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Antioxidants in OatsAntioxidants in Oats

Lena Dimberg and Rita Redaelli

OutlineOutlineWhy antioxidants?

Antioxidants in oats

Tocopherols /tocotrienols/avenanthramides

• Bioactivities• Effects of processing• Effects of cultivation measures

Concluding remarks

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

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

AntioxidantsAntioxidants

Ascorbic acid (Vitamin C)

Carotenoids (Vitamin A precursors)

Tocopherols/tocotrienols (Vitamin E)

Phenols

Color

Flavor and aroma

Texture

Keeping qualities

Pharmacological effects

Phenols in FoodsPhenols in Foods

Tocopherols/ tocotrienolsTocopherols/ tocotrienols

tocopherols

tocotrienols

Isomers R' R''

α CH3 CH3

β CH3 H

γ H CH3

δ H H

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

Preventive of foetuses' death

Membrane stabilizer

Tocopherols/tocotrienolsTocopherols/tocotrienols-bioactivities--bioactivities-

Antioxidantsstructure-activity relationship

Tocopherols- in germTocotrienols – in endosperm

Genetic variability

Tocotrienols are positively related to

the oil content

Tocopherols/tocotrienolsTocopherols/tocotrienols

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

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

Phytoalexin/Antifungal

AntioxidativeStructure- activity relationship

Anti-atheroscleroticAnti-inflammatory

AvenanthramidesAvenanthramides-bioactivities-bioactivities

Cooling sensation

Tranilast look alike

Mainly bran constituents

Not related to the oil content

AvenanthramidesAvenanthramides

Unique to oats

Tranilast MetabolitesTranilast Metabolites

Oat avenanthramide

Tranilast

Supression of vascular stenosis Supression of vascular stenosis by Tranilastby Tranilast

Control TranilastFukuyama et. al. 1996. European Journal of Pharmacology, 318, 327-332

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

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

Nitrogen/Light/Irrigation

Conventional /Organic Farming

Susceptible/ResistanceGenotype/Site/Year

AvenanthramidesAvenanthramides-effects of cultivation measures--effects of cultivation measures-

Developmental stage

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-

Concluding remarksConcluding remarks

Whole grain vs flour

Processing

BioavalabilityGroats Flour