Showing papers on "Ascorbic acid published in 1993"

Structure and function of plant cell wall proteins.

Abstract: Plant cell walls are amazingly complex amalgams of carbohy? drates, proteins, lignin, water, and incrusting substances such as cutin, suberin, and certain inorganic compounds that vary among plant species, cell types, and even neighboring cells Developmental events and exposure to any of a number of abiotic and biotic stresses further increase this compositional and structural variation Moreover, the dynamic nature and func? tions of plant cell walls in terms of growth and development, environmental sensing and signaling, plant defense, intercel? lular communication, and selective exchange interfaces are reflected in these variations Much is currently known about the structure and metabolic regulation of the various cell wall components, but relatively little is known about their precise functions and intermolecular interactions In this review, I will discuss the accumulated structural and regulatory data and the much more limited functional and in? termolecular interaction information on five plant cell wall protein classes These five protein classes, listed in Table 1, include the extensins, the glycine-rich proteins (GRPs), the proline-rich proteins (PRPs), the solanaceous lectins, and the arabinogalactan proteins (AGPs) These five proteins may be evolutionarily related to one another, most obviously because each of them, with the exception of the GRPs, contains hydroxyproline, and less obviously in the case of the GRPs because this class has nucleotide sequence similarity to the extensins For completeness, I should mention that these are not the only cell wall proteins that are known Others exist, such as cysteine-rich thionins, 28and 70-kD water-regulated proteins, a histidine-tryptophan-rich protein, and many cell wall enzymes such as peroxidases, phosphatases, invertases, a-mannosidases, P-mannosidases, p-1,3-glucanases, (3-1,4glucanases, polygalacturonase, pectin methylesterases, malate dehydrogenase, arabinosidases, a-galactosidases, (3-galactosidases, |3-glucuronosidases, p-xylosidases, proteases, and ascorbic acid oxidase (Varner and Lin, 1989) However, the above five classes generally represent the most abundant, and to date, the most well-studied and widely documented, plant cell wall proteins Before describing these five wall protein classes, I should point out that research on these individual proteins has oc? curred in several plant species, but relatively few examples exist where these cell wall proteins have been studied together in one plant, let alone in one particular plant organ or type of cell Thus, data from one plant species are often extrapolated to represent the situation in other plant species Although such extrapolations are usually valid, enough variations are now known that caution should be exercised in making or believing such claims

Development and Validation of a Food Frequency Questionnaire in Spain

Abstract: To create a suitable instrument to estimate intakes of total calories, protein, carbohydrate, fats (saturated, mono and polyunsaturated), alcohol, cholesterol, fibre, vitamin A and vitamin C in epidemiological studies conducted in Spain, a food frequency questionnaire was developed and tested. In particular, the questionnaire was designed to be used in a large population-based case-control study of dietary factors in relation to breast and colorectal cancer among women from different Spanish regions. After identifying the most important food sources of the relevant nutrients in the study population, the final version of the questionnaire asked about consumption of 118 food items. Its reproducibility and validity were tested among 147 Spanish women aged 18-74 years. These subjects were asked to complete the questionnaire before and after completing four 4-day food records. The records were obtained at 3-month intervals designed to represent daily and seasonal changes (between 1990 and 1991). Using the information available from standard Spanish food composition tables, an ad hoc computer program was created to translate food consumption into nutrient intake. The reproducibility of the questionnaire was assessed by means of estimating correlations between nutrient scores measured with the same instrument twice, with a period of 1 year between estimates. Pearson correlation coefficients ranged from 0.51 for saturated fat to 0.88 for alcohol. In the validity study, correlation coefficients between diet records and the first and second questionnaires ranged between r = 0.20 for vitamin A and r = 0.88 for alcohol.(ABSTRACT TRUNCATED AT 250 WORDS)

Mammalian facilitative hexose transporters mediate the transport of dehydroascorbic acid

Abstract: ALTHOUGH vitamin C is critical to human physiology1–5, it is not clear how it is taken up into cells. The kinetics of cell and tissue accumulation of ascorbic acid in vitro indicate that the process is mediated by specific transporters at the cell membrane6. Some experimental observations have linked the transport of ascorbic acid with hexose transport systems in mammalian cells, although no clear information is available regarding the specific role(s) of these transporters, if any, in this process7–16. Here we use the Xenopus laevis oocyte expression system to show that the mammalian facilitative hexose transporters are efficient transporters of the oxidized form of vitamin C (dehydroascorbic acid). Two transport pathways, one with low affinity and one with high affinity for dehydroascorbic acid, were found in oocytes expressing the mammalian transporters, and these oocytes accumulated vitamin C against a concentration gradient when supplied with dehydroascorbic acid. We obtained similar results in experiments using normal human neutrophils. These observations indicate that mammalian facilitative hexose transporters are a physiologically significant pathway for the uptake and accumulation of vitamin C by cells, and suggest a mechanism for the accumulation of ascorbic acid against a concentration gradient.

Biology of free radical scavengers: an evaluation of ascorbate.

Abstract: Reactive free radical species (R.) are associated with several forms of tissue damage and disease, and also with the process of aging. Protection is thought to be available in the form of endogenous compounds that react with and thereby "scavenge" the R.. Because many R. are reactive forms of oxygen, an effective scavenger is often referred to as an antioxidant. To be an effective antioxidant physiologically, a substance must have certain chemical and biological properties: it must be present in adequate amounts in the body; it must react with a variety of R.; it must be suitable for compartmentation; it must be readily available; it might be suitable for regeneration; it must be conserved by the kidneys; and it must have tolerable toxicity. Several water-soluble candidates are mentioned, with most having no more than one or two of the attributes listed. Ascorbic acid is discussed in detail, and an analysis is made of whether it has the properties mentioned.

Effect of dietary antioxidant combinations in humans. Protection of LDL by vitamin E but not by beta-carotene.

Abstract: Experimental and epidemiological evidence supports the hypothesis that oxidation of low density lipoprotein (LDL) appears to be important in mediating the atherogenicity of LDL. To test this hypothesis in humans, it will be necessary to perform intervention studies in large populations. We performed two studies to assess the effectiveness of supplementation with beta-carotene and vitamin E, used alone and in combination with each other, and with vitamin C, to protect LDL from oxidation. In phase 1, after a placebo period, eight subjects were given beta-carotene (60 mg/day) for 3 months, then beta-carotene plus vitamin E (1,600 mg/day) for another 3 months, and then beta-carotene plus vitamin E plus vitamin C (2 g/day) for 3 months. During phase 2, beta-carotene and vitamin C were discontinued, and subjects took only vitamin E for 5 months. During each period, LDL samples were isolated, and measurements of susceptibility to oxidation were performed. beta-Carotene levels in LDL increased nearly 20-fold, but LDL susceptibility to oxidation did not change. Addition of vitamin E increased LDL vitamin E levels nearly 2.5-fold, and this decreased LDL oxidation 30-40%. During the vitamin C supplementation period, plasma levels of beta-carotene and vitamin E rose, but only beta-carotene increased in LDL. However, the susceptibility of LDL to oxidation in this period was not decreased further. During phase 2, when subjects took only vitamin E, LDL susceptibility to oxidation was decreased by 50% as measured by thiobarbituric acid-reactive substances, conjugated dienes, and lipid peroxide formation as well as by macrophage degradation. Thus, long-term supplementation with large doses of vitamin E alone, but not beta-carotene, conferred increased protection to LDL in in vitro assays of oxidation. These data should be useful in planning therapeutic strategies to test the antioxidant hypothesis in humans.

Partners in defense, vitamin E and vitamin C

Abstract: In addition to the enzymic mechanism of free-radical removal, essential nutrients that can scavenge free radicals, such as vitamins E and C, constitute a strong line of defense in retarding free radical induced cellular damage. Distinct pathways for the repair of oxidized vitamin E in human cells have been recently identified. Within 0.5 min after the addition of arachidonic acid to a human platelet homogenate, over half of the platelet vitamin E and added arachidonate were metabolized by platelet cyclooxygenase and lipoxygenase pathways. After adding nordihydroguaiaretic acid, a lipoxygenase inhibitor and a strong reductant, over 60% of the oxidized vitamin E was regenerated. To test other physiological, water-soluble reductants that may help regenerate vitamin E, eicosatetraynoic acid, a lipoxygenase inhibitor that is not an antioxidant, was used. In this system, both ascorbate and glutathione provided significant vitamin E regeneration. Kinetic analysis and studies of vitamin E regeneration in a protein-denaturing system revealed that ascorbate regenerates vitamin E by a nonenzymic mechanism, whereas glutathione regenerates vitamin E enzymatically. These studies suggest that significant interaction occurs between water- and lipid-soluble molecules at the membrane-cytosol interface and that vitamin C may function in vivo to repair the membrane-bound oxidized vitamin E.

Cancer‐Protective Factors in Fruits and Vegetables: Biochemical and Biological Background.

Abstract: Cancer-protective factors are present in several fruits, vegetables and commonly used spices and herbs. They can be divided into several different groups, based on their chemical structure, e.g. polyphenols, thiols, carotenoids and retinoids, carbohydrates, trace metals, terpenes, tocopherols and degradation products of glucosinolates (i.e. isothiocyanates, indoles and dithiothiols) and others. Among each of these groups of compounds are substances, which may exert their cancer-protective action by more than one biochemical mechanism. The biochemical processes of carcinogenesis are still not known in detail and probably varies with the cancer disease in question. Accordingly, the description of the biochemical backgrounds for the actions of cancer-protective factors must be based on a simplified model of the process of carcinogenesis. The model used in this presentation is a generalised initiation-promotion-conversion model, in which initiators are thought to be directly or indirectly genotoxic, promoters are visualised as substances capable of inferring a growth advantage on initiated cells and converters are believed to be genotoxic, e.g. mutagens, clastogens, recombinogens or the like. Experimental evidence for the mechanisms of action of cancer-protective agents in fruits and vegetables that protect against initiation include the scavenging effects of polyphenols on activated mutagens and carcinogens, the quenching of singlet oxygen and radicals by carotenoids, the antioxidant effects of many compounds including ascorbic acid and polyphenols, the inhibition of activating enzymes by some flavonols and tannins, the induction of oxidation-and of conjugation (protective) enzymes by indoles, isothiocyanates and dithiothiones, the shielding of sensitive structures by some polyphenols and the stimulation of DNA-repair exerted by sulphur-containing compounds. Mechanisms at the biochemical level in anti-promotion include the antioxidant effects of carotenoids and the membrane stabilizing effects reported with polyphenols, the inhibition of proteases caused by compounds from soybeans, the stimulation of immune responses seen with carotenoids and ascorbic acid and the inhibition of ornithine decarboxylase by polyphenols and carotenoids. A few inhibitors of conversion have been identified experimentally, and it can be argued on a theoretical basis, that many inhibitors of initiation should also be efficient against conversion. The mechanisms of anticarcinogenic substances in fruits and vegetables are discussed in the light of cancer prevention and inhibition.

Self-assembled monolayers in electroanalytical chemistry: application of .omega.-mercapto carboxylic acid monolayers for the electrochemical detection of dopamine in the presence of a high concentration of ascorbic acid

Abstract: Self-assembled monolayers of ω-mercapto carboxylic acids, HS(CH 2 ) n CO 2 H (n=2, 5, 10), C n , on gold electrodes were used as a means to induce electrochemical differentiation between a neurotransmitter, dopamine (DO), and ascorbic acid (AA) Optimum differentiation is found for n=5, and it is attributed a compromise between as well-organized system that requires long ω-mercapto carboxylic acids and a reasonable rate of electron transfer which is observed with short ω-mercapto carboxylic acids

The role of metabolism in the antioxidant function of vitamin E.

Abstract: Vitamin E (α-tocopherol), the principal chain-breaking antioxidant in biological membranes, prevents toxicant- and carcinogen-induced oxidative damage by trapping reactive oxyradicals. Although α-t...

Autoxidation of lipids and antioxidation by alpha-tocopherol and ubiquinol in homogeneous solution and in aqueous dispersions of lipids: unrecognized consequences of lipid particle size as exemplified by oxidation of human low density lipoprotein

Abstract: Recent studies on the initial stages in oxidation of low density lipoprotein (LDL) have revealed certain previously unrecognized similarities to emulsion polymerization and some quite unexpected features including the following: (i) ascorbate is an extremely effective antioxidant for LDL containing alpha-tocopherol (alpha-TOH); (ii) in the presence of alpha-TOH and in the absence of both ascorbate and ubiquinol 10 (Q10H2), oxidation of LDL occurs via a free radical chain; (iii) Q10H2 is a much better antioxidant for LDL than alpha-TOH, although the reverse is true in homogeneous systems. We show here that these problems can be solved on the basis of three simple hypothesis, each of which is based on known chemistry: (i) alpha-TOH in LDL can be regenerated from its radical, alpha-TO., by ascorbate; (ii) in the absence of ascorbate and Q10H2, the alpha-TOH in LDL acts as a chain-transfer agent rather than as a radical trap; (iii) Q10H2 is a much more effective chain-breaking antioxidant than alpha-TOH in LDL because the semiquinone radical Q10H. exports its radical character from the LDL into the aqueous phase. Our conclusions imply that the search for better antiatherosclerotic drugs might profitably focus on antioxidants capable of exporting radicals from LDL particles or otherwise increasing the traffic of radicals between particles.

Role of Ascorbate in Detoxifying Ozone in the Apoplast of Spinach (Spinacia oleracea L.) Leaves

Abstract: Both reduced and oxidized ascorbate (AA and DHA) are present in the aqueous phase of the extracellular space, the apoplast, of spinach (Spinacia oleracea L.) leaves. Fumigation with 0.3 [mu]L L-1 of ozone resulted in ozone uptake by the leaves close to 0.9 pmol cm-2 of leaf surface area s-1. Apoplastic AA was slowly oxidized by ozone. The initial decrease of apoplastic AA was <0.1 pmol cm-2 s-1. The apoplastic ratio of AA to (AA + DHA) decreased within 6 h of fumigation from 0.9 to 0.1. Initially, the concentration of (AA + DHA) did not change in the apoplast, but when fumigation was continued, DHA increased and AA remained at a very low constant level. After fumigation was discontinued, DHA decreased very slowly in the apoplast, reaching control level after 70 h. The data show that insufficient AA reached the apoplast from the cytosol to detoxify ozone in the apoplast when the ozone flux into the leaves was 0.9 pmol cm-2 s-1. The transport of DHA back into the cytosol was slower than AA transport into the apoplast. No dehydroascorbate reductase activity could be detected in the apoplast of spinach leaves. In contrast to its extracellular redox state, the intracellular redox state of AA did not change appreciably during a 24-h fumigation period. However, intracellular glutathi-one became slowly oxidized. At the beginning of fumigation, 90% of the total glutathione was reduced. Only 10% was reduced after 24-h exposure of the leaves to 0.3 [mu]L L-1 of ozone. Necrotic leaf damage started to become visible when fumigation was extended beyond a 24-h period. A close correlation between the extent of damage, on the one hand, and the AA content and the ascorbate redox state of whole leaves, on the other, was observed after 48 h of fumigation. Only the youngest leaves that contained high ascorbate concentrations did not exhibit necrotic leaf damage after 48 h.

Oxidation of low-density lipoprotein with hypochlorite causes transformation of the lipoprotein into a high-uptake form for macrophages

Abstract: Oxidation of low-density lipoprotein (LDL) lipid is thought to represent the initial step in a series of oxidative modification reactions that ultimately transform this lipoprotein into an atherogenic high-uptake form that can cause lipid accumulation in cells. We have studied the effects of hypochlorite, a powerful oxidant released by activated monocytes and neutrophils, on isolated LDL. Exposure of LDL to reagent hypochlorite (NaOCl) at 4 degrees C resulted in immediate and preferential oxidation of amino acid residues of apoprotein B-100, the single protein associated with LDL. Neither lipoprotein lipid nor LDL-associated antioxidants, except ubiquinol-10, represented major targets for this oxidant. Even when high concentrations of NaOCl were used, only low levels of lipid hydroperoxides could be detected with the highly sensitive h.p.l.c. post-column chemiluminescence detection method. Lysine residues of apoprotein B-100 quantitatively represented the major target, scavenging some 68% of the NaOCl added, with tryptophan and cysteine together accounting for an additional 10% of the oxidant. Concomitant with the loss of LDL's amino groups, chloramines were formed and the anionic surface charge of the lipoprotein particle increased, indicated by a 3-4-fold increase in electrophoretic mobility above that of native LDL on agarose gels. While both these changes could be initially reversed by physiological reductants such as ascorbic acid and methionine, incubation of the NaOCl-modified LDL at 37 degrees C resulted in increasing resistance of the modified lysine residues against reductive reversal. Exposure of mouse peritoneal macrophages to NaOCl-oxidized LDL resulted in increased intracellular concentrations of cholesterol and cholesteryl esters. These findings suggest that lipid-soluble antioxidants associated with LDL do not efficiently protect the lipoprotein against oxidative damage mediated by hypochlorite, and that extensive lipid oxidation is not a necessary requirement for oxidative LDL modification that leads to a high-uptake form of the lipoprotein.

Effects of an antioxidant vitamin mixture on lipid peroxidation at rest and postexercise

Abstract: We studied the effects of ingesting an antioxidant vitamin mixture for 6 wk on breath pentane and serum malondialdehyde (MDA) levels before and after exercise. Twenty young (mean age 25.0 +/- 2.9 yr) healthy males were randomly assigned to either an antioxidant vitamin group (daily doses of 592 mg of alpha-tocopherol equivalents, 1,000 mg of ascorbic acid, and 30 mg of beta-carotene) or a placebo group. Exercise consisted of 30 min of treadmill running at 60% of maximal O2 consumption (VO2max) followed by 5 min of running at a pace that elicited approximately 90% of VO2max. Blood and breath samples were collected immediately after the two exercise bouts. The antioxidant supplement did not prevent the exercise-induced increase in lipid peroxidation, as reflected by the rate of pentane production and the increase in serum MDA concentration. However, ingestion of the antioxidant vitamins did result in significantly lower resting and postexercise levels of expired pentane and serum MDA. We conclude that taking ascorbate, alpha-tocopherol, and beta-carotene in the amounts used in this study serves to lower markers of lipid peroxidation at rest and after exercise but does not prevent the exercise-induced increase in oxidative stress.

A Prospective Study of the Intake of Vitamins C, E, and A and the Risk of Breast Cancer

Abstract: Background Although it has been hypothesized that large intakes of the antioxidant vitamins C, E, and A reduce the risk of breast cancer, few prospective data are available. Methods We prospectively studied 89,494 women who were 34 to 59 years old in 1980 and who did not have diagnosed cancer. Their intakes of vitamins C, E, and A from foods and supplements were assessed at base line and in 1984 with the use of a validated semiquantitative food-frequency questionnaire. Results Breast cancer was diagnosed in 1439 women during eight years of follow-up. After multivariate adjustment for known risk factors, the relative risk among women in the highest quintile group for intake of vitamin C as compared with the risk among those in the lowest quintile group was 1.03 (95 percent confidence interval, 0.87 to 1.21); for vitamin E, after vitamin A intake had been controlled for, the relative risk was 0.99 (95 percent confidence interval, 0.83 to 1.19). In contrast, among women in the highest quintile group for inta...

Antioxidative properties of methanolic extracts from peanut hulls

Abstract: Antioxidative properties of methanolic extracts from peanut hulls (MEPH) have been investigated. MEPH had good thermal stability and showed an 85.2% inhibition of peroxidation of linoleic acid when heated at 185°C for 2 h. Only a slight decrease in antioxidative activity of MEPH occurred when the extract was stored at different temperatures (∓20, 5 and 30°C) under air or nitrogen (30°C) for 70 d. Antioxidative activity of MEPH decreased with an increase of pH from 3 to 9. No synergistic effect of ascorbic acid, citric acid, cysteine or α-tocopherol was observed on the inhibitory effect of MEPH. The reducing power of MEPH increased with an increase in concentration and was significantly correlated (r=0.9793,P<0.05) to the extent of antioxidative activity. MEPH also showed good inhibitory activity in lard oxidation when compared with butylated hydroxyanisole.

Reduced Risk of Colon Cancer with High Intake of Vitamin E: The Iowa Women's Health Study

Abstract: Antioxidant micronutrients, including vitamin E, vitamin C, the carotenoids, and selenium, defend the body against free radicals and reactive oxygen molecules, suggesting a potential for these dietary components in cancer prevention. To investigate whether high intakes of antioxidant micronutrients protect against colon cancer in humans, we analyzed data from a prospective cohort study of 35,215 Iowa women aged 55-69 years and without a history of cancer who completed a dietary questionnaire in 1986. Through 1990, 212 incident cases of colon cancer were documented. Adjusted for age, total vitamin E intake was inversely associated with the risk of colon cancer (P for trend < 0.0001); the relative risk for the highest compared to the lowest quintile was 0.32 [95% confidence interval (95% CI) 0.19, 0.54]. Further adjustment for total energy intake and other risk factors in proportional hazards regression had little effect on these estimates. The association was not uniform across age groups: the multivariate relative risk of colon cancer for the highest compared to the lowest quintile of total vitamin E intake was 0.16 (95% CI 0.04, 0.70) for those 55-59 years old, 0.37 (95% CI 0.12, 1.16) for those 60-64 years old, and 0.93 (95% CI 0.27, 3.25) for those 65-69 years old. Multivariate-adjusted relative risks among women with higher total intakes of vitamins A and C and beta-carotene, and among users of selenium supplements, were not significantly different from 1.0. These prospective data provide evidence that a high intake of vitamin E may decrease the risk of colon cancer, especially in persons under 65 years of age.

Dietary micronutrient intake and risk of progression to acquired immunodeficiency syndrome (AIDS) in human immunodeficiency virus type 1 (HIV-1)-infected homosexual men

Abstract: The authors sought to determine if different levels of dietary intake of micronutrients are associated with the progression of human immunodeficiency virus type 1 (HIV-1) infection to acquired immunodeficiency syndrome (AIDS). A total of 281 HIV-1 seropositive homosexual/bisexual men were seen semiannually since 1984 at the Baltimore/Washington, DC site of the Multicenter AIDS Cohort Study. Participants completed a self-administered semiquantitative food frequency questionnaire at baseline. Levels of daily micronutrient intake at baseline were examined in relation to subsequent progression to AIDS (1987 Centers for Disease Control definition; n = 108) during a median follow-up period of 6.8 years. For each nutrient, the authors used a Cox proportional hazards model to adjust for age, presence of symptoms, CD4+ lymphocyte count, energy intake, use of antiretrovirals, and use of Pneumocystis carinii pneumonia prophylaxis. The highest levels of total intake (from food and supplements) of vitamins C and B1 and niacin were associated with a significantly decreased progression rate to AIDS: vitamin C (relative hazard (RH) = 0.55, 95% confidence interval (CI) 0.34-0.91), vitamin B1 (RH = 0.60, 95% CI 0.36-0.98), and niacin (RH = 0.52, 95% CI 0.31-0.86). The relation between total vitamin A intake and progression to AIDS appeared to be U-shaped; the lowest and highest quartiles of intake did most poorly, while the middle two quartiles were associated with significantly slower progression to AIDS (RH = 0.55, 95% CI 0.35-0.88). Increased intake of zinc was monotonically and significantly associated with an increased risk of progression to AIDS (for highest vs. lowest quartiles, RH = 2.06, 95% CI 1.16-3.64). In a final multinutrient model, vitamin A, niacin, and zinc remained significantly associated with progression to AIDS, while vitamin C was only marginally significant.

INHIBITION of APPLE POLYPHENOLOXIDASE (PPO) BY ASCORBIC ACID, CITRIC ACID and SODIUM CHLORIDE

Abstract: The inhibiting effect of ascorbic acid, citric acid and sodium chloride on Polyphenoloxidase (PPO) of Golden Delicious apple cubes was studied. Dipping in ascorbic acid (0.2-10 g/L range) and in NaCl (0.2-1 g/L range) solutions for 5 min increases the PPO activiry. Citric acid solutions (0.2-10 g/L range) have little or no inhibition of PPO. A 90-100% PPO inhibition was obtained with a 5 min dip in mixtures of ascorbic acid and citric acid (10 + 2 g/L), and of ascorbic acid and sodium chloride (I0 + 0.5 g/L).

Evaluation of the Antioxidant Actions of Ferulic Acid and Catechins

Abstract: We have evaluated the abilities of ferulic acid, (+/-) catechin, (+) catechin and (-) epicatechin to scavenge the reactive oxygen species hydroxyl radical (OH.), hypochlorous acid (HOCl) and peroxyl radicals (RO2.). Ferulic acid tested at concentrations up to 5 mM inhibited the peroxidation of phospholipid liposomes. Both (+/-) and (+) catechin and (-) epicatechin were much more effective. All the compounds tested reacted with trichloromethyl peroxyl radical (CCl3 O2.) with rate constants > 1 x 10(6) M-1 s-1. A mixture of FeCl3-EDTA, hydrogen peroxide (H2O2) and ascorbic acid at pH 7.4, has often been used to generate hydroxyl radicals (OH.) which are detected by their ability to cause damage to the sugar deoxyribose. Ferulic acid, (+) and (+/-) catechin and (-) epicatechin inhibited deoxyribose damage by reacting with OH. with rate constants of 4.5 x 10(9)M-1 s-1, 3.65 x 10(9) M-1 s-1, 2.36 x 10(9) M-1 s-1 and 2.84 x 10(9) M-1 s-1 respectively. (-) Epicatechin, ferulic acid and the (+) and (+/-) catechins exerted pro-oxidant action, accelerating damage to DNA in the presence of a bleomycin-iron complex. On a molar basis, ferulic acid was less effective in causing damage to DNA compared with the catechins. A mixture of hypoxanthine and xanthine oxidase generates O2-. which reduces cytochrome c to ferrocytochrome c. (+) Catechin and (-) epicatechin inhibited the reduction of cytochrome c in a concentration dependent manner. Ferulic acid and (+/-) catechin had only weak effects. All the compounds tested were able to scavenge hypochlorous acid at a rate sufficient to protect alpha-1-antiproteinase against inactivation. Our results show that catechins and ferulic acid possess antioxidant properties. This may become important given the current search for "natural" replacements for synthetic antioxidant food additives.