Emodin

Pharmacology & Research

Emodin is a trihydroxy-methyl anthraquinone (1,3,8-trihydroxy-6-methylanthraquinone) found across the anthraquinone-laxative herbs — rhubarb, yellow dock, cascara, Japanese knotweed and senna ^{20,21Reference 20Eom TJ et al. · 2020In-vitro antioxidant, anti-inflammation and anticancer activities and anthraquinone content from Rumex crispus rootView study →Reference 212024ReviewRumex crispus L.: a comprehensive review of its botany, phytochemistry, pharmacology and safetyView study →}. Two framing points matter before any claim. First, the purgative action of those herbs is driven by the anthraquinone glycosides (sennosides, cascarosides, anthraquinone-O-glucosides) surviving to the colon where flora liberate active anthrones — not by free emodin, which is absorbed upstream and is only a minor contributor to laxation ^{14Reference 14Malik EM · 2018Anthraquinones as pharmacological tools and drugs / cytotoxicity of structurally diverse anthranoids and correlation with mechanism and side effectsView study →}. Second, emodin has poor oral bioavailability (~3–5% in rats) because it is heavily glucuronidated on absorption, so free parent is largely undetectable in plasma ^{3,2Reference 3Liu Z et al. · 2012Coupling of UGTs and MRPs is responsible for the intestinal disposition and poor bioavailability of emodinView study →Reference 2Dong X et al. · 2016ReviewEmodin: a review of its pharmacology, toxicity and pharmacokineticsView study →}. Against that, emodin has an enormous preclinical literature — anti-inflammatory (NF-κB/NLRP3), anticancer, metabolic (11β-HSD1) and antiviral — but no human efficacy trial of the isolated molecule, and a materially heavier safety profile than most dietary constituents (see Toxicity).

1. Anti-inflammatory

Emodin suppresses NF-κB and NLRP3-inflammasome signalling and, in rats, attenuated severe-acute-pancreatitis-associated acute lung injury by blocking pancreatic-exosome-driven alveolar-macrophage activation ^{9Reference 9Xu M et al. · 2022Emodin attenuates severe acute pancreatitis-associated acute lung injury by suppressing pancreatic-exosome-mediated alveolar-macrophage activationView study →}. The one human-grade signal is a meta-analysis of RCTs adding crude rhubarb to somatostatin in acute pancreatitis, favourable on symptom and inflammatory endpoints ^{11Reference 112016Meta-analysisAdd-on effect of crude rhubarb to somatostatin for acute pancreatitis: a meta-analysis of randomized controlled trialsView study →}.

Gap: the human benefit is a whole-herb/formula effect that cannot be attributed to emodin specifically, and there is no isolated-emodin human trial ^{11Reference 112016Meta-analysisAdd-on effect of crude rhubarb to somatostatin for acute pancreatitis: a meta-analysis of randomized controlled trialsView study →}.

2. Anticancer

Across many cell lines and xenografts, emodin is anti-proliferative, pro-apoptotic (intrinsic/mitochondrial) and anti-angiogenic, with HER-2/neu tyrosine-kinase and casein-kinase-2 inhibition proposed as drivers; semi-synthetic glycoside derivatives improve potency and solubility in vitro ^{12,13,6Reference 122012Anticancer potential of emodinView study →Reference 132015In vitroAntitumor effects and mechanism of novel emodin rhamnoside derivatives against human cancer cells in vitroView study →Reference 6Zhang L et al. · 1998Tyrosine kinase inhibitors: emodin and its derivative repress HER-2/neu-induced cellular transformationView study →}.

Gap: essentially all data are cell-line/xenograft and heavily redundant, poor oral bioavailability undermines translation, and there are zero human oncology trials ^{3,12Reference 3Liu Z et al. · 2012Coupling of UGTs and MRPs is responsible for the intestinal disposition and poor bioavailability of emodinView study →Reference 122012Anticancer potential of emodinView study →}.

3. Metabolic (11β-HSD1)

Emodin is a selective 11β-hydroxysteroid-dehydrogenase-1 inhibitor (sparing the type-2 enzyme) that lowered glucose and insulin, improved insulin resistance and dyslipidaemia and reduced central fat in diet-induced-obese and ob/ob mice ^{4,5Reference 4Feng Y et al. · 2010AnimalEmodin, a natural product, selectively inhibits 11β-HSD1 and ameliorates metabolic disorder in diet-induced obese miceView study →Reference 52012AnimalEmodin, an 11β-HSD1 inhibitor, regulates adipocyte function and exerts an anti-diabetic effect in ob/ob miceView study →}.

Gap: rodent-only, with poor bioavailability — positioned as a lead scaffold, not a validated therapy ^{4,5Reference 4Feng Y et al. · 2010AnimalEmodin, a natural product, selectively inhibits 11β-HSD1 and ameliorates metabolic disorder in diet-induced obese miceView study →Reference 52012AnimalEmodin, an 11β-HSD1 inhibitor, regulates adipocyte function and exerts an anti-diabetic effect in ob/ob miceView study →}.

4. Antiviral / antimicrobial

Emodin blocked the SARS-coronavirus spike-protein–ACE2 interaction in vitro ^{8Reference 8Ho TY et al. · 2007Emodin blocks the SARS coronavirus spike protein and angiotensin-converting-enzyme-2 interactionView study →} and inhibited Candida albicans growth, hyphal development and biofilm via CK2 inhibition ^{7Reference 7Janeczko M et al. · 2017Emodin, a natural inhibitor of protein kinase CK2, suppresses growth, hyphal development and biofilm formation of Candida albicansView study →}.

Gap: in-vitro only, with no in-vivo antiviral efficacy or clinical data, and no established relevance to SARS-CoV-2 ^{8,7Reference 8Ho TY et al. · 2007Emodin blocks the SARS coronavirus spike protein and angiotensin-converting-enzyme-2 interactionView study →Reference 7Janeczko M et al. · 2017Emodin, a natural inhibitor of protein kinase CK2, suppresses growth, hyphal development and biofilm formation of Candida albicansView study →}.

5. Hepatoprotective ↔ hepatotoxic

The tension is real. Rhubarb free anthraquinones (emodin-containing) improved murine non-alcoholic fatty liver disease by inhibiting NLRP3 ^{10Reference 102022AnimalRhubarb free anthraquinones improved mouse non-alcoholic fatty liver disease by inhibiting the NLRP3 inflammasomeView study →}, yet emodin is also documented as dose- and duration-dependently hepatotoxic and nephrotoxic ^{15,2Reference 15Akkol EK et al. · 2021Is emodin with anticancer effects completely innocent? Two sides of the coinView study →Reference 2Dong X et al. · 2016ReviewEmodin: a review of its pharmacology, toxicity and pharmacokineticsView study →}.

Gap: the protective and toxic signals coexist and are dose-dependent, so the net effect is unresolved — do not present emodin as a clean hepatoprotectant ^{10,15Reference 102022AnimalRhubarb free anthraquinones improved mouse non-alcoholic fatty liver disease by inhibiting the NLRP3 inflammasomeView study →Reference 15Akkol EK et al. · 2021Is emodin with anticancer effects completely innocent? Two sides of the coinView study →}.

6. Laxative (class effect)

The anthraquinone/anthranoid class stimulates colonic motility and secretion, but the active species are the O-glycosides converted to anthrones by colonic flora; free emodin is only a secondary contributor ^{14Reference 14Malik EM · 2018Anthraquinones as pharmacological tools and drugs / cytotoxicity of structurally diverse anthranoids and correlation with mechanism and side effectsView study →}.

Gap: this is not an emodin-isolate indication — it belongs to the herb/glycoside, and it sits under the EU restriction of hydroxyanthracene derivatives ^{16Reference 16EFSA ANS Panel · 2018Safety of hydroxyanthracene derivatives for use in foodView study →}.

Mechanisms

Target / pathway	Effect	Relevant to
NF-κB signalling	↓ pro-inflammatory transcription	anti-inflammatory, pancreatitis
NLRP3 inflammasome	↓ activation → less IL-1β	anti-inflammatory, NAFLD
11β-HSD1 (selective vs type-2)	blocks tissue cortisone→cortisol regeneration	metabolic syndrome
Casein kinase 2 (CK2) inhibition	anti-proliferative; antifungal	anticancer, Candida biofilm
HER-2/neu receptor tyrosine kinase	↓ tyrosine phosphorylation/transformation	anticancer (HER2 lines)
Intrinsic/mitochondrial apoptosis	pro-apoptotic, anti-proliferative	anticancer (in vitro)
SARS-CoV spike–ACE2 interface	blocks binding in vitro	antiviral (in vitro)

Pharmacokinetics

Load-bearing and constraining. Free emodin has poor oral bioavailability (~3–5% in rats) driven by extensive intestinal and hepatic glucuronidation coupled to multidrug-resistance-protein efflux, so parent emodin is rapidly conjugated and largely undetectable in plasma while the glucuronide dominates systemic exposure ^{3,2Reference 3Liu Z et al. · 2012Coupling of UGTs and MRPs is responsible for the intestinal disposition and poor bioavailability of emodinView study →Reference 2Dong X et al. · 2016ReviewEmodin: a review of its pharmacology, toxicity and pharmacokineticsView study →}. It undergoes enterohepatic recycling — biliary excretion of conjugates, colonic deconjugation, reabsorption — producing secondary plasma peaks but sustained low free-drug levels ^{2Reference 2Dong X et al. · 2016ReviewEmodin: a review of its pharmacology, toxicity and pharmacokineticsView study →}. The consequence runs through every application above: the high in-vitro potencies almost certainly overstate the free-plasma concentrations achievable in vivo.

Clinical trials

There are no human efficacy trials of isolated emodin. The only clinical-grade human evidence in this space is for whole rhubarb or rhubarb-based formulas (e.g. crude rhubarb added to somatostatin for acute pancreatitis) ^{11Reference 112016Meta-analysisAdd-on effect of crude rhubarb to somatostatin for acute pancreatitis: a meta-analysis of randomized controlled trialsView study →} — multi-constituent preparations whose benefit cannot be attributed to the molecule. Treat all human data as herb/formula-level.

Last checked: July 2026.

Toxicity & Safety

Emodin carries a materially heavier safety profile than most encyclopedia constituents, which is why this page is flagged moderate rather than low.

• Genotoxicity / carcinogenicity signal. Emodin is genotoxic in multiple in-vitro assays and belongs to the anthranoid class flagged by regulators ^{17,14,19Reference 17Brusick D · 1997Assessment of the genotoxic risk from laxative senna productsView study →Reference 14Malik EM · 2018Anthraquinones as pharmacological tools and drugs / cytotoxicity of structurally diverse anthranoids and correlation with mechanism and side effectsView study →Reference 192025Phytotoxicity and cytogenotoxic effects of extracts from the medicinal bark of Rhamnus purshianaView study →}. The US National Toxicology Program 2-year feed bioassay (Technical Report TR-493, 2001) found no evidence of carcinogenicity in male rats, equivocal evidence in female rats (a marginal increase in Zymbal’s-gland carcinoma) and in male mice (uncommon renal-tubule neoplasms), and non-neoplastic renal-tubule changes across sexes and species ^{1Reference 1National Toxicology Program · 2001AnimalToxicology and carcinogenesis studies of emodin (CAS 518-82-1) in F344/N rats and B6C3F1 mice (feed studies)View study →}. The animal finding is therefore “equivocal,” not definitive — but real, and renal/Zymbal’s-gland-directed.
• Regulatory context. EFSA (2018) reviewed hydroxyanthracene derivatives (emodin, aloe-emodin, danthron and the parent extracts) and concluded they raise a genotoxicity/safety concern in food, underpinning the EU/EMA restriction on hydroxyanthracene derivatives in food and supplements ^{16Reference 16EFSA ANS Panel · 2018Safety of hydroxyanthracene derivatives for use in foodView study →}.
• Organ toxicity. Dose- and duration-dependent hepatotoxicity and nephrotoxicity are documented, coexisting with the hepatoprotective signal — net effect dose-dependent ^{2,15Reference 2Dong X et al. · 2016ReviewEmodin: a review of its pharmacology, toxicity and pharmacokineticsView study →Reference 15Akkol EK et al. · 2021Is emodin with anticancer effects completely innocent? Two sides of the coinView study →}.
• Reproductive/developmental. Developmental-toxicity evaluations in rats and mice, plus preclinical reports of testicular, oocyte and sperm-motility effects ^{18,2Reference 182004AnimalDevelopmental toxicity evaluation of emodin in rats and miceView study →Reference 2Dong X et al. · 2016ReviewEmodin: a review of its pharmacology, toxicity and pharmacokineticsView study →}.
• Interactions. As a UGT substrate and modulator, emodin may perturb glucuronidation-dependent drug clearance; the anthraquinone-laxative class can cause potassium loss, compounding digoxin, diuretic and antiarrhythmic risk ^{2Reference 2Dong X et al. · 2016ReviewEmodin: a review of its pharmacology, toxicity and pharmacokineticsView study →}.

Dosage

There is no established or safe human dose for isolated emodin, and nothing here is a recommendation. For reference only, rodent pharmacology used roughly 20–40 mg/kg intragastrically for pharmacokinetics/efficacy and 40–80 mg/kg in metabolic studies, and the NTP feed studies used 280–2,500 ppm in the diet ^{1,3Reference 1National Toxicology Program · 2001AnimalToxicology and carcinogenesis studies of emodin (CAS 518-82-1) in F344/N rats and B6C3F1 mice (feed studies)View study →Reference 3Liu Z et al. · 2012Coupling of UGTs and MRPs is responsible for the intestinal disposition and poor bioavailability of emodinView study →}. Human intake occurs incidentally via anthraquinone-containing laxative herbs, dosed to the herb’s hydroxyanthracene-glycoside content rather than to free emodin — and given poor oral bioavailability, oral free-emodin doses do not translate to meaningful systemic exposure.

References