Cyanidin

Cyanidin at a Glance

Cyanidin is the aglycone — the sugar-free core — of the most common anthocyanin pigments, and the parent of cyanidin-3-glucoside and its relatives that colour red and purple fruits and flowers.

Free cyanidin barely exists in food or in the body: anthocyanins occur as glycosides, and those are famously unstable and poorly absorbed, with much of their effect attributed to breakdown products formed in the gut.

It is a strong antioxidant by direct assay, which is the least informative thing about it.

Cyanidin Among the Anthocyanidins

The six common anthocyanidins share one flavylium core and differ only in the B-ring. Cyanidin carries a catechol B-ring — two adjacent free hydroxyls at 3’ and 4’ — which puts it one hydroxyl below delphinidin (three) and one above pelargonidin (one). Methylating cyanidin’s 3’-hydroxyl gives peonidin; the delphinidin branch gives petunidin and malvidin the same way ^{15Reference 15Mattioli R et al. · 2020ReviewAnthocyanins: a comprehensive review of their chemical properties and health effects on cardiovascular and neurodegenerative diseases — reviewView study →}.

Where cyanidin actually sits in the potency order is more interesting than the tidy hydroxyl-count story suggests. A study that purified 15 bilberry anthocyanins and ranked them under identical conditions produced two different orders, depending on the oxidant ^{12Reference 12Rahman MM et al. · 2006In vitroSuperoxide radical- and peroxynitrite-scavenging activity of anthocyanins; structure-activity relationship and their synergism — in vitroView study →}:

Radical	Potency order (most → least)
Superoxide (O₂⁻)	delphinidin > petunidin > malvidin ≈ cyanidin > (+)-catechin > peonidin > pelargonidin
Peroxynitrite (ONOO⁻)	delphinidin > cyanidin ≈ petunidin > malvidin ≈ (+)-catechin > peonidin > pelargonidin

Cyanidin is second only to delphinidin against peroxynitrite, but drops to level with the doubly-methylated malvidin against superoxide ^{12Reference 12Rahman MM et al. · 2006In vitroSuperoxide radical- and peroxynitrite-scavenging activity of anthocyanins; structure-activity relationship and their synergism — in vitroView study →} — so which radical a study measures decides where cyanidin ranks. Two further results from the same work bear on how cyanidin claims should be read: the aglycone structure mattered more than the attached sugar in setting activity, and the pigments assayed as a mixture showed synergism against both radicals, out-performing what their individual activities predicted ^{12Reference 12Rahman MM et al. · 2006In vitroSuperoxide radical- and peroxynitrite-scavenging activity of anthocyanins; structure-activity relationship and their synergism — in vitroView study →}. Berries deliver the assortment, not the winner.

What It's Used For

Cyanidin is the aglycone — the sugar-free core — of the most common anthocyanin pigments that color red, purple and blue fruits and flowers. The single most important thing to know is that the free aglycone is largely a paper entity in the body: in plants cyanidin occurs almost entirely as glycosides, chiefly cyanidin-3-glucoside (C3G), and the free molecule is chemically unstable at physiological pH (its colored flavylium cation converts to colorless carbinol and chalcone forms). So almost every human “cyanidin” finding is really about C3G or an anthocyanin mixture (berry/bilberry extract), and much of the apparent activity is actually its downstream metabolite protocatechuic acid ^{5Reference 5Vitaglione P et al. · 2007Protocatechuic acid is the major human metabolite of cyanidin-glucosidesView study →}.

The aglycone’s own best-supported property is direct antioxidant radical scavenging — where aglycones out-perform their glycosides ^{1Reference 1Kähkönen MP · 2003Antioxidant activity of anthocyanins and their aglyconsView study →} — and one of the few studies to test the aglycone directly showed it suppresses inducible nitric-oxide synthase in human coronary smooth-muscle cells ^{2Reference 2Xia N et al. · 2014Artichoke, cynarin and cyanidin downregulate the expression of inducible nitric-oxide synthase in human coronary smooth-muscle cellsView study →}.

Evidence by IndicationStrength of support · Beta

Support is an experimental score — weighted by study type (human > animal > in vitro) and volume. A beta, not a validated metric. The free aglycone has essentially no isolated human data, so scores stay low by design. Each application links to its write-up.

01Antioxidant (property)Shaky40%Cell-free / physicochemical; aglycone > glycoside ^{1Reference 1Kähkönen MP · 2003Antioxidant activity of anthocyanins and their aglyconsView study →}

02Anti-inflammatoryShaky34%Aglycone tested directly on iNOS in one cell model ^{2Reference 2Xia N et al. · 2014Artichoke, cynarin and cyanidin downregulate the expression of inducible nitric-oxide synthase in human coronary smooth-muscle cellsView study →}

03Vascular / endothelialShaky28%iNOS mechanism + anthocyanin-mixture human trials ^{2Reference 2Xia N et al. · 2014Artichoke, cynarin and cyanidin downregulate the expression of inducible nitric-oxide synthase in human coronary smooth-muscle cellsView study →}

04Metabolic / anti-obesityShaky24%Preclinical — the glycoside C3G, not the aglycone ^{7,8Reference 7Oumeddour DZ et al. · 2024Recent advances on cyanidin-3-O-glucoside in preventing obesity-related metabolic disordersView study →Reference 8Deepa P et al. · 2023ReviewA review of the role of the anthocyanin cyanidin-3-O-β-glucoside in obesity-related complicationsView study →}

05AnticancerShaky20%Cell/animal, anthocyanin mixtures ^{6Reference 6Wang LS · 2008Anthocyanins and their role in cancer preventionView study →}

06Vision / eye (mixture lore)Shaky12%Bilberry mixtures; robust RCTs negative ^{10Reference 10Canter PH · 2004Systematic reviewAnthocyanosides of Vaccinium myrtillus (bilberry) for night vision — a systematic review of placebo-controlled trialsView study →}

Mechanisms

Pharmacokinetics

This is the central caveat. Anthocyanins and anthocyanidins are notoriously poorly bioavailable: in the definitive ¹³C-labeled human tracer study of C3G (500 mg oral), relative bioavailability was ~12% with only trace parent in serum, most of the label appearing as downstream metabolites ^{3Reference 3Czank C et al. · 2013Human metabolism and elimination of the anthocyanin cyanidin-3-glucoside: a ¹³C-tracer studyView study →}, and human PK work confirms intact anthocyanins circulate at nanomolar levels while phenolic-acid metabolites dominate exposure ^{4Reference 4de Ferrars RM et al. · 2014The pharmacokinetics of anthocyanins and their metabolites in humansView study →}. The free aglycone is chemically unstable at neutral pH — the flavylium cation opens to colorless carbinol/chalcone forms — so cyanidin barely exists as such in plasma; it is a transient breakdown/deglycosylation species. Its major human metabolite is protocatechuic acid, which accounted for ~73% of ingested cyanidin-glucosides in one study, with serum protocatechuic acid (~490 nmol/L) vastly exceeding intact C3G (~2 nmol/L) ^{5Reference 5Vitaglione P et al. · 2007Protocatechuic acid is the major human metabolite of cyanidin-glucosidesView study →}. Much of the bioactivity attributed to “cyanidin” may in fact be that of protocatechuic acid and other phenolic acids.

Where along the gut those losses happen has been mapped directly. Feeding bilberry anthocyanins to healthy volunteers and to ileostomists — people without a colon — showed that about 30% of the ingested anthocyanins survived the 8-hour passage through the upper intestine, that only ~20% degradants formed there, and that mostly intact anthocyanins were absorbed from the small intestine. Circulating anthocyanins appeared chiefly as glucuronides, and subjects with an intact gut carried substantially more anthocyanins and degradants than the ileostomists — making the colon a significant absorption site rather than merely a place where pigments are destroyed ^{13Reference 13Mueller D et al. · 2017Clinical trialHuman intervention study to investigate the intestinal accessibility and bioavailability of anthocyanins from bilberries — human volunteersView study →}. A follow-up in the same groups found whey-protein encapsulation modulated short-term bioavailability while citrus-pectin encapsulation raised small-intestinal accessibility and altered plasma formation of the degradant phloroglucinol aldehyde ^{14Reference 14Mueller D et al. · 2018Clinical trialEncapsulation of anthocyanins from bilberries — effects on bioavailability and intestinal accessibility in humans — clinical trialView study →} — formulation moves these numbers, which is why an extract’s anthocyanin percentage says little about what is absorbed.

Clinical trials

There are essentially no trials of the isolated cyanidin aglycone — its instability makes that impractical. Human data labeled “cyanidin” are either C3G pharmacokinetic/metabolic studies ^{3,4,5Reference 3Czank C et al. · 2013Human metabolism and elimination of the anthocyanin cyanidin-3-glucoside: a ¹³C-tracer studyView study →Reference 4de Ferrars RM et al. · 2014The pharmacokinetics of anthocyanins and their metabolites in humansView study →Reference 5Vitaglione P et al. · 2007Protocatechuic acid is the major human metabolite of cyanidin-glucosidesView study →} or anthocyanin/berry/bilberry mixture trials ^{6,10Reference 6Wang LS · 2008Anthocyanins and their role in cancer preventionView study →Reference 10Canter PH · 2004Systematic reviewAnthocyanosides of Vaccinium myrtillus (bilberry) for night vision — a systematic review of placebo-controlled trialsView study →}; the vision claims specifically fail robust RCT support ^{10Reference 10Canter PH · 2004Systematic reviewAnthocyanosides of Vaccinium myrtillus (bilberry) for night vision — a systematic review of placebo-controlled trialsView study →}. Attribute all human evidence to C3G or mixtures, never the aglycone.

Last checked: July 2026.

Isolate vs. Plant Studies

Cyanidin’s evidence divides sharply, and almost none of it tests the free aglycone. The human data belong to cyanidin-3-glucoside (the ¹³C-tracer and pharmacokinetic studies) or to berry and bilberry mixtures — the vision, cardiovascular and cancer-prevention literature ^{3,4,6,10Reference 3Czank C et al. · 2013Human metabolism and elimination of the anthocyanin cyanidin-3-glucoside: a ¹³C-tracer studyView study →Reference 4de Ferrars RM et al. · 2014The pharmacokinetics of anthocyanins and their metabolites in humansView study →Reference 6Wang LS · 2008Anthocyanins and their role in cancer preventionView study →Reference 10Canter PH · 2004Systematic reviewAnthocyanosides of Vaccinium myrtillus (bilberry) for night vision — a systematic review of placebo-controlled trialsView study →}. The isolated aglycone appears in a handful of cell studies: the iNOS work in human coronary smooth muscle ^{2Reference 2Xia N et al. · 2014Artichoke, cynarin and cyanidin downregulate the expression of inducible nitric-oxide synthase in human coronary smooth-muscle cellsView study →} and the cell-free scavenging comparisons ^{1,12Reference 1Kähkönen MP · 2003Antioxidant activity of anthocyanins and their aglyconsView study →Reference 12Rahman MM et al. · 2006In vitroSuperoxide radical- and peroxynitrite-scavenging activity of anthocyanins; structure-activity relationship and their synergism — in vitroView study →}. Nothing tested in a person was cyanidin, and nothing shown for cyanidin has been tested in a person.

The plant side compounds the problem. Cyanidin is named across this catalogue’s berry, cherry and red-flower entries — raspberry, hibiscus, bilberry among them — always as its glycosides inside a mixed pigment fraction, and a herb’s “cyanidin content” is a measurement made after hydrolysing those glycosides. Read the human evidence as evidence for C3G or for whole berries, and the aglycone chemistry as chemistry.

Prevalence in Nature

Cyanidin is the most widely distributed of the six common anthocyanidins — the default red-purple plant pigment, present in blackberry, raspberry, cherry, blackcurrant, elderberry, red cabbage, purple corn, black rice, blood orange, cornflower and red hibiscus petals ^{15,16Reference 15Mattioli R et al. · 2020ReviewAnthocyanins: a comprehensive review of their chemical properties and health effects on cardiovascular and neurodegenerative diseases — reviewView study →Reference 16Fang J · 2015ReviewClassification of fruits based on anthocyanin types and relevance to their health effects — reviewView study →}. It occurs almost entirely as 3-O-glycosides, of which cyanidin-3-glucoside is the single most abundant anthocyanin in the human diet ^{16Reference 16Fang J · 2015ReviewClassification of fruits based on anthocyanin types and relevance to their health effects — reviewView study →}; 3-galactosides, 3-rutinosides, 3-sambubiosides and acylated forms account for most of the rest, and it is the glycoside profile rather than the aglycone that distinguishes one fruit from another ^{16Reference 16Fang J · 2015ReviewClassification of fruits based on anthocyanin types and relevance to their health effects — reviewView study →}.

Concentrations vary by orders of magnitude between and within species, tracking cultivar, ripeness, light exposure and growing conditions, so a single “cyanidin content” figure for a fruit is rarely meaningful. Red hibiscus petals are among the denser measured sources at roughly 36 mg/g fresh weight of cyanidin-type pigment ^{11Reference 11Mejía JJ et al. · 2023Colour, antioxidant capacity and flavonoid composition in Hibiscus rosa-sinensis cultivarsView study →}. Biosynthetically cyanidin sits mid-pathway: the flavonoid route runs through dihydroquercetin to leucocyanidin, which anthocyanidin synthase converts to cyanidin; O-methylation of its 3’-hydroxyl then yields peonidin, and further hydroxylation upstream diverts flux to delphinidin and its methylated derivatives ^{15Reference 15Mattioli R et al. · 2020ReviewAnthocyanins: a comprehensive review of their chemical properties and health effects on cardiovascular and neurodegenerative diseases — reviewView study →}. In the plant the pigment’s job is optical and protective — flower and fruit colouring for pollinators and seed dispersers, plus screening against UV and oxidative stress ^{15Reference 15Mattioli R et al. · 2020ReviewAnthocyanins: a comprehensive review of their chemical properties and health effects on cardiovascular and neurodegenerative diseases — reviewView study →}.

Discovery & Synthesis

Cyanidin takes its name from the cornflower, Centaurea cyanus, whose blue pigment cyanin was among the first anthocyanins isolated in the classical plant-pigment chemistry of the early twentieth century; cyanidin is the aglycone left when cyanin’s sugars are removed. That era of work established the six common anthocyanidins and their relationships, and the structural chemistry has not needed revision since ^{15Reference 15Mattioli R et al. · 2020ReviewAnthocyanins: a comprehensive review of their chemical properties and health effects on cardiovascular and neurodegenerative diseases — reviewView study →}. A precise first isolation of the free aglycone — worker and date — is not cleanly documented in the accessible literature. It is handled and sold for research as the stable cyanidin chloride salt.

There is no commercial production of the free aglycone, and the reason is the same instability: above about pH 4 the coloured flavylium cation opens to colourless carbinol and chalcone forms, so an isolated aglycone is not a storable ingredient ^{15Reference 15Mattioli R et al. · 2020ReviewAnthocyanins: a comprehensive review of their chemical properties and health effects on cardiovascular and neurodegenerative diseases — reviewView study →}. Cyanidin reaches people entirely as glycosides inside foods and berry extracts; where a pure sample is needed it is prepared by acid hydrolysis of a cyanidin glycoside rather than built by total synthesis. Anthocyanin colourants sold to the food industry are pigment mixtures, not single molecules.

Patents: not yet researched (future patent-loop pass).

Toxicity & Safety

Cyanidin and its glycosides are ubiquitous dietary pigments eaten in colored fruits, vegetables and flowers, and are regarded as safe at ordinary dietary levels with no significant toxicity from normal food intake. Anthocyanin and berry supplements are well tolerated in trials at doses well above dietary intake. There are no established drug interactions for the isolated aglycone; theoretical additive antioxidant, anti-inflammatory or mild antiplatelet effects from anthocyanin-rich intake are unconfirmed, and the poor systemic bioavailability further limits any systemic-toxicity concern.

Dosage

There is no established dose for isolated cyanidin — it is not used as a standalone supplement and is unstable. For research context only (glycoside/mixture figures, not aglycone dosing, and not a recommendation): the human ¹³C tracer study used a 500 mg oral bolus of C3G ^{3Reference 3Czank C et al. · 2013Human metabolism and elimination of the anthocyanin cyanidin-3-glucoside: a ¹³C-tracer studyView study →}; anthocyanin/bilberry supplement trials commonly use extracts up to ~320–720 mg/day ^{10Reference 10Canter PH · 2004Systematic reviewAnthocyanosides of Vaccinium myrtillus (bilberry) for night vision — a systematic review of placebo-controlled trialsView study →}; and typical Western dietary anthocyanin intake is on the order of ~200 mg/day ^{6Reference 6Wang LS · 2008Anthocyanins and their role in cancer preventionView study →}.

References

1. Kähkönen MP, Heinonen M (2003). Antioxidant activity of anthocyanins and their aglycons. Journal of Agricultural and Food Chemistry. https://pubmed.ncbi.nlm.nih.gov/12537433/
2. Xia N, et al. (2014). Artichoke, cynarin and cyanidin downregulate the expression of inducible nitric-oxide synthase in human coronary smooth-muscle cells. Molecules. https://pubmed.ncbi.nlm.nih.gov/24662080/
3. Czank C, et al. (2013). Human metabolism and elimination of the anthocyanin cyanidin-3-glucoside: a ¹³C-tracer study. The American Journal of Clinical Nutrition. https://pubmed.ncbi.nlm.nih.gov/23604435/
4. de Ferrars RM, et al. (2014). The pharmacokinetics of anthocyanins and their metabolites in humans. British Journal of Pharmacology. https://pubmed.ncbi.nlm.nih.gov/24602005/
5. Vitaglione P, et al. (2007). Protocatechuic acid is the major human metabolite of cyanidin-glucosides. The Journal of Nutrition. https://pubmed.ncbi.nlm.nih.gov/17709440/
6. Wang LS, Stoner GD (2008). Anthocyanins and their role in cancer prevention. Cancer Letters. https://pubmed.ncbi.nlm.nih.gov/18571839/
7. Oumeddour DZ, Al-Dalali S, Zhao L, et al. (2024). Recent advances on cyanidin-3-O-glucoside in preventing obesity-related metabolic disorders. Biochemical and Biophysical Research Communications. https://pubmed.ncbi.nlm.nih.gov/38976946/
8. Deepa P, Hong M, Sowndhararajan K, et al. (2023). A review of the role of the anthocyanin cyanidin-3-O-β-glucoside in obesity-related complications. Plants (Basel). https://pubmed.ncbi.nlm.nih.gov/38005786/
9. Miyake S, Takahashi N, Sasaki M, et al. (2012). Vision preservation during retinal inflammation by anthocyanin-rich bilberry extract. Laboratory Investigation. https://pubmed.ncbi.nlm.nih.gov/21894150/
10. Canter PH, Ernst E (2004). Anthocyanosides of Vaccinium myrtillus (bilberry) for night vision — a systematic review of placebo-controlled trials. Survey of Ophthalmology. https://pubmed.ncbi.nlm.nih.gov/14711439/
11. Mejía JJ, et al. (2023). Colour, antioxidant capacity and flavonoid composition in Hibiscus rosa-sinensis cultivars. Molecules. https://pubmed.ncbi.nlm.nih.gov/36838766/
12. Rahman MM, Ichiyanagi T, Komiyama T, et al. (2006). Superoxide radical- and peroxynitrite-scavenging activity of anthocyanins; structure-activity relationship and their synergism — in vitro. Free Radical Research. https://pubmed.ncbi.nlm.nih.gov/17015281/
13. Mueller D, Jung K, Winter M, et al. (2017). Human intervention study to investigate the intestinal accessibility and bioavailability of anthocyanins from bilberries — human volunteers. Food Chemistry. https://pubmed.ncbi.nlm.nih.gov/28450007/
14. Mueller D, Jung K, Winter M, et al. (2018). Encapsulation of anthocyanins from bilberries — effects on bioavailability and intestinal accessibility in humans — clinical trial. Food Chemistry. https://pubmed.ncbi.nlm.nih.gov/29329847/
15. Mattioli R, Francioso A, Mosca L, et al. (2020). Anthocyanins: a comprehensive review of their chemical properties and health effects on cardiovascular and neurodegenerative diseases — review. Molecules. https://pubmed.ncbi.nlm.nih.gov/32825684/
16. Fang J (2015). Classification of fruits based on anthocyanin types and relevance to their health effects — review. Nutrition. https://pubmed.ncbi.nlm.nih.gov/26250485/

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