Flavonoids Classification

Flavonoids
Flavonoida classifications

1. Presented by : Heera Karemore Assistant Professor

2. ⦿ Flavonoids are the products of secondary metabolism of plants and are the most abundant polyphenols in human diet. ⦿ Flavonoids are also commonly referred to as bioflavonoids . ⦿ The flavonoids possess 15 carbon atoms; two benzene rings joined by a linear three- carbon chain. ⦿ Currently over 4000 have been isolated and identified. In fruits and vegetables, they are usually found in the form of glycosides and sometimes as acylglycosides, while acylated, methylated and sulfate molecules are less frequent and in lower concentrations. ⦿ They are water-soluble and accumulate in cell vacuoles.

3. ⦿ Their basic structure is a skeleton of diphenylpropane , namely, two benzene rings (ring A and B, ) linked by a three carbon chain that forms a closed pyran ring (heterocyclic ring containing oxygen, the C ring) with benzenne A ring. ⦿ Therefore, their structure is also referred to as C6- C3-C6. In most cases, B ring is attached to position 2 of C ring, but it can also bind in position 3 or 4; this, together with the structural features of the ring B and the patterns of glycosylation and hydroxylation of the three rings, makes the flavonoids one of the larger and more diversified groups of phytochemicals.

4. ⦿ According to the IUPAC nomenclature, they can be classified into: ⦿ i. Flav o noid s, de r iv e d f r o m 2 - phenylchromen- 4-one (2-phenyl-l ,4- benzopyrone) structure. ⦿ ii. Iso-flavonoids, derived from 3- phenylchromen- 4-one (3-phenyl-1,4- benzopyrone) structure. ⦿ iii . N e o -flav o noid s , deri v e d f r o m 4 - phenylcoumarine (4-phenyl-1,2- benzopyrone) structure.

5. ⦿ They can be subdivided into different subgroups depending on the carbon of the C ring on which B ring is attached, and the degree of unsaturation and oxidation of the C ring. ⦿ Those in which the B ring is linked in position 2 can be further subdivided into several subgroups on the basis of the structural features of the C ring. These subgroup are: ⦿ flavones, ⦿ flavonols , ⦿ flavanones, ⦿ flavanonols, ⦿ flavanols or catechins or flavans and ⦿ Anthocyanins ⦿ . Flavonoids in which B ring is linked in position 3 of the ring C are called ⦿ isoflavones ; Ex. Genistein, Daidzein , Glycitein ⦿ Those in which B ring is linked in position 4, neoflavonoids , ⦿ Dalbergin, ⦿ Dalbergichromene ⦿ Finally, flavonoids with open C ring are called chalcones.

6. ⦿ Flavonoids (or bioflavonoids ) (from the Latin word flavus meaning yellow, their color in nature) are a class of plant and fungus secondary metabolites . ⦿ Chemically, flavonoids have the general structure of a 15-carbon skeleton, which consists of two phenyl rings (A and B) and heterocyclic ring (C). This carbon structure can be abbreviated C6-C3-C6. According to the IUPAC nomenclature, [1][2] they can be classified into: ⦿ flavonoids or bioflavonoids ⦿ isoflavonoids , derived from 3-phenyl chromen-4-one (3-phenyl-1,4- benzopyrone ) structure ⦿ neoflavonoids , derived from 4-phenyl coumarine (4-phenyl-1,2- benzopyrone ) structure ⦿ The three flavonoid classes above are all ketone -containing compounds, and as such, are anthoxanthins ( flavones and flavonols ). This class was the first to be termed bioflavonoids . The terms flavonoid and bioflavonoid have also been more loosely used to describe non-ketone polyhydroxy polyphenol compounds which are more specifically termed flav a noids. The three cycle or heterocycles in the flavonoid backbone are generally called ring A, B and C. Ring A usually shows a phloroglucinol substitution pattern.

7. ⦿ Flavonoids are widely distributed in plants, fulfilling many functions. Flavonoids are the most important plant pigments for flower coloration, producing yellow or red/blue pigmentation in petals designed to attract pollinator animals. In higher plants, flavonoids are involved in UV filtration, symbiotic nitrogen fixation and floral pigmentation. They may also act as chemical messengers, physiological regulators, and cell cycle inhibitors. Flavonoids secreted by the root of their host plant help Rhizobia in the infection stage of their symbiotic relationship with legumes like peas, beans, clover, and soy. Rhizobia living in soil are able to sense the flavonoids and this triggers the secretion of Nod factors , which in turn are recognized by the host plant and can lead to root hair deformation and several cellular responses such as ion fluxes and the formation of a root nodule . In addition, some flavonoids have inhibitory activity against organisms that cause plant diseases, e.g. Fusarium oxysporum

8. ⦿ L u te o li n , apige n in

9. ⦿ Q u e r c e ti n , kampf e r o l , iso r ham n etin

10. ⦿ Hesper e ti n , Na r i nge n i n ,

11. ⦿ T axifoli n (o r Di h ydr o querc e ti n ), Dihydr o kaem pferol

12. ⦿ Includ e flava n - 3-ols (fl a vanol s ), ⦿ flava n -4-ols and ⦿ fla v a n- 3,4 - diol s .

13. ⦿ Flavan-3-ols (flavanols) ⦿ Examples : Catechin ⦿ Gallocatechin ⦿ Catechin 3-gallate ⦿ Gallocatechin 3-gallate, ⦿ Epicatechins, ⦿ Epigallocatechin, ⦿ Epicatechin 3-gallate, ⦿ Epigallocatechin 3-gallate ⦿ Theaflavin ⦿ Examples : Theaflavin-3-gallate, Theaflavin-3'- gallate, Theaflavin-3,3'-digallate ⦿ Thearubigin ⦿ Proanthocyanidins are dimers, trimers, oligomers, or polymers of the flavanols

14. ⦿ Anthocyanidins ⦿ A n thocyan i di n s ar e th e agly co ne s o f anth o cyani ns o r Anthocyanins are glycosides of anthocyanidins . ⦿ They use the flavylium (2-phenylchromenylium) ion skeleton ⦿ Examples : Cyanidin, ⦿ Delphinidin, ⦿ Malvidin, ⦿ Pelargonidin, ⦿ Peonidin, ⦿ Petunidin

15. ⦿ Ch a lcones Chalcones and dihydrochalcones are flavonoids with open structure; they are classified as flavonoids because they have similar synthetic pathways.

16. ⦿ Gen istei n , Daidzei n , Glycitein

17. ⦿ Coutareagen i n f o u n d i n Hi n t o n i a lat i flora ⦿ Dalbergin ⦿ Niv e ti n isolate d f r om Echi n ops n i veus

18. ⦿ Shinoda test ⦿ Four pieces of magnesium filings are added to the ethanolic extract followed by few drops of concentrated hydrochloric acid. A pink or red colour indicates the presence of flavonoid. ⦿ Colours varying from orange to red indicated flavones, red to crimson indicated flavonoids, crimson to magenta indicated flavonones. ⦿ Sodium hydroxide test ⦿ About 5 mg of the compound is dissolved in water, warmed and filtered. 10% aqueous sodium hydroxide is added to 2 ml of this solution. This produces a yellow coloration. A change in color from yellow to colorless on addition of dilute hydrochloric acid is an indication for the presence of flavonoids. ⦿ p-Dimethylaminocinnamaldehyde test ⦿ A colorimetric assay based upon the reaction of A-rings with the chromogen p-dimethylaminocinnamaldehyde(DMACA) has been developed for flavanoids in beer that can be compared with the vanillin procedure.

19. Thank You !