpenoid CDDO-MA, a potent activator of the Nrf2/ARE signaling. CDDO-MA treatment of neuroblastoma SH-SY5Y cells resulted in Nrf2 upregulation and translocation from cytosol to nucleus and subsequent activation of ARE pathway genes. CDDO-MA blocked t-butylhydroperoxide-induced production of reactive oxygen species (ROS) by activation of ARE genes only in wild type, but not Nrf2 knockout mouse embryonic fibroblasts. Oral administration of CDDO-MA resulted in significant protection against MPTP-induced nigrostriatal dopaminergic neurodegeneration, pathological alpha-synuclein accumulation and oxidative damage in mice. Additionally, CDDO-MA treatment in rats produced significant rescue against striatal lesions caused by the neurotoxin 3-NP, and associated increases in the oxidative damage markers malondialdehyde, F₂-Isoprostanes, 8-hydroxy-2-deoxyguanosine, 3-nitrotyrosine, and impaired glutathione homeostasis. Our results indicate that the CDDO-MA renders its neuroprotective effects through its potent activation of the Nrf2/ARE pathway, and suggest that triterpenoids may be beneficial for the treatment of neurodegenerative diseases like Parkinson's disease and Huntington's disease.

Three lignans and one coumarinolignoid with quinone reductase activity from Eurycorymbus cavaleriei

Four compounds, including one new lignan cavaol H (1), one new coumarinolignoid 5'-hydroxycleomiscosin B (4) and two known lignans (2-3) were isolated from the 95% ethanol extract of the twigs of Eurycorymbus cavaleriei. Their structures were established on the basis of various spectroscopic analyses including 1D-(1H, 13C, and DEPT) and 2D-NMR (COSY, HMQC, and HMBC). The absolute stereochemistry of the two known lignans was firstly reported in this article by 1H NMR studies on Mosher's ester derivatives. In the present study, quinone reductase induction activities of compounds 1-4 were assayed, compound 4 showed moderate quinone reductase induction with concentration to double the enzyme activity (CD) of 10.5 +/- 0.8 microg/mL. Then we established LC-MS-MS analysis of glutathione (GSH) incubation with compound 4 to explain whether compound 4 induced quinone reductase through alkylating of the sulfhydryl groups of Keap1. Reconstructed selected ion chromatogram (SIC) of m/z 706 after compound 4 incubation with GSH was different from that with Tris-HCl buffer solution, which meant the quinone reductase induction activity of compound 4 attributed to alkylating the sulfhydryl groups of Keap1.

Angelica sinensis and its alkylphthalides induce the detoxification enzyme NAD(P)H: quinone oxidoreductase 1 by alkylating Keap1

The roots of Angelica sinensis (Oliv.) Diels (Dang Gui; Apiaceae) have a long history in traditional Chinese medicine as a remedy for women's disorders and are often called "lady's ginseng". Currently, extracts of A. sinensis are commonly included in numerous dietary supplements used for women's health and as antiaging products. In the present study, we examined the potential chemopreventive activity of A. sinensis extracts by measuring the relative ability to induce the detoxification enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO1). The lipophilic partitions showed strong NQO1 induction with concentrations to double the enzyme activity (CD) of 5.5 +/- 0.7 (petroleum ether) and 3.9 +/- 0.5 microg/mL (chloroform). Fractionation led to the isolation of phenolic esters and alkylphthalides, especially Z-ligustilide, the main lipophilic compound, which showed strong NQO1 inducing properties (CD = 6.9 +/- 1.9 microM). Transcription of many detoxifying enzymes is regulated through the antioxidant response element (ARE) and its transcription factor Nrf2, which is repressed under basal conditions by Keap1. However, exposure to electrophilic inducers that alkylate Keap1 results in higher concentrations of free Nrf2 and ARE activation. The ARE reporter activity was therefore analyzed in HepG2-ARE-C8 cells after incubation with lipophilic extracts of A. sinensis or ligustilide for 24 h. Under these conditions, both the extract and the ligustilide increased ARE-luciferase reporter activity in a dose-dependent manner. Incubation of ligustilide with GSH and subsequent LC-MS-MS analysis revealed that ligustilide as well as oxidized ligustilide species covalently modified GSH. In addition, using MALDI-TOF mass spectrometry and LC-MS-MS, it was demonstrated that the lipophilic extracts, ligustilide, and monooxygenated ligustilide alkylated important cysteine residues in human Keap1 protein, thus activating Nrf2 and transcription of ARE regulated genes. These observations suggest that A. sinensis dietary supplements standardized to ligustilide have potential as chemopreventive agents through induction of detoxification enzymes.

Rapid screening for cyclo-dopa and diketopiperazine alkaloids in crude extracts of Portulaca oleracea L. using liquid chromatography/tandem mass spectrometry

A simple and rapid qualitative liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed and validated for screening cyclo-dopa and diketopiperazine alkaloids in crude extracts of Portulaca oleracea L. at sub-ppm levels. An electrospray ionization orbitrap mass spectrometer, which provides accurate full scan MS and MS/MS data, was used in this study. After simple extraction with ethanol and purification by AB-8 resin, the extracts were subjected to LC/MS/MS analysis. A high mass tolerance (10 ppm) was used in the initial screening to filter the full scan MS data. The cyclo-dopa and diketopiperazine alkaloid standards gave limits of detection (LODs) at or below 5 ng/mL. The results also indicated that the method had an acceptable precision for day-to-day use in the identification of compounds. The alkaloids could be identified based on their MS/MS data, elemental compositions, and retention behavior. This system was used to assay trace amounts of cyclo-dopa and diketopiperazine alkaloids in crude extracts of Portulaca oleracea L., leading to the identification of 5/2 confirmed/unconfirmed cyclo-dopa and 7/6 confirmed/unconfirmed diketopiperazine alkaloids, respectively. The screening method considerably reduces the time and cost involved in the identification of cyclo-dopa and diketopiperazine alkaloids in Portulaca oleracea L., as well as being a simple and convenient approach to the identification of other structural families of natural products.

The University of Illinois at Chicago/National Institutes of Health Center for Botanical Dietary Supplements Research for Women's Health: from plant to clinical use

The University of Illinois at Chicago/National Institutes of Health Center for Botanical Dietary Supplements Research began in 1999 with an emphasis on botanical dietary supplements for women's health. We have concentrated on plants that may improve women's health, especially to reduce hot flashes in menopausal women, alleviate the symptoms of premenstrual syndrome, and reduce persistent urinary tract infections. The primary focus of this article is to describe the operation of our center, from acquiring and identifying botanicals to isolating and identifying active constituents, to elucidating their mechanisms of action, and to conducting phase I and phase II clinical studies. Black cohosh (Actaea racemosa; syn Cimicifuga racemosa) has been used as a model to illustrate the steps involved in taking this plant from the field to clinical trials. Bioassays are described that were necessary to elucidate the pertinent biological studies of plant extracts and their mechanisms of action. We conclude that this type of research can only be successful with the use of a multidisciplinary approach.

EST analysis of hop glandular trichomes identifies an O-methyltransferase that catalyzes the biosynthesis of xanthohumol

The glandular trichomes (lupulin glands) of hop (Humulus lupulus) synthesize essential oils and terpenophenolic resins, including the bioactive prenylflavonoid xanthohumol. To dissect the biosynthetic processes occurring in lupulin glands, we sequenced 10,581 ESTs from four trichome-derived cDNA libraries. ESTs representing enzymes of terpenoid biosynthesis, including all of the steps of the methyl 4-erythritol phosphate pathway, were abundant in the EST data set, as were ESTs for the known type III polyketide synthases of bitter acid and xanthohumol biosynthesis. The xanthohumol biosynthetic pathway involves a key O-methylation step. Four S-adenosyl-l-methionine-dependent O-methyltransferases (OMTs) with similarity to known flavonoid-methylating enzymes were present in the EST data set. OMT1, which was the most highly expressed OMT based on EST abundance and RT-PCR analysis, performs the final reaction in xanthohumol biosynthesis by methylating desmethylxanthohumol to form xanthohumol. OMT2 accepted a broad range of substrates, including desmethylxanthohumol, but did not form xanthohumol. Mass spectrometry and proton nuclear magnetic resonance analysis showed it methylated xanthohumol to 4-O-methylxanthohumol, which is not known from hop. OMT3 was inactive with all substrates tested. The lupulin gland-specific EST data set expands the genomic resources for H. lupulus and provides further insight into the metabolic specialization of glandular trichomes.

The Nrf2-Keap1 defence pathway: role in protection against drug-induced toxicity

The metabolic biotransformation of xenobiotics to chemically reactive metabolites can, in some instances, underlie the pathogenesis of certain adverse drug reactions, due to the development of chemical or oxidative stress. In order to guard against such stresses, mammalian cells have evolved multi-faceted, highly-regulated defence systems, one of the most important being that which is regulated by the transcription factor Nrf2. Through regulating the expression of numerous cytoprotective genes, Nrf2 serves as a critical determinant of a cell's capacity to survive, or succumb, to a toxic insult. The aim of this review is to summarise our current understanding of the biochemistry that underlies the Nrf2 defence pathway, and highlight the important role of this transcription factor in the protection against drug-induced toxicity, primarily through the examination of recent investigations that have demonstrated an increased vulnerability to various toxins in animals lacking Nrf2.

The value of natural products to future pharmaceutical discovery

Natural products have provided considerable value to the pharmaceutical industry over the past half century. In particular, the therapeutic areas of infectious diseases and oncology have benefited from numerous drug classes derived from natural product sources. Unfortunately, pharmaceutical companies have significantly decreased activities in natural product discovery during the past several years. Biotechnology companies working in the fields of combinatorial biosynthesis, genetic engineering and metagenomic approaches to identify novel natural product lead molecules have had limited success. Despite what appears to be a slow death of natural product discovery research, many new and interesting molecules with biological activity have been published in the past few years. If natural product materials continue to be tested for desirable therapeutic activities, we believe that significant progress in identifying new antibiotics, oncology therapeutics and other useful medicines will be made.

Rapid screening for bisbibenzyls in bryophyte crude extracts using liquid chromatography/tandem mass spectrometry

A simple and rapid qualitative liquid chromatography-diode-array detection/tandem mass spectrometry (LC-DAD/MS/MS) method was developed and validated for screening bisbibenzyl compounds in bryophyte crude extracts at sub-ppm levels. After simple extraction with ethanol and analyte concentration with diethyl ether, the extracts were subjected to LC-DAD/MS/MS analysis. The overall instrument turnaround time was 50 min to obtain baseline separation of bisbibenzyl isomers in bryophytes. MS full scan, MS/MS precursor ion scan and MS/MS product ion scan modes were used for the screening. The bisbibenzyl standards studied gave limits of detection (LODs) at or below 10 ng/mL. The results also indicated that the method had acceptable precision to be used on a day-to-day basis for qualitative identification. The bisbibenzyl types, i.e. one biphenyl ether bond (A-type), two biphenyl ether bonds (B-type), one biphenyl ether and one biphenyl bond (C-type), or other biphenyl types can be differentiated by their ESI-MS/MS product profiles, and the number of alkoxyl substituents can also be identified. The linkage sites of biphenyl and biphenyl ether bonds cannot be identified for an unknown bisbibenzyl solely from its mass spectra. This system was used to support three screening assays of bryophytes including Marchantia polymorpha L., Ptagiochasm intermedium L. and Asterella angusta, which were collected from different places in China. From them, 7/12, 8/5 and 8/9 confirmed/unconfirmed bisbibenzyls were identified, respectively, based on their MS/MS data, UV spectra and the retention behavior. The screening method considerably reduced the time and the cost for the qualitative analyses, and the structure-fragmentation-UV relationships will facilitate the high-throughput screening (HTS) of bisbibenzyl compounds in bryophytes. It is also intended as a simple and convenient way for the determination of other structural families of natural products.

Plasticity in cell defence: access to and reactivity of critical protein residues and DNA response elements

Cellular and whole organ defence against pathogenic or chemical challenge is manifest as an adaptive response. Where appropriate, this may lead to induction of a cellular defence programme, thereby enhancing cell survival. When the challenge is overwhelming, the defence is breached and a switch is made to yield cell death, either by apoptosis or necrosis. Thus, a cell will defend itself where possible, but in extremis, it may recognise the futility of its resistance and allow itself to die. Transcription factor activation and access to the DNA regulatory elements that control a particular pattern of expression of defence genes is a major issue that may ultimately decide the fate of a cell in a changed environment. It is possible to visualise the access to the nucleus and to the genome, of paradigm gene loci or transcription factors, using a number of molecular techniques such as chromatin immunoprecipitation, in vivo footprinting and live/whole cell imaging. These methods are informative as to the array of transcription factors that may regulate a given gene, as well as the transitory nature of the transcriptional activation. The initial triggering of active transcription factor complexes typically occurs within the cytoplasm of the cell. Protein-protein interactions and signal transduction pathways, elucidated using a classical molecular genetics approach, have long been recognised as pivotal to the initial control of the levels and activity of transcription factors. We can now visualise modifications in critical residues of transcription factors and regulators during cellular response to chemical stress. These modifications may yield enhanced or repressed activity of transcription factors, they may be non-covalent or covalent, and they may occur in response to a variety of classes of chemicals. Such promiscuous signalling can provide plasticity in the cellular response to a wide array of chemical agents.

Xanthohumol, a prenylflavonoid derived from hops induces apoptosis and inhibits NF-kappaB activation in prostate epithelial cells

There is increasing evidence that certain natural compounds found in plants may be useful as cancer chemopreventive or chemotherapeutic agents. Limited in vitro studies indicate that several prenylated flavonoids present in the hop plant (Humulus lupulus) possess anticarcinogenic properties. The purpose of this study was to investigate the anti-tumorigenic effects of xanthohumol (XN), the major prenylflavonoid in hops, on prostate cancer and benign prostate hyperplasia. BPH-1 and PC3 cell lines were used in our study to represent both non-tumorigenic hyperplasia and malignant prostate cancer. In both BPH-1 and PC3 cells, XN and its oxidation product, XAL, decreased cell viability in a dose dependent manner (2.5-20 microM) as determined by MTT assay and caused an increase in the formation of early and late apoptotic cells as determined by Annexin V staining and multicaspase assays. XN and its oxygenated derivative also induced cell cycle changes in both cells lines, seen in an elevated sub G1 peak at 48h treatment. Western blot analysis was performed to confirm the activation of proapoptotic proteins, Bax and p53. XN and its derivative caused decreased activation of NFkappaB. This work suggests that XN and its oxidation product, XAL, may be potentially useful as a chemopreventive agent during prostate hyperplasia and prostate carcinogenesis, acting via induction of apoptosis and down-regulation of NFkappaB activation in BPH-1 cells.