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Lecture18Antioxidants
Freeradicalsmoleculecontaining?1unpairedelectron(s)highlyreactiveunstablemoleculescanexistindependently
FreeradicalsproducedduringOXIDATIONofasubstrate(eg.CHO)REDUCTIONofO2toH2Oandenergycauseoxidativedamagetovariousbiologicalmaterialsgenerationofreactiveoxygenspeciescausecascadingoxidativetissuedamageeg.tomusclecells,LDLmembranePUFA,arterywalls
ExamplesofFreeRadicalssuperoxideanion?2HydrogenperoxideH2O2hydroxylradicalOH-pollutantseg.cigarettesmoke,smog
AntioxidantsAntioxidantshaveprotectivemodeofactiondonate?1electrons(e-)e-interceptfreeradicalsmopthemup(‘quench’)convertthemintolessreactivemoleculesneutralize/deactivatethefreeradicals?protectothersubstancesfromdamageactas‘bodyguards’
sacrificethemselves
AntioxidantsantioxidantscanbeREACTIVATEDbyreceivingelectron(s)ie.antioxidantsareRECYCLEDmorethan400compoundsdisplayanti-oxidantpotentialVitaminsMineralsPolyphenols(eg.resveratrolinwine)elaborateantioxidantdefencesystems…protectscellsfromfree-radicalattack
Antioxidantdefencesystems1.Endogenousantioxidantdefencesystemsuperoxidedismutasecatalaseglutathioneperoxidase
Antioxidantdefencesystems2.ExogenousAntioxidantsprovidedfromdietaryintakeVitamins(A,CE)seleniumironcopperzincmanganesePolyphenolsactasenzymeCo-factors
FatsolublevitaminantioxidantsVitaminE(4tocopherols)α-tocopherolhighestbiologicalactivityβ-,?-,δ-tocopherollessbiologicallyactivedifferentpositionsofmethyl(CH3)groupspreventsfreeradicalmediatedoxidationofmembranePUFAv.importantforLDLprotectionagainstatheroscleroticplaqueformationv.importantinmusclecellsminimiseoxidativeexercisedamage
Foodsourcesα-TocopherolFatsoilsPalmoilSoybeanoilMargarineNutsAlmondsPeanutsBreadscerealsWheatgermOatwheatbranWholemealflourBrownrice(riceoil)FruitVegSweetpotatoOtherstraceamountMeat,chicken,fishOilyfish
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