Flavonoids: 2-phenylchromone is the basic core, with no oxygen-containing substitution at the 3-position

Flavonols: flavonoids have a hydroxyl group or other oxygen-containing group at position 3 of the basic nucleus.

Dihydroflavones: The double bonds at positions 2 and 3 of the basic core of flavonoids are hydrogenated

Dihydroflavonols: Flavonols are hydrogenated at the 2 and 3 positions and often coexist with flavonols

Chalcones: The three-carbon chain of flavonoids does not form a ring (under acidic conditions, chalcones can be converted into dihydroflavones)

Dihydrochalcone: Chalcone alpha, beta double bond hydrogenation

Isoflavones: The mother core is 3-phenylchromone, and the B ring is connected to the 3rd position of the C ring.

Dihydroisoflavones: Isoflavones are hydrogenated at the 2 and 3 positions

Ring C is an oxygen-containing five-membered ring, and the number of carbon atoms in the parent nucleus is also different.

No carbonyl group, divided into flavan 3-ols and flavan 3,4-ols

Oxygen ions are present

Form: Flavonoids are crystalline solids Flavonoid glycosides as powder

Color: ① Due to the formation of a cross-conjugated system, the conjugated chain is extended and the color appears ②The color deepens after introducing electron-donating groups such as -oH and -OCH3 at the 7-position and 4'-position. ③Dihydroflavones and dihydroflavonols do not develop color ④The color of anthocyanins is related to ph

Optical activity: ① Dihydroflavones, dihydroflavoneols, dihydroisoflavones and flavanols are optically active ②All flavonoid glycosides are optically active

Solubility: Aglycone: flavonoid aglycone is poorly soluble or insoluble in water, but soluble in organic solvents (Anthocyanins > Isoflavones, dihydroflavonols > Flavonols, Chalcones) Flavonoid glycosides: introduced sugars, more water-soluble than aglycones, 3-OH glycosides > 7-OH glycosides

Acidity and alkalinity

Color reaction

Free flavonoids: less polar solvents Flavonoid glycosides and more polar aglycones: water-soluble solvents Polyglycoside: boiling water Anthocyanins: add 0.1% hydrochloric acid during extraction to inhibit ionization

Alkaline water extraction (The alkalinity should not be too strong. So as not to damage the flavonoid mother core)

chromatography

pH gradient extraction

Solvent extraction method

Physical and chemical examination

Chromatographic identification

UV spectrum

NMR