Yukihiko Hara

Georgetown University, Washington, Washington, D.C., United States

Are you Yukihiko Hara?

Claim your profile

Publications (46)90.72 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Previous studies showed that the 7-(1',2'-dihydroxyheptyl) substituted etheno DNA adducts are products from reactions with epoxide of (E)-4-hydroxy-2-nonenal (HNE), an oxidation product of ω-6 polyunsaturated fatty acids (PUFAs). In this work, we report the detection of 7-(1',2'-dihydroxyheptyl)-1,N(6)-ethenodeoxyadenosine (DHHedA) in rodent and human tissues by two independent methods: a (32)P-postlabeling/HPLC method and an isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry method (ID-LC-ESI-MS/MS), demonstrating for the first time that DHHedA is a background DNA lesion in vivo. We showed that DHHedA can be formed upon incubation of arachidonic acid (AA) with deoxyadenosine (dA), supporting the notion that ω-6 PUFAs are the endogenous source of DHHedA formation. Because cyclic adducts are derived from the oxidation of PUFAs, we subsequently examined the effects of antioxidants, α-lipoic acid, Polyphenon E and vitamin E, on the formation of DHHedA and γ-hydroxy-1,N(2)-propanodeoxyguanosine (γ-OHPdG), a widely studied acrolein-derived adduct arising from oxidized PUFAs, in the livers of Long Evans Cinnamon (LEC) rats. LEC rats are inflicted with elevated lipid peroxidation and prone to the development of hepatocellular carcinomas. The results showed that while the survival of LEC rats increased significantly by α-lipoic acid, none of the antioxidants inhibited the formation of DHHedA and only Polyphenon E decreased the formation of γ-OHPdG. In contrast, vitamin E caused a significant increase in the formation of both γ-OHPdG and DHHedA in the livers of LEC rats.
    No preview · Article · May 2014 · Free Radical Biology and Medicine
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Chemoprevention crossover trials of tea can be more efficient than parallel designs but the attrition and compliance rates with such trials are unknown. Attrition (dropouts) and compliance with treatment were assessed in a 25-week randomized, placebo controlled, crossover, feasibility clinical trial of four tea treatments to investigate the effect of tea on oral cancer biomarkers. Each treatment lasted 4 weeks with 2 weeks of washout in between. Participants were 32 smokers and 33 non-smokers without any evidence of premalignant oral lesions. The interventions consisted of packets of green tea, black tea, caffeinated water, or placebo. Participants were assigned to each treatment for four weeks, and were instructed to drink five packets per day while on the treatment. Dropout from the trial and compliance (consumption of ≥85% of the prescribed treatment packets) are the main outcome measures reported. There was a high rate of dropout (51%) from the study, and the rates were significantly higher among smokers (64%) than non-smokers (36%). Among participants who completed the study the rate of compliance was 72%. The highest rates of dropouts occurred between the first and second treatment visits in both smokers (38% dropout) and non-smokers (18% dropout). Throughout the study smokers were more likely to dropout than non-smokers. Black tea treatment was associated with the highest rates of dropout among smokers (37%), but was associated with the lowest rate of dropout among non-smokers (4%). In a study conducted to test the feasibility of a four-treatment crossover tea trial, a high rate of dropout among smokers and non-smokers was observed. Multi-arm crossover tea trials might pose a higher burden on participants and research is needed to improve adherence and treatment compliance in such trials. ISRCTN70410203.
    Full-text · Article · Jul 2012 · BMC Complementary and Alternative Medicine
  • Source
    Akiko Takagaki · Katsuhiko Fukai · Fumio Nanjo · Yukihiko Hara
    [Show abstract] [Hide abstract]
    ABSTRACT: In the reaction of green tea catechins with formaldehyde at room temperature (25°C), tea catechins were found to have reactivity. In particular, (-)-epicatechin gallate and (-)-epigallocatechin gallate, which have a galloyl moiety at the C-3 position, showed higher reactivity than (+)-catechin, (-)-epicatechin, or (-)-epigallocatechin. Reactivity of various kinds of simple phenolic compounds and flavonoids with formaldehyde was also examined. Among these compounds, only phloroglucinol showed reactivity to the same degree as that of nongalloylated catechins. These results suggest that factors for reactivity with formaldehyde at room temperature may be the presence of a phloroglucinolic A-ring structure and the absence of the electron-attractive group such as a carbonyl group in Cring. The comparison of the reactivity of 3-O-acylated catechins with that of 3-O-galloylated catechins indicated that only a galloyl group effectively enhanced reactivity with formaldehyde.
    Full-text · Article · Apr 2012 · Journal of Wood Science
  • Source
    F. NANJO · Yukihiko Hara · Y. KIKUCHI
    [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    Full-text · Article · Apr 2010 · ChemInform
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Effects of green tea catechins comprising EGCg, EGC, ECg, EC, GCg, GC, Cg, and C were determined on blood glucose tolerance and oxidative stress status in type 2 diabetic Goto-Kakizaki (GK) rats. GK rats fed the catechin-containing diet tended to maintain blood glucose and systolic blood pressure at lower levels in the latter stages of the feeding period of 76 d, compared to those not receiving dietary catechins (control group). The blood glucose tolerance test performed on days 48-49 showed that GK rats fed the catechins had lower blood glucose levels than GK rats not fed catechins during the 120 min after glucose loading. In catechin-fed rats, amounts of 8-OH dG and albumin excreted into the urine determined on days 71-72, and kidney ACE activity determined on day 76, were lower than those in control rats. From these results it is concluded that dietary catechins may be effective in delaying the progression of diabetes and the associated oxidative stress.
    Full-text · Article · Jan 2008 · Journal of Nutritional Science and Vitaminology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: It has recently been reported that the major green tea polyphenolic constituent, epigallocatechin 3-gallate (EGCG), mimics the cellular effects of insulin including the reductive effect on the gene expression of rate-limiting gluconeogenic enzymes in a cell culture system. We show that administration of green tea that contains EGCG caused a reduction in the level of mRNAs for gluconeogenic enzymes, phosphoenolpyruvate carboxykinase and glucose-6-phosphatase in the mouse liver. EGCG alone was also found to down-regulate the gene expression of these enzymes but not so curcumin or quercetin. The results of this study support the idea that green tea intake may be beneficial in the prevention of diabetes mellitus.
    Full-text · Article · Dec 2004 · Planta Medica
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: (-)-Epigallocatechin gallate (EGCG), a major constituent of green tea, has been shown to exhibit anti-cancer activity. Sulindac is also well known as a cancer-preventive agent against colon cancer, but its usage is restricted because of its adverse effects, as exemplified by gastrointestinal bleeding. In the present study, we examined whether a combination of EGCG and sulindac shows synergistic effects for cancer-preventive activity for rat colon carcinogenesis induced by azoxymethane (AOM); we examined the number of aberrant crypt foci (ACF) representing preneoplastic lesions, the argyrophilic nucleolar organizer region (AgNOR) as an indicator of cell proliferation, and the incidence of apoptosis. The AOM treatment induced an average of 46.2+/-4.9 ACF/colon, and sulindac and EGCG significantly reduced the incidence of ACF/colon to 21.4+/-3.4 and 19.5+/-5.8, respectively (P<0.01). The co-treatment with EGCG and sulindac resulted in significantly reduced ACF formation (10.0+/-3.2; P<0.01). The results of the AgNOR analysis indicated that the treatment with EGCG and/or sulindac suppressed AOM-induced cell proliferation. The present results also revealed that the combination of EGCG and sulindac synergistically enhanced apoptosis significantly (P<0.01). Thus, our findings suggest that EGCG with sulindac synergistically suppresses ACF formation by enhancing apoptosis and, therefore, that EGCG is a suitable candidate for use in combination with cancer-preventive agents, such as sulindac, to reduce their adverse effects.
    Full-text · Article · Apr 2002 · Cancer Letters
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A thermo-acidophilic gram-positive bacterium, strain CP-1T, which grows aerobically at 35-65 degrees C (optimum 55-60 degrees C) and at pH 3.5-6.0 (optimum pH 4.5-5.0), was isolated from a herbal tea made from the dried flowers of hibiscus. Phylogenetic analysis of the 16S rRNA gene sequences showed that this bacterium was clearly distinguishable from previously described species of the genera Alicyclobacillus and Sulfobacillus. Strain CP-1T had unique omega-cycloheptane fatty acids as the major membrane lipid component, a characteristic which is peculiar to Alicyclobacillus cycloheptanicus. However, phenotypic and chemotaxonomic characteristics of strain CP-1T were different from those of the type strain of A. cycloheptanicus. DNA-DNA hybridization between the type strains of Alicyclobacillus species and Sulfobacillus disulfidooxidans was <20%, indicating that strain CP-1T represents a distinct species. On the basis of these results, the name Alicyclobacillus herbarius is proposed for this organism. The type strain is strain CP-1T (= DSM 13609T = IAM 14883T = NRIC 0477T).
    Preview · Article · Feb 2002 · International Journal of Systematic and Evolutionary Microbiology
  • [Show abstract] [Hide abstract]
    ABSTRACT: After oral administration of [4-(3)H]EGCg to rats, the radioactivity in blood, major tissues, urine, and feces was measured over time. The radioactivity in blood and most tissues remained low for 4 h postdose, began to increase after 8 h, peaked at 24 h, and then decreased. Major urinary excretion of radioactivity occurred in the 8-24 h period, and the cumulative radioactivity excreted by 72 h was 32.1% of the dose. The radioactivity in the feces was 35.2% of the dose within 72 h postdose. In the case of rats pretreated with antibiotics (antibiotic-pretreated rats), the radioactivity levels of the blood and urine were definitely lower than those in rats not pretreated with antibiotics (normal rats). The radioactivity recovered in the antibiotic-pretreated rat urine was estimated to be only (1)/(100) of that in the normal rat urine. These results clearly demonstrated that the radioactivity detected in the blood and urine of normal rats mostly originated from degradation products of EGCg produced by intestinal bacteria. Furthermore, a main metabolite in the normal rats was purified and identified as 5-(5'-hydroxyphenyl)-gamma-valerolactone 3'-O-beta-glucuronide (M-2). In feces of the normal rats, EGC (40.8% of the fecal radioactivity) and 5-(3',5'-dihydroxyphenyl)-gamma-valerolactone (M-1, 16.8%) were detected. These results suggested that M-1 was absorbed in the body after degradation of EGCg by intestinal bacteria, yielding M-1 with EGC as an intermediate. Furthermore, M-2 was thought to be formed from M-1 in the intestinal mucosa and/or liver, then to enter the systemic circulation, and finally to be excreted in the urine. Taking into account all of the above findings, a possible metabolic route of EGCg orally administered to rats is proposed.
    No preview · Article · Sep 2001 · Journal of Agricultural and Food Chemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: Because a great deal of attention has been focused on the metabolism of (-)-epigallocatechin gallate (EGCg), quantitative analysis of this compound is required. For this purpose we developed a method of chemical synthesis of [4-(3)H]EGCg. Synthesized [4-(3)H]EGCg showed 99.5% radiochemical purity and a specific activity of 13 Ci/mmol. To clarify the excretion route of EGCg, the radioactivity levels of bile and urine were quantified after intravenous administration of [4-(3)H]EGCg to bile-duct-cannulated rats. Results showed that the radioactivity of the bile sample excreted within 48 h accounted for 77.0% of the dose, whereas only 2.0% of the dose was recovered in the urine. The excretion ratio of bile to urine was calculated to be about 97:3. These results clearly showed that bile was the major excretion route of EGCg. Time-course analysis of the radioactivity in blood was also performed to estimate the pharmacokinetic parameters following intravenous administration of [4-(3)H]EGCg. In addition, EGCg metabolites excreted in the bile within 4 h after the intravenous dose of [4-(3)H]EGCg were analyzed by HPLC. The results showed that 4',4"-di-O-methyl-EGCg was present in the conjugated form and made up about 14.7% of the administered radioactivity.
    No preview · Article · Mar 2001 · Journal of Agricultural and Food Chemistry
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Because a great deal of attention has been focused on the metabolism of (-)-epigallocatechin gallate (EGCg), quantitative analysis of this compound is required. For this purpose we developed a method of chemical synthesis of [4-H-3]EGCg. Synthesized [4-H-3]EGCg showed 99.5% radiochemical purity and a specific activity of 13 Ci/mmol. To clarify the excretion route of EGCg, the radioactivity levels of bile and urine were quantified after intravenous administration of [4-H-3]EGCg to bile-duct-cannulated rats. Results showed that the radioactivity of the bile sample excreted within 48 h accounted for 77.0% of the dose, whereas only 2.0% of the dose was recovered in the urine. The excretion ratio of bile to urine was calculated to be about 97:3. These results clearly showed that bile was the major excretion route of EGCg. Time-course analysis of the radioactivity in blood was also performed to estimate the pharmacokinetic parameters following intravenous administration of [4-H-3]EGCg. In addition, EGCg metabolites excreted in the bile within 4 h after the intravenous dose of [4-H-3]EGCg were analyzed by HPLC. The results showed that 4',4"-di-O-methyl-EGCg was present in the conjugated form and made up about 14.7% of the administered radioactivity.
    Full-text · Article · Feb 2001 · Journal of Agricultural and Food Chemistry
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Green tea contains various antioxidative flavan-3ols (tea catechins), such as (-)-epigallocatechin gallate (EGCg, the major catechin), which exert potent inhibitory effects on LDL oxidation in vitro and ex vivo in humans. In this study, the antiatherogenic effects of tea catechins were examined in atherosclerosis-susceptible C57BL/6J, apoprotein (apo)E-deficient mice. Male apoE-deficient mice (10 wk old) were fed an atherogenic diet for 14 wk; during that time, one group (tea) was supplied drinking water supplemented with green tea extract (0.8 g/L), and another group (control) was offered the vehicle only. The tea extract consisted of the following (g/100 g): EGCg, 58.4; (-)-epigallocatechin (EGC), 11.7; (-)-epicatechin (EC), 6.6; (-)-gallocatechingallate (GCg), 1.6; (-)-epicatechin gallate (ECg), 0.5; and caffeine, 0.4. The estimated actual intake of tea catechin was 1.7 mg/(d. mouse). Tea ingestion did not influence plasma cholesterol or triglyceride concentrations. Plasma lipid peroxides were reduced in the tea group at wk 8, suggesting that the in vivo oxidative state is improved by tea ingestion. Atheromatous areas in the aorta from the arch to the femoral bifurcation and aortic weights were both significantly attenuated by 23% in the tea group compared with the control group. Aortic cholesterol and triglyceride contents were 27 and 50% lower, respectively, in the tea group than in the control group. These results suggest that chronic ingestion of tea extract prevents the development of atherosclerosis without changing the plasma lipid level in apoE-deficient mice, probably through the potent antioxidative activity of the tea.
    Full-text · Article · Feb 2001 · Journal of Nutrition
  • [Show abstract] [Hide abstract]
    ABSTRACT: After oral administration of (-)-epigallocatechin gallate (EGCg) to rats, its biliary metabolites were examined. Although a large part of the biliary metabolites was found to exist in conjugated forms, it was difficult to separate the conjugated forms. Thus the free form of biliary metabolites was prepared by beta-glucuronidase/sulfatase treatment and was purified by HPLC. Six compounds purified were subjected to FABeta-MS and NMR analyses. The six metabolites thus obtained were shown to be EGCg, 3'-O-methyl-EGCg, 4'-O-methyl-EGCg, 3' '-O-methyl-EGCg, 4' '-O-methyl-EGCg, and 4',4' '-di-O-methyl-EGCg, respectively. The six EGCg metabolites and their conjugates excreted during a 4-h period were estimated to be roughly 0.1% and 3.3% of the administered EGCg, respectively. In addition, 4' '-O-methyl-EGCg and 4',4' '-di-O-methyl-EGCg were estimated to exist only in the sulfate form, but the other four metabolites existed in both glucuronide (and/or sulfoglucuronide) and sulfate forms.
    No preview · Article · Oct 2000 · Journal of Agricultural and Food Chemistry
  • Keiichi Goto · Tomoko Omura · Yukihiko Hara · Yoshito Sadaie
    [Show abstract] [Hide abstract]
    ABSTRACT: A comparison of 16S rRNA gene (rDNA) sequences was made among type strains of 69 Bacillus species approved in the International Journal of Systematic Bacteriology (IJSB) until 1998. The results suggested that 5' end region (approx. 275 bp) was the hypervariant region (HV region) in the gene and was highly specific for each type strain. Furthermore, a sequence analysis of the HV region of Bacillus strains revealed that this region was highly conserved within the species. These results indicate that the HV region is a useful index for the identification or grouping of Bacillus species.
    No preview · Article · Mar 2000 · The Journal of General and Applied Microbiology
  • Masayuki Suzuki · Masao Mori · Fumio Nanjo · Yukihiko Hara
    [Show abstract] [Hide abstract]
    ABSTRACT: Catechins, which are the main constituents of tea, have been shown to have strong scavenging activity against many kinds of radicals. In this study, the radical scavenging mechanisms of catechol type catechin on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging were evaluated by identifying the structure of the reaction products. 4-Methylcatechol (4-MC) which is a B-ring model of the catechol type catechin was reacted with DPPH radicals in EtOH. 4-Methyl-5-ethoxy-benzoquinone was isolated as a reaction product, and 4-methyl-ortho-benzoquinone was identified as an intermediate of this reaction in EtOH. Next, (+)-Catechin (+C) was reacted with DPPH in EtOH under dark conditions. The B-ring of +C showed the same type of reaction as 4-MC. While under irradiation of fluorescent or day light, new C-C linkage between 6′ and 4a-carbon of +C was formed. The conversion of 4-MC and B-ring of +C to ortho-quinone form consumed 2 molecules of DPPH radical which agreed with the stoichiometric factors of 4-MC and +C.
    No preview · Chapter · Jan 2000
  • [Show abstract] [Hide abstract]
    ABSTRACT: On the basis of the high reactivity of green tea catechins with formaldehyde in aqueous solution at room temperature, we investigated the possibility of utilizing a green tea extract containing 30% tea catechins as a formaldehyde scavenger. Firstly, the ability of green tea extract to trap free formaldehyde in the air was tested in experiments using tea extract-treated filter paper. Results showed that the filter paper treated with green tea extract had the ability to absorb formaldehyde and that formaldehyde once absorbed was hardly released again. In addition, release of formaldehyde was not observed even when the test temperature was raised to 60°C. Secondly, applications of green tea extract to plywood were investigated. It became clear that an application of green tea extract to the entire surface of F2 plywood remarkably suppressed the amount of formaldehyde emission. An application of the green tea extract on the surface of F1 plywood somewhat increased the inherent ability of the original plywood to absorb formaldehyde, and remarkably suppressed the release of formaldehyde once absorbed. Furthermore, the formaldehyde-absorbing ability of an air purifier filter treated with tea extract was also investigated. Results showed that the tea extract-treated filter had a superior formaldehyde-trapping ability, as compared to an untreated filter which was ineffective. These results suggested that green tea extract has a superior scavenging effect which serves to decrease free formaldehyde in the air ; thus it is assumed that green tea extract may have great potential for its use as a formaldehyde scavenger.
    No preview · Article · Jan 2000
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Interaction of tea catechins with lipid bilayers was investigated with liposome systems, which enabled us to separate liposomes from the external medium by centrifugation. We found that epicatechin gallate had the highest affinity for lipid bilayers, followed by epigallocatechin gallate, epicatechin, and epigallocatechin. Epicatechin gallate and epigallocatechin gallate in the surface of lipid bilayer perturbed the membrane structure.
    Preview · Article · Jan 2000 · Bioscience Biotechnology and Biochemistry
  • Source
    Fumio Nanjo · Masao Mori · Keiichi Goto · Yukihiko Hara
    [Show abstract] [Hide abstract]
    ABSTRACT: (-)-Epigallocatechin gallate was found to be the most effective scavenger among tea catechins for the superoxide anion, hydroxyl radical, and 1,1-diphenyl-3-picrylhydrazyl radical. Examination of the scavenging effects of tea catechins and their glucosides on superoxide anion showed that the presence of at least an ortho-dihydroxyl group in the B ring and a galloyl moiety at the 3 position was important in maintaining the effectiveness of the radical scavenging ability. Stoichiometric factors of tea catechins were estimated to be 2 for (+)-catechin and (-)-epicatechin, 5 for (-)-epigallocatechin, 7 for (-)-epicatechin gallate, and 10 for (-)-epigallocatechin gallate.
    Full-text · Article · Sep 1999 · Bioscience Biotechnology and Biochemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: The effects of tea polyphenols on the invasion of highly metastatic human fibrosarcoma HT1080 cells through a monolayer of human umbilical vein endothelial cells (HUVECs) and the accompanying basal membrane were investigated. Among the tea polyphenols tested, epicatechin gallate (ECg), epigallocatechin gallate (EGCg), and theaflavin strongly suppressed the invasion of HT1080 cells into the monolayer of HUVECs/gelatin membrane, whereas epicatechin, epigallocatechin, tea flavonols, tea flavones, and gallate derivatives had no effect. Both theaflavin-digallate and theasinensin D showed a weak invasion inhibitory effect. ECg significantly inhibited the invasion without cytotoxicity against cancer cells and HUVECs. Ester-type catechins (ECg and EGCg) and theaflavin strongly suppressed the gelatin degradation mediated by matrix metalloproteinase (MMP) 2 and MMP-9, which were secreted into the conditioned medium of HT1080 cells. In conclusion, among the tea polyphenols tested, ECg was considered to be the agent with the most potential antimetastasis activity because it inhibited invasion in the absence of cytotoxicity. Keywords: Invasion; tea polyphenols; epicatechin gallate; human fibrosarcoma HT1080; matrix metalloproteinases
    No preview · Article · May 1999 · Journal of Agricultural and Food Chemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: Polyphenolic compounds derived from tea catechins were examined for apoptosis-inducing activity in human histiolytic lymphoma U937 cells. (-)-Epigallocatechin gallate, theasinensin D, compound OH-5, theaflavin, and theaflavin digallate induced apoptosis as evidenced by DNA ladder formation, its inhibition by a caspase inhibitor, and chromatin condensation. Theasinensin D was the most potent inducer and the data suggest the importance of the number and three dimensional localization of their phenolic groups in this activity. These apoptosis-inducible compounds may be useful as a cancer chemopreventive and chemotherapeutic agent.
    No preview · Article · Apr 1999 · Bioscience Biotechnology and Biochemistry

Publication Stats

3k Citations
90.72 Total Impact Points

Institutions

  • 2012
    • Georgetown University
      Washington, Washington, D.C., United States
  • 1999-2000
    • National Food Research Institute
      Ibaragi, Ōsaka, Japan
  • 1989-1999
    • University of Shizuoka
      • • School of Pharmaceutical Sciences
      • • Department of Food and Nutritional Sciences
      Shizuoka-shi, Shizuoka-ken, Japan
  • 1986-1999
    • Japan Food Research Laboratories
      Ōsaka, Ōsaka, Japan