FLAVONOID
Flavonoids are a group of multi-ring and
hydroxyl-containing compounds that are widely studied for their nutritional
value and their use in a large variety of cures and preventive measures
(Middleton, 2000). According to their substituents, they are usually
subdivided into Flavans, Anthocyanidins, Flavones, Flavanones and
Chalcones. The flavonoid consumed most in the diet is Quercetin (Hertog, 1993).
The basic structure is comprised of two benzene rings (A and B) linked together
by an heterocyclic (with a double bond) Pyran or Pyrone ring (C), in the
middle. Formed in plants, Flavonoids participate in the light-dependent phase
of photosynthesis during which they catalyze electron transport. They are found
in fruits, vegetables and herbs, and synthesized from the aromatic amino acids Phenylalanine
and Tyrosine, together with acetate units (Middleton, 2000). Flavonoids
are complex and highly evolved molecules with intricate structural variations.
After their uptake dietary, flavonoids circulate the blood stream mainly as
glucuronide complex (Walgren, 2000). It has been also reported that flavonoids
induce insulin secretion on pancreatic islets of Langerhans by an ATP- and
temperature-dependent mechanism (Hii, 1984). Following this observation, it
might be hypothized that Flavonoids could stimulate furtherly production or
release of Dynorphins by the secretory granules in the pancreatic beta-cells.
.
Flavonoids
and Isoflavonoids Classes
|
CLASS
|
FLAVONOIDS
|
SUBSTITUENTS
|
||||||
|
RING A-C
|
RING B
|
|||||||
|
3
|
5
|
7
|
3'
|
4'
|
5'
|
|||
|
FIavan-3-ols
|
(+)-Catechin
|
Catechina
|
OH
|
OH
|
OH
|
OH
|
OH
|
H
|
|
Anthocyanidins
|
Cyanidin
|
Cianidina
|
OH
|
OH
|
OH
|
OH
|
OH
|
H
|
|
Pelargonidin
|
Pelargonidina
|
OH
|
OH
|
OH
|
OH
|
H
|
H
|
|
|
Flavones
|
Apigenin
|
Apigenina
|
H
|
OH
|
OH
|
H
|
OH
|
H
|
|
Diosmin
|
Diosmina
|
H
|
OH
|
Oru
|
OH
|
Ome
|
H
|
|
|
Luteolin
|
Luteolina
|
H
|
OH
|
OH
|
OH
|
OH
|
H
|
|
|
Flavanones
|
Naringenin
|
Naringenina
|
H
|
OH
|
OH
|
H
|
OH
|
H
|
|
Naringin
|
Naringina
|
H
|
OH
|
Oru
|
H
|
OH
|
H
|
|
|
Hesperetin
|
Esperitina
|
H
|
OH
|
OH
|
OH
|
Ome
|
H
|
|
|
Hesperedin
|
Esperidina
|
H
|
OH
|
Oru
|
OH
|
Ome
|
H
|
|
|
Chalcones
|
Phloretin
|
Floretina
|
OH (2) a
|
OH (4)
|
OH (6)
|
H
|
H
|
OH (6')
|
|
Phloridzin
|
Floridzina
|
Ogl (2)
|
H (4)
|
OH (6)
|
H
|
H
|
OH (6')
|
|
|
Flavon-3-ols
|
Quercetin
|
Quercitina
|
OH
|
OH
|
OH
|
OH
|
OH
|
H
|
|
Kaempferol
|
Kaemferolo
|
OH
|
OH
|
OH
|
H
|
OH
|
H
|
|
|
Myricetin
|
Miricetina
|
OH
|
OH
|
OH
|
OH
|
OH
|
OH
|
|
|
Fisetin
|
Fisetina
|
OH
|
H
|
OH
|
OH
|
OH
|
H
|
|
|
Morin b
|
Morina b
|
OH
|
OH
|
OH
|
H
|
OH
|
H
|
|
|
ISOFLAVONOIDS
|
||||||||
|
Isoflavones
|
Genistein
|
Genisteina
|
H
|
OH
|
OH
|
H
|
OH
|
H
|
|
Daidzein
|
Daidzeina
|
H
|
H
|
OH
|
H
|
OH
|
H
|
|
|
Genistin
|
Genistina
|
OH
|
OH
|
Ogluc
|
H
|
OH
|
H
|
|
·
ru, rutinose.
·
a,
Number in parentheses denotes additional similar substituent at the position
indicated by the number.
·
b, Morin
has one more OH group at position 2'.