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