Quinone Reductase Activity Research Articles

Potential Cancer Chemopreventive in Vitro Activities of Monomeric Xanthone Derivatives from the Marine Algicolous Fungus Monodictys putredinis

Investigation of the fungal strain Monodictys putredinis isolated from the inner tissue of a marine green alga led to the isolation of four new monomeric xanthones and a benzophenone. All structures were elucidated by extensive spectroscopic measurements. The relative configuration of compound 1 was determined by X-ray crystal structure analysis, while for 2 and 3 configurations were confirmed by NOE experiments. Absolute configurations for compounds 1-3 were deduced by comparing experimental circular dichroism spectroscopic data with those calculated employing quantum-chemical time-dependent density functional theory (TDDFT). The compounds were examined for their cancer chemopreventive potential. Xanthone 2 was shown to inhibit cytochrome P450 1A activity with an IC50 value of 3.0 microM. Compounds 2 and 3 displayed moderate activity as inducers of NAD(P)H:quinone reductase (QR) in cultured mouse Hepa 1c1c7 cells, with CD values (concentration required to double the specific activity of QR) of 12.0 and 12.8 microM, respectively. Compound 3 showed weak inhibition of aromatase activity.

Synechocystis DrgA protein functioning as nitroreductase and ferric reductase is capable of catalyzing the Fenton reaction

In order to identify an enzyme capable of Fenton reaction in Synechocystis, we purified an enzyme catalyzing one-electron reduction of t-butyl hydroperoxide in the presence of FAD and Fe(III)-EDTA. The enzyme was a 26 kDa protein, and its N-terminal amino acid sequencing revealed it to be DrgA protein previously reported as quinone reductase [Matsuo M, Endo T and Asada K (1998) Plant Cell Physiol39, 751-755]. The DrgA protein exhibited potent quinone reductase activity and, furthermore, we newly found that it contained FMN and highly catalyzed nitroreductase, flavin reductase and ferric reductase activities. This is the first demonstration of nitroreductase activity of DrgA protein previously identified by a drgA mutant phenotype. DrgA protein strongly catalyzed the Fenton reaction in the presence of synthetic chelate compounds, but did so poorly in the presence of natural chelate compounds. Its ferric reductase activity was observed with both natural and synthetic chelate compounds with a better efficiency with the latter. In addition to small molecular-weight chemical chelators, an iron transporter protein, transferrin, and an iron storage protein, ferritin, turned out to be substrates of the DrgA protein, suggesting it might play a role in iron metabolism under physiological conditions and possibly catalyze the Fenton reaction under hyper-reductive conditions in this microorganism.

Effect of carotenoid rich‐food Kang Lieng on NAD(P)H: quinone reductase (QR) activity in Wistar rats

Introduction: Antioxidant enzyme NAD(P)H: quinone reductase (QR) has important role in cancer prevention, which is inducible by several chemopreventive agents including carotenoids. Kang Lieng (KL) is a traditional Thai food rich in carotenoids from many kinds of vegetables. This study was investigated the QR activity in rat livers that were received carotenoids from KL. Methods: Lyophilyzed KL was prepared in large amount for the entire experiment using standard recipe. Twelve five weeks male Wistar rats were divided up equally among control and experimental groups. Lyophilyzed KL was dissolved in distilled water and daily gavaged to rats in experimental group. The given dose was 0.8% of rat body weight which was twice of human serving size. Animals were terminated after two weeks of feeding. Bloods and livers were collected for pathological examination, carotenoid analysis and QR activity determination. Results: Carotenoid contents in KL using in this experiment were 7.2, 1.0, 71.3, 70.2, 15.5 nmol/g (fresh wt.) for β-carotene, α-carotene, lutein, zeaxanthin, canthaxanthin respectively which was significant higher than in chow. The abnormalities were not detected in all organs of rats. β-carotene, zeaxanthin and canthaxanthin were detected only in liver. These carotenoids were greater in treatment group than control group (14, 15, and 44% respectively). QR activity in treatment group was significant higher than control group. (Supported by Graduate Program, Mahidol University, Thailand and National Research Council of Thailand)

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

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

The Chemopreventive Effects of Saussurea salicifolia through Induction of Apoptosis and Phase II Detoxification Enzyme

The ethanol extract of the aerial part of the Mongolian medicinal plant Saussurea salicifolia induced a dose-dependent cell growth inhibition in both human gastric adenocarcinoma AGS cells and mouse hepatoma Hepa 1c1c7 cells (IC(50)=30.22 and 116.96 mug/ml), respectively. The extract induced an apoptosis in AGS cells inference from the externalization of the phosphatidylserine, the increase of the sub G0/G1 content (%) and the apoptotic morphological changes including membrane blebbing, the formation of apoptotic bodies and chromatin condensation. In order to identify active substances causing the apoptosis, we further isolated major compounds present in Saussurea salicifolia and 7 compounds were isolated including a sesquiterpene lactone, cynaropicrin, 3 lignans (trachelogenin, matairesinol and arctigenin) and 3 lignan glycosides (tracheloside, matairesinoside and arctiin). In general the lignan aglycones were more cytotoxic than their lignan glycosides in both AGS cells and Hepa 1c1c7 cells. Cynaropicrin not only showed the most potent cytotoxicity among the 7 major compounds but also it induced an apoptosis and a weak G2/M arrest in AGS cells. Arctigenin had the second-best cytotoxicity among 7 major compounds, and induced an apoptosis. In order to evaluate the induction of the phase II detoxification enzyme, we measured the induction of quinone reductase activity of the extract, fractions and compounds in Hepa 1c1c7 cells. The ethyl acetate fraction and arctigenin showed the strongest cancer chemopreventive activity (chemoprevention index=9.88 and 7.57, respectively). These data suggest that the extract as well as the lignan compounds (especially arctigenin) originated from Saussurea salicifolia may be served as potential cancer chemopreventive agents for prevention or treatment of human cancers.

Role of the Conserved Arginine 274 and Histidine 224 and 228 Residues in the NuoCD Subunit of Complex I from Escherichia coli

The conserved arginine 274 and histidine 224 and 228 residues in subunit NuoCD of complex I from Escherichia coli were substituted for alanine. The wild-type and mutated NuoCD subunit was expressed on a plasmid in an E. coli strain bearing a nuoCD deletion. Complex I was fully expressed in the H224A and H228A mutants, whereas the R274A mutation yielded approximately 50% expression. Ubiquinone reductase activity of complex I was studied in membranes and with purified enzyme and was 50% and 30% of the wild-type activity in the H224A and H228A mutants, respectively. The activity of R274A was less than 5% of the wild type in membranes but 20% in purified complex I. Rolliniastatin inhibited quinone reductase activity in the mutants with similar affinity as in the wild type, indicating that the quinone-binding site was not significantly altered by the mutations. Ubiquinone-dependent superoxide production by complex I was similar to the wild type in the R274A mutant but slightly higher in the H224A and H228A mutants. The EPR spectra of purified complex I from the H224A and H228A mutants did not differ from the wild type. In contrast, the signals of the N2 cluster and another fast-relaxing [4Fe-4S] cluster, tentatively assigned as N6b, were drastically decreased in the NADH-reduced R274A mutant enzyme but reappeared on further reduction with dithionite. These findings show that the redox potential of the N2 and N6b centers is shifted to more negative values by the R274A mutation. Purified complex I was reconstituted into liposomes, and electric potential was generated across the membrane upon NADH addition in all three mutant enzymes, suggesting that none of the mutations directly affect the proton-pumping machinery.

Changes in glucoraphanin content and quinone reductase activity in broccoli ( Brassica oleracea var. italica) florets during cooling and controlled atmosphere storage

The effects of cooling and controlled atmosphere (CA) treatments on glucoraphanin content and induction of quinone reductase (QR) activity in broccoli florets were investigated. The results showed that both the glucoraphanin content and QR activity of broccoli florets increased during the initial 6 day of storage, and then decreased markedly at different temperatures of 0, 5, and 10 °C. Immediate cooling of broccoli florets at 0 and 5 °C could preserve the glucoraphanin content and QR activity for 12 days. Keeping broccoli florets at 20 °C for 6 h before cooling at 5 °C had little effects on shelf-life, glucoraphanin content and QR activity. CA treatments with elevated CO 2 (21% O 2 + 10% CO 2, and 21% O 2 + 20% CO 2) and an air treatment (21% O 2) were found to increase the glucoraphanin content and the QR activity over the first 5 days of storage at 5 °C, while CA treatments with reduced O 2 concentrations (1% O 2, 1% O 2 + 10% CO 2) led to a steady decrease of glucoraphanin content and the QR activity during 20 days of storage at 5 °C. The highest content of glucoraphanin and QR activity was found in florets stored under 21% O 2 + 10% CO 2 at 5 °C. These conditions were able to maintain the visual quality, glucoraphanin content and QR activity of the broccoli florets for 20 days.

Induction of Phase II Enzyme Activity by Various Selenium Compounds

: Twenty-seven selenium compounds and sixteen structurally related organosulfur compounds were tested for quinone reductase (QR) and glutathione-S-transferase (GST) inducing activity in murine hepatoma (Hepa 1c1c7) cells. Sixteen selenium compounds were able to double QR activity, and seven of them also doubled GST activity. The nine most potent compounds, dimethyl diselenide, 2,5-diphenyl- selenophene, dibenzyl diselenide, methylseleninic acid, diphenyl diselenide, benzeneseleninic acid, benzene selenol, triphenylselenonium chloride, and ebselen (2-phenyl- 1,2-benzisoselenazol-3(2H)-one), doubled QR-specific activity at levels lower than 7 μM. The concentration-dependence of QR induction and cell growth inhibition were linearly correlated (P < 0.001, r2 = 0.96) among the group of organoselenium compounds with putative selenol-generating potential, implying that both responses of Hepa 1c1c7 cells were based on these selenol metabolites.

단삼 분획추출물의 암예방 효과

본 연구는 단삼 분획추출물로부터 in vitro와 in vivo상에서 QR과 GST의 활성 유도와 GSH의 함량변화를 지표로 암예방 효과를 측정하였다. Hepalcla7 세포에 대한 in vitro상에서의 실험결과 QR 활성 유도율은 70% EtOH 추출물 50 <TEX>${\mu}g/ml$</TEX> 처리군에서 2.5배로 가장 높은 유도율을 나타내었고, GST 활성 측정은 EtOAc추출물 50 <TEX>${\mu}g/ml$</TEX>농도에서 1.4배의 유도율을 나타내었다. GSH 생성변화를 살펴본 결과에서는 <TEX>$H_2O$</TEX>추출물, 70% EtOH 추출물 그리고 water layer 추출물 50 <TEX>${\mu}g/ml$</TEX> 농도에서 높은 생성율을 나타내었다. 이상의 결과에서 QR활성과 GSH 함량변화에서 높은 증가효과를 나타낸 70% EtOH 추출물을 관류법으로 마우스에 투여하여 in vivo 상에서의 QR과 GST의 활성 변화와 GSH 함량을 측정한 결과 QR, GST활성과 GSH함량이 250 mg 투여시 각각 1.7배 및 1.5배의 활성 증가와 1.4배 함량증가를 측정할 수 있었음으로 70% EtOH추출물은 암예방효과가 가장 높은 것으로 생각된다. Six fractions of Salvia miltiorrhiza were tested for their chemopreventive potentials using biochemical markers of carcinogenesis such as quinone reductase (QR), glutathione S-transferase (GST) and glutathione (GSH). Seventy percentage of EtOH extract was potent inducer of QR activity in Hepa1c1c7 murine hepatoma cells. GST activity was increased about 1.4-fold with EtOAc extract at concentration of 50 <TEX>${\mu}g/ml$</TEX>. GSH levels were significantly increased with <TEX>$H_2O$</TEX> extract, 70% EtOH extract and water extract at concentration of 50 <TEX>${\mu}g/ml$</TEX> (p<0.005). From these results, 70% EtOH extract (250 mg/kg) was intragastrically administered to ICR mice for 14 days. QR, GST and GSH levels were significantly increased with the 70% EtOH treatment. These studies suggest that the 70% EtOH extract of S. miltiorrhiza could be considered as a potential agent for cancer chemoprevention.

NAD(P)H:Quinone Oxidoreductase 1 (NQO1) Pro187Ser Polymorphism and the Risk of Lung, Bladder, and Colorectal Cancers: a Meta-analysis

NAD(P)H:quinone oxidoreductase 1 (NQO1) is a cytosolic enzyme that catalyzes the two-electron reduction of quinoid compounds into hydroquinones, their less toxic form. A sequence variant at position 609 (C --> T) in the NQO1 gene encodes an enzyme with reduced quinone reductase activity in vitro and thus was hypothesized to affect cancer susceptibility. We conducted meta-analyses focusing on three cancer sites (lung, bladder, and colorectum) to summarize the findings from the current literature and to explore sources of heterogeneity. There is no clear association between the NQO1 Pro187Ser polymorphism and lung cancer risk in the three ethnic groups examined: odds ratio (OR(White)) C/T + T/T versus C/C = 1.04 [95% confidence interval (95% CI), 0.96-1.13], OR(Asian) = 0.99 (95% CI, 0.72-1.34), and OR(Blacks) = 0.95 (95% CI, 0.66-1.36). However, a modestly increased risk was suggested for the variant homozygotes in whites (OR T/T versus C/C, 1.19; 95% CI, 0.94-1.50). Analysis excluding one outlier study suggested the variant allele may be associated with reduced lung cancer risk in Asians. Meta-analyses for bladder and colorectal cancer suggested a statistically significant association with the variant genotypes in whites. In stratified analyses, the NQO1 Pro187Ser variant genotypes were associated with slightly increased lung cancer risk in white ever smokers but not in white never smokers and were mainly associated with a reduced risk of lung adenocarcinoma but not squamous cell carcinoma in Asians. Results from our meta-analyses suggest that the variant NQO1 Pro187Ser genotype may affect individual susceptibility to lung, bladder, and colorectal cancer. Such effects of the NQO1 polymorphism seem to be modified by ethnicity and smoking status.

LOT6 from Saccharomyces cerevisiae has an unexpected NAD(P)H-dependent quinone reductase activity

LOT6 from Saccharomyces cerevisiae has an unexpected NAD(P)H-dependent quinone reductase activity

Dietary Lycopene Downregulates Carotenoid 15,15′-Monooxygenase and PPAR-γ in Selected Rat Tissues1–3

In vitro studies have suggested that lycopene is an efficient substrate for carotenoid 9'10'-monooxygenase II (CMO2) but an inhibitor of carotenoid 15,15'-monooxygenase I (CMO1). The objectives of this study were to clone the rat CMO2 gene, determine whether feeding lycopene for different lengths of time (3-37 d) altered the expression of genes related to carotenoid cleavage [CMO1, CMO2 and peroxisomal proliferator-activated receptor gamma (PPAR-gamma)] or increased the activity of selected phase I and phase II detoxification enzymes in rat tissues. The cloned rat CMO2 gene was 92 and 82% homologous to the mouse and human CMO2 nucleotide sequence, respectively. The relative abundance of CMO1, CMO2, and PPAR-gamma were differentially expressed among rat tissues. CMO1 and PPAR-gamma expression were decreased in the kidney and adrenal with lycopene intake (P < 0.05), whereas CMO2 expression was reduced only in the kidney. Lycopene did not alter hepatic phase I activity, but hepatic quinone reductase activity increased after 3 and 7 d of lycopene feeding (P < 0.05). Lycopene intake decreased a PPAR-gamma target gene, fatty acid binding protein 3 (FABP3), in the kidney and adrenal (P < 0.05). Thus, these data show that although the intake of 0.25 g lycopene/kg diet does not induce hepatic P450 detoxification enzymes, lycopene feeding alters CMO1, PPAR-gamma, and FABP3 mRNA expression in selected rat tissues with a moderate effect on kidney CMO2 expression. These data suggest that lycopene may play an important role in the modulation of beta-carotene, retinoid, and/or lipid metabolism.

Genistein and daidzein modulate the activities of kidney and small intestinal quinone reductase and UDP‐glucuronosyltransferase biotransformation enzymes in Swiss Webster mice

It has been suggested soy isoflavones, genistein (G) and daidzein (D), are protective against the risk of chronic disease such as cancer. One postulated mechanism is modulation of phase I and II biotransformation enzymes that participate in detoxifying carcinogenic substances. We previously reported (EB 2005 Abstract #585.5) that G decreases hepatic CYP1A1/2 and D increases QR activities in Swiss Webster (SW) mice. This study expanded upon this and analyzed enzyme activities in extrahepatic tissues - the small intestine (SI) and kidneys (K). It was hypothesized that G and D decrease extrahepatic cytochrome P450 1A1/2 (CYP1A1/2) and increase quinone reductase (QR) and UDP-glucuronosyltransferase (UGT) enzyme activities. SW mice (n=170) were divided into 4 treatments (control, genistein, daidzein, and flavone) that contained equal numbers of males and females. Mice were fed an AIN-93G diet for 1, 3, 5, or 7 days (d) with 1,500 ppm or no phytochemical added. CYP1A1/2 activities were not detected in the SI and K. K QR activities were higher at d 3, 5, and 7 for males, and d 5 and 7 for female D treatment mice compared to controls. G increased K QR activity at d 3 for the males. K UGT activity was increased at d 7 for the female G treatment mice. SI QR activity was increased at d 1 for the male G and D treatment mice. SI UGT activity was increased at d 5 for the male G and D treatment mice. In conclusion, G and D significantly increased extrahepatic phase II enzyme activities, and therefore may decrease the risk for cancer.

A Potential Chemopreventive Agent, Taxifolin, Upregulates Phase II Detoxification Enzymes Through Antioxidant Response Element

Phase II detoxification enzymes are known to be responsible for detoxification and elimination of activated carcinogens suggesting that induction of these enzymes is an important biomarker for chemoprevention. In this study, we have tested chemopreventive activity of taxifolin, a flavanon compound purified from mongolian medicinal plant, using quinone reductase (QR) activity in HCT 116 cells. Taxifolin significantly induced QR activity while it showed relatively low cytotoxicity in the cells (chemoprevention index = 5.74). In order to identify the target genes regulated by taxifolin, cDNA microarray was performed using 3K human cancer chip containing 3000 human genes associated with carcinogenesis. According to significant analysis of microarray (SAM), 428 DE genes were found to be statistically significant with false discovery rate (FDR) of 57.2% (delta = 0.3366). Sixty five genes including few detoxification enzymes (NQO1, GST-M1, TXNRD1) were up-regulated and 363 genes were down-regulated in the presence of 60 μM taxifolin. Since the genes of interest selected contained antioxidant response element (ARE) located in the promoter region of detoxification enzymes, we hypothesized that taxifolin may act through ARE for upregulation of phase II detoxification enzymes. Transient transfection experiments using pARE-CAT construct showed that taxifolin activated ARE significantly while it did not activate XRE. In conclusion, these results suggest that taxifolin is a novel monofunctional inducer upregulating only phase II enzymes through ARE, implicating that taxifolin could be a potential chemopreventive agent.

Chemopreventive effect of protein extract ofAsterina pectinifera in HT-29 human colon adenocarcinoma cells

We investigated the effect of protein extract of Asterina pectinifera on the activity of 4 enzymes that may play a role in adenocarcinoma of the colon: quinone reductase (QR), glutathione S-transferase (GST), ornithine decarboxylase (ODC), and cyclooxygenase (COX)-2. QR and GST activity increased in HT-29 human colon adenocarcinoma cells increased that had been exposed to 4 concentrations of the protein extract (80, 160, 200, and 240 microg/mL). Additionally, 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ODC activity decreased significantly in cells exposed to the extract in concentrations of 160 microg/mL (p<0.05), 200 microg/mL (p<0.005), and 240 microg/mL (p<0.005). TPA-induced COX-2 activity also decreased in cells exposed to extract concentrations of 10, 20, 40, and 60 microg/mL. COX-2 expression was also inhibited in cells exposed to this extract. These results suggest that this protein extract of A pectinifera has chemopreventive activity in HT-29 human colon adenocarcinoma cells, and therefore, may have the potential to function as a chemopreventive agent in human colorectal cancer.

Induction of quinone reductase activity in murine hepatoma cells by extracts of Thunbergia Laurifolia Lindl

Thunbergia laurifolia Lindl or Rang Chuet (RC) is widely prescribed in traditional Thai medicine for protection against dietary and environmental toxicants with little substantiation. To better assess the potential of RC as a medicinal plant, extracts were prepared by infusion of dried leaves with water, ethanol and acetone. Extracts were subsequently assayed for major phytochemical constituents including phenolics, carotenoids and chlorophylls. Total phenolic content was 24.39, 4.14 and 1.42 mg gallic acid equivalents (GAE) per g dry leaf for water, ethanol and acetone extracts respectively. HPLC analysis tentatively identified caffeic acid and apenginin as primary constituents of water extracts. Acetone and ethanol extracts contained primarily chlorophyll a and b, pheophorbide a, pheophytin a and lutein. The detoxification potential of RC was determined by measuring the ability of standardized extracts to increase NAD(P)H:quinone oxidoreductase (QR) activity in Hepa 1c1c7 cells. Treatment of hepatoma cells with RC extracts resulted in a dose dependent increase in QR specific activity for all extracts. Acetone extracts (140 μg GAE/mL) increased QR activity 2.8 fold, compared to controls, while ethanol (120 μg GAE/mL) and water (1000 μg GAE/mL) extracts increased QR activity 1.56 and 1.35 fold, respectively. These results demonstrate that RC preparations have biological activities consistent with protection from toxicants and that both phenolic and natural pigment constituents likely contribute to these activities.

Japanese Kelp (Kombu) Extract Suppressed the Formation of Aberrant Crypt Foci in Azoxymethane Challenged Mouse Colon

Japanese kelp (kombu) includes a xanthophy, fucoxanthin. In the present study, the chemopreventive activity against the formation of aberrant crypt foci (ACF, a preneoplastic marker for colon cancer) was examined. Four groups of mice were housed with drinking water containing 5 mg/ml of a kombu ethanol extract, and 0.05 mg/ml and 0.1 mg/ml of purified fucoxanthin, and with water alone as the positive control. They were subcutaneously injected with 10 mg/kg b.w. of azoxymethane (AOM) on the 1st and 8th days. Another group served as a negative control without kombu and AOM. The positive control produced a substantial number of ACF by the 28th day. Significant reductions were found in the frequency of ACF: 36% for the kombu extract, 30% for 0.05 mg/ml fucoxanthin and 35% for 0.1 mg/ml fucoxanthin. In the liver of these mice, the kombu extract raised the level of activity of glutathione S-transferase (GST) and quinone reductase, and stimulated the antioxidant responsive element (ARE). Fucoxanthin enhanced the GST activity but did not affect the ARE. Thus, one of the kombu ingredients, fucoxanthin, can suppress the ACF formation induced by the colon carcinogen AOM, and other unknown ingredients can induce the ARE activation.

Aqueous extracts of selenium-fertilized broccoli increase selenoprotein activity and inhibit DNA single-strand breaks, but decrease the activity of quinone reductase in Hepa 1c1c7 cells

Depending on growth conditions, broccoli may be enriched in the isothiocyanate sulforaphane and/or the mineral selenium (Se); both compounds may play an important role in the reduction of intracellular oxidative stress and chronic disease prevention. Sulforaphane up-regulates transcription of Phase II detoxification proteins (e.g. quinone reductase [QR]), whereas Se is needed for the production of thioredoxin reductase (TR) and glutathione peroxidase-1 (GPx1), both of which exhibit antioxidant activity. The objective of the present study was to determine whether the fertilization of broccoli with Se increases the antioxidant ability of broccoli. Hydrogen peroxide-induced DNA single-strand breaks (measured by single cell electrophoresis, Comet assay) and activity of antioxidant enzymes (GPx, TR and QR) were measured in mouse hepatoma cells (Hepa 1c1c7 cells) treated with purified sulforaphane, sodium selenite or extracts of selenized broccoli. When supplied separately as chemically pure substances, sodium selenite was more effective than sulforaphane for reduction of single-strand breaks. Se-fertilized broccoli extracts were the most effective for reduction of DNA single-strand breaks, and extracts that contained 0.71 μM Se and 0.08 μM sulforaphane inhibited 94% of DNA single-strand breaks. A significant positive association ( r = 0.81, p = 0.009) between GPx1 activity and inhibition of DNA single-strand breaks as well as a 24 h lag time between addition of Se, sulforaphane or broccoli extract and inhibition of single-strand breaks suggests that some of the antioxidant protection is mediated through selenoproteins. Conversely, fertilization of broccoli with Se decreased the ability of broccoli extract to induce QR activity. These results demonstrate that Se and sulforaphane, alone or as a component of broccoli, may help decrease oxidative stress. They further suggest that Se is the most important for decreasing oxidative stress, but maximizing the Se content of broccoli also may compromise its ability to induce Phase II detoxification proteins.

김 분획물의 in vitro에서의 항발암효과

본 실험은 홍조해조류의 하나인 김을 메탄올로 추출 후 각 용매별로 다시 분획하여 암세포 성장억제 효과와 QR 유도활성 효과 등 생리활성을 연구하였다. 김을 이용하여 4종의 암세포주 C6, HepG2, MCF-7 및 HT-29 세포주에 대한 암세포 증식억제 실험을 한 결과 사용한 4종의 암세포주에서 모두 시료첨가 농도에 의존적으로 증식저지 효과가 나타났고, 특히 김의 hexan 분획물에서 가장 높은 암세포 성장 억제효과를 나타내었다. 그리고 본 시료는 신경종양, 간암 및 여성암의 대표적인 유방암세포의 성장억제효과가 탁월하였다. 또한, 사용한 4가지 암세포주중 유일하게 quinone reductase를 가지고 있는 HepG2를 이용한 암 예방지표인 quinone reductase 효소 유도 활성 여부를 측정한 결과 분획물 첨가농도를 50, 100 및 150 g/mL로 첨가하였을 때 PTMH의 첨가농도 50 ㎍/mL에서 대조군에 비해 약 1.5배 이상의 높은 QR 유도효과를 나타내었고 최종농도 150 ㎍/mL에서는 약 6.6배의 높은 암 예방 QR 유도효과를 나타내었다.

Dietary artepillin C suppresses the formation of aberrant crypt foci induced by azoxymethane in mouse colon

Artepillin C, a prenylated phenylpropanoid found specifically in Brazilian propolis, has been shown to be a bioavailable antioxidant. In this study, artepillin C was tested for colon cancer-preventing activity using azoxymethane-challenged ddY mice. Oral doses of 80 and 160 mg/kg body weight of propolis or 10 mg/kg of artepillin C (equi-amounts to 160 mg propolis) reduced significantly the frequency of colonic aberrant crypt foci (ACF) by 39.2, 43.7 and 43.4%, respectively. In liver of the mice, glutathione S-transferase and NADPH:quinone reductase activity increased with the doses of propolis or artepillin C, and an antioxidant-responsive element (ARE) was found to be activated for binding DNA. Artepillin C is considered to suppress the formation of colonic ACF through the activation of ARE and induction of phase II enzymes in liver.