Isoliquiritigenin (Chalcone · Antioxidant · Antidepressant-like · Anti-tumour)

Compound	Isoliquiritigenin (4,2′,4′-Trihydroxychalcone; Chalconaringenin-related; Licorice chalcone)
Chemical class	Polyphenol — Chalcone (open-chain flavonoid precursor; alpha,beta-unsaturated ketone; licorice characteristic)
CAS	961-29-5
Primary source	Glycyrrhiza glabra (licorice root), Glycyrrhiza uralensis, Glycyrrhiza inflata (Chinese licorice)
Key applications	Antioxidant; antidepressant-like (monoamine modulation); anti-tumour; estrogenic; anti-inflammatory
Claim strength	Moderate
Typical form	Licorice Root Extract Powder (isoliquiritigenin as minor co-active); DGL Licorice Extract; Licorice flavonoid extract
Buy from Herbuno	Licorice Root Extract Powder | Mulethi → DGL Licorice Extract Powder | Mulethi →

Name origin: Isoliquiritigenin is named after licorice (Glycyrrhiza, liquiritia in Latin) with the "iso-" prefix denoting its positional relationship to liquiritigenin — both are chalcones derived from licorice, with isoliquiritigenin being the open-chain chalcone precursor to liquiritigenin (the flavanone). The chalcone-to-flavanone cyclisation — converting isoliquiritigenin to liquiritigenin via chalcone isomerase — is one of the key steps in plant isoflavonoid biosynthesis. Traditional use: Isoliquiritigenin's traditional use is subsumed within licorice root's ancient pharmacopoeia — the same uses as Yashtimadhu (Ayurveda) and Gan Cao (TCM) described under Liquiritin (see that entry). The chalcone fraction of licorice contributes to the herb's antioxidant, anti-inflammatory, and anti-ulcer activities. Isoliquiritigenin was identified as a pharmacologically significant licorice chalcone distinct from glycyrrhizin and flavanones in the 1980s–1990s as licorice phytochemistry was systematically investigated. Research trajectory: Isoliquiritigenin has a diverse and growing research profile — antioxidant, estrogenic (ERα and ERβ binding), antidepressant-like (serotonin/dopamine pathway modulation), and antiproliferative activities are documented. Its alpha,beta-unsaturated ketone (chalcone) Michael acceptor character is pharmacologically significant for enzyme inhibition — the same electrophilic reactivity that allows chalcones to covalently modify cysteine residues in enzyme active sites. Commercial source: Isoliquiritigenin is available from Herbuno via Licorice Root Extract Powder and DGL Licorice Extract, both of which deliver isoliquiritigenin alongside liquiritin, glabridin, and glycyrrhizin (non-DGL).

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Evidence for Isoliquiritigenin Applications

Antioxidant activity: Isoliquiritigenin's chalcone enone system (alpha,beta-unsaturated carbonyl) provides dual antioxidant mechanisms: (1) direct radical scavenging via the phenolic 4-hydroxyl groups; (2) electrophilic activation of Nrf2 pathway (via Michael addition to Keap1 cysteine residues, releasing Nrf2 for HO-1/NQO1 induction). The Nrf2 activation mechanism gives isoliquiritigenin sustained cellular antioxidant induction beyond direct radical scavenging capacity. Claim strength: Moderate.

Antidepressant-like activity: Isoliquiritigenin has demonstrated significant antidepressant-like effects in rodent forced swim, tail suspension, and chronic unpredictable mild stress (CUMS) models at 5–20 mg/kg. Mechanisms include: monoamine oxidase (MAO) inhibition (reducing serotonin and dopamine breakdown); BDNF upregulation in the hippocampus; HPA axis normalisation (reduced corticosterone). In the CUMS model — the most validated animal model of depression — isoliquiritigenin reversed anhedonia, cognitive impairment, and neuroinflammatory biomarker elevation. Claim strength: Moderate (preclinical).

Anti-tumour activity: Isoliquiritigenin demonstrates antiproliferative activity in breast, gastric, prostate, and colorectal cancer cell lines at 10–50 μM via G2/M arrest, mitochondrial pathway apoptosis, and STAT3 signalling inhibition. The chalcone Michael acceptor character contributes to covalent enzyme inhibition relevant to kinase-dependent tumour cell survival pathways. Research is preclinical. Claim strength: Emerging.

Estrogenic and bone: Isoliquiritigenin binds both ERα and ERβ, with ERβ preference similar to genistein. In osteoblast models, ER-mediated bone-forming activity (RUNX2, ALP upregulation) and osteoclastogenesis inhibition have been documented. Claim strength: Emerging (isolated).

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Dosage & Formulator Specification

No isolated isoliquiritigenin human dosing data exist. Rodent antidepressant studies used 5–20 mg/kg doses translating to estimated human equivalent doses of 50–200 mg/day — achievable with concentrated isoliquiritigenin isolate but not with standard licorice extract (which contains 0.01–0.1% isoliquiritigenin by dry weight). For mood support formulations, DGL Licorice Extract co-delivering isoliquiritigenin alongside liquiritin represents the most practical whole-extract approach; the antidepressant activity in whole licorice preparations may reflect synergistic contribution of both liquiritin and isoliquiritigenin.

For formulator specification: Licorice Root Extract Powder delivers isoliquiritigenin within the full licorice polyphenol spectrum. DGL preparations retain isoliquiritigenin alongside glabridin and liquiritin while removing glycyrrhizin — the preferred vehicle for extended internal use. For applications specifically targeting isoliquiritigenin's Nrf2-mediated antioxidant or antidepressant effects, isolated isoliquiritigenin (≥98% HPLC) from specialty licorice phytochemistry suppliers is required.

Isoliquiritigenin's chalcone scaffold is less stable than flavanone and flavonol scaffolds in aqueous solution — the alpha,beta-unsaturated ketone undergoes slow cyclisation to the corresponding flavanone (liquiritigenin) under acidic or basic conditions. pH 5–7 aqueous formulations and solid dosage forms are preferred for shelf stability. The Michael acceptor character raises the question of non-specific protein reactivity at high concentrations; at typical licorice extract doses, this is not a documented concern.

Licorice root (non-DGL) carries glycyrrhizin considerations as detailed in the Liquiritin entry. DGL preparations are preferred for extended internal use. Isoliquiritigenin's estrogenic activity should be communicated appropriately in formulation contexts involving hormone-sensitive conditions.

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Frequently Asked Questions — Isoliquiritigenin

What is the structural difference between isoliquiritigenin and liquiritigenin?
Isoliquiritigenin is the chalcone: an open-chain alpha,beta-unsaturated ketone (Ar-CO-CH=CH-Ar′) with two hydroxylated aromatic rings. Liquiritigenin is the corresponding flavanone — formed by intramolecular Michael addition/cyclisation of isoliquiritigenin, closing the C-ring and converting the open-chain enone to a chromanone ring system. The chalcone-to-flavanone conversion is catalysed by chalcone isomerase in plants, or occurs non-enzymatically under acidic conditions. In vivo, some intestinal conversion of isoliquiritigenin to liquiritigenin may occur, contributing cross-activity between the two licorice polyphenols.

What is the Michael acceptor mechanism and why is it pharmacologically significant for isoliquiritigenin?
The alpha,beta-unsaturated carbonyl (chalcone enone) is a Michael acceptor — an electrophile that reacts with nucleophilic thiol groups (cysteine residues) in enzyme active sites via a 1,4-addition reaction. This covalent interaction can irreversibly or slowly-reversibly inhibit enzymes with critical active-site cysteines, including: Keap1 (releasing Nrf2 for antioxidant gene induction), certain kinases involved in tumour cell survival, and potentially MAO-B (relevant to monoamine modulation). The Michael acceptor mechanism distinguishes chalcones pharmacologically from non-electrophilic flavonoids (flavones, flavanones) and contributes to their typically broader enzyme inhibition profiles.

How does isoliquiritigenin contribute to licorice root's antidepressant effects alongside liquiritin?
Both contribute via overlapping but distinct mechanisms: liquiritin's antidepressant activity involves monoamine reuptake inhibition, BDNF upregulation, and HPA axis modulation (as detailed in the Liquiritin monograph); isoliquiritigenin adds MAO inhibitory activity and direct Nrf2-mediated neuronal antioxidant protection. The combination of reuptake inhibition (liquiritin), MAO inhibition (isoliquiritigenin), and neuroplasticity support (BDNF from both) in whole licorice preparations mirrors the multi-mechanistic approach of modern antidepressant pharmacotherapy. This mechanistic synergy provides rationale for preferring whole licorice extract preparations over isolated single compounds for mood support applications.

Is isoliquiritigenin the same compound as the chalcone found in Glycyrrhiza inflata?
Glycyrrhiza inflata (Chinese licorice, Gan Cao Zhi) contains particularly high concentrations of the prenylated chalcone licochalcone A and licochalcone E — these are structurally distinct prenylated chalcones not present in G. glabra. Isoliquiritigenin is present in G. inflata as a minor constituent but is not the characteristic chalcone of that species. G. glabra and G. uralensis are the primary commercial sources of non-prenylated isoliquiritigenin. This species distinction is pharmacologically relevant for chalcone-targeted applications.

Related compounds: Liquiritin, Glabridin, Xanthohumol, Butein

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Claim-strength scale – High = multiple human RCTs; Moderate = limited trials or strong preclinical convergence; Emerging = early-stage lab or animal data.

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