Flavonoid is any
member of a class of widely distributed biological natural products containing
aromatic heterocyclic skeleton of flavan (2-Phenylbenzopyran) but no nitrogen in
plants. Generally, flavonoids are biological pigments providing colours from red
to blue in flowers, fruit and leaves. Besides their coloring in plants,
flavonoids have important roles in the growth and development of plants;
protection against UV-B radiation; forming antifungal barriers; antimicrobial,
insecticidal and oestrogenic activities; plant reproduction. Flavonoids also
exhibit a wide range of biological properties including anti-microbial,
insecticidal and oestrogenic activities. Flavonoids are usually classified into
main 6 subgroups as below plus flavans, neoflavonoids,
flavonols, aurons, catechins according to the structural
patterns.
- Flavonols
(Hydroxy derivatives of flavone): Fisetin, Galangin,
Kaempferide, Kaempferol, Morin, Myricetin, Myricitrin, Quercetin, Quercetrin,
Rhamnetin, Robinin, Rutin, Spirenoside
- Flavones
(skeleton: 2-phenylchromen-4-one): Apigenin, Baicalein,
Chrysin, Diosmetin, Diosmin, Flavone, Luteolin, Rpoifolin,Tangeretin,
Techtochrysin, Rhamnazin, Nobiletin, Natsudaidain.
- Isoflavones
(skeleton: 3-phenylchromen-4-one): Daidzin, Genistein,
Irilone, Luteone, Prunetin, Pratensein,
- Flavonones
(derivation by reduction of the 2(3) C=C bond): Eriodictyol,
Hesperidin, Hesperetin, Likvirtin, Naringin; Naringenin; Pinocembrin
- Flavanols
(derivation by reduction of the keto group):(+)-Catechin,
(+)-Gallocatechin, (-)-Epicatechin (EC), (-)-Epigallocatechin (EGC),
(-)-Epicatechin 3-gallate (ECG), (-)-Epigallocatechin 3-gallate (EGCG),
Theaflavin, Theaflavin 3-gallate, Theaflavin 3'-gallate, Theaflavin 3,3'
digallate, Thearubigins
- Anthocyanidins (aglycones of the
glycoside anthocyanins): Apigeninidin, Cyanidin, Delphinidin, Diosmetinidin,
Guibourtinidin, Fisetinidin, Luteolinidin, Malvidin, Pelargonidin, Peonidin,
Robinetinidin, Tricetinidin, Capensinidin, Petunidin, Europinidin, Aurentinidin,
Columnidin, 5-Desoxy-malvidin, 5-Desoxy-peonidin, Hirsutinidin,
Rosinidin