FLAVONOIDS

Plant Pigments

PLANT PIGMENTS

Flavonoids and anthocyanins are conspicuous plant pigments in nature thatare responsible for the beauty and splendor of flowers, fruits, fruit tree blossoms and of the autumn leaves.

Flavones are responsible for the yellow and orange colors; and the anthocyaninsare the source of red, violet and blue colors. These compounds occur mainly inhigher plants and are less common in the lower orders. You don’t find them inalgae, fungi or bacteria.

The flavonoids play a major role in attracting insects to feed and pollinate theseplants. Some of them also have a bitter taste and repel harmful insects like caterpillars.

Flavonoids are thought to be antioxidants, and play a major role in our diet, preventing the ravages of aging caused by free-radicals.

These compound have their biosynthetic origin in both the skimic acid pathwayand the acetogenin pathway - they are of hybrid origin.

NARINGENIN

O

CoAS

OH

malonyl-CoA3x

OH

SCoA

OO

O

O

OH

OH O

OH

O

:

OH

OH O

OH

O

H

naringenin

A FLAVONE

internal Claisenand enolizations

A different starterthan acetyl-CoA.

acetogeninpathway

shikimic acidpathway

MIXED-ORIGINCOMPOUND

found in grapefruit

Michaeladdition

flavones are yellowor orange pigments

AnthocyaninFlower Pigments

Anthocyanin Leaf PigmentsAutumn Leaves

In Spring and Summerchlorophyll (green) masksthe anthocyanin colors.

OH

OH O

OH

O

R

naringenin (R=H)

OH

OH O

OH

O

OH

R

OH

OH O

OH

OH

OH

R

NADPH

[O]

OH

OH O

OH

OH

OH

R

OH

OH

OH O

OH

OH

R

+

- 2 H2O

O2

pelargonidin (R=H)cyanidin (R=OH)

ANTHOCYANIDINS AND ANTHOCYANINS

plant flower andleaf pigmentsANTHOCYANIDINS

cyanidin is bluepelargonidin is pink

Anthocyanins arered, violet or bluepigments.