Showing papers on "Ascorbic acid published in 2002"

Thermal Processing Enhances the Nutritional Value of Tomatoes by Increasing Total Antioxidant Activity

Abstract: Processed fruits and vegetables have been long considered to have lower nutritional value than their fresh commodities due to the loss of vitamin C during processing This research group found vitamin C in apples contributed < 04% of total antioxidant activity, indicating most of the activity comes from the natural combination of phytochemicals This suggests that processed fruits and vegetables may retain their antioxidant activity despite the loss of vitamin C Here it is shown that thermal processing elevated total antioxidant activity and bioaccessible lycopene content in tomatoes and produced no significant changes in the total phenolics and total flavonoids content, although loss of vitamin C was observed The raw tomato had 076 +/- 003 micromol of vitamin C/g of tomato After 2, 15, and 30 min of heating at 88 degrees C, the vitamin C content significantly dropped to 068 +/- 002, 064 +/- 001, and 054 +/- 002 micromol of vitamin C/g of tomato, respectively (p < 001) The raw tomato had 201 +/- 004 mg of trans-lycopene/g of tomato After 2, 15, and 30 min of heating at 88 degrees C, the trans-lycopene content had increased to 311+/- 004, 545 +/- 002, and 532 +/- 005 mg of trans-lycopene/g of tomato (p < 001) The antioxidant activity of raw tomatoes was 413 +/- 036 micromol of vitamin C equiv/g of tomato With heat treatment at 88 degrees C for 2, 15, and 30 min, the total antioxidant activity significantly increased to 529 +/- 026, 553 +/- 024, and 670 +/- 025 micromol of vitamin C equiv/g of tomato, respectively (p < 001) There were no significant changes in either total phenolics or total flavonoids These findings indicate thermal processing enhanced the nutritional value of tomatoes by increasing the bioaccessible lycopene content and total antioxidant activity and are against the notion that processed fruits and vegetables have lower nutritional value than fresh produce This information may have a significant impact on consumers' food selection by increasing their consumption of fruits and vegetables to reduce the risks of chronic diseases

Growth and form of gold nanorods prepared by seed-mediated, surfactant-directed synthesis

Abstract: Gold nanorods were prepared via a seed-mediated sequential growth process involving the use of citrate-stabilised seed crystals and their subsequent growth in a series of reaction solutions containing [AuCl4]−, ascorbic acid and the cationic surfactant cetyltrimethylammonuim bromide (CTAB). Electron diffraction analysis and HRTEM images of mature nanorods showed superpositions of two specific pairs of crystallographic zones, either and or and , which were consistent with a cyclic penta-twinned crystal with five {111} twin boundaries arranged radially to the [110] direction of elongation. The nanorods have an idealised 3-D prismatic morphology with ten {111} end faces and five {100} or {110} side faces, or both. TEM studies of crystals at various stages of growth indicated that the seed crystals are initially transformed by growth and aggregation into decahedral penta-twinned crystals, 4% of which become elongated when a fresh reaction solution is added, whilst the remaining twins grow isometrically. Reiteration of this procedure increases the length of the existing nanorods, induces further transformation of isometric particles to produce a second (and third) population of shorter, wider nanorods, and increases the size of the isometric crystals. The data indicate that symmetry breaking in fcc metallic structures to produce anisotropic nanoparticles is based on an intrinsic structural mechanism (twinning) that is subsequently modulated extrinsically during growth in solution by specific adsorption of AuI–surfactant complexes on the side faces/edges of the isometric penta-twinned crystals and which is responsible for the preferential growth along the common [110] axis. We propose that the coupling of multiple twinning and habit modification is a general mechanism that applies to other experimental procedures (electrochemical, inverse micellar media) currently used to prepare metallic nanoparticles with a high aspect ratio.

Vitamin C equivalent antioxidant capacity (VCEAC) of phenolic phytochemicals

Abstract: To express the antioxidant capacity of plant foods in a more familiar and easily understood manner (equivalent to vitamin C mg/100 g), two stable radical species, ABTS•- and DPPH•, commonly used for antioxidant activity measurements, were employed independently to evaluate their efficacies using apple polyphenolic extracts and seven polyphenolic standards including synthetic Trolox. Their antioxidant activities were expressed as vitamin C equivalent antioxidant capacity (VCEAC) in mg/100 g apple or mg/100 mL of the reference chemical compounds in 10 and 30 min using the ABTS•- and DPPH• scavenging assays, respectively. The antioxidant capacity of Gala apples and seven phenolic standards, determined by both ABTS•- and DPPH• scavenging assays, showed a dose−response of the first-order. Fresh Gala apples had a VCEAC of 205.4 ± 5.6 mg/100 g using the ABTS assay, and the relative VCEACs of phenolic standards were as follows: gallic acid > quercetin > epicatechin > catechin > vitamin C > rutin > chlorogenic ac...

Identification and quantification of antioxidant components of honeys from various floral sources.

Abstract: Little is known about the individual components of honey that are responsible for its antioxidant activity. The present study was carried out to characterize the phenolics and other antioxidants present in honeys from seven floral sources. Chromatograms of the phenolic nonpolar fraction of the honeys indicated that most honeys have similar but quantitatively different phenolic profiles. Many of the flavonoids and phenolic acids identified have been previously described as potent antioxidants. A linear correlation between phenolic content and ORAC activity was demonstrated (R(2) = 0.963, p < 0.0001). Honeys were separated by solid-phase extraction into four fractions for sugar removal and separation based on solubility to identify the relative contribution of each fraction to the antioxidant activity of honey. Antioxidant analysis of the different honey fractions suggested that the water-soluble fraction contained most of the antioxidant components. Specific water-soluble antioxidant components were quantified, including protein; gluconic acid; ascorbic acid; hydroxymethylfuraldehyde; and the combined activities of the enzymes glucose oxidase, catalase and peroxidase. Of these components, a significant correlation could be established only between protein content and ORAC activity (R(2) = 0.674, p = 0.024). In general, the antioxidant capacity of honey appeared to be a result of the combined activity of a wide range of compounds including phenolics, peptides, organic acids, enzymes, Maillard reaction products, and possibly other minor components. The phenolic compounds contributed significantly to the antioxidant capacity of honey but were not solely responsible for it.

Antioxidant capacities, phenolic compounds, carotenoids, and vitamin C contents of nectarine, peach, and plum cultivars from California.

Abstract: Genotypic variation in composition and antioxidant activity was evaluated using 25 cultivars, 5 each of white-flesh nectarines, yellow-flesh nectarines, white-flesh peaches, yellow-flesh peaches, and plums, at the ripe (ready-to-eat) stage. The ranges of total ascorbic acid (vitamin C) (in mg/100 g of fresh weight) were 5−14 (white-flesh nectarines), 6−8 (yellow-flesh nectarines), 6−9 (white-flesh peaches), 4−13 (yellow-flesh peaches), and 3−10 (plums). Total carotenoids concentrations (in μg/100 g of fresh weight) were 7−14 (white-flesh nectarines), 80−186 (yellow-flesh nectarines), 7−20 (white-flesh peaches), 71−210 (yellow-flesh peaches), and 70−260 (plums). Total phenolics (in mg/100 g of fresh weight) were 14−102 (white-flesh nectarines), 18−54 (yellow-flesh nectarines), 28−111 (white-flesh peaches), 21−61 (yellow-flesh peaches), and 42−109 (plums). The contributions of phenolic compounds to antioxidant activity were much greater than those of vitamin C and carotenoids. There was a strong correlation...

Processed Sweet Corn Has Higher Antioxidant Activity

Abstract: Processed fruits and vegetables have been long considered to have lower nutritional value than the fresh produce due to the loss of vitamin C during processing. Vitamin C in apples has been found to contribute <0.4% of total antioxidant activity, indicating most of the activity comes from the natural combination of phytochemicals. This suggests that processed fruits and vegetables may retain their antioxidant activity despite the loss of vitamin C. Here it is shown that thermal processing at 115 degrees C for 25 min significantly elevated the total antioxidant activity of sweet corn by 44% and increased phytochemical content such as ferulic acid by 550% and total phenolics by 54%, although 25% vitamin C loss was observed. Processed sweet corn has increased antioxidant activity equivalent to 210 mg of vitamin C/100 g of corn compared to the remaining 3.2 mg of vitamin C in the sample that contributed only 1.5% of its total antioxidant activity. These findings do not support the notion that processed fruits and vegetables have lower nutritional value than fresh produce. This information may have a significant impact on consumers' food selection by increasing their consumption of fruits and vegetables to reduce the risk of chronic diseases.

Assessment of Antioxidant Activity by Using Different In Vitro Methods

Abstract: In this study, six common tests for measuring antioxidant activity were evaluated by comparing four antioxidants and applying them to beverages (tea and juices): Trolox equivalent antioxidant capacity assay (TEAC I-III assay), Total radical-trapping antioxidant parameter assay (TRAP assay), 2,2-diphenyl-l-picrylhydrazyl assay (DPPH assay), N,N-dimethyl-p-phenylendiamine assay (DMPD assay), Photochemiluminescence assay (PCL assay) and Ferric reducing ability of plasma assay (FRAP assay) The antioxidants included gallic acid representing the group of polyphenols, uric acid as the main antioxidant in human plasma, ascorbic acid as a vitamin widely spread in fruits and Trolox as water soluble vitamin E analogue The six methods presented can be divided into two groups depending on the oxidising reagent Five methods use organic radical producers (TEAC I-III, TRAP, DPPH, DMPD, PCL) and one method works with metal ions for oxidation (FRAP) Another difference between these tests is the reaction procedure Three assays use the delay in oxidation and determine the lag phase as parameter for the antioxidant activity (TEAC I, TRAP, PCL) They determine the delay of radical generation as well as the ability to scavenge the radical In contrast, the assays TEAC II and III, DPPH, DMPD and FRAP analyse the ability to reduce the radical cation (TEAC II and III, DPPH, DMPD) or the ferric ion (FRAP) The three tests acting by radical reduction use preformed radicals and determine the decrease in absorbance while the FRAP assay measures the formed ferrous ions by increased absorbance Gallic acid was the strongest antioxidant in all tests with exception of the DMPD assay In contrast, uric acid and ascorbic acid showed low activity in some assays Most of the assays determine the antioxidant activity in the micromolar range needing minutes to hours Only one assay (PCL) is able to analyse the antioxidant activity in the nanomolar range Black currant juice showed highest antioxidant activity in all tests compared to tea, apple juice and tomato juice Despite these differences, results of these in vitro assays give an idea of the protective efficacy of secondary plant products It is strongly recommended to use at least two methods due to the differences between the test systems investigated

Common Components, Networks, and Pathways of Cross-Tolerance to Stress. The Central Role of “Redox” and Abscisic Acid-Mediated Controls

Abstract: The vigor and responsiveness of plants to environmental stress result from the constant re-adjustment of physiology and metabolism throughout the life cycle within the framework of the genetic background. Plants have developed unique strategies for responding to ever-changing environmental conditions, exhaustively monitoring their surroundings and adjusting their metabolic systems to maintain homeostasis. The severity of stress, the genetic background of the plant, and its individual history determine everyday survival or death. These factors dictate the destiny of any individual. The genomeenvironment interaction is, therefore, an essential focus for the elucidation of the nature of the phenotypic variation leading to the successful response of plants to environmental cues. Plants acclimate to biotic and abiotic stresses by triggering a cascade or network of events that starts with stress perception and ends with the expression of a battery of target genes. The key components of the stress-response relationship are illustrated in Fig. 1. These are stress stimulus, signals, transducers, transcription regulators, target genes, and stress responses, including morphological, biochemical, and physiological changes. In evolutionary terms, components that are near to the end of the stressresponse cascade are not predicted to be the ones whose actions significantly affect the operation of other genes. However, factors that act at early stages are critical for other cell functions. Plants make use of common pathways and components in the stressresponse relationship. This phenomenon, which is known as cross-tolerance, allows plants to adapt/ acclimate to a range of different stresses after exposure to one specific stress. The major focus of this review, therefore, concerns the basic features of signaling that underpin cross-tolerance and result from the action of common elements, which are likely to occur early in the stress response cascade. First, using drought and chilling as examples, we explore the evidence for common signals and elements that confer cross-tolerance. Second, we highlight the importance of “redox signals” in such networks and discuss the evidence to date for the existence of such pathways in plants. The elucidation of common components has enormous potential and has, therefore, become a priority in research and breeding programs aimed at improving plant stress tolerance.

Dietary intake of antioxidant nutrients and the risk of incident Alzheimer disease in a biracial community study.

Abstract: ContextOxidative processes have been suggested as elements in the development of Alzheimer disease (AD), but whether dietary intake of vitamin E and other antioxidant nutrients prevents its development is unknown.ObjectiveTo examine whether intake of antioxidant nutrients, vitamin E, vitamin C, and beta carotene is associated with incident AD.Design, Setting, and ParticipantsProspective study, conducted from 1993 to 2000, of individuals selected in a stratified random sample of community-dwelling residents. The 815 residents 65 years and older were free of AD at baseline and were followed up for a mean of 3.9 years. They completed food frequency questionnaires an average of 1.7 years after baseline.Main Outcome MeasureIncident AD diagnosed in clinical evaluations with standardized criteria.ResultsIncreasing vitamin E intake from foods was associated with decreased risk of developing AD after adjustment for age, education, sex, race, APOE ∊4, and length of follow-up. Relative risks (95% confidence intervals [CIs]) from lowest to highest quintiles of intake were 1.00, 0.71 (0.24-2.07), 0.62 (0.26-1.45), 0.71 (0.27-1.88), and 0.30 (0.10-0.92) (P for trend = .05). The protective association of vitamin E was observed only among persons who were APOE ∊4 negative. Adjustment for other dietary factors reduced the protective association. After adjustment for baseline memory score, the risk was 0.36 (95% CI, 0.11-1.17). Intake of vitamin C, beta carotene, and vitamin E from supplements was not significantly associated with risk of AD.ConclusionThis study suggests that vitamin E from food, but not other antioxidants, may be associated with a reduced risk of AD. Unexpectedly, this association was observed only among individuals without the APOE ∊4 allele.

Chemistry and Reaction of Singlet Oxygen in Foods.

Abstract: Singlet oxygen is a highly reactive, electrophilic, and nonradical molecule. It is different from diradical triplet oxygen in its electron arrangement. Photosensitizers can form singlet oxygen from triplet oxygen in the presence of light. The reaction rate of singlet oxygen with foods is much greater than that of triplet oxygen due to the low activation energy. Singlet oxygen oxidation produces undesirable compounds in foods during processing and storage. However, carotenoids and tocopherols in foods can minimize singlet oxygen oxidation. The in-depth scientific knowledge on the formation, reactions, quenching mechanisms, and kinetics of singlet oxygen can greatly improve the quality of foods by minimizing the oxidation during processing and storage. The single oxygen oxidation of foods has contributed to the explanation of several important chemical reactions in the reversion flavor in soybean oil, sunlight flavor in milk products, and the rapid losses of vitamin D, riboflavin, and ascorbic acid in milk under light storage.

Effects of hormone replacement therapy and antioxidant vitamin supplements on coronary atherosclerosis in postmenopausal women: A randomized controlled trial

Abstract: ContextHormone replacement therapy (HRT) and antioxidant vitamins are widely used for secondary prevention in postmenopausal women with coronary disease, but no clinical trials have demonstrated benefit to support their use.ObjectiveTo determine whether HRT or antioxidant vitamin supplements, alone or in combination, influence the progression of coronary artery disease in postmenopausal women, as measured by serial quantitative coronary angiography.Design, Setting, and PatientsThe Women's Angiographic Vitamin and Estrogen (WAVE) Trial, a randomized, double-blind trial of 423 postmenopausal women with at least one 15% to 75% coronary stenosis at baseline coronary angiography. The trial was conducted from July 1997 to January 2002 in 7 clinical centers in the United States and Canada.InterventionsPatients were randomly assigned in a 2 × 2 factorial design to receive either 0.625 mg/d of conjugated equine estrogen (plus 2.5 mg/d of medroxyprogesterone acetate for women who had not had a hysterectomy), or matching placebo, and 400 IU of vitamin E twice daily plus 500 mg of vitamin C twice daily, or placebo.Main Outcome MeasureAnnualized mean (SD) change in minimum lumen diameter (MLD) from baseline to concluding angiogram of all qualifying coronary lesions averaged for each patient. Patients with intercurrent death or myocardial infarction (MI) were imputed the worst rank of angiographic outcome.ResultsThe mean (SD) interval between angiograms was 2.8 (0.9) years. Coronary progression, measured in mean (SD) change, worsened with HRT by 0.047 (0.15) mm/y and by 0.024 (0.15) mm/y with HRT placebo (P = .17); and for antioxidant vitamins by 0.044 (0.15) mm/y and with vitamin placebo by 0.028 (0.15) mm/y (P = .32). When patients with intercurrent death or MI were included, the primary outcome showed an increased risk for women in the active HRT group (P = .045), and suggested an increased risk in the active vitamin group (P = .09). Fourteen patients died in the HRT group and 8 in the HRT placebo group (hazard ratio [HR], 1.8; 95% confidence interval [CI], 0.75-4.3), and 16 in the vitamin group and 6 in the vitamin placebo group (HR, 2.8; 95% CI, 1.1-7.2). Death, nonfatal MI, or stroke occurred in 26 HRT patients vs 15 HRT controls (HR, 1.9; 95% CI, 0.97-3.6) and in 26 vitamin patients and 18 vitamin controls (HR, 1.5; 95% CI, 0.80-2.9). There was no interaction between the 2 treatment interventions.ConclusionIn postmenopausal women with coronary disease, neither HRT nor antioxidant vitamin supplements provide cardiovascular benefit. Instead, a potential for harm was suggested with each treatment.

Randomized, Prospective Trial of Antioxidant Supplementation in Critically Ill Surgical Patients

Abstract: ObjectiveTo determine the effectiveness of early, routine antioxidant supplementation using α-tocopherol and ascorbic acid in reducing the rate of pulmonary morbidity and organ dysfunction in critically ill surgical patients.Summary Background DataOxidative stress has been associated with the develo

Vitamins for Chronic Disease Prevention in Adults: Scientific Review

Abstract: Context Although vitamin deficiency is encountered infrequently in developed countries, inadequate intake of several vitamins is associated with chronic disease. Objective To review the clinically important vitamins with regard to their biological effects, food sources, deficiency syndromes, potential for toxicity, and relationship to chronic disease. Data sources and study selection We searched MEDLINE for English-language articles about vitamins in relation to chronic diseases and their references published from 1966 through January 11, 2002. Data extraction We reviewed articles jointly for the most clinically important information, emphasizing randomized trials where available. Data synthesis Our review of 9 vitamins showed that elderly people, vegans, alcohol-dependent individuals, and patients with malabsorption are at higher risk of inadequate intake or absorption of several vitamins. Excessive doses of vitamin A during early pregnancy and fat-soluble vitamins taken anytime may result in adverse outcomes. Inadequate folate status is associated with neural tube defect and some cancers. Folate and vitamins B(6) and B(12) are required for homocysteine metabolism and are associated with coronary heart disease risk. Vitamin E and lycopene may decrease the risk of prostate cancer. Vitamin D is associated with decreased occurrence of fractures when taken with calcium. Conclusions Some groups of patients are at higher risk for vitamin deficiency and suboptimal vitamin status. Many physicians may be unaware of common food sources of vitamins or unsure which vitamins they should recommend for their patients. Vitamin excess is possible with supplementation, particularly for fat-soluble vitamins. Inadequate intake of several vitamins has been linked to chronic diseases, including coronary heart disease, cancer, and osteoporosis

Factors Associated with Oxidative Stress in Human Populations

Abstract: Oxidation of biomolecules may play a role in susceptibility to a number of diseases. However, there are few large-scale survey data describing oxidative damage that occurs in humans and the demographic, physical, or nutritional factors that may be associated with it. Such information is essential for the design and analysis of studies investigating the role of oxidative stress in health and disease. This paper presents data on levels of two biomarkers of lipid peroxidation, malondialdehyde and F(2)-isoprostanes, in 298 healthy adults aged 19-78 years. The study was conducted in Berkeley and Oakland, California, in 1998-1999. Sex was the strongest predictor of lipid peroxidation as measured by both biomarkers (p < 0.0001); it was stronger than smoking. C-reactive protein was positively associated with lipid peroxidation (p = 0.004), as was plasma cholesterol. Plasma ascorbic acid had a strong inverse relation (p < 0.001) with both biomarkers. Plasma beta-carotene was also associated with F(2)-isoprostanes. Other plasma antioxidants were not associated with lipid peroxidation biomarkers, once ascorbic acid was included in the multivariate model. Future surveys and epidemiologic studies should measure at least one marker of oxidative damage, as well as plasma ascorbic acid. These data would permit a better understanding of the role that oxidants and antioxidants play in the health of human populations.

Potential applications of laccase in the food industry

Abstract: Laccase is a widely studied enzyme because of its potential use in several areas such as textile, paper and pulp industries. This review presents the potential application of this enzyme in the food industry. Laccase can be used in bioremediation, beverage (wine, fruit juice and beer) processing, ascorbic acid determination, sugar beet pectin gelation, baking, and as biosensor and to improve food sensory parameters. Laccase could increase productivity, efficiency and quality of food products without a costly investment and has the advantage of being a mild technology.

Changes in oxidative processes and components of the antioxidant system during tomato fruit ripening.

Abstract: Analysis of the oxidative processes taking place during fruit ripening in a salad tomato variety (Lycopersicon esculentum Mill. cv. Ailsa Craig) revealed changes in oxidative and antioxidative parameters. Hydrogen peroxide content, lipid peroxidation and protein oxidation were measured as indices of oxidative processes and all were found to increase at the breaker stage. The levels of the aqueous-phase antioxidants, glutathione and ascorbate, increased during the ripening process and these increases were associated with significant changes in their redox status, becoming more reduced as ripening progressed. Changes in the activities of superoxide dismutase, catalase and the enzymes involved in the ascorbate-glutathione cycle during ripening indicated that the antioxidative system plays a fundamental role in the ripening of tomato fruits.

Does Anticipation of Pain Affect Cortical Nociceptive Systems

Abstract: Anticipation of pain is a complex state that may influence the perception of subsequent noxious stimuli. We used functional magnetic resonance imaging (fMRI) to study changes of activity of cortical nociceptive networks in healthy volunteers while they expected the somatosensory stimulation of one foot, which might be painful (subcutaneous injection of ascorbic acid) or not. Subjects had no previous experience of the noxious stimulus. Mean fMRI signal intensity increased over baseline values during anticipation and during actual stimulation in the putative foot representation area of the contralateral primary somatosensory cortex (SI). Mean fMRI signals decreased during anticipation in other portions of the contralateral and ipsilateral SI, as well as in the anteroventral cingulate cortex. The activity of cortical clusters whose signal time courses showed positive or negative correlations with the individual psychophysical pain intensity curve was also significantly affected during the waiting period. Positively correlated clusters were found in the contralateral SI and bilaterally in the anterior cingulate, anterior insula, and medial prefrontal cortex. Negatively correlated clusters were found in the anteroventral cingulate bilaterally. In all of these areas, changes during anticipation were of the same sign as those observed during pain but less intense ( approximately 30-40% as large as peak changes during actual noxious stimulation). These results provide evidence for top-down mechanisms, triggered by anticipation, modulating cortical systems involved in sensory and affective components of pain even in the absence of actual noxious input and suggest that the activity of cortical nociceptive networks may be directly influenced by cognitive factors.

Nutrients and their role in host resistance to infection.

Abstract: Almost all nutrients in the diet play a crucial role in maintaining an "optimal" immune response, such that deficient and excessive intakes can have negative consequences on immune status and susceptibility to a variety of pathogens. Iron and vitamin A deficiencies and protein-energy malnutrition are highly prevalent worldwide and are important to the public health in terms of immunocompetence. There are also nutrients (i.e., glutamine, arginine, fatty acids, vitamin E) that provide additional benefits to immunocompromised persons or patients who suffer from various infections. The remarkable advances in immunology of recent decades have provided insights into the mechanisms responsible for the effects of various nutrients in the diet on specific functions in immune cells. In this review, we will present evidence and proposed mechanisms for the importance of a small group of nutrients that have been demonstrated to affect host resistance to infection will be presented. An inadequate status of some of these nutrients occurs in many populations in the world (i.e., vitamin A, iron, and zinc) where infectious disease is a major health concern. We will also review nutrients that may specifically modulate host defense to infectious pathogens (long-chain polyunsaturated n-3 fatty acids, vitamin E, vitamin C, selenium, and nucleotides). A detailed review of the effect of long-chain polyunsaturated n-3 fatty acids on host defense is provided as an example of how the disciplines of nutrition and immunology have been combined to identify key mechanisms and propose nutrient-directed management of immune-related syndromes.

Carbon nanotube-modified electrodes for the simultaneous determination of dopamine and ascorbic acid.

Abstract: The voltammetric separation of dopamine and ascorbic acid was studied with cyclic voltammetry at two kinds of carbon nanotube-modified electrodes (coated and intercalated) The anodic peak difference reached 270 mV under the present conditions The separation mechanism and effect factors were carefully studied Using various types of surfactants as coating dispersants of carbon nanotubes, it was demonstrated that the charge nature of the surfactants had a strong effect on the electrochemical behavior of dopamine and ascorbic acid When the oxidation solution of carbon nanotubes was changed from the most commonly used mixed concentrated nitric acid and sulfuric acid (1 + 3 v/v) to dilute nitric acid and to hydrochloric acid, the anodic peak separation value of dopamine and ascorbic acid increased significantly, and it was shown that carboxylic acid groups attached to the carbon nanotubes were an adverse factor for the discrimination of DA from AA These results indicated that the resolution of DA and AA was mainly attributable to the stereo porous interfacial layer formed from aggregated pores and inner cavities of the carbon nanotubes The modified electrodes exhibited an attractive ability to measure DA and AA simultaneously and showed good stability and reproducibility

Fortification: Overcoming Technical and Practical Barriers

Abstract: The main barriers to successful iron fortification are the following: 1) finding an iron compound that is adequately absorbed but causes no sensory changes to the food vehicle; and 2) overcoming the inhibitory effect on iron absorption of dietary components such as phytic acid, phenolic compounds and calcium. These barriers have been successfully overcome with some food vehicles but not with others. Iron-fortified fish sauce, soy sauce, curry powder, sugar, dried milk, infant formula and cereal based complementary foods have been demonstrated to improve iron status in targeted populations. The reasons for this success include the use of soluble iron such as ferrous sulfate, the addition of ascorbic acid as an absorption enhancer or the use of NaFeEDTA to overcome the negative effect of phytic acid. In contrast, at the present time, it is not possible to guarantee a similar successful fortification of cereal flours or salt. There is considerable doubt that the elemental iron powders currently used to fortify cereal flours are adequately absorbed, and there is an urgent need to investigate their potential for improving iron status. Better absorbed alternative compounds for cereal fortification include encapsulated ferrous sulfate and NaFeEDTA, which, unlike ferrous sulfate, do not provoke fat oxidation of cereals during storage. Encapsulated compounds also offer a possibility to fortify low grade salt without causing off-colors or iodine loss. Finally, a new and useful additional approach to ensuring adequate iron absorption from cereal based complementary foods is the complete degradation of phytic acid with added phytases or by activating native cereal phytases.

Real-time quantitative RT-PCR analysis of human bone marrow stromal cells during osteogenic differentiation in vitro.

Abstract: We developed and used real-time RT-PCR assays to investigate how the expression of typical osteoblast-related genes by human bone marrow stromal cells (BMSC) is regulated by (i) the culture time in medium inducing osteogenic differentiation and (ii) the previous expansion in medium enhancing cell osteogenic commitment. BMSC from six healthy donors were expanded in medium without (CTR) or with fibroblast growth factor-2 and dexamethasone (FGF/Dex; these factors are known to increase BMSC osteogenic commitment) and further cultivated for up to 20 days with ascorbic acid, beta-glycerophosphate and dexamethasone (these factors are typically used to induce BMSC osteogenic differentiation). Despite a high variability in the gene expression levels among different individuals, we identified the following statistically significant patterns. The mRNA levels of bone morphogenetic protein-2 (BMP-2), bone sialo protein-II (BSP), osteopontin (OP) and to a lower extent cbfa-1 increased with culture time in osteogenic medium (OM), both in CTR- and FGF/Dex-expanded BMSC, unlike levels of alkaline phosphatase, collagen type I, osteocalcin, and osteonectin. After 20 days culture in OM, BMP-2, BSP, and OP were more expressed in FGF/Dex than in CTR-expanded BMSC (mRNA levels were, respectively, 9.5-, 14.9-, and 5.8-fold higher), unlike all the other investigated genes. Analysis of single-colony-derived strains of BMSC further revealed that after 20 days culture in OM, only a subset of FGF/Dex-expanded clones expressed higher mRNA levels of BMP-2, BSP, and OP than CTR-expanded clones. In conclusion, we provide evidence that mRNA levels of BMP-2, BSP, and OP, quantified using real-time RT-PCR, can be used as markers to monitor the extent of BMSC osteogenic differentiation in vitro; using those markers, we further demonstrated that only a few subpopulations of BMSC display enhanced osteogenic differentiation following FGF/Dex expansion.