Biomedical Engineering Reference
In-Depth Information
R
8
R
7
R
1
O
O
R
5
O
R
6
R
2
R
1
R
4
R
3
R
2
Coumarins
Flavonoids
Compound
Functional
Group
Compound
Functional
Group Position
R
3
R
1
R
2
R
1
R
2
R
4
R
5
R
6
R
7
R
8
Umbelliferone
Aesculetin
Scopoletin
OH
OH
OH
H
OH
OCH
H
OH
H
H
H
H
H
H
H
H
H
H
OH
OH
OH
OH
OH
OH
H
H
H
H
H
H
OH
OH
OH
OH
OH
OH
H
OH
OH
H
OH
OCH
3
H
OH
OH
OH
OH
H
H
H
OH
H
H
OCH
3
Kaemferol
Quercetin
Myricetin
Apigenin
Luteolin
Tricin
Isovitexin
3
H
H
OH
GLU
OH
H
OH
H
FIGURE 6.11
Structure of selected coumarins and flavonoids. GLU = glucose.
R
5
R
4
O
R
2
R
3
R
1
Compound
Pelargonidin
Cyanidin
Delphinidin
Peonidin
Petunidin
Malvidin
R
1
R
2
R
3
R
4
R
5
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
H
H
OH
H
OCH
OCH
OH
OH
OH
OH
OH
OH
H
OH
OH
OCH
OH
OCH
3
3
3
3
FIGURE 6.12
Chemical structure of anthocyanidins.
PHENOLIC ACIDS AS ANTIOXIDANTS
As discussed earlier, phenolic compounds have the capacity to function as antioxi-
dants. Consequently, natural antioxidants are primarily plant phenolic compounds
including flavonoids, phenolic acid derivatives, coumarins, tocopherols, and poly-
functional acids.
31
Synthetic antioxidants as well as tocopherols and ascorbic acid
are commercially exploited as antioxidants and will not be discussed further as the
focus of this chapter is on some of the natural phenolics previously reviewed.
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