Common characteristics: Band I and Band II are both strong

Difference: The position of belt I is different Flavonoids: 304~350 nm Flavonols: 3-OH free: 352~385 nm; 3-OH substituted: 328~357 nm

Common characteristics: Band I is very strong and is the main peak; Band II is weak and is the secondary peak.

Difference: Band I peak position is different Chalcones: 340～390nm Orange ketone: 370～430nm

Common features: Band II is the main peak; Band I is very weak and is the shoulder of the main peak.

Difference: Band II peak position is different Isoflavones: 245~278 nm Dihydroflavone (alcohol): 270~295 nm

7-OH flavonoids: similar to dihydroflavones (peak band II is strong because of the introduction of hydroxyl group in the A ring) 4’-OH flavonoids: similar to chalcones (peak band I is strong because of the introduction of hydroxyl group in the B ring) 4’, 7-dihydroxyflavone: normal That is, the introduction of 7-OH will enhance the peak band II; the introduction of 4’-OH will enhance the peak band I.

Introduction of -OH into the A ring: with II red shift, especially 5,7-OH has a great influence Introduction of -OH into ring B: red shift of I, especially 2’, 4’, 6’-OH Introduction of -OH (3-OH) into the C ring: band I red-shifts 30~50 nm, band II has little effect OH→OCH3: The corresponding peak band shifts purple by 15~20 nm

If the intensity of band I does not decrease, it means there is 4’-OH; if the intensity of band I decreases, it means there is 3-OH but no 4’-OH.

Band II, 5~20 nm (red shift): 7-OH

Band II: 5~10nm, indicating that ring A contains ortho-diAr-OH (excluding 5,6-dihydroxy) Band I: 12~30nm, it means that the B ring contains ortho-di-Ar-OH

The presence or absence of o-diphenolic hydroxyl group:

3-OH, 5-OH presence or absence (?):

• Mainly cleavage pathway I • M is usually the base peak • The main fragments are A1 ·, B1 ·, medium intensity • [M-CO] and [A1-CO] are also prominent

• Mainly cleavage pathway II • M is usually the base peak • The main fragments are B2, [B2-CO], and [A1 H]

• Quasi-molecular ion peaks: [M H] , [M Na] , [M K] • Excimer peaks are fragmented peaks that lose sugar groups sequentially from the end

B ring > 3-H > A ring

5-H

3-H

6, 8-H

1H-NMR signal of active protons

dominant conformation

absolute configuration

Features: Typical ABX coupling system

relative configuration

absolute configuration

feature

Isoflavones

orange ketone

Chalcones

dihydrochalcone

The J value of the sugar terminal proton is used to determine the configuration

Flavonoid (alcohol) glycosides

diglycoside

Cross-conjugated system: δC shifts upfield 13~20

No cross-conjugated system: C-2,3 is sp3 hybridized; chalcone, cross-conjugated system is destroyed

Presence of 5-OH: formation of intramolecular H bond; δC shifts downfield 3~6

C Differences in the degree of epoxidation: dihydroisoflavones < dihydroflavones < dihydroflavonols < chalcones < Flavonols < Orange ketones < Isoflavones < Flavonoids

2’ or 6’-OR substituent

Effect of 3-OH