Flavones: Structural Features, Physicochemical Properties, and Key Points for Research and Applications

Flavones are a class of polyphenolic compounds built on the C6–C3–C6 scaffold and represent an important group of plant secondary metabolites. They widely participate in plant stress resistance, signaling regulation, and pigment formation. Natural flavones have high research and application value in pharmaceuticals, foods, and functional products. Their chemical diversity mainly arises from differences in core oxidation state, variation in the B-ring linkage position, and substituent modifications such as hydroxylation, methoxylation, and glycosylation, as well as polymerization or fusion with other scaffolds. Based on whether a hydroxyl group is present at the C5 position of the A ring, flavonoids can be divided into C5-hydroxylated flavonoids and C5-deoxy flavonoids. The former are widely distributed in plants, while the latter are relatively rare and mainly found in legumes. Because natural sources of C5-deoxy flavonoids are limited, heterologous biosynthesis and pathway rewiring in engineered microorganisms has become an important route to scalable production.

Keywords: flavone; C6–C3–C6; flavone glycosides; O-glycosides; C-glycosides; C5-hydroxylation; 5-deoxy flavones; antioxidation; TLR/NF-κB; HPLC; heterologous biosynthesis

I. Structural Basis and Physicochemical Properties

1.1 Core scaffold and sources of structural diversity

(1) Core scaffold:

Flavones follow the C6–C3–C6 framework, consisting of two aromatic rings (A and B) linked by a three-carbon unit that commonly cyclizes into an oxygen-containing heterocycle (C ring), yielding a benzopyranone-like core.

(2) Structural diversity

① Oxidation differences in the central three-carbon unit: define subclasses such as flavones, flavonols, and dihydroflavones.

② B-ring linkage position: 2-position linkage yields “flavone-type” frameworks, while 3-position linkage yields “isoflavone-type” frameworks, and related variants.

③ Substituent modifications: hydroxylation, methoxylation, glycosylation, and acylation can strongly shift polarity, stability, membrane permeability, and activity spectra.

1.2 Glycosylation and solubility–stability relationships

(1) Prevalence of glycosides:

Many natural flavones occur as glycosides. Sugar type (e.g., glucose, rhamnose), number of sugars, and linkage mode (O-glycoside vs C-glycoside) govern polarity and physicochemical behavior.

(2) Solubility patterns:

Longer sugar chains generally increase polarity and water solubility. Aglycones (e.g., quercetin, in a broader flavonoid context) typically show low water solubility but moderate solubility in methanol or ethanol.

(3) Solid-state behavior:

Glycosides are often amorphous powders, whereas aglycones more readily form crystalline solids, reflecting how glycosidic substitution disrupts lattice regularity.

1.3 Phenolic hydroxyls: acidity, chelation, and redox properties

(1) Acidity:

Flavones are weak acids due to phenolic hydroxyls, with acidity depending on hydroxyl number and position; catechol motifs can enhance acidity via hydrogen bonding and resonance.

(2) Chelation:

Specific hydroxyl arrangements can chelate metal ions, affecting color reactions and antioxidant behavior.

(3) Redox activity:

Conjugation and H-donating capacity support radical scavenging and lipid oxidation chain suppression, but activity is strongly modulated by substitution patterns and aggregation state.

II. Classification Systems and Representative Subclasses

2.1 Common classification by core type

(1) Flavones and flavonols:

2-phenylchromenone cores and hydroxylated derivatives; flavonols are abundant, with common representatives including quercetin and kaempferol.

(2) Dihydroflavones and dihydroflavonols:

Saturation at the C2–C3 bond; often co-occur with corresponding flavones/flavonols.

(3) Isoflavones and dihydroisoflavones:

Altered B-ring linkage (3-phenylchromenone skeleton), enriched in legumes; representatives include puerarin and daidzein derivatives.

(4) Chalcones and dihydrochalcones:

Open-chain analogs lacking C-ring closure; can interconvert with dihydroflavones and are associated with color changes.

(5) Flavanones, anthocyanins, and flavan-3-ols:

Cover structural shifts and ionic chromophore derivatives associated with yellow/orange and red/blue/purple coloration, respectively.

2.2 C5 hydroxylation vs 5-deoxy flavones

(1) C5-hydroxylated flavonoids:

Widely distributed and dominate common plant flavonoid structures.

(2) C5-deoxy flavonoids:

Relatively rare, mainly in legumes. Limited natural availability motivates engineered-microbe heterologous biosynthesis as an alternative production route.

III. Color Reactions and Analytical Identification

3.1 Structural basis of coloration

(1) Conjugation-driven color:

Cross-conjugated systems in flavone cores determine visible-light absorption and color. Electron transfer, rearrangements, or conjugation extension can red-shift absorption and shift color from yellow toward orange/red.

3.2 Common qualitative reactions and analytical indicators

(1) HCl–Mg (or Zn) reaction:

A classical qualitative test for rapid flavonoid screening.

(2) NaBH4 reaction:

Relatively selective for certain dihydroflavonoid contexts and can help differentiate structural types.

(3) Metal-complex coloration:

Complexes with AlCl3 or aluminum nitrate often appear yellow and may fluoresce, supporting qualitative and quantitative analysis and spectroscopic detection.

3.3 Quantitation and structure elucidation workflows

(1) HPLC/UPLC:

Used for separation and quantitation in complex matrices; external or internal standard strategies support concentration calculation. DAD coupling provides characteristic UV–Vis spectra.

(2) LC-MS:

Supports molecular mass, fragmentation patterns, and glycosylation-type assignment, especially for complex glycoside systems.

(3) NMR:

Critical for confirming substitution positions, glycosidic linkage sites, and stereochemical information.

IV. Bioactivity Mechanism Framework and Evidence Chains

4.1 Antioxidation and metal chelation mechanisms

(1) Radical scavenging:

Via hydrogen donation, electron transfer, and resonance stabilization, reducing ROS-driven chain reactions.

(2) Lipid peroxidation suppression:

Can inhibit lipid peroxidation at different stages; some reports compare effects to vitamin E, but outcomes depend on structure, concentration, and system context.

(3) Chelation of pro-oxidant metals:

Chelation of Fe/Cu can reduce Fenton-type ROS generation, acting as an indirect antioxidant mechanism.

4.2 Inflammation modulation and immune signaling

(1) TLR/NF-κB axis:

Many studies link anti-inflammatory effects to modulation of TLR/NF-κB signaling, reflected by reduced inflammatory gene expression and enzymatic activity readouts.

(2) COX/LOX pathways:

Impacts on cyclooxygenase and lipoxygenase-related mediator production can shift inflammatory mediator profiles.

(3) Leukocyte migration and tissue injury:

In some models, flavones modulate immune-cell recruitment and activation, lowering inflammatory injury risk, but extrapolation requires model- and dose-window constraints.

4.3 Antimicrobial and anticancer research signals

(1) Antimicrobial activity:

May involve membrane interactions, metal chelation, redox perturbation, and signaling regulation, typically species- and structure-dependent.

(2) Anticancer activity:

In cell models, flavones can induce apoptosis or suppress proliferation with strong cell-type and dose-window dependence; hematologic malignancy cells sometimes show higher sensitivity, whereas solid tumors often require higher exposure.

(3) Evidence requirements:

Anticancer conclusions should integrate cell-cycle/apoptosis markers, ROS/mitochondrial readouts, and pathway-protein changes to avoid confusing non-specific cytotoxicity with mechanism-based anticancer effects.

V. Natural Sources and Preparation Strategies

5.1 Natural sources and representative materials

(1) Broad distribution:

Flavones occur widely across plants, berries, and botanical medicines; common sources include green tea, propolis, and various aromatic/medicinal plants.

(2) Source-material differences:

Plant part (leaf, flower, peel, seed) drives strong compositional differences, so extraction and standardization should be guided by target analytes.

5.2 Extraction, purification, and formulation

(1) Solvent extraction:

Glycosides favor more polar solvents; aglycones often extract better in moderately polar organic solvents. Processes balance recovery, impurity profiles, and safety.

(2) Purification routes:

Macroporous resin adsorption, column chromatography, and preparative HPLC are common.

(3) Solubility enhancement:

For aglycones with limited water solubility, strategies include nanonization, cyclodextrin inclusion, salt formation, or carrier complexation to improve dispersion and bioaccessibility.

5.3 Heterologous biosynthesis in engineered microorganisms

(1) Motivation:

5-deoxy flavones have limited natural distribution, making plant extraction insufficient for scale and cost targets.

(2) Technical route:

Reconstruct phenylpropanoid and flavone biosynthesis modules in microbes, and use enzyme engineering to improve key-step selectivity and flux.

(3) Quality control:

Monitor product and byproduct profiles quantitatively to ensure structural consistency and process stability.

VI. Industrial Applications and R&D Focus Points

6.1 Pharmaceutical and nutraceutical contexts

(1) Functional directions:

Antioxidation, anti-inflammation, and metabolism-related phenotypes are common themes, but product contexts require dose–response mapping and safety boundaries.

(2) Drug–metabolism interactions:

Flavones can inhibit or induce drug-metabolizing enzymes; evaluate PK interaction risks, especially under high-dose or long-term exposure.

6.2 Food and additive applications

(1) Antioxidation and preservation:

Can suppress lipid oxidation and improve shelf stability, but must be assessed for flavor, color, and processing stability impacts.

(2) Coloring and color development:

Certain flavone and anthocyanin-related systems act as natural colorants; pH, metals, light, and oxygen control is required to maintain color stability.

6.3 Cosmetics and topical formulations

(1) Skin antioxidation and anti-inflammation:

Used as candidate antioxidant/soothing ingredients, requiring evaluation of photostability, formulation compatibility, and irritation risk.

(2) Delivery systems:

Nano-carriers or inclusion complexes can improve stability and skin access but require parallel safety and long-term stability validation.

VII. Research Use Notes and Quality Control

7.1 Structural heterogeneity and standardization

(1) Chemical heterogeneity:

“Total flavones” is not equivalent to consistent activity; bioactivity differs strongly across substitution and glycosylation forms.

(2) Standardization strategy:

Combine fingerprint profiling with quantitation of key marker compounds, defining batch-variation thresholds.

7.2 Bioavailability and in vitro–in vivo gaps

(1) Solubility limits:

Low water solubility of aglycones can reduce in vivo effective exposure; high-dose in vitro results should not be directly extrapolated.

(2) Metabolic transformation:

Glycoside hydrolysis, phase II metabolism (glucuronidation/sulfation), and microbiome conversion alter active forms and exposure windows; clarify whether the measured target is parent compound or metabolites.

7.3 Assay and model control essentials

(1) Antioxidant assays:

Chemical assays (DPPH, ABTS) reflect only in vitro scavenging; link to cellular ROS, lipid peroxidation, and antioxidant-enzyme readouts.

(2) Anti-inflammatory assays:

Report cytotoxicity, apply cell-number normalization, and include pathway-protein readouts to avoid pseudo anti-inflammatory effects driven by reduced viability.

(3) Antimicrobial/anticancer assays:

Include solvent controls, assess permeability and protein binding, and use multi-endpoint designs to close mechanistic loops.

VIII. Aladdin-Related Products

8.1 Representative Compounds and Reference Standards for Flavone/Isoflavone Structure–Property–Analytics Studies

Catalog No.	Product Name	CAS No.	Grade and Purity	Use Stage	Role in the System
F156758	Flavone	525-82-6	Moligand™, ≥98%	Core scaffold / benchmark	Benchmark flavone scaffold for establishing UV absorption features, chromatographic retention behavior, and structure–property comparison references
F424512	Flavone	525-82-6	Moligand™, 10 mM in DMSO	Cell / mechanistic studies	Ready-to-use stock enables standardized dosing and concentration gradients; used to assess baseline scaffold effects and control solvent variables
H157350	3-Hydroxyflavone	577-85-5	≥98%(HPLC)(T)	Structure–property control	Evaluates effects of introducing 3-OH on acidity, hydrogen bonding, conjugation, and redox behavior
H424860	3-Hydroxyflavone	577-85-5	10 mM in DMSO	Cell / mechanistic studies	Stock solution supports reproducible cellular exposure and structure–effect relationship validation
H157353	5-Hydroxyflavone	491-78-1	≥98%(HPLC)	Classification / structural control	Assesses how A-ring C5 hydroxylation affects metal chelation, antioxidant readouts, and spectral behavior
H157351	6-Hydroxyflavone	6665-83-4	≥98%	Structure–property control	Compares positional substitution effects on solubility, stability, and spectroscopic responses
H425356	6-Hydroxyflavone	6665-83-4	10 mM in DMSO	Cell / mechanistic studies	Facilitates dose–response modeling and reduces preparation error
H157352	7-Hydroxyflavone	6665-86-7	≥97%(T)	Structure–color/chelation	Probes 7-OH-associated metal-complexation color/fluorescence features and spectroscopic differences
H425357	7-Hydroxyflavone	6665-86-7	10 mM in DMSO	Cell / mechanistic studies	Stock supports pathway assays and time-window studies with improved exposure consistency
D709740	3,7-Dihydroxyflavone	492-00-2	≥97%	Hydroxyl number effects	Compares the gain from multi-hydroxylation on radical scavenging, chelation strength, and antioxidant readouts
D137213	7,8-Dihydroxyflavone Hydrate	38183-03-8	≥98%(HPLC)	Structure–activity linkage	Catechol motif is highly sensitive to H-donating capacity and metal chelation; used to validate structure-driven effects
D423768	7,8-Dihydroxyflavone Hydrate	38183-03-8	10 mM in DMSO	Cell / mechanistic studies	Enables cellular evaluation of catechol-driven effects while controlling solvent volume fraction
D155146	3',4'-Dihydroxyflavone	4143-64-0	≥97%	B-ring catechol control	Assesses B-ring catechol effects on metal chelation, antioxidant potency, and chromogenic responses
D1495822	3',4'-Dihydroxyflavone	4143-64-0	Moligand™, 10 mM in DMSO	Cell / mechanistic studies	Stock supports reproducible dosing and high-throughput dose screening
D155769	3',4'-Dimethoxyflavone	4143-62-8	≥98%(HPLC)	Methoxylation control	Hydroxyl-masked control to decouple “H-donation/chelation” from “hydrophobicity/permeability” contributions
M157947	6-Methoxyflavone	26964-24-9	≥97%	Methoxylation control	Evaluates methoxylation effects on solubility, stability, chromatographic behavior, and spectral response
M158434	7-Methoxyflavone	22395-22-8	≥98%(GC)	Methoxylation control	Paired with hydroxylated analogs to compare substituent impacts on chelation/chromogenic behavior and antioxidant readouts
T340764	5,6,7-Trimethoxyflavone	973-67-1	≥96%	Polymethoxylated representative	Characterizes how polymethoxylation shifts hydrophobicity, membrane-permeation tendency, and effect profiles
T427186	5,6,7-Trimethoxyflavone	973-67-1	10 mM in DMSO	Cell / mechanistic studies	Stock supports standardized exposure and dose gradients for low-solubility compounds
S118322	Sinensetin	2306-27-6	≥98%	Natural polymethoxylated flavone	Representative natural polymethoxylated flavone for comparing structural diversity and physicochemical behavior
S422737	Sinensetin	2306-27-6	10 mM in DMSO	Cell / mechanistic studies	Enables cellular dose–response studies and improves cross-batch reproducibility
G106672	Genistein	446-72-0	analytical standard, ≥98%	Quantitation standard	External standard for HPLC/LC-MS quantitation, method validation, and fingerprint reference
G106673	Genistein	446-72-0	Moligand™, ≥97%	Mechanistic studies	Representative isoflavone for structure–effect studies (e.g., antioxidant/anti-inflammatory contexts)
G408928	Genistein (NPI 031L)	446-72-0	10 mM in DMSO	Cell / mechanistic studies	Stock supports dose-window screening and minimizes preparation variability
C123665	Calycosin	20575-57-9	Moligand™, ≥98%(HPLC)	Isoflavone representative	Comparator for isoflavone structural features, physicochemical properties, spectral behavior, and effect differences
C422499	Calycosin	20575-57-9	10 mM in DMSO	Cell / mechanistic studies	Stock enables reproducible exposure and dose–response construction
C418567	Calycosin-7-O-beta-D-glucoside	20633-67-4	≥98%	Glycosylation control	Evaluates glycosylation effects on solubility, stability, chromatographic behavior, and in vitro readouts
H105437	Hesperidin	520-26-3	≥97%	Flavonoid glycoside representative	Representative flavonoid glycoside for solubility, stability, and analytical identification benchmarking
H105438	Hesperidin	520-26-3	analytical standard	Quantitation standard	For content determination, method validation, and batch-to-batch comparability
H409084	Hesperidin	520-26-3	10 mM in DMSO	Cell / mechanistic studies	Stock supports in vitro evaluation while controlling solvent volume fraction

8.2 Key Reagents and Condition-Control Components Commonly Used for Flavonoid Chromogenic Identification, Quantitative Analysis, and Mechanistic Studies

Category	Reagent	CAS No.	Applicable Experiments	Role in the System	Use Notes
Chromogenic/total flavonoids	Aluminum chloride (AlCl3, anhydrous)	7446-70-0	AlCl3 complexation colorimetry for total flavonoids; fluorescence/UV complexation verification	Forms complexes with flavonoids yielding characteristic absorbance/fluorescence for colorimetric quantitation or spectral discrimination	Fix pH, solvent ratio, and reaction time; include blanks and spike-recovery controls
Chromogenic/total flavonoids	Aluminum chloride hexahydrate (AlCl3·6H2O)	7784-13-6	AlCl3 complexation colorimetry for total flavonoids	Common Al(III) source for preparing stable working solutions	Account for crystal water in weighing; store moisture-protected
Chromogenic/total flavonoids	Aluminum nitrate nonahydrate (Al(NO3)3·9H2O)	7784-27-2	Al(III)-salt complexation colorimetry (alternative to AlCl3); complexation control experiments	Provides Al(III) for complexation-based chromogenic systems	Note acidity background; run paired controls
Chromogenic/total flavonoids	Sodium hydroxide (NaOH)	1310-73-2	NaNO2–AlCl3–NaOH assay; alkaline endpoint adjustment	Provides alkaline conditions for stable endpoint readout	Strong base safety; fix endpoint pH
Chromogenic/total flavonoids	Potassium acetate (CH3COOK)	127-08-2	AlCl3 method (in some protocols)	Adjusts ionic environment and stabilizes complexation readout	Keep consistent with solvent system; avoid salting-out
Qualitative identification	Magnesium (Mg)	7439-95-4	Shinoda test (rapid flavonoid screening)	Supports reduction-based chromogenic response	Fix particle size/dose; include positive controls
Qualitative identification	Zinc (Zn)	7440-66-6	HCl–Zn qualitative test	Alternative reducing metal for some systems	Same as above; avoid oxidation-driven drift
Structure-aided identification	Sodium borohydride (NaBH4)	16940-66-2	NaBH4 reaction to differentiate certain structural classes; reactivity-based verification	Selective reactions help infer functional-group/structure differences	Water-sensitive and exothermic; control temperature and include solvent controls
Metal complexation/mechanism	Ferric chloride (FeCl3)	7705-08-0	Complexation control; complexation-driven spectral-change verification	Creates Fe(III) complexation background to probe absorbance/chromogenic shifts	Control pH to avoid hydrolysis; monitor turbidity/precipitation
Metal pro-oxidation/mechanism	Ferrous sulfate heptahydrate (FeSO4·7H2O)	7782-63-0	Pro-oxidation background (Fenton-related); “chelation-mediated inhibition” verification	Provides Fe(II) oxidative background to assess chelation/indirect antioxidant contribution	Prepare fresh and control dissolved oxygen; prevent oxidation artifacts
Metal pro-oxidation/mechanism	Copper sulfate pentahydrate (CuSO4·5H2O)	7758-99-8	Pro-oxidation background; Cu(II) complexation control	Provides Cu(II) background for chelation/pro-oxidation discussions	Avoid phosphate to prevent precipitation; control ionic strength
Metal complexation/mechanism	Copper(II) chloride dihydrate (CuCl2·2H2O)	10125-13-0	Cu(II) complexation control (alternative salt)	Alternative Cu(II) source to verify complexation effects	Hygroscopic; keep salt form consistent for comparability
Chelation control	EDTA (acid form)	60-00-4	Metal-chelation interference check; mechanism dissection (±EDTA)	Strong chelator used to isolate metal-chelation contributions	Dissolution may require pH adjustment; avoid metal contamination
Chelation control	Disodium EDTA dihydrate (EDTA·2Na·2H2O)	6381-92-6	Same as above (more soluble salt form)	Same role as EDTA	Note added Na+ and ionic strength changes
Chelation control	EGTA	67-42-5	Ca-related contribution checks; chelation control	More Ca-selective chelator to separate Ca-linked complexation/precipitation effects	Strongly alters Ca availability; interpret cautiously
Antioxidant assessment	DPPH	1898-66-4	DPPH radical scavenging assay (chemical method)	Stable radical for comparing antioxidant capacity	Protect from light; fix reaction time and solvent system
Antioxidant assessment	ABTS	30931-67-0	ABTS•+ scavenging assay	Radical cation system for antioxidant assessment	Standardize ABTS•+ generation and initial absorbance
Antioxidant assessment	Potassium persulfate (K2S2O8)	7727-21-1	ABTS•+ generation (paired with ABTS assay)	Oxidizes ABTS to ABTS•+	Control generation time; fresh preparation improves stability
Antioxidant assessment	AAPH	2997-92-4	ORAC assay (peroxyl radical source)	Generates peroxyl radicals to model chain oxidation	Control temperature; note batch-related activity variability
Antioxidant assessment	Fluorescein	2321-07-5	ORAC assay (fluorescent probe)	Probe substrate reporting radical damage	Protect from light; keep concentrations within linear range
Antioxidant assessment	Ferric chloride hexahydrate (FeCl3·6H2O)	10025-77-1	FRAP assay (oxidant component)	Fe(III) acceptor reduced to Fe(II) for color development	Hygroscopic; fresh prep improves consistency
Antioxidant assessment	Neocuproine	484-11-7	CUPRAC reducing-power assay	Forms chromogenic complex with Cu(I)	Protect from light; control solvent ratio and timing
Polyphenol/auxiliary	Folin–Ciocalteu reagent	9003-99-0	Total phenolics/reducing capacity (auxiliary profiling of flavonoid extracts)	Captures overall reducing capacity as a supportive descriptor	Mixture reagent; strict method conditions and blanks required
Polyphenol/auxiliary	Sodium carbonate (Na2CO3)	497-19-8	Folin assay development (paired reagent)	Provides alkalinity to drive color formation	Fix endpoint pH; manage CO2 absorption
LC sample prep	Methanol (MeOH)	67-56-1	Flavonoid/flavonoid glycoside extraction; HPLC/UPLC prep and injection	Common solvent for dissolution and sample handling	Include solvent blanks; volatility/toxicity management
LC sample prep	Acetonitrile (ACN)	75-05-8	Protein precipitation; HPLC/UPLC mobile phase/sample handling	Improves peak shape and reproducibility in LC systems	Salt co-presence can cause salting-out; ensure compatibility
LC/MS	Formic acid	64-18-6	LC-MS mobile phase additive (flavonoids/glycosides)	Improves peak shape and ionization efficiency	Fix acidity and gradients; reduce batch drift
LC/UPLC	Acetic acid	64-19-7	Mobile phase acidity control	Tunes retention and peak shape via acidity adjustment	Keep consistent with validated method; do not switch acid sources casually
LC/MS	Ammonium formate	540-69-2	Volatile buffer salt for LC-MS	Provides controlled ionic strength and pH background	Control concentration to avoid salt deposition; keep constant
Quench/deproteinization	Trichloroacetic acid (TCA)	76-03-9	Reaction quench; deproteinization prior to colorimetry/LC	Stops reactions and precipitates proteins to reduce interference	Verify compatibility with downstream detection
Glycoside studies	beta-Glucosidase	9001-22-3	O-glycoside hydrolysis; glycoside vs aglycone conversion verification	Hydrolyzes O-glycosides to aglycones to confirm glycosylation effects	Control enzyme dose/time/temperature; include blanks and heat-inactivated enzyme controls
Cellular ROS	DCFH-DA	4091-99-0	Cellular ROS assays (supports cell-level antioxidant evidence)	Intracellular probe reporting ROS changes after conversion	Protect from light; include probe auto-oxidation and solvent controls
Cytotoxicity control	MTT	298-93-1	Cell viability/toxicity controls for anti-inflammatory/antioxidant assays	Excludes false mechanistic conclusions driven by cell death	Compound color/reducing properties may interfere; include proper blanks
Cytotoxicity control	Resazurin	62758-13-8	High-throughput viability alternative to MTT	Metabolic activity readout for screening	Reducing compounds can interfere; standardize incubation/readout windows
Inflammation readout	Sulfanilamide	63-74-1	Griess assay for NO/nitrite (anti-inflammatory readout)	Reacts with nitrite to form azo intermediates	Protect from light; strict addition order and standards
Inflammation readout	N-(1-naphthyl)ethylenediamine dihydrochloride (NED·2HCl)	1465-25-4	Griess assay (paired chromogenic coupling)	Couples to form chromophore for quantitation	Control reaction time; run standard curves

Flavones are C6–C3–C6 polyphenolic secondary metabolites with high structural diversity driven by hydroxylation, glycosylation, and other substitutions, producing broad differences in physicochemical behavior and bioactivity. Their research value and application potential in antioxidation, anti-inflammation, antimicrobial, and anticancer directions rely on systematic evidence chains linking structure, properties, mechanism, and dose windows. For development and industrial translation, prioritize standardized compositional profiling, reproducible quantitative analytics, and practical delivery/solubility-improvement strategies, while controlling model and measurement biases to ensure comparability and transferability of conclusions.

For more related articles, please see below:

[1] Isoflavones

[2] Determination of the content of plant flavonoid compounds