Basic structure: 2-(or 3-)phenylbenzoγ-pyrone

Structural classification: • Diflavonoids: 2 molecules of flavonoids, 2 molecules of dihydroflavones, 1 molecule of flavonoids and 1 molecule of dihydroflavones, connected through C-O-C, C-C • Flavonolignans: 1 molecule of flavonoid and 1 molecule of lignan (silymarin has both flavonoid and lignan structures) • Alkaloid flavonoids • There are alkaloids attached to the flavonoid skeleton

Master the abbreviations and structural differences of several sugars (sophorose and gentiobiose are composed of two molecules of glucose; rutose and noriose are composed of one molecule of rhamnose and one molecule of glucose)

Glc,Man,Gal,Xyl,Ara,Rha

A ring: from 2 malonylCoA B C ring: from cinnamyl CoA dihydroflavone Other types of flavonoids are derived from dihydroflavones

• Effect on the cardiovascular system: Reduce capillary fragility and abnormal permeability: rutin (flavonol), hesperidin; dilate coronary arteries, treat coronary heart disease: puerarin; lower blood pressure; inhibit platelet aggregation and thrombosis • Anti-hepatotoxic effects: silymarin, ( )-catechin • Anti-inflammatory effect: dihydroquercetin • Estrogen-like effects: daidzein, genistein, etc. • Antibacterial and antiviral effects: luteolin, baicalin (flavonoid), baicalein (flavonoid), quercetin (flavonol), kaempferin, etc. • Purgative effect: pyroside A • Antispasmodic effect: isoliquiritigenin, daidzein

Material state: mostly crystalline solids, a few amorphous powders

Optical activity: Glycones: flavonoids (alcohols), optically inactive; dihydroflavones (alcohols), flavanols, optically active Glycoside: Optically active

The existence of cross-conjugated systems: Introduction of auxiliary chromophore → color deepening 7,4’ introduces auxochromophores (-OH, -OCH3, etc.) → deepens the color

• Glycoside and aglycone: similar and compatible • Related to the planarity of the molecule: the stronger the planarity, the worse the water solubility; flavones (alcohols) < chalcones < dihydroflavones < dihydroflavonols < anthocyanins (the molecules exist in ionic form) • Depends on the type of parent core substituent: -OH substitution, water solubility ↑; after hydroxymethylation, water solubility ↓ • Depends on the position of the parent core substituent: 3-O-glycoside > 7-O-glycoside

Source of acidity: phenol OH Affects acidity: number and position of OH; 7,4′-diOH > 7-OH or 4'-OH > generally Ar-OH > 5-OH; soluble in (strong base extracts weak acid): 5% NaHCO3 → 5% Na2CO3 → 0.2% NaOH → 4% NaOH

Source: γ-pyrone ring-O-lone pair of electrons

Hydrochloric acid-magnesium powder (or zinc powder) reaction (HCl-Mg/Zn)

Sodium tetrahydroborate (NaBH4) reaction

Dihydroflavone and phosphomolybdic acid reagent → brown

Aluminum salt reaction: AlCl3 reaction

Magnesium salt reaction: MgAc2 reaction (dihydroflavones (alcohols), other flavonoids)

Zirconium salt-citric acid reaction (flavonoids containing 3-OH/5-OH)

Ammoniacal strontium chloride reaction (o-diphenolic hydroxyl group)

Lead salt reaction (o-diphenol hydroxyl/3-OH 4-C=O/5-OH 4-C=O)

FeCl3 reaction (5-OH)

Reaction conditions: acidic conditions; 5-OH flavonoids (alcohols), 2-OH chalcone Phenomenon: bright yellow Dihydroflavones (alcohols), isoflavones, orange ketones: (-)

Under the acidic condition of flavonoid 6,8-C, hydrolysis cannot occur and rearrangement reaction occurs!

Choice of extraction solvent

refined

R

pH gradient extraction method

The stationary phase of paper chromatography: water adsorbed on paper fibers. Belongs to partition chromatography

Normal phase PC and reversed phase PC: depends on the polarity of the mobile phase • Alcoholic flow agent: less polar than water, for reversed-phase chromatography • Aqueous developing agent: more polar than water, normal phase chromatography

bidirectional paper chromatography

Silica gel • Normal phase adsorption chromatography • Separation mechanism including normal phase partitioning when using aqueous mobile phases

Commonly used mobile phases • CHCl3-CH3OH system • CHCl3-CH3OH-H2O system

Adsorption principle: intermolecular hydrogen bonding, semi-chemical adsorption

Factors affecting adsorption (solute): strong • More -OH • C=O more • Few H bonds in the molecule • High degree of aromatization • Small MW

reversed phase mobile phase • Ethanol-water system • Water-ethanol-acetylacetone system • Water saturated n-butanol-acetic acid system • Acetone-water system • Acetone-ethanol-water system • Ethanol-acetic acid system

Normal phase mobile phase • Chloroform-methanol system • Chloroform-methanol-butanone system