Enzyme Quinone Reductase Research Articles

Effects of paving asphalt fume exposure on genotoxic and mutagenic activities in the rat lung

Asphalt fumes are complex mixtures of aerosols and vapors containing various organic compounds, including polycyclic aromatic hydrocarbons (PAHs). Previously, we have demonstrated that inhalation exposure of rats to asphalt fumes resulted in dose-dependent induction of CYP1A1 with concomitant down-regulation of CYP2B1 and increased phase II enzyme quinone reductase activity in the rat lung. In the present study, the potential genotoxic effects of asphalt fume exposure due to altered lung microsomal enzymes were studied. Rats were exposed to air or asphalt fume generated under road paving conditions at various concentrations and sacrificed the next day. Alveolar macrophages (AM) were obtained by bronchoalveolar lavage and examined for DNA damage using the comet assay. To evaluate the systemic genotoxic effect of asphalt fume, micronuclei formation in bone marrow polychromatic erythrocytes (PCEs) was monitored. Lung S9 from various exposure groups was isolated from tissue homogenates and characterized for metabolic activity in activating 2-aminoanthracene (2-AA) and benzo[a]pyrene (BaP) mutagenicity using the Ames test with Salmonella typhimurium YG1024 and YG1029. This study showed that the paving asphalt fumes significantly induced DNA damage in AM, as revealed by DNA migration in the comet assay, in a dose-dependent manner, whereas the micronuclei formation in bone marrow PCEs was not detected even at a very high exposure level (1733 mg h/m 3). The conversion of 2-AA to mutagens in the Ames test required lung S9-mediated metabolic activation in a dose-dependent manner. In comparison to the controls, lung S9 from rats exposed to asphalt fume at a total exposure level of 479±33 mg h/m 3 did not significantly enhance 2-AA mutagenicity with either S. typhimurium YG1024 or YG1029. At a higher total asphalt fume exposure level (1150±63 mg h/m 3), S9 significantly increased the mutagenicity of 2-AA as compared to the control. However, S9 from asphalt fume-exposed rats did not significantly activate the mutagenicity of BaP in the Ames test. These results show that asphalt fume exposure, which significantly altered both phases I and II metabolic enzymes in lung microsomes, is genotoxic to AM and enhances the metabolic activation of certain mutagens through altered S9 content.

Transcriptional regulation by the estrogen receptor of antioxidative stress enzymes and its functional implications.

We previously reported that antiestrogen-liganded estrogen receptor beta (ERbeta) transcriptionally activates the major detoxifying enzyme quinone reductase (QR) (NAD(P)H:quinone oxidoreductase). Our studies also indicate that upregulation of QR, either by overexpression or induction by tamoxifen, can protect breast cells against oxidative DNA damage caused by estrogen metabolites. We now report on the upregulation of glutathione S-transferases Pi (GST-Pi) and gamma-glutamylcysteine synthetase heavy subunit (GCSh) expression by antiestrogens. Studies indicate the regulation of GST-Pi and GCSh transcriptional activity by ER. While ER regulation is mediated by an electrophile response element (EpRE), we identified mechanistic differences in the involvement of other transcription factors. Regardless of these differences, ER beta-mediated regulation of GST-Pi and GCSh point towards an important role for ER beta in cellular protection against oxidative stress. A protective role is supported by our observation of inhibition of estrogen-induced DNA damage upon upregulation of GST-Pi and GCSh expression.

Effect of Dietary Constituents With Chemopreventive Potential on Adduct Formation of a Low Dose of the Heterocyclic Amines PhIP and IQ and Phase II Hepatic Enzymes

We conducted a study to evaluate dietary chemopreventive strategies to reduce genotoxic effects of the carcinogens 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). PhIP and IQ are heterocyclic amines (HCAs) that are found in cooked meat and may be risk factors for cancer. Typical chemoprevention studies have used carcinogen doses many thousand-fold higher than usual human daily intake. Therefore, we administered a low dose of [14C] PhIPand [3H] IQand utilized accelerator mass spectrometry to quantify PhIP adducts in the liver, colon, prostate, and blood plasma and IQadducts in the liver and blood plasma with high sensitivity. Diets supplemented with phenethylisothiocyanate (PEITC), genistein, chlorophyllin, or lycopene were evaluated for their ability to decrease adduct formation of [14C] PhIPand [3H] IQin rats. We also examined the effect of treatments on the activity of the phase II detoxification enzymes glutathione S-transferase (GST), UDP-glucuronyltransferase (UGT), phenol sulfotransferase (SULT) and quinone reductase (QR). PEITC and chlorophyllin significantly decreased PhIP-DNA adduct levels in all tissues examined, which was reflected by similar changes in PhIP binding to albumin in the blood. In contrast, genistein and lycopene tended to increase PhIP adduct levels. The treatments did not significantly alter the level of IQ-DNA or -protein adducts in the liver.With the exception of lycopene, the treatments had some effect on the activity of one or more hepatic phase II detoxification enzymes. We conclude that PEITC and chlorophyllin are protective of PhIP-induced genotoxicity after a low exposure dose of carcinogen, possibly through modification of HCA metabolism.

Functional implications of antiestrogen induction of quinone reductase: inhibition of estrogen-induced deoxyribonucleic acid damage.

Recent studies have shown that the antiestrogens tamoxifen and raloxifene may protect against breast cancer, presumably because of a blockade of estrogen receptor (ER)-mediated transcription. Another possible explanation is that antiestrogen-liganded ER transcriptionally induces genes that are protective against cancer. We previously reported that antiestrogen-liganded ERbeta transcriptionally activates the major detoxifying enzyme quinone reductase (QR) [NAD(P)H:quinone oxidoreductase]. It has been established that metabolites of estrogen, termed catecholestrogens, can form DNA adducts and cause oxidative DNA damage. We hypothesize that QR inhibits estrogen-induced DNA damage by detoxification of reactive catecholestrogens. We report here that physiological concentrations of 17beta-estradiol cause oxidative DNA damage, as measured by levels of 8- hydroxydeoxyguanine, in ER-positive MCF7 breast cancer cells, MDA-MB-231 breast cancer cells (ERalpha negative/ERbeta positive) and nontumorigenic MCF10A breast epithelial cells (very low ER), which is dependent on estrogen metabolism. Estrogen-induced 8-hydroxydeoxyguanine was inversely correlated to QR and ERbeta levels and was followed by downstream induction of the DNA repair enzyme XPA. Trans-hydroxytamoxifen, raloxifene, and the pure antiestrogen ICI-182,780 protected against estradiol-mediated damage in breast cancer cells containing ERbeta. This is most likely due to the ability of these antiestrogens to activate expression of QR via ERbeta. We conclude that up-regulation of QR, either by overexpression or induction by tamoxifen, can protect breast cells against oxidative DNA damage caused by estrogen metabolites, representing a possible novel mechanism of tamoxifen prevention against breast cancer.

Melatonin receptors and their regulation: biochemical and structural mechanisms

There is growing evidence demonstrating the complexity of melatonin's role in modulating a diverse number of physiological processes. This complexity could be attributed to the fact that melatonin receptors belong to two distinct classes of proteins, that is, the G-protein coupled receptor superfamily (MT 1, MT 2) and the quinone reductase enzyme family ( MT 3 ) which makes them unique at the molecular level. Also, within the G-protein coupled receptor family of proteins, the MT 1 and MT 2 receptors can couple to multiple and distinct signal transduction cascades whose activation can lead to unique cellular responses. Also, throughout the 24-hour cycle, the receptors' sensitivity to specific cues fluctuates and this sensitivity can be modulated in a homologous fashion, that is, by melatonin itself, and in a heterologous manner, that is, by other cues including the photoperiod or estrogen. This sensitivity of response may reflect changes in melatonin receptor density that also occurs throughout the 24-hour light/dark cycle but out of phase with circulating melatonin levels. The mechanisms that underlie the changes in melatonin receptor density and function are still not well-understood, but data is beginning to show that transcriptional events and G-protein uncoupling may be involved. Even though this area of research is still in its infancy, great strides are being made everyday in elucidating the mechanisms that underlie melatonin receptor function and regulation. The focus of this review is to highlight some of these discoveries in an attempt to reveal the uniqueness of the melatonin receptor family while at the same time provide thought-provoking ideas to further advance this area of research. Thus, a brief overview of each of the mammalian melatonin receptor subtypes and the signal transduction cascades to which they couple will be discussed with a greater emphasis placed on the mechanisms underlying their regulation and the domains within the receptors essential for proper signaling.

Diesel Exhaust Particle-Induced Alterations of Pulmonary Phase I and Phase II Enzymes of Rats

Although diesel exhaust particles (DEP) are known to produce pulmonary disorders, the xenobiotic metabolic pathways associated with DEP detoxification and bioactivation remain unclear. In this study, the effect of acute exposure of DEP on phase I and phase II enzymes of rat lung was investigated. Intratracheal administration of DEP produced an induction of cytochrome P-450 (CYP) 1A1 enzyme protein and activity at 1 d postexposure, with the enzyme level returning to control at 5 d postexposure. On the other hand, carbon black (CB), a particle control, did not show any induction of CYP1A1 protein or enzyme activity. However, both DEP and CB significantly decreased CYP2B1 protein and enzyme activity at 1 d postexposure. The decrease in CYP2B1 enzyme protein and activity by DEP or CB treatment was observed up to 7 d postexposure. DEP and CB treatments also significantly attenuated glutathione S-transferase (GST)- ~ protein at 1 d postexposure. Both DEP and CB at 35 mg/kg significantly decreased the activities of GST and catalase at 1 and 7 d postexposure. DEP, but not CB, significantly induced quinone reductase (QR) activity at 7 d postexposure. This study suggests that DEP may induce CYP1A1 and QR enzymes via a chemical effect, while the carbonaceous core may be involved in the attenuation of CYP2B1, GST, and catalase proteins and enzyme activities.

Selective Induction of Phase II Enzymes in the Urinary Bladder of Rats by Allyl Isothiocyanate, a Compound Derived From Brassica Vegetables

Allyl isothiocyanate (AITC) is formed from sinigrin, a glucosinolate that is present in many Brassica vegetables. In the present study, the effect of various dose levels of AITC on the activities of the phase II detoxification enzymes quinone reductase (QR) and glutathione S-transferase (GST) in rat tissues has been examined. High dose levels of AITC, given daily for 5 days, increased the activity of QR and/or GST in the liver, kidneys, lungs, spleen, urinary bladder, glandular and nonglandular stomach, duodenum, jejunum, ileum, cecum, and colon plus rectum of the animals. At low doses, however, increases in enzyme activity were observed only in the urinary bladder of the rats, with a significant effect being recorded in this tissue at a dose of AITC of only 10 mmol/kg/day. The effect of duration of exposure to AITC on enzyme levels in the urinary bladder was also investigated, with rats receiving the isothiocyanate each day for 1-21 days. In the case of QR, a plateau of activity was reached after 15 daily doses of AITC, but GST activity continued to increase with continued exposure, and no plateau was reached after 21 doses. The dose level of AITC found to be effective in rats approaches the level that could be achieved through human consumption of Brassica vegetables, suggesting that induction of phase II enzymes by food-derived isothiocyanates could contribute to the lower incidence of bladder cancer observed in individuals who regularly consume such vegetables.

Induction of quinone reductase activity by stilbene analogs in mouse Hepa 1c1c7 cells.

Based on the potential cancer chemopreventive activity of resveratrol, a trihydroxystilbene with the induction of quinone reductase activity, this study was designed to determine if stilbene-related compounds were inducers of phase II detoxifying metabolic enzyme quinone reductase (QR) in the mouse hepatoma Hepa 1c1c7 cells. Among the thirteen compounds tested, several compounds including 3,4,5,3',5'-pentamethoxy-trans-stilbene were found to potentially induce QR activity in this cell line. In addition, substitution with 3-thiofurane ring instead of phenyl ring in the stilbene skeleton also exhibited potential induction of QR activity. This result will give primary information to design the potential inducers of QR activity in the stilbene analogs.

Relative Activities of Organosulfur Compounds Derived From Onions and Garlic in Increasing Tissue Activities of Quinone Reductase and Glutathione Transferase in Rat Tissues

There is evidence that onions and garlic protect against cancer in humans. It has been suggested that this effect is due to the organosulfur compounds in these vegetables and that these substances act through induction of phase II detoxification enzymes. In the present studies, we have compared the ability of diallyl sulfide, diallyl disulfide, and diallyl trisulfide, compounds that are derived from garlic, to increase the activity of the phase II enzymes quinone reductase and glutathione transferase in a variety of rat tissues. We have also examined the onion-derived substances, dipropyl sulfide, dipropyl disulfide, dipropenyl sulfide, and dipropenyl disulfide, under identical conditions. Diallyl trisulfide and diallyl disulfide were potent inducers of the phase II enzymes. Dipropenyl disulfide was much less active, while little effect on enzyme activity was seen in animals dosed with dipropyl disulfide. Diallyl sulfide and dipropyl sulfide were weak inducers of quinone reductase and glutathione transferase, but dipropenyl sulfide was very active, with an effect similar to that of diallyl disulfide. It is possible that diallyl disulfide and diallyl trisulfide are important in the anticancer action of garlic, while dipropenyl sulfide could be involved in the beneficial action of onions.

The antioxidant enzyme quinone reductase is up-regulated in vivo following cerebral ischemia

An astrocyte antioxidant enzyme, quinone reductase (QR), was studied in vivo to assess whether its activity was up-regulated following cerebral ischemia. Rats were given a unilateral focal cerebral infarct and regions of interest within the ischemic penumbra compared to the non-ischemic side for QR activity. At 7 days post-ischemia, QR activity was significantly up-regulated within cells of astrocyte morphology in the cortex (p = 0.007) and subcortical (p = 0.005) areas adjacent to the infarct. This enzyme activity peaked at 7 days but was still significantly up-regulated at 14 days. Up-regulation of QR activity occurs within the ischemic penumbra of a stroke in this animal model and may contribute to factors that limit ischemic damage to neurons in this area.

Chemoprevention of DMBA-induced Mammary Carcinogenesis: Relationship Between Induction of Phase II Enzymes, Effects on DMBA-induced Hemoglobin Adducts and Decreases in Mammary Tumor Multiplicity

The chemopreventive potential of 1,2-dithiole-3-thione, ethoxyquin, butylated hydroxanisole (BHA) and β-naphthoflavone (BNF) was investigated in the 7,12-dimethylbenz(a)anthracene (DMBA) rat mammary tumor model. Female Sprague-Dawley rats received a single dose of DMBA (15 mg) at 50 days of age. Chemopreventive agents were administered via the diet, beginning one week prior to DMBA dosing and continuing until one week following DMBA. Tumor latency, multiplicity and incidence were not affected by BHA (2.5 or 5.0 g/kg diet), but administration of low or high doses of β-napthflavone (1.65 and 3.3 g/kg diet), or high doses of ethoxyquin (5.0 g/kg diet) or 1,2-dithiole-3-thione (0.6 g/kg diet), effectively inhibited all parameters of tumorigenesis. It is presumed that many of these agents which decrease the tumorigenicity act by altering the metabolism of the carcinogen resulting in diminished numbers of reactive ultimate carcinogens. We examined both for the induction of enzymes that might alter carcinogen metabolism as well as alterations in levels of DMBA adducts to hemoglobin. A strong correlation was observed between the effect of these agents on carcinogenesis and the induction of phase I1 enzymes (quinone reductase and glutathione S-transferase) and glutathione in the mammary gland. We also examined the effects of BNF, 1.2- dithiol-3-thione and BHA on formation of hemoglobin adducts by DMBA. Similarly to the results on carcinogenesis the relative efficacy of compounds in inhibiting DMBA adduct formation and DMBA induced mammary tumorigenesis was BNF > 1,2 Dithiolthione >> BHA. These results support the hypothesis that these agents work by altering metabolism of DMBA to reactive intermediates but further offer the possibility that modulation of hemoglobin adducts may serve as a surrogate marker of efficacy.

Induction of quinone reductase and glutathione transferase in rat tissues by juglone and plumbagin.

The ability of the naturally-occurring naphthoquinone derivatives, juglone and plumbagin, to increase tissue activities of the Phase II detoxification enzymes quinone reductase (QR) and glutathione transferase (GT) has been investigated in rats. Groups of female Sprague-Dawley rats were dosed by oral intubation on 5 consecutive days with either juglone or plumbagin at 12.5, 25, 50, 75, 100 or 125 mumoles/kg/day. The animals were then killed and the activities of QR and GT determined in tissue homogenates. The naphthoquinone derivatives had no significant effect on enzyme activities in the liver, spleen, heart, lung or urinary bladder. Increases in the activities of one or both enzymes were recorded, however, in the caecum, kidney, forestomach, duodenum, colon, glandular stomach and jejunum. The possibility that induction of Phase II enzymes could contribute to the previously-reported ability of juglone and plumbagin to protect animals against chemically-induced intestinal neoplasia is discussed.

Plant Secondary Metabolites as Potential Anticancer Agents and Cancer Chemopreventives

A. Douglas KinghornProgram for Collaborative Research in the Pharmaceutical Sciences and Department of MedicinalChemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, 833 SouthWood Street, Chicago, IL 60612, U.S.ATel.: (312) 996-0914, Fax: (312) 996-7107, E-mail: kinghorn@uic.eduThere is considerable interest in the screening of plant and other natural product extracts in moderndrug discovery programs, since structurally novel chemotypes with potent and selective biological ac-tivity may be obtained [1-4]. A consideration of biological activity in addition to the isolation andstructure elucidation stages in a phytochemical investigation may add a great deal to the overall scien-tific significance of the work. Phytochemists may gain considerable information by using panels ofsimple bioassays and/or more specialized in vitro bioassays to follow each step of a purification proce-dure [3]. In the following paragraphs, recent examples of bioactive compounds obtained in the author’slaboratory in projects directed towards the search for novel anticancer agents and cancer chemopre-ventives from higher plants will be presented.In the United States in 1999, it is estimated that over 1.2 million persons will be diagnosed with in-vasive forms of cancer, and over 1,500 people will die as a result of cancer each day [5]. Among manyrecent advances in cancer chemotherapy, plant natural products have played an important role in con-tributing to the arsenal of the approximately 60 cancer chemotherapeutic drugs on the market. For in-stance, in the United States, there are now four structural classes of plant anticancer agents available,constituted by the Catharanthus (Vinca) alkaloids (vinblastine, vincristine, vinorelbine), the epipodo-phyllotoxins (etoposide, etoposide phosphate, teniposide), the taxanes (paclitaxel and docetaxel), andthe camptothecin derivatives (irinotecan and topotecan) [6]. Several other plant-derived compoundsare currently in preclinical and clinical trials [6,7].As part of a National Cooperative Natural Products Drug Discovery Group (NCNPDDG) researchproject funded by the United States National Cancer Institute (1995-2000), our collaborative team atthe College of Pharmacy, University of Illinois at Chicago (Chicago, Illinois), and Research TriangleInstitute (Research Triangle Park, North Carolina), and Bristol-Myers Squibb (Princeton, New Jersey)is evaluating about 400 plant samples per year, with the aim of discovering and evaluating novel plant-derived anticancer agents. During the funding period 1990-1995, the industrial partner was GlaxoWellcome Medicines Research Centre (Sevenage, U.K.), and past progress made in the project hasbeen reviewed [8]. Since 1995, the primary plant samples have been collected in the Dominican Re-public, Peru, and Indonesia. Plant recollections have taken place mainly in Thailand and Zimbabwe in

Low Doses of Diallyl Disulfide, a Compound Derived From Garlic, Increase Tissue Activities of Quinone Reductase and Glutathione Transferase in the Gastrointestinal Tract of the Rat

Diallyl disulfide (DADS), a substance that is formed from the organosulfur compounds present in garlic, is known to increase tissue activities of the phase II detoxification enzymes quinone reductase (QR) and glutathione transferase (GT) in animals. In previous experiments, however, high doses of DADS were employed and only a limited range of tissues were examined. In the present studies, increased activities of QR and GT were recorded in the forestomach, glandular stomach, duodenum, jejunum, ileum, cecum, colon, liver, kidneys, spleen, heart, lungs, and urinary bladder of rats given DADS over a wide range of dose levels. Large variations in response were recorded among the different organs, with forestomach, duodenum, and jejunum being the most sensitive to enzyme induction by DADS. In these organs, significant increases in QR activity were observed at a dose of only 0.3 mg/kg/day. Such a dose level is close to that which may be achieved through human consumption of garlic, suggesting that induction of phase II enzymes may contribute to the protection that is afforded by this vegetable against cancer of the gastrointestinal tract in humans.

Induction of quinone reductase by a methanol extract of Scutellaria baicalensis and its flavonoids in murine Hepa 1c1c7 cells.

The effect of extracts of scutellariae radix (Scutellaria baicalensis Georgi) and its flavonoids, baicalin, baicalein and wogonin, on induction of quinone reductase (QR) in the Hepa 1c1c7 murine hepatoma cell line was examined. A significant and dose-dependent induction of QR activity was observed in the methanol extract of scutellariae radix and baicalin. HPCL analysis showed that baicalin was contained as a main component in the methanol extract of scutellariae radix, indicating that baicalin may be the major active principle of QR induction mediated by scutellariae radix extract. To elucidate the mechanism of baicalin-mediated induction of QR enzyme activity, the effect on QR mRNA levels in Hepa 1c1c7 cell cultures was investigated. Using reverse transcriptase-polymerase chain reaction techniques, time- and dose-dependent induction of QR mRNA levels by baicalin were demonstrated in Hepa 1c1c7 cells. On the basis of these results, the scutellariae radix extract or baicalin can be regarded as a readily available, promising, novel cancer chemopreventive agent.

Activation of endogenous antioxidant defenses in neuronal cells prevents free radical-mediated damage.

Dopamine (DA) is oxidized to the neurotoxic prooxidant species H2O2, OH., and DA quinones. We tested whether dimethyl fumarate (DMF), an electrophile shown to induce a pleiotropic antioxidant response in nonneuronal cells, could reduce the toxicity of DA metabolites in neural cells. Treatment of the N18-RE-105 neuroblastoma-retina hybridoma cell line with 30-150 microM dopamine led to cell death within 24 h, which increased steeply with dose, decreased with higher plating density, and was blocked by the H2O2-metabolizing enzyme catalase. Pretreatment with DMF (30 microM, 24 h) significantly attenuated DA and H2O2 toxicity (40-60%) but not that caused by the calcium ionophore ionomycin. DMF treatment also elevated total intracellular GSH and increased activities of the antioxidant enzymes quinone reductase (QR), glutathione S-transferase (GST), glutathione reductase, and the pentose phosphate enzyme glucose-6-phosphate dehydrogenase. To assess the protective efficacy of QR and GST, a stable cell line was constructed in which these enzymes were overexpressed. Cell death in the overexpressing line was not significantly different from that in a cell line expressing normal QR and GST activities, indicating that these two enzymes alone are insufficient for protection against DA toxicity. Although the relative importance of a single antioxidant enzyme such as QR or GST may be small, antioxidant inducers such as DMF may prove valuable as agents that elicit a broad-spectrum neuroprotective response.

Selective increase of the potential anticarcinogen 4-methylsulphinylbutyl glucosinolate in broccoli.

The putative anticarcinogenic activity of Brassica vegetables has been associated with the presence of certain glucosinolates. 4-Methylsulphinylbutyl isothiocyanate (sulphoraphane), derived from the corresponding glucosinolate found in broccoli, has previously been identified as a potent inducer of the anticarcinogenic marker enzyme quinone reductase [NADP(H):quinone-acceptor oxidoreductase] in murine hepatoma Hepa 1c1c7 cells. We have therefore produced a broccoli hybrid with increased levels of this anticarcinogenic glucosinolate and tested the ability of extracts to induce quinone reductase. A 10-fold increase in the level of 4-methylsulphinylbutyl glucosinolate was obtained by crossing broccoli cultivars with selected wild taxa of the Brassica oleracea (chromosome number, n = 9) complex. Tissue from these hybrids exhibited a >100-fold increase in the ability to induce quinone reductase in Hepa 1c1c7 cells over broccoli cultivars, due to both an increase in 4-methylsulphinylbutyl glucosinolate content and increased percentage conversion to sulphoraphane.

Isolation of bioactive constituents from Vaccinium myrtillus (bilberry) fruits and cell cultures

Tissues from bilberry ( Vaccinium myrtillus L.) fruits and callus cultures were extracted and fractionated to investigate phytochemical bioactivity. Major fractions containing flavonoids (proanthocyanidins and anthocyanin pigments) and a hexane extract containing largely chlorophylls, carotenoids, sterols and lipids were isolated, and further screened for anticancer activity by in vitro testing of their ability to induce the phase II xenobiotic detoxification enzyme quinone reductase (QR) in murine hepatoma cells. Although flavonoid fractions were inactive in the assay, a clear, significant induction of QR activity resulted from testing the hexane extract. The concentration of the extract required to double QR specific activity was 9 μg/150 μl per well, which indicates that one or more components possess substantial QR-inducing capacity, comparable to known QR inducers such as furanone and catechol. β-Sitosterol and the carotenoids lutein and zeaxanthin were identified as components of the active hexane extract, which also exhibited a growth suppressing effect against two human breast cancer cell lines MCF-7 and BT-20.

In vitro anticancer activity of fruit extracts from Vaccinium species.

Fruit extracts of four Vaccinium species (lowbush blueberry, bilberry, cranberry, and lingonberry) were screened for anticarcinogenic compounds by a combination of fractionation and in vitro testing of their ability to induce the Phase II xenobiotic detoxification enzyme quinone reductase (QR) and to inhibit the induction of ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine synthesis, by the tumor promoter phorbol 12-myristate 13-acetate (TPA). The crude extracts, anthocyanin and proanthocyanidin fractions were not highly active in QR induction whereas the ethyl acetate extracts were active QR inducers. The concentrations required to double QR activity (designated CDqr) for the ethyl acetate extracts of lowbush blueberry, cranberry, lingonberry, and bilberry were 4.2, 3.7, 1.3, and 1.0 microgram tannic acid equivalents (TAE), respectively, Further fractionation of the bilberry ethyl acetate extract revealed that the majority of inducer potency was contained in a hexane/chloroform subfraction (CDqr = 0.07 microgram TAE). In contrast to their effects on QR, crude extracts of lowbush blueberry, cranberry, and lingonberry were active inhibitors of ODC activity. The concentrations of these crude extracts needed to inhibit ODC activity by 50% (designated IC50) were 8.0, 7.0, and 9.0 micrograms TAE, respectively. The greatest activity in these extracts appeared to be contained in the polymeric proanthocyanidin fractions of the lowbush blueberry, cranberry, and lingonberry fruits (IC50 = 3.0, 6.0, and 5.0 micrograms TAE, respectively). The anthocyanidin and ethyl acetate extracts of the four Vaccinium species were either inactive or relatively weak inhibitors of ODC activity. Thus, components of the hexane/chloroform fraction of bilberry and of the proanthocyanidin fraction of lowbush blueberry, cranberry, and lingonberry exhibit potential anticarcinogenic activity as evaluated by in vitro screening tests.

AlliumChemistry: Microwave Spectroscopic Identification, Mechanism of Formation, Synthesis, and Reactions of (E,Z)-PropanethialS-Oxide, the Lachrymatory Factor of the Onion (Allium cepa)

Flow pyrolysis of 2-methyl-2-propyl 1‘-propenyl sulfoxide (9b) affords a 98:2 mixture of (Z)- and (E)-propanethial S-oxide ((Z)- and (E)-5b), both characterized by Fourier transform microwave (FT-MW) spectroscopy. Sulfines (Z)- and (E)-5b are also identified by FT-MW in chopped onion volatiles and by NMR spectroscopy in onion extracts. Similarly, flow pyrolysis of 2-methyl-2-propyl vinyl sulfoxide (9c) affords (Z)- and (E)-isomers of ethanethial S-oxide (5a), identified by FT-MW methods. Pyrolysis in the presence of D2O affords (Z)-5a-d1 and (Z)-5a-d2 from 9c and (Z)-5b-d1 from 9b; (Z)-5b-d1 is also produced when an onion is homogenized in D2O. Pyrolysis of 9c with ethyl propiolate gives ethyl (E)-3-(vinylsulfinyl)acrylate (10). Neat 5a at 100 °C gives acetaldehyde. On standing, 5b dimerizes to trans-3,4-diethyl-1,2-dithietane 1,1-dioxide (12a); Me3SiCHS+−O- (5f) undergoes an analogous dimerization. Compound 5b shows moderate potency as an anticarcinogen in inducing the enzyme quinone reductase.