Antioxidant reactions of green tea catechins and soy isoflavones.
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Antioxidants↗
Biomedical subjects
J A Burr
Publications and source records attributed to J A Burr.
Antioxidant reactions of alpha-tocopherolhydroquinone.
Alpha-tocopherolhydroquinone (TQH2) is a product of alpha-tocopherol oxidation/reduction that exerts antioxidant effects in biological systems. TQH2 inhibited autoxidation of methyl linoleate initiated by peroxyl radicals derived from thermolysis of 2,2'-azobis(2,4-dimethylvaleronitrile) in acetonitrile. TQH2 oxidation yielded alpha-tocopherolquinone (TQ) as a major product and 2,3-epoxy-alpha-tocopherolquinone and 5,6-epoxy-alpha-tocopherolquinone as minor products. Each TQH2 consumed approximately two peroxyl radicals in the course of the oxidation. The data suggest that TQH2 scavenges peroxyl radicals primarily by electron transfer to form TQ and secondarily by addition-elimination to form the epoxyquinones.
Antioxidants↗
Antioxidant chemistry of green tea catechins. New oxidation products of (-)-epigallocatechin gallate and (-)-epigallocatechin from their reactions with peroxyl radicals.
The green tea catechins (-)-epigallocatechin gallate (EGCG) and (-)-epigallocatechin (EGC) react with peroxyl radicals generated by thermolysis of the azo initiator 2,2'-azobis(2, 4-dimethylvaleronitrile) (AMVN) to produce several oxidation products. Structure elucidation of these products can provide insights into specific mechanisms of antioxidant reactions. We isolated and identified a previously unreported reaction product of EGCG and three reaction products of EGC. In the EGCG product, the B-ring was transformed into a ring-opened unsaturated dicarboxylic acid moiety. The EGC products include a seven-membered B-ring anhydride and a symmetrical EGC dimer, both analogues of previously described EGCG oxidation products. The third EGC product was an unsymmetrical dimer. In all identified products, changes occurred solely in the B-ring of EGCG or EGC. This confirmed our previous observation that the principal site of antioxidant reactions in EGCG and EGC is the trihydroxyphenyl B-ring, regardless of the presence of a 3-galloyl moiety. A stoichiometric factor n of 4.16 +/- 0.51 was measured for EGCG, whereas factors of 2.20 +/- 0.26 was found for EGC and 2.33 +/- 0.18 measured for methyl gallate. These values represent the net peroxyl radical trapping per catechin molecule by several competing reactions. EGCG and EGC oxidation involves addition of oxygen, which is not derived from water, but most likely from atmospheric oxygen via peroxyl radicals. Characteristic oxidation products may be useful markers for antioxidant actions in living systems.
Anticarcinogenic Agents↗
Effects of UV light and tumor promoters on endogenous vitamin E status in mouse skin.
Recent reports indicate that both orally administered and topically applied alpha-tocopherol (vitamin E, TH) prevent UVB-induced skin carcinogenesis in mice. Because UVB exposure causes the formation of oxidants associated with tumor promotion, epidermal TH status may be an important determinant of susceptibility to photocarcinogenesis. To test this hypothesis, we studied the status of epidermal TH in C3H mice following exposure to single and repeated UVB exposures at doses typical of chronic photocarcinogenesis protocols. Exposure of mice to a single 13 kJ/m(2) dose over 60 min resulted in no acute depletion of epidermal TH and a modest increase in TH within 6-12 h. Daily exposure to 6.5 kJ/m(2) over 30 min resulted in a gradual increase in epidermal TH, which reached 5-fold after five daily exposures. The increase in epidermal TH was accompanied by an increase in the TH oxidation products alpha-tocopherolquinone (TQ) and alpha-tocopherolhydroquinone (THQ). We also studied the effect of the prooxidant chemical tumor promoter benzoyl peroxide and the prooxidant azo initiators azobis(amidinopropane HCl) and azobis(2, 4-dimethylvaleronitrile). Topical application of these prooxidant chemicals acutely oxidized epidermal TH to TQ and THQ. Topical treatments with the phorbol ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) increased epidermal TH levels without producing a significant accumulation of TH oxidation products. The results indicate that UVB and tumor promoting chemicals all exert qualitatively different effects on epidermal TH status and that UVB and TPA trigger an adaptive response involving epidermal TH accumulation.
Amidines↗
Gas chromatography-mass spectrometry analysis of vitamin E and its oxidation products.
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Animals↗
alpha-tocopherol oxidation in beef and in bovine muscle microsomes.
The oxidation of alpha-tocopherol (TH) in beef was analyzed using a stable isotope dilution capillary gas chromatography-mass spectrometry assay. TH decreased while alpha-tocopherolquinone (TQ) and 2,3-epoxy-alpha-tocopherolquinone (TQE(2)) increased in ground longissimus lumborum (LL) and psoas major (PM) muscles during storage (P < 0.10). In LL steaks, the relative concentrations of TH decreased and TQ and TQE(2) increased in surface samples; changes were less dramatic in deep samples. Deuterated alpha-tocopherolhydroquinone (THQ) standard was not recovered and endogenous THQ was not detected in meat; THQ was measurable in microsomes isolated from PM and incubated in the presence of 2, 2'-azobis(2-amidopropane)HCl (ABAP) or myoglobin. ABAP-challenged microsomes yielded a tocopherol product profile which favored 5, 6-epoxy-alpha-tocopherolquinone (TQE(1)) and TQE(2), while the use of myoglobin as prooxidant resulted in a higher proportion of TQ and THQ. Results demonstrated that concentrations of TH decreased and TQ and TQE(2) increased in meat during storage and are consistent with the peroxy-radical scavenging function of tocopherol.
Animals↗
Work transitions and health in later life.
OBJECTIVES: The goal of the analysis was to examine the association between health status and work behavior among men aged 55-69. We specifically examined the conditions under which health is most strongly associated with labor force exit and reentry. METHODS: The association between health and labor force transitions was examined using logistic regression analyses, based on data from the 1984 and 1985 panels of the Survey of Income and Program Participation. RESULTS: We found that for men aged 55-69 in the mid-1980s, poor health was positively associated with labor force exit, and negatively associated with returns to work. Although these main effects are very strong, we found that health was particularly important among individuals for whom retirement was least attractive. Health had its most substantial association with work transitions among men with working wives, as well as among men who were younger, or who had limited nonwork financial resources. Health also had a particularly strong association with work transitions among Black men, but only with reference to reentry decisions. DISCUSSION: Our results suggest that continued work may have limited appeal for men who are prepared for retirement, even when they are in excellent health.
Black or African American↗
Infant mortality: a multi-level analysis of individual and community risk factors.
This paper reports the results of an analysis of infant mortality based on a conceptual model that combines micro-level and macro-level variables taken from demographic, sociological and epidemiological research traditions. Using generalized hierarchical linear modeling techniques, we analyze 1988 and 1989 linked birth and death records for Upstate New York matched with county-level data from government and private sources. Net of health and sociodemographic risk factors. our results show that the number of per capita primary care physicians and local government expenditures on health care services and hospitals are positively linked to an increase in the probability of infant death and that our indicator of hospital facilities is negatively related to risk of death. We also find that some negative health behaviors and health resources of mothers are mediated by the local health care environment. Our results demonstrate the utility of combining perspectives from several disciplines when evaluating infant death, especially the impact of policy-related issues concerning health care service in
Humans↗
Some reflections on cultural and social considerations in mental health nursing.
This article critiques the contribution of two main theoretical perspectives on mental health care and ethnicity, with particular reference to Asian women. It considers the work of those who highlight the impact of culture on the health and illness experience (Kleinman 1980, Rack 1982, Fernando 1989) and the work of authors who argue that the impact of broader socio-economic structures must be considered (Donovan 1989, Pearson 1989, Ahmad 1993). It is posited that the emphasis on cultural difference results in crude monolithic generalizations about Asian culture and operates as a smokescreen for the impact of poverty and racism. The backdrop to this article is provided by an assessment of the problematic conceptual framework of Western mental health and the role it plays in perpetuating stereotypes. It is concluded that mental health nurses need a thorough understanding of the complexity of the cultural and social factors that influence health and illness; an understanding which falls somewhere between these two theoretical perspectives. Such an approach needs to be grounded in the experience of mental health clients themselves if it is to be appropriate.
Attitude to Health↗
Female labor force participation and suicide.
To test the role conflict and role enhancement hypotheses, this paper examines the link between female labor force participation and suicide. Using a special tabulation of age/sex-specific suicide data for metropolitan areas in the United States, we estimate separate multivariate regression models for women and men in 1970 and 1980. Our findings show that in 1970 the level of female labor force participation among married women with small children is not related to the female suicide rate but is related to the male suicide rate in a positive direction. By 1980 the relationship between female labor force participation and the male and female suicide rate is negative, suggesting that the well-being of both men and women is enhanced by role accumulation among women.
Adult↗
Pathways to labor force exit: work transitions and work instability.
The purpose of this study is to examine alternative pathways to labor force exit among older men. Based on the life course perspective, we distinguish between crisp exits from the labor force, which are characterized as being unidirectional, and blurred transition patterns, which include repeated exists, entrances, and unemployment spells. Using longitudinal data from the 1984 Survey of Income and Program Participation, we find that one-quarter of the sample of men aged 55 to 74 at first interview experienced at least one transition in labor force status over a 28-month observation period. Fewer than half of these can be characterized as crisp exists from the labor force. Our multivariate analysis suggests that blurred transition patterns are likely part of an effort to maintain economic status in later life.
Age Factors↗
The reduction of alpha-tocopherolquinone by human NAD(P)H: quinone oxidoreductase: the role of alpha-tocopherolhydroquinone as a cellular antioxidant.
alpha-Tocopherolquinone (TQ), a product of alpha-tocopherol oxidation, can function as an antioxidant after reduction to alpha-tocopherolhydroquinone (TQH2). We examined the ability of human NAD(P)H:quinone oxidoreductase (NQO1) to catalyze the reduction of TQ to TQH2 in cell-free and cellular systems. In reactions with purified human NQO1, TQ was reduced to TQH2. Kinetic parameters for the reduction of TQ by NQO1 (Km = 370 microM; k(cat) = 5.6 x 10(3) min(-1); k(cat)/Km = 15 min(-1) x microM(-1)) indicate that NQO1 can efficiently reduce TQ to TQH2. A comparison of the rate of reduction of TQ and coenzyme Q10 by NQO1 showed that TQ is reduced more efficiently than coenzyme Q10. Experiments with either Chinese hamster ovary (CHO) cells stably transfected with human NQO1 or CHO cell sonicates demonstrated a correlation between NQO1 activity and TQ reduction to TQH2. CHO cells with elevated NQO1 generated and maintained higher levels of TQH2 after treatment with TQ relative to NQO1-deficient CHO cells. TQH2 generated from NQO1-mediated reduction of TQ prevented cumene hydroperoxide-induced lipid peroxidation in rat liver microsomes. In addition, cumene hydroperoxide-induced lipid peroxidation was inhibited more efficiently by TQ in CHO cell lines with elevated NQO1 activity. These data demonstrate that NQO1 can reduce TQ to TQH2 and that TQH2 can function as an efficient antioxidant. This work suggests that one of the physiological functions of NQO1 may be to regenerate antioxidant forms of alpha-tocopherol.
Animals↗
Gas chromatography-mass spectrometry analysis of vitamin E and its oxidation products.
To facilitate studies of vitamin E ( alpha-tocopherol) antioxidant actions in tissues, we have developed a stable isotope dilution capillary gas chromatography-mass spectrometry assay for alpha-tocopherol and its three principal oxidation products, alpha-tocopherolquinone, 5,6-epoxy-alpha-tocopherolquinone, 2, 3-epoxy-alpha-tocopherolquinone, and for alpha-tocopherolhydroquinone, a reduction product of alpha-tocopherolquinone. Deuterium-labeled internal standards (5, 7-[2H3-methyl]-alpha-tocopherol, 2,6-[2H3-methyl]- alpha-tocopherolquinone, 2,6-[2H3-methyl]-5,6-epoxy- alpha-tocopherolquinone, 2,6-[2H3-methyl]-2,3-epoxy- alpha-tocopherolquinone, and 2-[2H3-methyl]- alpha-tocopherolhydroquinone are added to cell or tissue homogenates. The products then are extracted and converted to O-trimethylsilyl derivatives. Products are analyzed by capillary gas chromatography with on-column injection and detected by selected ion monitoring of characteristic fragment ions in electron ionization mode. Standard curves were linear from 25 fmol to 2 pmol for products and from 25 fmol to 4 pmol for alpha-tocopherol. The use of 2H6- and 2H3-internal standards for alpha-tocopherolquinone and alpha-tocopherolhydroquinone permits simultaneous analysis of both products despite possible redox interconversion during sample workup. alpha-Tocopherol oxidized in microsomes treated with azo-bis(amidinopropane HCl) was quantitatively accounted for as the epoxyquinones, alpha-tocopherolquinone, and alpha-tocopherolhydroquinone. However, over half of the oxidation products were present in microsomes as acid-labile tocopherone precursors. This method permits comprehensive assessment of vitamin E status in tissues and quantitative studies of vitamin E antioxidant actions and turnover.
Animals↗
Reproducibility of nutrient intake in a food frequency questionnaire used in a general population.
This study evaluates the reproducibility of nutrient intake in a 45-item food frequency questionnaire (FFQ). The FFQ was mailed in 1980 to persons eligible to participate in a large cohort study on diet and cancer risk; a follow-up version with 75 food items was mailed in 1988 to selected original participants. A random sample of 500 men and 500 women from the New York State general population was selected from individuals who responded to both waves of the study. The subjects' 1988 responses were compared with their original 1980 responses; Pearson's correlations ranged from 0.25 for retinol to 0.55 for vitamin C with or without supplements and vitamin E with supplements in women. Reproducibility of nutrient intake in this questionnaire indicates that brief FFQs may be a useful tool to study nutrient intake and chronic disease relationships, although they are subject to substantial measurement error and dietary change.
Adolescent↗
Antioxidant stoichiometry and the oxidative fate of vitamin E in peroxyl radical scavenging reactions.
Oxidation of R,R,R-alpha-tocopherol (vitamin E; TH) by peroxyl radicals generated from the azo initiator azobis(2,4-dimethylvaleronitrile) in acetonitrile, hexane, or in phospholipid liposomes yields 8a-(alkyldioxy)tocopherone adducts, 8a-(hydroxy)tocopherone, and their hydrolysis product alpha-tocopherolquinone. TH oxidation also yields 4a,5-epoxy- and 7,8-epoxy-8a-(hydroperoxy)tocopherones and their respective hydrolysis products 2,3-epoxy-alpha-tocopherolquinone and 5,6-epoxy-alpha-tocopherolquinone. Previous work indicates that the distribution of TH oxidation products varies with reaction environment. We investigated the dependence of antioxidant stoichiometry on TH oxidation product distribution for reactions in hexane, acetonitrile, and in phosphatidylcholine liposomes. Yields of 8a-substituted tocopherones were highest in hexane and lowest in phosphatidylcholine liposomes. In contrast, yields of epoxide products were highest in the liposome system and lowest in hexane. Yields of alpha-tocopherolquinone were similar in all three systems. Antioxidant stoichiometry, measured by the inhibited autoxidation method, was approximately 2.0 peroxyl radicals trapped per TH consumed in acetonitrile and in liposomes. In hexane, a slightly larger stoichiometric factor of approximately 2.5 was measured. This may, in part, reflect the generation of more reactive alkoxyl radicals in hexane. The reaction environment thus markedly affects the balance between competing TH oxidation pathways but produces comparatively little effect on antioxidant stoichiometry. These results imply that competing reaction pathways contribute similarly to the antioxidant chemistry of TH.
Acetonitriles↗
Reproducibility of food intake in a food frequency questionnaire used in a general population.
This study evaluates the reproducibility of food intake reports in a 45-item self-administered food frequency questionnaire (FFQ) used for a diet study in a large cohort in New York State. The first FFQ was mailed in 1980, and a followup version containing 75 food items was mailed in 1988 to the eligible original participants. Reproducibility was evaluated by comparing the subjects' 1988 responses with their original 1980 responses. Spearman's correlations ranged from 0.27 (nuts other than peanuts) to 0.56 (summer squash) in men and from 0.25 (tomatoes) to 0.51 (summer squash) in women. Analyses stratified by age, education, marital status, body mass index, cigarette smoking, alcohol drinking, and special diet revealed few substantial differences in correlations. The moderate reproducibility of foods in this questionnaire indicates that brief FFQs may be a useful tool to study food intake and chronic disease relationships in this population.
Adolescent↗
Women's labor force participation in later life: the effects of early work and family experiences.
The purpose of this study was to develop and evaluate a model of labor force participation among a group of older women in the United States. A comprehensive measure of women's combined work and family experiences across the adult life course was created. Employing data from the 1984 Survey of Income and Program Participation, we applied multinomial logistic regression techniques to examine the association between work-family experiences and later life labor supply. Our findings generally support an attachment hypothesis, showing that women who were the most work-oriented throughout the life course were more likely than women who experienced family-related spells of nonlabor-market activity to participate in the labor force, either full-time or part-time, later in life.
Adult↗
Nativity, acculturation, and economic status: explanations of Asian American living arrangements in later life.
Using 1980 Census data, we examined the household and nonhousehold living arrangements for older, unmarried women of Japanese, Chinese, Filipino, and Korean descent, finding substantial variation across ethnic groups. We tested three hypotheses regarding the effects of acculturation, economic status, and nativity/immigration status. The results from our multivariate analyses show that Chinese-origin and Filipino-origin women who are less acculturated are more likely to live with others than those who are more acculturated. Members from each Asian American group who can afford independent living are more likely to purchase their privacy. The most consistent finding shows that older, unmarried Asian American women who have migrated to the United States since 1965 are more likely than similar native-born women to live in a complex household as compared to living alone.
Acculturation↗