Phenolic Compounds - Natural Products Chemistry: Sources, Separations, and Structures - page 60

5.127

9.260

0.0600

Peak Results

Ret Time
(min)

# Name

0.0400

10.543

1
2
3

5.127
9.260
10.543

Quercetin
Kaempferol
Isorhamnetin

0.0200

0.0000

FIGURE 6.5 HPLC analysis of flavonoid glycosides in a Ginkgo biloba extract.

R 3'

3'

R 4'

4'

2'

1

8

1'

O +

R 7

7

5'

R 5'

2
3

6'

6

R 3

R 6

5

4

R 5

FIGURE 6.6 Chemical structure of an anthocyanin.

There have been many preclinical research and clinical studies conducted on
ginkgo extracts that contain both the flavone glycosides and ginkgolides. The studies
have generated somewhat conflicting results. It is believed that the ginkgo extracts
may improve blood flow including microcirculation in small capillaries and offer
protection against oxidative cell damage from free radicals.

6.5 ANTHOCYANINS
Anthocyanins (Figure 6.6) are found in flowers and are responsible for various red,
pink, blue, and purple colors. Nature may have designed these molecules to attract
animal pollinators and seed dispersers.

6.6 TANNINS
Tannin is the general name given to a large group of complex phenolic substances.
The name comes from the leather industry of “tanning” animal hides into leather.
Tannins are found in almost every plant part and are particularly abundant in unripe
fruit. It is thought they deter herbivores due to their astringent properties and pos-
sess antimicrobial activity. A representative structure of tannic acid is shown in
Figure 6.7.