210 likes | 214 Vues
Vitamin E is lipophilic in character and is found in association with lipoproteins, fat deposits and cellular membranes. Che m ic a l n a tu r e:. Vitamin E is chemically known as tocopherol (Greek: tocos= childbirth , piro= to bear and ol= alcohol ) An alcohol was capable to prevent
E N D
VitaminEislipophilicincharacterandisfoundinassociationwithlipoproteins,fatdepositsandcellularmembranesVitaminEislipophilicincharacterandisfoundinassociationwithlipoproteins,fatdepositsandcellularmembranes
Chemicalnature: • VitaminEischemicallyknownastocopherol(Greek:tocos=childbirth,piro=tobearandol=alcohol) • Analcoholwascapabletoprevent • reproductivefailureinanimals • Henceitisknownasanti-sterilityvitamin • Chemistry: • VitaminEisthenamegiventogroupoftocopherolsandtocotrienols
About8tocopherolshavebeenidentified • Alpha-tocopherolismostactive • Thetocopherolsarederivativesof6-hydroxychromane(tocol)ringwithisoprenoidsidechain • Theantioxidantpropertyisduetothechromanering • Therearefourmainformsoftocopherols • Theyare
α -tocopherol:5,7,8trimethyltocol • β -tocopherol:5,8dimethyltocol • γ -tocopherol:7,8dimethyltocol • δ -tocopherol:8methyltocopherol • α –tocopherolismostactiveandpredominantformofvitaminE • Tocotrienols:TherearefourrelatedvitaminE • compoundscalled α,β,γ and δ tocotrienols
CH3 CH3CH3 CH • 3 • CH2-(CH2-CH2-CH-CH2)3-H • OH • CH3 • α-Tocopherol(5,7,8-trimethyltocol)
CH3 CH3CH3 CH2-(CH2-CH2-CH-CH2)3-H OH CH3 β-Tocopherol(5,8-dimethyltocol CH3 CH3CH3 CH2-(CH2-CH2-CH-CH2)3-H CH 3 OH γ-Tocopherol(7,8-dimethyltocol)
ABSORPTION • VitaminEisabsorbedalongwithfatinthe • uppersmallintestine • Mechanism:VitaminEcombineswithBilesalts(micelles)toformmixedmicelleandtakenupbythemucosalcell • Inthemucosalcell,itisincorporatedinto • chylomicrons
DietaryvitaminEisincorporatedtochylomicrons • Inthecirculation,chylomicronstransportvitaminEtotheperipheraltissueortotheliver • HepaticvitaminEisincorporatedtoVLDL • Inthecirculation,VLDLisconvertedLDL • VitaminEistransportedwithLDLtoreachtheperipheraltissuesincludingadiposetissue
Storage: • Mainlystoredinliverandadiposetissue • Presentinbiologicalmembranes,becauseofitsaffinitytophospholipids
MostofthefunctionsofthevitaminEare • relatedtoitsantioxidantproperty • Itpreventsthenon-enzymaticoxidationsofvariouscellcomponentsbymolecularoxygenandfreeradicalssuchassuperoxideandhydrogenperoxide(H2O2) • Seleniumhelpsinthesefunctions • ItprotectsthePUFAfromperoxidationreactions
VitaminEisessentialformembranestructureandintegrityofthecell,henceitismembraneantioxidant.VitaminEisessentialformembranestructureandintegrityofthecell,henceitismembraneantioxidant. Itpreventstheper oxidationofPUFA ItprotectstheRBCfromhemolysisby oxidizingagents(H2O2) Itisassociatedwithreproductivefunctionandpreventssterility
VitaminEpreservesandmaintainsgerminalepitheliumofgonadsforproperreproductivefunctionVitaminEpreservesandmaintainsgerminalepitheliumofgonadsforproperreproductivefunction Itincreasesthesynthesisofhemebyenhancingtheactivityofenzyme– δ aminolevulinicacid(ALA)synthaseandALAdehydratase Itisrequiredforcellularrespiration–through ETC(StabilizecoenzymeQ) VitaminEpreventstheoxidationofVitaminAandcarotenes
Itisrequiredforproperstorageofcreatineinskeletalmuscle Itisrequiredforabsorptionofaminoacids fromintestine Itisinvolvedinsynthesisofnucleicacids Itprotectstheliverfromtoxiccompounds suchascarbon tetra chloride. 13.ItworksinassociationwithvitaminA,Cand beta-carotene,todelaytheonsetofcataract
14.VitaminEisrecommendedforthe • preventionofchronicdiseasessuchascancer • andheartdisease • VitaminEpreventsoxidationofLDL • OxidizedLDLpromotesheartdiseases • Selinium:Itisacomponentofglutathioneperoxidaseandfunctionasantioxidant • ItreducestherequirementofvitaminEindiet • ItisrequiredfornormalpancreaticfunctionandenhancingtheabsorptionofvitaminE
-10mg/day • 8mg/day • 10mg/day • 12mg/day • Males • Females • Pregnancy • Lactation • 15mgofvitaminEisequivalentto33IU • Pharmacologicaldoseis200-400IU/day • Sources: • Richsourcesarevegetableoils • Includesgermoil,sunfloweroil,cornoilandmargarine
Inhumans,deficiencyofvitaminEisseenin • Prematureinfants: • TransferofvitaminEfrommaternalbloodoccursduringlastfewweeksofpregnancy • PrematureinfantswillhavevitaminEdeficiency • Impairedabsorption:Seeninconditionssuchas • abetalipoproteinemia(fatmalabsorption) • Obstructivejaundice • Intestinaldiseasessuchasceliacspure DEFICIENCY
GeneticvitaminEdeficiency:ItiscausedbylackofaproteinthatnormallytransportsGeneticvitaminEdeficiency:Itiscausedbylackofaproteinthatnormallytransports • α-tocopherolfromhepatocytestoVLDL • Clinicalfeatures: • Hemolyticanemiaormacrocyticanemiaseen • inprematureinfants • Inadults,increasedsusceptibilityofRBCs to hemolysisunderoxidativestress. • Muscleweaknessandproteinuriaisseen
Musculardystrophy • VitaminEdeficiencyleadstoincreasedoxidationofPUFA,withconsumptionofoxygenandproductionofperoxides • Peroxidesincreasetheintracellularhydrolase • activity, which catalyzebreakdownsinmuscleandproducemusculardystrophy • Themusclecreatineislowandcreatinuriaoccurs
Hepaticnecrosis • VitaminEandseleniumpreventshepaticnecrosis • Cerebellarataxiaandimpairedvision: • Chronicdeficiencyinchildrenisassociatedwithataxia,weakness,lossoftouchandpositionsenses,impairedvisionandretinopathy • Increasedlipidperoxidationinnervoustissuecausesneurologicallesions
OxidationofPUFAinrodsleadstooxidativedamageinretina • Deficiencyinanimals: • Musculardystrophyandreproductivefailure • VitaminEisleasttoxic