Biotransformation of the chemopreventive agent 2',4',4-trihydroxychalcone (isoliquiritigenin) by UDP-glucuronosyltransferases

Pharmacokinetic Interactions of a Licorice Dietary Supplement with Cytochrome P450 Enzymes in Female Participants

Licorice, the roots and rhizomes of Glycyrrhiza glabra L., has been used as a medicinal herb, herbal adjuvant, and flavoring agent since ancient times. Recently, licorice extracts have become popular as dietary supplements used by females to alleviate menopausal symptoms. Exposure to licorice products containing high levels of glycyrrhizic acid can cause hypokalemia, but independent from this effect, preclinical data indicate that licorice can inhibit certain cytochrome P450 (P450) enzymes. To evaluate whether clinically relevant pharmacokinetic interactions of licorice with P450 enzymes exist, a phase 1 clinical investigation was carried out using a licorice extract depleted in glycyrrhizic acid (content <1%) and a cocktail containing caffeine, tolbutamide, alprazolam, and dextromethorphan, which are probe substrates for the enzymes CYP1A2, CYP2C9, CYP3A4/5, and CYP2D6, respectively. The botanically authenticated and chemically standardized extract of roots from G. glabra was consumed by 14 healthy menopausal and postmenopausal female participants twice daily for 2 weeks. The pharmacokinetics of each probe drug were evaluated immediately before and after supplementation with the licorice extract. Comparison of the average areas under the time-concentration curves (AUCs) for each probe substrate in serum showed no significant changes from licorice consumption, whereas time to reach peak concentration for caffeine and elimination half-life for tolbutamide showed small changes. According to the US Food and Drug Administration guidance, which is based on changes in the AUC of each probe substrate drug, the investigated licorice extract should not cause any clinically relevant pharmacokinetic interactions with respect to CYP3A4/5, CYP2C9, CYP2D6, or CYP1A2. SIGNIFICANCE STATEMENT: Despite generally-recognized-as-safe status, the licorice species Glycyrrhiza glabra has been associated with some toxicity. Preclinical studies suggest that G. glabra might cause pharmacokinetic drug interactions by inhibiting several cytochrome P450 enzymes. This phase 1 clinical study addressed these concerns by evaluating clinically relevant effects with respect to CYP3A4/5, CYP2C9, CYP2D6, and CYP1A2. These results showed that a standardized G. glabra extract did not cause any clinically relevant pharmacokinetic drug interactions with four major cytochrome P450 enzymes.

Regiospecific Hydrogenation of Bromochalcone by Unconventional Yeast Strains

This research aimed to select yeast strains capable of the biotransformation of selected 2′-hydroxybromochalcones. Small-scale biotransformations were carried out using four substrates obtained by chemical synthesis (2′-hydroxy-2″-bromochalcone, 2′-hydroxy-3″-bromochalcone, 2′-hydroxy-4″-bromochalcone and 2′-hydroxy-5′-bromochalcone) and eight strains of non-conventional yeasts. Screening allowed for the determination of the substrate specificity of selected microorganisms and the selection of biocatalysts that carried out the hydrogenation of tested compounds in the most effective way. It was found that the position of the bromine atom has a crucial influence on the degree of substrate conversion by the tested yeast strains. As a result of the biotransformation of the 2′-hydroxybromochalcones, the corresponding 2′-hydroxybromodihydrochalcones were obtained. The products obtained belong to the group of compounds with high potential as precursors of sweet substances.

Biotransformation of Liquiritigenin into Characteristic Metabolites by the Gut Microbiota

The bioavailability of flavonoids is generally low after oral administration. The metabolic transformation of flavonoids by the gut microbiota may be one of the main reasons for this, although these metabolites have potential pharmacological activities. Liquiritigenin is an important dihydroflavonoid compound found in Glycyrrhiza uralensis that has a wide range of pharmacological properties, such as antitumor, antiulcer, anti-inflammatory, and anti-AIDS effects, but its mechanism of action remains unclear. This study explored the metabolites of liquiritigenin by examining gut microbiota metabolism and hepatic metabolism in vitro. Using LC-MS/MS and LC/MSⁿ-IT-TOF techniques, three possible metabolites of liquiritigenin metabolized by the gut microbiota were identified: phloretic acid (M3), resorcinol (M4), and M5. M5 is speculated to be davidigenin, which has antitumor activity. By comparing these two metabolic pathways of liquiritigenin (the gut microbiota and liver microsomes), this study revealed that there are three main metabolites of liquiritigenin generated by intestinal bacteria, which provides a theoretical basis for the study of pharmacologically active substances in vivo.

Extensive metabolism of flavonoids relevant to their potential efficacy on Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disorder, the incidence of which is climbing with ever-growing aged population, but no cure is hitherto available. The epidemiological studies unveiled that chronic intake of flavonoids was negatively associated with AD risk. Flavonoids, a family of natural polyphenols widely distributed in human daily diets, were readily conjugated by phase II drug metabolizing enzymes after absorption in vivo, and glucuronidation could occur in 1 min following intravenous administration. Recently, as many as 191 metabolites were obtained after intragastric administration of a single flavonoid, indicating that other bioactive metabolites, besides conjugates, might be formed and account for the contradiction between efficacy of flavonoids in human or animal models and low systematic exposure of flavonoid glycosides or aglycones. In this review, metabolism of complete 68 flavonoid monomers potential for AD treatment, grouped in flavonoid O-glycosides, flavonoid aglycones, flavonoid C-glycosides, flavonoid dimers, flavonolignans and prenylated flavonoids according to their common structural elements, respectively, has been systematically retrospected, summarized and discussed, including their unequivocally identified metabolites, metabolic interconversions, metabolic locations, metabolic sites (regio- or stereo-selectivity), primarily involved metabolic enzymes or intestinal bacteria, and interspecies correlations or differences in metabolism, and their bioactive metabolites and the underlying mechanism to reverse AD pathology were also reviewed, providing whole perspective about advances on extensive metabolism of diverse potent flavonoids in vivo and in vitro up to date and aiming at elucidation of mechanism of actions of flavonoids on AD or other central nervous system (CNS) disorders.

Dual Strategy for Improving the Oral Bioavailability of Resveratrol: Enhancing Water Solubility and Inhibiting Glucuronidation

Resveratrol (RES) suffers from poor water solubility and extensive metabolism, which lead to low bioavailability. A phospholipid complex (PC) containing RES and a UDP-glucuronosyltransferase (UGT) inhibitor was prepared to address these two limiting factors, thereby improving RES bioavailability. First, 11 natural active ingredients metabolized by similar enzyme subtypes to RES were screened in a glucuronidation assay in liver microsomes. Then, glycyrrhetinic acid (GA), the strongest inhibitor, was prepared with RES in a PC. RES-PC was prepared as a control. As expected, the water solubility and the cumulative dissolution of RES were significantly enhanced by RES-PC and RES/GA-PC. Compared with the RES group, the AUC_0-10 of RES and resveratrol-3-glucuronide (R-3-G) in the RES/GA-PC group showed increases of 2.49- and 1.70-fold, respectively, with the proportion of RES absorption to total absorption increasing 1.45 times. These results demonstrated that RES/GA-PC could improve the bioavailability of RES by increasing its water solubility and inhibiting its glucuronidation.

Effectiveness of the Natural Antioxidant 2,4,4'-Trihydroxychalcone on the Oxidation of Sunflower Oil during Storage

This study aimed to investigate the effectiveness of 2,4,4′-trihydroxychalcone as a natural antioxidant on the oxidation of sunflower oil during an 88-day storage period and to compare its strength with the synthetic antioxidant butylated hydroxytoluene (BHT). Seven groups of the sunflower oil samples were prepared: pure oil (control), oil treated with different concentrations (100, 500, and 1000 ppm) of 2,4,4′-trihydroxychalcone, and oil treated with different concentrations (100, 500, and 1000 ppm) of BHT. Specific parameters, namely, the peroxide value (PV), acid value (AV), p-anisidine value (p-AnV), thiobarbituric acid reactive substance (TBARS) value and total oxidation (TOTOX) value were used to assess the extent of the deterioration of the oil by estimating the primary and secondary oxidation products. The results showed that 2,4,4′-trihydroxychalcone effectively decreased the production of the primary and secondary oxidation products of sunflower oil during storage, as indicated by reductions in the PVs, AVs, p-AnVs, TBARS values and TOTOX values of the sunflower oil. When compared to BHT, 2,4,4′-trihydroxychalcone showed either a similar or stronger effect in inhibiting the primary and secondary oxidation products. These findings suggest that, 2,4,4′-trihydroxychalcone is a suitable natural alternative to synthetic antioxidants to improve the oxidative stability of sunflower oil.

Natural Products Targeting Amyloid Beta in Alzheimer's Disease

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by severe brain damage and dementia. There are currently few therapeutics to treat this disease, and they can only temporarily alleviate some of the symptoms. The pathogenesis of AD is mainly preceded by accumulation of abnormal amyloid beta (Aβ) aggregates, which are toxic to neurons. Therefore, modulation of the formation of these abnormal aggregates is strongly suggested as the most effective approach to treat AD. In particular, numerous studies on natural products associated with AD, aiming to downregulate Aβ peptides and suppress the formation of abnormal Aβ aggregates, thus reducing neural cell death, are being conducted. Generation of Aβ peptides can be prevented by targeting the secretases involved in Aβ-peptide formation (secretase-dependent). Additionally, blocking the intra- and intermolecular interactions of Aβ peptides can induce conformational changes in abnormal Aβ aggregates, whereby the toxicity can be ameliorated (structure-dependent). In this review, AD-associated natural products which can reduce the accumulation of Aβ peptides via secretase- or structure-dependent pathways, and the current clinical trial states of these products are discussed.

A comprehensive profiling and identification of liquiritin metabolites in rats using ultra-high-performance liquid chromatography coupled with linear ion trap-orbitrap mass spectrometer

Liquiritin (LQ), a main component of liquorice, exerts various biological activities. However, insufficient attentions have been paid to the metabolism study on this natural compound until now. Our present study was conducted to investigate the LQ metabolites in rats urine, faeces and plasma using UHPLC-LTQ-Orbitrap mass spectrometer in both positive and negative ion modes. Meanwhile, post-acquisition data-mining methods including high-resolution extracted ion chromatogram (HREIC), multiple mass defect filters (MMDFs), neutral loss fragments (NLFs) and diagnostic product ions (DPIs) were utilised to screen and identify LQ metabolites from HR-ESI-MS to ESI-MSⁿ stage. As a result, a total of 49 metabolites were detected and characterised unambiguously or tentatively. These metabolites were presumed to generate through glucuronidation, sulfation, deglucosylation, dehydrogenation, methylation, hydrogenation, hydroxylation, ring cleavage and their composite reactions. Our results not only provided novel and useful data to better understand the biological activities of LQ, but also indicated that the proposed strategy was reliable for a rapid discovery and identification drug-related constituents in vivo.

Perspectives on the Role of Isoliquiritigenin in Cancer

Isoliquiritigenin (2',4',4-trihydroxychalcone, ISL), one of the most important bioactive compounds with a chalcone structure, is derived from licorice root. Licorice is commonly known as Glycyrrhiza, including Glycyrrhiza uralensis, Glycyrrhiza radix, and Glycyrrhiza glabra, which are generally available in common foods and Chinese herbal medicines based on a wide variety of biological functions and pharmacological effects, and its derivative (ISL) is utilized as a food additive and adjunct disease treatment. In this review, we summarized the progress over the last 10 years in the targeted pathways and molecular mechanisms of ISL that are involved in the regulation of the onset and progression of different types of cancers.

Isoliquiritigenin Attenuates Anxiety-Like Behavior and Locomotor Sensitization in Rats after Repeated Exposure to Nicotine

As important components of positive and negative reinforcement, locomotor sensitization and withdrawal anxiety following repeated exposure to nicotine (NIC) constitute crucial risk factors for relapse to NIC use after abstinence. Glycyrrhiza radix (G. radix), an important tonic used in traditional Oriental medicine, has not only anxiolytic effects but also reduces NIC-induced locomotor sensitization. Isoliquiritigenin (ISL), a bioactive ingredient of G. radix, also exhibits neuropharmacological effects, including anxiolytic action. Previously, we reported that ISL suppressed cocaine-induced extracellular dopamine release in the nucleus accumbens shell (NaccSh) and attenuated methamphetamine-induced neurotoxicity. The present study was performed to evaluate the effects of ISL on both NIC withdrawal anxiety and locomotor sensitization. Adult male rats received subcutaneous administration of NIC hydrogen tartrate (0.4 mg/kg, twice a day) for 7 days followed by 4 days of withdrawal. During the period of NIC withdrawal, the rats received four intragastric treatments with ISL (3, 10, or 30 mg/kg/day). All three doses of ISL significantly inhibited NIC withdrawal-induced anxiety-like behaviors in the elevated plus maze (EPM) test, but only the 10 mg/kg/day and 30 mg/kg/day ISL doses attenuated locomotor sensitization induced by a challenge dose of NIC. Intracerebroventricular ISL also inhibited both NIC-induced withdrawal anxiety and locomotor sensitization, but intra-NaccSh injection of ISL blocked only NIC locomotor sensitization, which was abolished by post-ISL infusion of tert-butyl hydroperoxide (an oxidant) or N-methyl-d-aspartate (NMDA) into the NaccSh. Moreover, there was increased protein expression of phosphorylated Erk1/2 in the NIC-sensitized NaccSh, which was suppressed by ISL. Taken together, these results suggest that ISL can inhibit repeated NIC-induced withdrawal anxiety and locomotor sensitization, and the latter is mediated by antagonizing accumbal reactive oxygen species and NMDA receptor signaling.

A targeted strategy to identify untargeted metabolites from in vitro to in vivo: Rapid and sensitive metabolites profiling of licorice in rats using ultra-high performance liquid chromatography coupled with triple quadrupole-linear ion trap mass spectrometry

It is challenging to conduct in vivo metabolic study for traditional Chinese medicines (TCMs) because of complex components, unpredictable metabolic pathways and low metabolite concentrations. Herein, we proposed a sensitive strategy to characterize TCM metabolites in vivo at an orally clinical dose using ultra-high performance liquid chromatography-triple quadrupole-linear ion trap mass spectrometry (UHPLC-QTRAP-MS). Firstly, the metabolism of individual compounds in rat liver microsomes was studied to obtain the metabolic pathways and fragmentation patterns. The untargeted metabolites in vitro were detected by multiple ion monitoring-enhanced product ion (EPI) and neutral loss-EPI scans. Subsequently, a sensitive multiple reaction monitoring-EPI method was developed according to the in vitro results and predicted metabolites to profile the in vivo metabolites. Licorice as a model herb was used to evaluate and validate our strategy. A clinical dose of licorice water extract was orally administered to rats, then a total of 45 metabolites in urine, 21 metabolites in feces and 35 metabolites in plasma were detected. Among them, 18 minor metabolites have not been reported previously and 6 minor metabolites were first detected in vivo. Several isomeric metabolites were well separated and differentiated in our strategy. These results suggested that this new strategy could be widely used for the detection and characterization of in vivo metabolites of TCMs.

Hepatic metabolism of licochalcone A, a potential chemopreventive chalcone from licorice (Glycyrrhiza inflata), determined using liquid chromatography-tandem mass spectrometry

The metabolism of the chemoprevention agent licochalcone A, which is a chemopreventive chalcone found in abundance in the licorice species Glycyrrhiza inflata, was investigated using human liver microsomes and human hepatocytes combined with analysis using high performance liquid chromatography-mass spectrometry (LC-MS). Five oxygenated phase I metabolites of licochalcone A were formed by human liver microsomes, including a catechol on the A-ring, two intramolecular cyclization products following epoxidation of the exocyclic alkene at position 5 of the B-ring, and two dioxygenated products. Nine phase II monoglucuronides of licochalcone A and its oxygenated phase I metabolites were formed during incubation with human hepatocytes. These included (E)-licochalcone A-4-glucuronide, (E)-licochalcone A-4'-glucuronide, (Z)-licochalcone A-4-glucuronide, glucuronic acid conjugates of all of the monooxygenated phase I metabolites, and glucuronides of the licochalcone catechol after methylation by catechol-O-methyl transferase. In addition, human hepatocytes formed one sulfate conjugate and one glutathione conjugate of licochalcone A. The structures of all major metabolites were determined using a combination of accurate mass measurement, LC-tandem mass spectrometry, LC-UV, nuclear magnetic resonance, and comparison with standards. The cytochrome P450 enzymes and UDP-glucuronosyltransferases responsible for the formation of the major metabolites were identified. Based on in vitro hepatic clearance calculations, licochalcone A is predicted to be metabolized primarily by phase II conjugation reactions. Graphical abstract Phase I and II metabolism of licochalcone A from the licorice species Glycyrrhiza inflata by human liver microsomes and hepatocytes determined using LC-MS/MS, LC-UV and NMR.

New Insights toward Colorectal Cancer Chemotherapy Using Natural Bioactive Compounds

Combination therapy consists in the simultaneous administration of a conventional chemotherapy drug (or sometimes, a radiotherapy protocol) together with one or more natural bioactives (usually from plant or fungal origin) of small molecular weight. This combination of anticancer drugs may be applied to cell cultures of tumor cells, or to an animal model for a cancer type (or its xenograft), or to a clinical trial in patients. In this review, we summarize current knowledge describing diverse synergistic effects on colorectal cancer cell cultures, animal models, and clinical trials of various natural bioactives (stilbenes, flavonoids, terpenes, curcumin, and other structural families), which may be important with respect to diminish final doses of the chemotherapy drug, although maintaining its biological effect. This is important as these approaches may help reduce side effects in patients under conventional chemotherapy. Also, these molecules may exerts their synergistic effects via different cell cycle pathways, including different ones to those responsible of resistance phenotypes: transcription factors, membrane receptors, adhesion and structural molecules, cell cycle regulatory components, and apoptosis pathways.

The application of HPLC-MS/MS to studies of pharmacokinetics and interconversion of isoliquiritigenin and neoisoliquiritigenin in rats

A specific and sensitive HPLC-MS/MS method was developed and validated for the simultaneously quantification of isoliquiritigenin (ISL) and neoisoliquiritin (NIS) in rat plasma by oral administration. Analytes were analyzed on an Agilent 6460 LC-MS/MS system (Agilent, USA) using an Agilent Zorbax SB-C18 column (4.6 × 150 mm, 5 μm). Gradient elution was applied for the analyte separation using a mobile phase composed of 0.1% formic acid aqueous solution and methanol at a flow rate of 1.0 mL/min with a total running time of 12 min. The calibration curves for ISL and NIS showed good linearity in the concentrations ranging from 0.001 to 4.000 μg/mL with correlation coefficients >0.998. The precision, accuracy, recovery and stability were deemed acceptable. The method was applied to the pharmacokinetics study of ISL and NIS in rats by single and combination administration. The result showed that Cmax and AUC0→t of ISL were markedly increased from 0.53 to 1.20 μg/mL, and from 69.63 to 200.74 min μg/mL by combination administration. The mean t1/2 value was also prolonged from 64.55 to 203.74 min in the combination group. These results indicated that NIS may have been metabolized to ISL which increased the absorption and extended the elimination of ISL. However, little difference was found for NIS pharmacokinetics parameters between single NIS and the combination group, which suggested that there was no significant biotransformation of ISL to NIS. Copyright © 2015 John Wiley & Sons, Ltd.

Development of Safe and Effective Botanical Dietary Supplements

Regulated differently than drugs or foods, the market for botanical dietary supplements continues to grow worldwide. The recently implemented U.S. FDA regulation that all botanical dietary supplements must be produced using good manufacturing practice is an important step toward enhancing the safety of these products, but additional safeguards could be implemented, and unlike drugs, there are currently no efficacy requirements. To ensure a safe and effective product, botanical dietary supplements should be developed in a manner analogous to pharmaceuticals that involves identification of mechanisms of action and active constituents, chemical standardization based on the active compounds, biological standardization based on pharmacological activity, preclinical evaluation of toxicity and potential for drug-botanical interactions, metabolism of active compounds, and finally, clinical studies of safety and efficacy. Completing these steps will enable the translation of botanicals from the field to safe human use as dietary supplements.

Dose-Independent ADME Properties and Tentative Identification of Metabolites of α-Mangostin from Garcinia mangostana in Mice by Automated Microsampling and UPLC-MS/MS Methods

The information about a marker compound's pharmacokinetics in herbal products including the characteristics of absorption, distribution, metabolism, excretion (ADME) is closely related to the efficacy/toxicity. Also dose range and administration route are critical factors to determine the ADME profiles. Since the supply of a sufficient amount of a marker compound in in vivo study is still difficult, pharmacokinetic investigations which overcome the limit of blood collection in mice are desirable. Thus, we have attempted to investigate concurrently the ADME and proposed metabolite identification of α-mangostin, a major constituent of mangosteen, Garcinia mangostana L, in mice with a wide dose range using an in vitro as well as in vivo automated micro-sampling system together. α-mangostin showed dose-proportional pharmacokinetics at intravenous doses of 5–20 mg/kg and oral doses of 10–100 mg/kg. The gastrointestinal absorption of α-mangostin was poor and the distribution of α-mangostin was relatively high in the liver, intestine, kidney, fat, and lung. α-mangostin was extensively metabolized in the liver and intestine. With regards to the formation of metabolites, the glucuronidated, bis-glucuronidated, dehydrogenated, hydrogenated, oxidized, and methylated α-mangostins were tentatively identified. We suggest that these dose-independent pharmacokinetic characteristics of α-mangostin in mice provide an important basis for preclinical applications of α-mangostin as well as mangosteen. In addition, these experimental methods can be applied to evaluate the pharmacokinetics of natural products in mice.

Regiospecificity of human UDP-glucuronosyltransferase isoforms in chalcone and flavanone glucuronidation determined by metal complexation and tandem mass spectrometry

The glucuronidation of a series of chalcones (2'-hydroxychalcone, 2',4'-dihydroxychalcone, 3,2'-dihydroxychalcone, 4,2'-dihydroxychalcone, and cardamonin) and their corresponding cyclized flavanones (7-hydroxyflavanone, 3'-hydroxyflavanone, 4'-hydroxyflavanone, and alpinetin) by eight human UDP-glucuronosyltransferase (UGT) 1A enzymes was evaluated. A postcolumn metal complexation LC-MS/MS strategy was used successfully to produce characteristic mass spectrometric product ions that were utilized in combination with elution order trends to identify chalcone and flavanone monoglucuronides unambiguously, thus allowing determination of the regioselectivities of the UGT1A isoforms. The presence of hydroxy groups on the A- or B-ring had a significant effect on the glucuronide product yield and the site where glucuronidation occurred. For example, for reaction with UGT1A9, formation of the 2'-O-glucuronide was increased for dihydroxychalcones with A-ring hydroxy substituents. In contrast, although UGT1A8 reacted with 3,2'-dihydroxychalcone and 4,2'-dihydroxychalcone to yield 2'-O-glucuronide products, the presence of a B-ring hydroxy group at the 4' position on cardamonin and 2',4'-dihydroxychalcone quenched the reaction at the OH-2' position. Moreover, the A-ring OH-4 group promoted glucuronidation at the 2' position for the reaction of 4,2'-dihydroxychalcone with UGT1A1 and 1A3. For UGT1A7, hydroxy group substituents on the chalcone A-ring also promoted cyclization and formation of the corresponding flavanone glucuronide.

Induction of apoptosis through tubulin inhibition in human cancer cells by new chromene-based chalcones

CONTEXT

As microtubules are highly involved in cellular growth, it appears to be a preferential target for cancer treatment. Therefore, many efforts have been performed to discover drugs that affect on microtubule function. Several microtubule inhibitors are in various stages of laboratory evaluations and clinical trials.

OBJECTIVE

A series of chromene-based chalcones with chlorine, methoxy, fluorine, tetrahydropyranyloxy and cyanide substituents were prepared and evaluated for cytotoxic effects against K562 and SK-N-MC cell lines, and the inhibitory effect on tubulin polymerization was studied as well.

MATERIALS AND METHODS

MTT, tubulin polymerization assays and binding measurements were evaluated by using related spectroscopy. Immunocytochemical study, morphological observations and apoptosis assay were examined using a fluorescence microscope and a flow cytometer.

RESULTS

(E)-3-(6-Chloro-2H-chromen-3-yl)-1-(3,4,5-trimethoxyphenyl) prop-2-en-1-one (compound 14) proved to be the most active in this series as an inhibitor of tubulin assembly [IC₅₀, 19.6 µM] and cytotoxic agent on K562 cells [IC₅₀, 38.7 µM]. Furthermore, these compounds exhibited a strong inhibitory effect on tubulin polymerization and reduced the in vitro assembly and bundling of proto-filaments. Also, compound 14 bound to the tubulin with a dissociation constant of 9.4 ± 0.7 µM and induced conformational changes in this protein.

DISCUSSION AND CONCLUSION

This study suggests that the compound 14 could be a good antitumor agent because of its biological functions. Compound 14 appears to bind directly to tubulin and thereby perturbs microtubule stability and the function of the spindle apparatus, which causes cancer cells to arrest and undergo apoptosis.

Inhibition of liver X receptor-α-dependent hepatic steatosis by isoliquiritigenin, a licorice antioxidant flavonoid, as mediated by JNK1 inhibition

Isoliquiritigenin (ILQ), a flavonoid obtained from Glycyrrhizae species, has an antioxidant effect. This study investigated the potential of ILQ for inhibiting liver X receptor-α (LXRα)-mediated lipogenesis and steatosis in hepatocytes and its underlying molecular basis. Treatment with ILQ antagonized the ability of an LXRα agonist (T0901317) to activate sterol regulatory element binding protein-1c (SREBP-1c), thereby repressing transcription of fatty acid synthase, acetyl-CoA carboxylase, ATP-binding cassette transporter-A1, and stearoyl-CoA desaturase-1. ILQ treatment inhibited activating phosphorylation of JNK1 elicited by palmitate or TNFα. JNK1, but not JNK2, increased LXRα phosphorylation at serine residues, promoting LXRα activation. The ability of ILQ to inhibit JNK1 downstream of ASK1-MKK7 led to the repression of T0901317-inducible LXRα and SREBP-1c activation. In mice fed a high-fat diet, ILQ treatment inhibited hepatic steatosis, as shown by a decrease in fat accumulation and repression of lipogenic genes. The results of blood biochemistry and histopathology confirmed attenuation of high-fat diet-induced liver injury by ILQ. Moreover, ILQ inhibited oxidative stress, as indicated by decreases in thiobarbituric acid-reactive substance formation, iNOS and COX2 induction, and nitrotyrosinylation. Our results demonstrate that ILQ has the ability to repress LXRα-dependent hepatic steatosis through JNK1 inhibition and protect hepatocytes from oxidative injury inflicted by fat accumulation.

Radiosensitization of cancer cells by hydroxychalcones

Radiation sensitization is significantly increased by proteotoxic stress, such as a heat shock. We undertook an investigation, seeking to identify natural products that induced proteotoxic stress and then determined if a compound exhibited radiosensitizing properties. The hydroxychalcones, 2',5'-dihydroxychalcone (D-601) and 2,2'-dihydroxychalcone (D-501), were found to activate heat shock factor 1 (Hsf1) and exhibited radiation sensitization properties in colon and pancreatic cancer cells. The radiosensitization ability of D-601 was blocked by pretreatment with α-napthoflavone (ANF), a specific inhibitor of cytochrome P450 1A2 (CYP1A2), suggesting that the metabolite of D-601 is essential for radiosensitization. The study demonstrated the ability of hydroxychalcones to radiosensitize cancer cells and provides new leads for developing novel radiation sensitizers.

Cancer chemopreventive activity and metabolism of isoliquiritigenin, a compound found in licorice

Isoliquiritigenin (2',4',4-trihydroxychalcone; ILG), a chalcone found in licorice root and many other plants, has shown potential chemopreventive activity through induction of phase II enzymes such as quinone reductase-1 in murine hepatoma cells. In this study, the in vivo metabolism of ILG was investigated in rats. In addition, ILG glucuronides and ILG-glutathione adducts were observed in human hepatocytes and in livers from rats treated with ILG. ILG glucuronides were detected in both plasma and rat liver tissues. In addition, in a full-term cancer chemoprevention study conducted with 7,12-dimethylbenz(a)anthracene-treated female Sprague-Dawley rats, dietary administration of ILG slightly increased tumor latency but had a negative effect on the incidence of mammary tumors starting at approximately 65 days after 7,12-dimethylbenz(a)anthracene administration. Further, no significant induction of phase II enzymes was found in mammary glands, which is consistent with the low level of ILG observed in these tissues. However, ILG significantly induced quinone reductase-1 activity in the colon, and glutathione as well as glutathione S-transferase in the liver. Analysis of mRNA expression in tissues of rats treated with ILG supported these findings. These results suggest that ILG should be tested for chemopreventive efficacy in nonmammary models of cancer.