Browsing by Subject "ASCORBIC-ACID"

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  • Raudsepp, Piret; Koskar, Julia; Anton, Dea; Meremäe, Kadrin; Kapp, Karmen; Laurson, Peeter; Bleive, Uko; Kaldmäe, Hedi; Roasto, Mati; Püssa, Tõnu (2019)
    BACKGROUND It is important to find plant materials that can inhibit the growth of Listeria monocytogenes and other food-spoiling bacteria both in vitro and in situ. The aim of the study was to compare antibacterial and antioxidative activity of selected plant-ethanol infusions: leaves and berries of blackcurrant (Ribes nigrum L.), berries of chokeberry (Aronia melanocarpa (Michx.) Elliott) and blue honeysuckle (Lonicera caerulea L. var. edulis); petioles and dark and light roots of garden rhubarb (Rheum rhaponticum L.) for potential use in food matrices as antibacterial and antioxidative additives. RESULTS The strongest bacterial growth inhibition was observed in 96% ethanol infusions of the dark roots of rhubarbs. In 96% ethanol, nine out of ten studied plant infusions had antibacterial effect against L. monocytogenes, but in 20% ethanol only the infusions of dark rhubarb roots had a similar effect. Chokeberry and other berries had the highest antioxidative activity, both in 20% and 96% ethanol infusions. CONCLUSION The combination of dark rhubarb roots or petioles and berries of black chokeberry, blackcurrant or some other anthocyanin-rich berries would have potential as both antibacterial and antioxidative additives in food. (c) 2018 Society of Chemical Industry
  • Hemilä, Harri (2005)
    In their paper discussing the assessment of blinding in clinical trials, Bang et al. based their analysis on the premise that "all participants randomly guess their assignment... This is the most ideal scenario in reality". However, this premise makes an implicit assumption that the drug does not differ from placebo in any physiological effects that a person could observe subjectively, which is a very strong assumption. If a drug is truly effective, such as penicillin for pneumococcal pneumonia, both the patient and the physician can infer the treatment with high certainty by subjective observations. Thus, when the drug is truly effective, we are expecting "breaking of blindness".
  • Hemilä, Harri (2008)
    In their paper discussing the importance of double-blinding in controlled trials, Furberg and Soliman stated that one of the established and fundamental principles for avoiding the problem of bias is to keep the study participants and the investigators blinded, or masked, to the identity of the assigned interventions. As a support to this argument they described the subgroup findings of Karlowski et al.s trial, which examined the effect of vitamin C supplementation on the commoncold[2,3]. Furberg and Soliman put a great weight on the importance of double-blinding, yet they are lax on other fundamental principles of controlled trial.
  • Hemilä, Harri; Chalker, Elizabeth (2021)
    A Commentary on: The Long History of Vitamin C: From Prevention of the Common Cold to Potential Aid in the Treatment of COVID-19. A review of the effects of vitamin C on the immune system and respiratory tract infections was recently published (1). We are the authors of a review of vitamin C and the common cold (2), which was cited in the article. We consider that some of the authors’ statements are inaccurate and here we describe the issues on which we disagree.
  • Rahkila, Jani; Ekholm, Filip S.; Leino, Reko (2018)
    Biomass derived oligo- and polysaccharides are important compounds for various applications, including biomedicine and material science. Their use, however, is often limited by inherent structural inhomogeneity of the starting materials. Here, a method for depolymerization of naturally occurring polysaccharides, including dextran, starch, xylan and galactoglucomannan, into well-defined fragments of narrow polydispersities is described, based on the use of in situ generated Cu-I species under the commonly employed CuAAC reaction conditions. The main strength of the reported method is its high versatility, both in terms of substrate scope and operational simplicity.
  • Mäkelä, Noora; Maina, Ndegwa H.; Vikgren, Päivi; Sontag-Strohm, Tuula (2017)
    Viscosity of cereal beta-glucan during digestion is considered to be a vital factor for its health effects. Thus, studies on solution properties and gelation are essential for understanding the mechanisms of the beta-glucan functionality. The aim of this study was to investigate the effect of the dissolution temperature on gelation of cereal beta-glucan at low concentrations that are relevant for food products. The rheological properties of oat and barley beta-glucans (OBG and BBG) using three dissolution temperatures (37 degrees C, 57 degrees C and 85 degrees C) at low concentration (1.5% and 1%, respectively) were studied for 7 days. Additionally, the beta-glucans were oxidised with 70 mM H2O2 and 1 mM FeSO4 x 7H(2)O as a catalyst, to evaluate the consequence of oxidative degradation on the gelation properties. The study showed that dissolution at 85 degrees C did not result in gelation. The optimal dissolution temperature for gelation of OBG was 37 degrees C and for gelation of BBG 57 degrees C. At these temperatures, also the oxidised OBG and BBG gelled, although the gel strength was somewhat lower than in the non-oxidised ones. Gelation was suggested to require partial dissolution of beta-glucan, which depended on the molar mass and aggregation state of the beta-glucan molecule. Therefore, the state of beta-glucan in solution and its thermal treatment history may affect its technological and physiological functionality. (C) 2017 Elsevier Ltd. All rights reserved.
  • Hemilä, Harri (2011)
    Lykkesfeldt and Poulsen's review has a promising title, and in the introductory paragraph, they state that ‘over the years, it has been suggested that vitamin C be used as a remedy against many diseases as different as common colds and cancers’(1). Given their title and introduction, one would expect a discussion about randomised controlled trials (RCT) on vitamin C and the common cold. However, this topic is ignored in their review. This is an unfortunate omission because the common cold studies give interesting information on the issues that Lykkesfeldt and Poulsen discuss.
  • Mäkelä, Noora; Sontag-Strohm, Tuula; Schiehser, Sonja; Potthast, Antje; Maaheimo, Hannu; Maina, Ndegwa H. (2017)
    Oxidation of cereal beta-glucans may affect their stability in food products. Generally, polysaccharides oxidise via different pathways leading to chain cleavage or formation of oxidised groups within the polymer chain. In this study, oxidation pathways of oat and barley beta-glucans were assessed with different concentrations of hydrogen peroxide (H2O2) or ascorbic acid (Asc) with ferrous iron (Fe2+) as a catalyst. Degradation of beta-glucans was evaluated using high performance size exclusion chromatography and formation of carbonyl groups using carbazole-9-carbonyloxyamine labelling. Furthermore, oxidative degradation of glucosyl residues was studied. Based on the results, the oxidation with Asc mainly resulted in glycosidic bond cleavage. With H2O2, both glycosidic bond cleavage and formation of carbonyl groups within the beta-glucan chain was found. Moreover, H2O2 oxidation led to production of formic acid, which was proposed to result from Ruff degradation where oxidised glucose (gluconic acid) is decarboxylated to form arabinose. (C) 2016 Elsevier Ltd. All rights reserved.
  • Marciani, L.; Garsed, K. C.; Hoad, C. L.; Fields, A.; Fordham, I.; Pritchard, S. E.; Placidi, E.; Murray, K.; Chaddock, G.; Costigan, C.; Lam, C.; Jalanka-Tuovinen, J.; De Vos, W. M.; Gowland, P. A.; Spiller, R. C. (2014)
  • Hemila, Harri (2014)
    Physical activity increases oxidative stress and therefore the antioxidant effects of vitamin C administration might become evident in people undertaking vigorous exercise. Vitamin C is involved in the metabolism of histamine, prostaglandins, and cysteinyl leukotrienes, all of which appear to be mediators in the pathogenesis of exercise-induced bronchoconstriction (EIB). Three studies assessing the effect of vitamin C on patients with EIB were subjected to a meta-analysis and revealed that vitamin C reduced postexercise FEV1 decline by 48% (95% CI: 33% to 64%). The correlation between postexercise FEV1 decline and respiratory symptoms associated with exercise is poor, yet symptoms are the most relevant to patients. Five other studies examined subjects who were under short-term, heavy physical stress and revealed that vitamin C reduced the incidence of respiratory symptoms by 52% (95% CI: 36% to 65%). Another trial reported that vitamin C halved the duration of the respiratory symptoms in male adolescent competitive swimmers. Although FEV1 is the standard outcome for assessing EIB, other outcomes may provide additional information. In particular, the mean postexercise decline of FEF50 is twice the decline of FEV1. Schachter and Schlesinger (1982) reported the effect of vitamin C on exercise-induced FEF60 levels in 12 patients suffering from EIB and their data are analyzed in this paper. The postexercise FEF60 decline was greater than 60% for five participants and such a dramatic decline indicates that the absolute postexercise FEF60 level becomes an important outcome in its own right. Vitamin C increased postexercise FEF60 levels by 50% to 150% in those five participants, but had no significant effect in the other seven participants. Thus, future research on the effects of vitamin C on EIB should not be restricted to measuring only FEV1. Vitamin C is inexpensive and safe, and further study on those people who have EIB or respiratory symptoms associated with exercise is warranted.
  • Mäkelä, Noora; Brinck, Outi; Sontag-Strohm, Tuula (2020)
    The physiological functionality of cereal beta-glucan (beta-glucan) has been mainly attributed to its ability to form viscous solutions in the gastrointestinal (GI) tract. The viscosity is dependent on the concentration, extractability and molecular weight of beta-glucan, and to enable maximal functionality, these factors should therefore be acknowledged and their role in the physiological functionality of cereal beta-glucan further studied. An in vitro GI simulation with separate oral, gastric and small intestine phases was used to model the state of beta-glucan from various oat products in the GI tract. A rather large variation (from 26% to 99%) was observed in the extractabilities between product categories, with the highest extractabilities observed in spoonable products. The viscosities also varied highly within categories. When the comparison was done at similar concentration levels, the highest viscosities were observed in the products produced through dry processes, and moisture content during processing was suggested to be essential to the extent of beta-glucan degradation. The viscosity in samples that were likely to exhibit enzymatic activity was shown to be rather low, and thus the physiological functionality of beta-glucan may be threatened if the product also contains grain ingredients other than kiln-dried oat. Clear differences were observed in the functionality of beta-glucan in the GI tract model depending on a product type, and these were explained by differences in ingredients and processes. However, further studies are needed to specify the influence of each factor and to clarify the factors determining the physiological functionality of beta-glucan in food products.
  • Hemilä, Harri; Douglas, R M (1999)
  • Hemila, Harri (2014)
  • Hemila, Harri; de Man, Angelique M. E. (2021)
    In numerous animal studies, vitamin C has prevented and alleviated viral and bacterial infections. In a few dozen placebo-controlled trials with humans, vitamin C has shortened infections caused by respiratory viruses, which indicates that the vitamin can also influence viral infections in humans. In critically ill patients, plasma vitamin C levels are commonly very low. Gram doses of vitamin C are needed to increase the plasma vitamin C levels of critically ill patients to the levels of ordinary healthy people. A meta-analysis of 12 trials with 1,766 patients calculated that vitamin C reduced the length of ICU stay on average by 8%. Another meta-analysis found that vitamin C shortened the duration of mechanical ventilation in ICU patients. Two randomized placebo-controlled trials found statistically significant reduction in the mortality of sepsis patients. The effects of vitamin C on acute respiratory distress syndrome (ARDS) frequently complicating COVID-19 pneumonia should be considered. Vitamin C is a safe and inexpensive essential nutrient.
  • Hemilä, Harri (2003)
  • Hemilä, Harri (1992)
    The effect of vitamin C on the common cold has been the subject of several studies. These studies do not support a considerable decrease in the incidence of the common cold with supplemental vitamin C. However, vitamin C has consistently decreased the duration of cold episodes and the severity of symptoms. The benefits that have been observed in different studies show a large variation and, therefore, the clinical significance may not be clearly inferred from them. The biochemical explanation for the benefits may be based on the antioxidant property of vitamin C. In an infection, phagocytic leucocytes become activated and they produce oxidizing compounds which are released from the cell. By reacting with these oxidants, vitamin C may decrease the inflammatory effects caused by them. Scurvy, which is caused by a deficiency in vitamin C, is mostly attributed to the decreased synthesis of collagen. However, vitamin C also participates in several other reactions, such as the destruction of oxidizing substances. The common cold studies indicate that the amounts of vitamin C which safely protect from scurvy may still be too low to provide an efficient rate for other reactions, possibly antioxidant in nature, in infected people.
  • Hemilä, Harri; Herman, Zelek S (American College of Nutrition, 1995)
    In 1975 Thomas Chalmers analyzed the possible effect of vitamin C on the common cold by calculating the average difference in the duration of cold episodes in vitamin C and control groups in seven placebo-controlled studies. He found that episodes were 0.11 +/- 0.24 (SE) days shorter in the vitamin C groups and concluded that there was no valid evidence to indicate that vitamin C is beneficial in the treatment of the common cold. Chalmers' review has been extensively cited in scientific articles and monographs. However, other reviewers have concluded that vitamin C significantly alleviates the symptoms of the common cold. A careful analysis of Chalmers' review reveals serious shortcomings. For example, Chalmers did not consider the amount of vitamin C used in the studies and included in his meta-analysis was a study in which only 0.025-0.05 g/day of vitamin C was administered to the test subjects. For some studies Chalmers used values that are inconsistent with the original published results. Using data from the same studies, we calculated that vitamin C (1-6 g/day) decreased the duration of the cold episodes by 0.93 +/- 0.22 (SE) days; the relative decrease in the episode duration was 21%. The current notion that vitamin C has no effect on the common cold seems to be based in large part on a faulty review written two decades ago.