Pro-oxidant activity of vitamin C in drinking water ... - Ãbo Akademi

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ConclusionsCONCLUSIONSThe main focus of this thesis was to study the pro-oxidant effect of vitamin C (ascorbicacid) in metal contaminated drinking water. The main findings of this study are:1. Bicarbonate and pH regulate the pro-oxidant activity of ascorbic acid in drinkingwater contaminated with trace amounts of copper. Ascorbic acid will induce hydroxylradicals in copper-contaminated drinking water buffered with high amounts of bicarbonate(II), and hydrogen peroxide in weakly bicarbonate-buffered drinking water (IV). Of theother metals tested (iron, manganese, cadmium, nickel, cobalt, aluminium, magnesium,calcium or zinc), none could significantly support ascorbic acid induced hydroxyl radicalsor hydrogen peroxide formation in drinking water (IV, V).Ascorbic acid and copper induced hydroxyl radical formation and hydrogen peroxideaccumulation could be important modulators of various molecules. The pro-oxidantactivity of vitamin C in the presence of copper ions as observed in the bicarbonatebuffereddrinking water might be linked to the reported occurrence of benzene inbeverages supplemented with vitamin C and benzoic acid. 202 Furthermore, the vitaminC/Cu 2+ -induced hydrogen peroxide formation during acidic conditions, as demonstrated inpoorly buffered drinking water, could be of importance in host defence against bacterialinfections. On the other hand, excessive production of hydrogen peroxide could induceincreased oxidative stress on tissues, or alternatively be involved in cell activation.2. Iron displays an inhibitory effect on the ascorbic acid/copper induced hydroxylradical formation, as well as on hydrogen peroxide accumulation in drinking water (IV, V).Paper V demonstrates that ascorbic acid-derived oxalic acid is necessary for the inhibitoryeffect of iron on ascorbic acid/Cu 2+ -induced hydrogen peroxide accumulation.Bicarbonate and iron might function as important regulators of copper/reductant-inducedhydroxyl radical/hydrogen peroxide formation and copper mediated tissue damage. Theiron/oxalic acid induced inhibition of hydrogen peroxide formation as demonstrated herein drinking water might also be linked to the protective effect of iron against ascorbic acid(vitamin C) and copper-induced cell toxicity in cell cultures. Our results in paper IV and Valso indicate that complete removal of iron from the raw water of the water plants can tosome extent increase the redox activity of copper, and the formation of ROS in drinkingwater.47
Conclusions3. Significant amounts of ascorbic acid are rapidly oxidized into DHA when added to astrongly bicarbonate-buffered copper-contaminated drinking water (III). The results alsodemonstrate that DHA is further decomposed into oxalic- and threonic acid inbicarbonate-buffered copper-contaminated drinking water. Thus, copper-contaminateddrinking water could possibly deplete vitamin C and hence interfere with vitamin C uptakefrom the stomach and intestine, leading to vitamin C deficiencies. Furthermore, peopleconsuming this type of water will most likely ingest, or generate more DHA in theirstomachs than people using bottled water. The impact of long-term intake of DHA andoxalic acid obtained from vitamin C supplemented copper-contaminated drinking water isnot known.48
Page 1 and 2:
Pro-oxidant activity of vitamin C i
Page 3 and 4: Supervised byDocent Tommy Nordströ
Page 5 and 6: ContentsCONTENTSLIST OF ORIGINAL PU
Page 8 and 9: List of original publicationsLIST O
Page 10 and 11: AcknowledgementsACKNOWLEDGEMENTSThi
Page 12 and 13: AbbreviationsABBREVIATIONSAsc …
Page 14 and 15: Review of the literatureREVIEW OF T
Page 16 and 17: Review of the literatureSince vitam
Page 18 and 19: Review of the literaturestill added
Page 20 and 21: Review of the literatureantioxidant
Page 22 and 23: Review of the literatureThe α-toco
Page 24 and 25: Review of the literatureCopper, wil
Page 26 and 27: Review of the literatureOH • + H
Page 28 and 29: Review of the literatureFormation o
Page 30 and 31: Review of the literature3.2. The ro
Page 32 and 33: Review of the literaturecopper conc
Page 34 and 35: Experimental proceduresEXPERIMENTAL
Page 36 and 37: Experimental procedures2.2. Measure
Page 38 and 39: Experimental procedurestetrahydrate
Page 40 and 41: ResultsRESULTS1. Vitamin C induces
Page 42 and 43: Results3. Oxidative decomposition o
Page 44 and 45: Resultsdifferent water samples vari
Page 46 and 47: DiscussionDISCUSSIONNowadays, ascor
Page 48 and 49: DiscussionCu 2+ + Asc → Cu + + As
Page 50 and 51: Discussion3. Iron inhibits vitamin
Page 52 and 53: Discussionperoxide might have an im
Page 56 and 57: ReferencesREFERENCES1. Arrigoni O,
Page 58 and 59: References34. Padayatty SJ, Katz A,
Page 60 and 61: References66. Sies H, Stahl W, Sund
Page 62 and 63: References95. Halliwell B. Role of
Page 64 and 65: References127. Park S, Han SS, Park
Page 66 and 67: References157. Critchley MM, Cromar
Page 68 and 69: References185. Liao CH, Kang SF, Wu
Page 70 and 71: References214. Orr CW. Studies on a
Page 72: References243. Miller C, Kennington
Page 88 and 89: Free Radical Research, Volume 38 Nu
Page 90 and 91: VITAMIN C OXIDATION IN DRINKING WAT
Page 92 and 93: VITAMIN C OXIDATION IN DRINKING WAT
Page 94 and 95: Free Radical Research, May 2005; 39
Page 96 and 97: Iron inhibits Vitamin C/copper-indu
Page 98 and 99: Iron inhibits Vitamin C/copper-indu
Page 100 and 101: Free Radical Research, November 200
Page 102 and 103: Hydrogen peroxide formation in drin
Page 104 and 105:
Hydrogen peroxide formation in drin
Page 106 and 107:
Hydrogen peroxide formation in drin
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