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AVEQAVEQ
WP 8
Antioxidants in OatsAntioxidants in Oats
Lena Dimberg and Rita Redaelli
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OutlineOutlineWhy antioxidants?
Antioxidants in oats
Tocopherols /tocotrienols/avenanthramides
• Bioactivities• Effects of processing• Effects of cultivation measures
Concluding remarks
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OxidationOxidation
Oxidation of lipids generates free radicals
which are very reactive
– may results in reduction of shelf-life of foods
– may cause damage to various body tissues,
and may thereby initiate various diseases
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AntioxidantsAntioxidants
Antioxidants effectively retard the onset of
lipid oxidation with different mechanisms
– may protect food from rancidity
– may protect the body from free radical
damages
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AntioxidantsAntioxidants
Ascorbic acid (Vitamin C)
Carotenoids (Vitamin A precursors)
Tocopherols/tocotrienols (Vitamin E)
Phenols
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Color
Flavor and aroma
Texture
Keeping qualities
Pharmacological effects
Phenols in FoodsPhenols in Foods
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Tocopherols/ tocotrienolsTocopherols/ tocotrienols
tocopherols
tocotrienols
Isomers R' R''
α CH3 CH3
β CH3 H
γ H CH3
δ H H
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0.0475
Volts
0.0225
0.0250
0.0275
0.0300
0.0325
0.0350
0.0375
0.0400
0.0425
0.0450
0.0475
Minutes 0 1 2 3 4 5 6 7 8 9 10 11 12
volt
s
0.0225
0.0250
0.0275
0.0300
0.0325
0.0350
0.0375
0.0400
0.0425
0.0450
αT
αT3
βT
γT
βT3
γT3
δT
δT3
Pisacane et al. 2004
NP-HPLC OF TOCOLSNP-HPLC OF TOCOLS
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Preventive of foetuses' death
Membrane stabilizer
Tocopherols/tocotrienolsTocopherols/tocotrienols-bioactivities--bioactivities-
Antioxidantsstructure-activity relationship
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Tocopherols- in germTocotrienols – in endosperm
Genetic variability
Tocotrienols are positively related to
the oil content
Tocopherols/tocotrienolsTocopherols/tocotrienols
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Range of variation in tocol contentRange of variation in tocol content
Content
(mg/kg)
Cultivar origin Authors
19-30 12 US Peterson & Qureshi, 1993
25-67 25 high-oil lines Peterson & Wood, 1997
14-25 7 Swedish Bryngelsson et al. 2002
21-54 8 Italian Redaelli et al. 2004
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AvenanthramidesAvenanthramides
R
R
NH
O
OH
R
R
COOH
n
R= H, OH or OCHR= H, OH or OCH33
n= 1 or 2n= 1 or 2
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Phytoalexin/Antifungal
AntioxidativeStructure- activity relationship
Anti-atheroscleroticAnti-inflammatory
AvenanthramidesAvenanthramides-bioactivities-bioactivities
Cooling sensation
Tranilast look alike
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Mainly bran constituents
Not related to the oil content
AvenanthramidesAvenanthramides
Unique to oats
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Tranilast MetabolitesTranilast Metabolites
Oat avenanthramide
Tranilast
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Supression of vascular stenosis Supression of vascular stenosis by Tranilastby Tranilast
Control TranilastFukuyama et. al. 1996. European Journal of Pharmacology, 318, 327-332
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Storage stable in whole grains
Increase during germination
Instable in raw oat flour soaked in water
AvenanthramidesAvenanthramides-effects of processing--effects of processing-
Heat stable
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0
2
4
6
8
10
2 4 6 8 10 12 14 16 18 20
Time (min)
Pea
k ar
ea (
AU
)
120 h germination Raw grains
1
2
32c
567 8
2p
2f
1112
13
14=3f
15
16
171819 20
21
Effect of germinationEffect of germination
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Nitrogen/Light/Irrigation
Conventional /Organic Farming
Susceptible/ResistanceGenotype/Site/Year
AvenanthramidesAvenanthramides-effects of cultivation measures--effects of cultivation measures-
Developmental stage
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0
50
100
150
200
250
300
350
400
450
500
Am
ount
s (n
mol
/g)
Different genotypes
Black bars-2000White bars-2001
AvenanthramidesAvenanthramides--the same variety different year-the same variety different year-
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Concluding remarksConcluding remarks
Whole grain vs flour
Processing
BioavalabilityGroats Flour