Capsorubin

Capsorubin at a Glance

Capsorubin is the second red pigment of ripe Capsicum — the deeper-red, scarcer companion to capsanthin in paprika, cayenne and sweet peppers. Chemically it is a keto-xanthophyll: a C40 carotenoid whose polyene chain terminates in two hydroxylated cyclopentyl ketone rings rather than the six-membered ionone rings of β-carotene or zeaxanthin.

Those rings — κ-end groups — are what make this molecule worth its own page. Capsanthin carries one; capsorubin carries two, which is close to unique in nature and makes the pigment a near-signature of the genus Capsicum ^{11,19Reference 11Fernández-García E et al. · 2016Carotenoids exclusively synthesized in red pepper (capsanthin and capsorubin) protect human dermal fibroblasts against UVB induced DNA damageView study →Reference 19Jeknić Z et al. · 2012Cloning and functional characterization of a gene for capsanthin-capsorubin synthase from tiger lily (Lilium lancifolium Thunb. ‘Splendens’)View study →}.

Its practical role is as a colourant. Capsorubin is one of the two named components of the EU food additive paprika extract, capsanthin, capsorubin (E 160c) ^{20,21Reference 20EFSA Panel on Food Additives et al. · 2015Scientific opinion on the re-evaluation of paprika extract (E 160c) as a food additiveView study →Reference 21Rodriguez-Amaya DB et al. · 2023Comprehensive update on carotenoid colorants from plants and microalgae: challenges and advances from research laboratories to industryView study →}, where it rides commercially on capsanthin’s coat-tails — capsanthin is roughly ten times more abundant ^{3Reference 3Deli J et al. · 2001Carotenoid composition in the fruits of red paprika (Capsicum annuum var. lycopersiciforme rubrum) during ripening; biosynthesis of carotenoids in red paprikaView study →}. Its pharmacology, by contrast, is genuinely thin: the isolate’s bioactivity record is chemical and cell-culture antioxidant work, and the one human absorption study that looked for it could not find it in blood at all ^{6Reference 6Pérez-Gálvez A et al. · 2003Incorporation of carotenoids from paprika oleoresin into human chylomicronsView study →}. It is also not a provitamin A carotenoid.

Capsorubin vs. Capsanthin

The pair is best understood as one enzyme’s two products.

Capsanthin-capsorubin synthase (CCS) is a bifunctional enzyme, purified from Capsicum annuum chromoplasts and cloned in 1994, that converts the ubiquitous 5,6-epoxycarotenoids antheraxanthin → capsanthin and violaxanthin → capsorubin ^{1Reference 1Bouvier F et al. · 1994Xanthophyll biosynthesis in chromoplasts: isolation and molecular cloning of an enzyme catalyzing the conversion of 5,6-epoxycarotenoid into ketocarotenoidView study →}. Antheraxanthin has one epoxidised ring; violaxanthin has two. So the difference between the two red pigments is not a difference in enzyme but a difference in how many epoxide rings the substrate brought to the reaction.

	Capsanthin	Capsorubin
Substrate	Antheraxanthin (mono-epoxide)	Violaxanthin (di-epoxide) 1,2Reference 1Bouvier F et al. · 1994Xanthophyll biosynthesis in chromoplasts: isolation and molecular cloning of an enzyme catalyzing the conversion of 5,6-epoxycarotenoid into ketocarotenoidView study →Reference 2Camara B · 1980In vitroCarotenoid biosynthesis: in vitro conversion of violaxanthin to capsorubin by a chromoplast enriched fraction of Capsicum fruitsView study →
End groups	one κ (cyclopentyl), one β (ionone)	two κ 11,19Reference 11Fernández-García E et al. · 2016Carotenoids exclusively synthesized in red pepper (capsanthin and capsorubin) protect human dermal fibroblasts against UVB induced DNA damageView study →Reference 19Jeknić Z et al. · 2012Cloning and functional characterization of a gene for capsanthin-capsorubin synthase from tiger lily (Lilium lancifolium Thunb. ‘Splendens’)View study →
Formula	C40H56O3	C40H56O4
Share of ripe-paprika carotenoids	~37%	~3.2% 3Reference 3Deli J et al. · 2001Carotenoid composition in the fruits of red paprika (Capsicum annuum var. lycopersiciforme rubrum) during ripening; biosynthesis of carotenoids in red paprikaView study →
Colour	red	deeper red / red-orange
Provitamin A	no	no

Three consequences follow. Capsorubin is rarer — a few percent of the carotenoid pool where capsanthin is a third or more ^{3,25Reference 3Deli J et al. · 2001Carotenoid composition in the fruits of red paprika (Capsicum annuum var. lycopersiciforme rubrum) during ripening; biosynthesis of carotenoids in red paprikaView study →Reference 25de Azevedo-Meleiro CH · 2009Qualitative and quantitative differences in the carotenoid composition of yellow and red peppers determined by HPLC-DAD-MSView study →}. It is redder, because two conjugated carbonyls extend the chromophore further than one. And it is more chemically stable: in a free-radical oxidation assay across the pepper carotenoid profile, capsorubin degraded most slowly of all, ahead of zeaxanthin, capsanthin and β-carotene, an effect the authors attributed directly to the keto groups at both ends of the polyene chain ^{9,10Reference 9Pérez-Gálvez A · 2002Degradation of non-esterified and esterified xanthophylls by free radicalsView study →Reference 10Pérez-Gálvez A · 2001Structure-reactivity relationship in the oxidation of carotenoid pigments of the pepper (Capsicum annuum L.)View study →}.

The Doubled κ-End Group

A κ-end group is a five-membered ring bearing a ketone and a hydroxyl, formed by contracting the usual six-membered carotenoid ring. Formally the transformation is a pinacol-type rearrangement of a 5,6-epoxide: the epoxide opens, the ring contracts, and a cyclopentyl ketone is left behind. It is a skeletal rearrangement, not an oxidation — consistent with the finding that plant carotenoid cyclases of the CCS family operate as flavoproteins with no net redox change ^{30Reference 30Mialoundama AS et al. · 2010Characterization of plant carotenoid cyclases as members of the flavoprotein family functioning with no net redox changeView study →}.

The chemistry is real enough that synthetic chemists reproduced it deliberately: Yamano and Ito’s 2007 total synthesis of both capsanthin and capsorubin was built around a Lewis-acid-promoted, regio- and stereoselective rearrangement of a tetrasubstituted epoxide to install the C15 cyclopentyl ketone — the laboratory analogue of what CCS does in the ripening fruit ^{17Reference 17Yamano Y · 2007Total synthesis of capsanthin and capsorubin using Lewis acid-promoted regio- and stereoselective rearrangement of tetrasubstituted epoxidesView study →}.

Because capsorubin needs the rearrangement to happen twice, it depends on a plant that both makes violaxanthin in quantity and expresses CCS in its chromoplasts. That combination is rare, which is why the molecule is so strongly associated with peppers.

The doubled κ-end also changes how the molecule reacts with oxidants. Where capsanthin forms 5,6- and 5,8-epoxides with superoxide and hydroxyl radicals and 5,6-/5,8-endoperoxides with singlet oxygen, capsorubin was more stable against all three species and reacted at a different position, giving the 7,8-epoxide and 7,8-endoperoxide ^{8Reference 8Nishino A et al. · 2016Reaction of paprika carotenoids, capsanthin and capsorubin, with reactive oxygen speciesView study →}.

The Capsanthin-to-Capsorubin Ratio

Because the two pigments come from one enzyme acting on two substrates, their ratio is a readout of the fruit’s violaxanthin/antheraxanthin balance during ripening — and it is remarkably lopsided. In fully ripe red paprika, capsanthin made up 37% of total carotenoids against capsorubin’s 3.2%, with total carotenoid content around 1.3 g per 100 g dry weight ^{3Reference 3Deli J et al. · 2001Carotenoid composition in the fruits of red paprika (Capsicum annuum var. lycopersiciforme rubrum) during ripening; biosynthesis of carotenoids in red paprikaView study →}. A supercritical-CO2 extract of Senise pepper waste showed the same picture in an industrial matrix: capsanthin 5.88 mg/g of extract, capsorubin 0.38 mg/g — a ratio near 15:1 ^{22Reference 22Larocca V et al. · 2026Senise red pepper (Capsicum annuum L.) wastes as source of rich capsanthin extracts by supercritical CO2 extractionView study →}. In Brazilian red bell pepper, capsanthin was the dominant carotenoid at 29–36 µg/g fresh weight while capsorubin was listed only among the minor pigments ^{25Reference 25de Azevedo-Meleiro CH · 2009Qualitative and quantitative differences in the carotenoid composition of yellow and red peppers determined by HPLC-DAD-MSView study →}.

Both pigments appear de novo during ripening; neither is present in the green fruit, where the chloroplast pigments lutein and neoxanthin dominate before disappearing ^{4Reference 4Hornero-Méndez D et al. · 2000Carotenoid biosynthesis changes in five red pepper (Capsicum annuum L.) cultivars during ripeningView study →}.

A caveat on the “authentication marker” idea. Capsorubin’s near-exclusivity to Capsicum makes it an attractive marker for genuine paprika, and validated ultra-HPLC methods for quantifying free capsorubin and capsanthin in red pepper powder exist — with recovery above 83% and a limit of detection of 0.043 mg/kg for capsorubin ^{24Reference 24Shim YS et al. · 2013Simultaneous determination of free capsorubin and capsanthin in red pepper powder using u-HPLCView study →}. But we found no published authentication or anti-adulteration protocol built on the capsanthin:capsorubin ratio itself. Treat it as a plausible chemical fingerprint that the analytical tooling would support, not as an established regulatory test.

Not a Provitamin A Carotenoid

This needs stating plainly, because “carotenoid” is often read as “vitamin A”.

Provitamin A activity requires at least one unsubstituted β-ionone ring for the cleavage enzyme to act on. Capsorubin has none — both of its ends are κ-rings bearing a ketone and a hydroxyl. It therefore contributes no vitamin A activity whatsoever. Neither does capsanthin, which has a substituted (3-hydroxy-oxo) β-ring.

The human absorption study on paprika oleoresin makes the same division explicitly: the oleoresin is described as a good source of the provitamin A carotenoids β-carotene and β-cryptoxanthin and of the macular pigment zeaxanthin — the paprika-specific oxocarotenoids capsanthin and capsorubin are listed separately, on the grounds of very low bioavailability ^{6Reference 6Pérez-Gálvez A et al. · 2003Incorporation of carotenoids from paprika oleoresin into human chylomicronsView study →}. Any vitamin A you get from red pepper comes from its β-carotene and β-cryptoxanthin, not from its red pigments.

Paprika Oleoresin & E 160c

Capsorubin’s one unambiguous commercial role is as a colourant. The EU food additive is named after both pigments — “paprika extract, capsanthin, capsorubin” (E 160c) — and was re-evaluated by EFSA in 2015 ^{20Reference 20EFSA Panel on Food Additives et al. · 2015Scientific opinion on the re-evaluation of paprika extract (E 160c) as a food additiveView study →}. Paprika (capsanthin and capsorubin) sits alongside annatto, saffron crocin, tomato lycopene, marigold lutein and microalgal β-carotene and astaxanthin on the short list of commercially produced plant and algal carotenoid colorants ^{21Reference 21Rodriguez-Amaya DB et al. · 2023Comprehensive update on carotenoid colorants from plants and microalgae: challenges and advances from research laboratories to industryView study →}.

In practice capsorubin is never sold on its own. It is a minority component of an extract whose colour strength is dominated by capsanthin, so its commercial fate is entirely tied to paprika oleoresin’s. Extraction has been moving from organic solvents toward supercritical CO2 and other assisted methods, partly for residue-free colourants and partly to valorise pepper-processing waste ^{21,22Reference 21Rodriguez-Amaya DB et al. · 2023Comprehensive update on carotenoid colorants from plants and microalgae: challenges and advances from research laboratories to industryView study →Reference 22Larocca V et al. · 2026Senise red pepper (Capsicum annuum L.) wastes as source of rich capsanthin extracts by supercritical CO2 extractionView study →}.

Two things limit it industrially. First, thermal fragility: heating paprika oleoresin generates a characterised set of carotenoid degradation products, which is why colour loss during processing and storage is a live problem ^{29Reference 29Pérez-Gálvez A et al. · 2005Thermal degradation products formed from carotenoids during a heat-induced degradation process of paprika oleoresins (Capsicum annuum L.)View study →}. Second, scarcity — you cannot enrich capsorubin without enriching capsanthin first. That has driven interest in making it outside the plant: CCS has been expressed in E. coli and in engineered microbial systems designed for plant chloroplast enzymes, and metabolic engineering in carrot germplasm has been used to generate high-purity capsanthin and capsorubin ^{27,28Reference 27Chen H et al. · 2025Designing a microbial factory suited for plant chloroplast-derived enzymes to efficiently and green synthesize natural products: capsanthin and capsorubin as examplesView study →Reference 28Deng YJ et al. · 2024Generation of high purity capsanthin and capsorubin through synthetic metabolic engineering in carrot germplasmView study →}. These are proof-of-concept routes, not current commercial supply.

Esterification in the Fruit

Almost none of the capsorubin in a ripe pepper is free. As the chloroplast converts to a chromoplast during ripening, the xanthophylls are progressively esterified with fatty acids — a constitutive process so tightly coupled to ripening that the esterification profile works as a ripeness index. At the fully ripe stage the carotenoid pool settles at roughly 24% free, 31% partially esterified and 44% fully esterified, largely independent of cultivar, with capsorubin present as both mono- and di-esters ^{5Reference 5Hornero-Méndez D · 2000Xanthophyll esterification accompanying carotenoid overaccumulation in chromoplast of Capsicum annuum ripening fruits is a constitutive process and useful for ripeness indexView study →}.

This matters in three ways:

• Extraction. The pigment you recover is a mixture of free capsorubin, monoesters and diesters. Analytical methods that quantify only free capsorubin — as the validated u-HPLC method explicitly does — measure a minority fraction unless the sample is saponified first ^{24Reference 24Shim YS et al. · 2013Simultaneous determination of free capsorubin and capsanthin in red pepper powder using u-HPLCView study →}.
• Stability. Unlike zeaxanthin, whose esters degrade faster than the free pigment because the esterifying fatty acids are unsaturated, capsorubin and its esters degraded at the same rate, so esterification neither protects nor destabilises it ^{9Reference 9Pérez-Gálvez A · 2002Degradation of non-esterified and esterified xanthophylls by free radicalsView study →}.
• Absorption. Esters must be hydrolysed before a xanthophyll can be absorbed. In the one human study, only free zeaxanthin and free β-cryptoxanthin appeared in chylomicrons even though the oleoresin’s xanthophylls were mainly mono- or di-esters — capsorubin appeared in neither form ^{6Reference 6Pérez-Gálvez A et al. · 2003Incorporation of carotenoids from paprika oleoresin into human chylomicronsView study →}.

What It's Used For

The honest summary: capsorubin’s evidence is chemical and cell-culture antioxidant work, plus a colourant licence. There is no clinical literature on the isolate, and the human pharmacokinetic data are actively discouraging.

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. Note that row 1 scores an approved industrial/food use, not a health benefit; rows 2–5 are health-directed and all preclinical. Read the per-row basis.

01Food colourant (E 160c)Promising58%Authorised EU additive + established commercial pigment chemistry ^{20,21Reference 20EFSA Panel on Food Additives et al. · 2015Scientific opinion on the re-evaluation of paprika extract (E 160c) as a food additiveView study →Reference 21Rodriguez-Amaya DB et al. · 2023Comprehensive update on carotenoid colorants from plants and microalgae: challenges and advances from research laboratories to industryView study →}

02Antioxidant & ROS resistanceShaky30%In-vitro radical/ROS chemistry and structure-reactivity studies ^{8,9,10Reference 8Nishino A et al. · 2016Reaction of paprika carotenoids, capsanthin and capsorubin, with reactive oxygen speciesView study →Reference 9Pérez-Gálvez A · 2002Degradation of non-esterified and esterified xanthophylls by free radicalsView study →Reference 10Pérez-Gálvez A · 2001Structure-reactivity relationship in the oxidation of carotenoid pigments of the pepper (Capsicum annuum L.)View study →}

03Photoprotection (UVB, cell culture)Shaky22%One human dermal fibroblast study at 1 µM; whole-mixture human skin trial ^{11,26Reference 11Fernández-García E et al. · 2016Carotenoids exclusively synthesized in red pepper (capsanthin and capsorubin) protect human dermal fibroblasts against UVB induced DNA damageView study →Reference 26Yatsuhashi H et al. · 2022RCTEffects of oral supplementation with paprika xanthophylls on human skin moisture — a randomized single-blind parallel-group controlled trialView study →}

04Metabolic & anti-inflammatoryShaky16%Paprika pigment mixture in 3T3-L1 adipocytes; apocarotenoid metabolite data ^{13,15Reference 13Maeda H et al. · 2013Paprika pigments attenuate obesity-induced inflammation in 3T3-L1 adipocytesView study →Reference 15Takatani N et al. · 2024Apo-12’-capsorubinal exhibits anti-inflammatory effects and activates nuclear factor erythroid 2-related factor 2 in RAW264.7 macrophagesView study →}

05Multidrug-resistance reversalShaky12%Single in-vitro rhodamine-123 accumulation study in transfected cell lines ^{14Reference 14Molnár J et al. · 2004AnimalModulation of multidrug resistance and apoptosis of cancer cells by selected carotenoidsView study →}

Mechanisms

The load-bearing point is the mismatch between rows: the chemistry rows are strong and the human-relevance rows are empty or negative. A molecule that quenches singlet oxygen beautifully in a cuvette but cannot be found in blood after an oral dose has an antioxidant profile that is real and largely irrelevant to human physiology.

Pharmacokinetics

This is the section that governs how the rest of the page should be read, and it is unusually decisive for a compound this obscure.

Absorption is effectively nil at dietary doses. Nine fasted volunteers ingested a single dose of paprika oleoresin containing 6.4 mg zeaxanthin, 4.2 mg β-cryptoxanthin, 6.2 mg β-carotene, 35.0 mg capsanthin and 2.0 mg capsorubin. Only zeaxanthin, β-cryptoxanthin and β-carotene appeared in the chylomicron fraction in appreciable amounts; the authors concluded that “the bioavailability of the pepper-specific carotenoids capsanthin and capsorubin from paprika oleoresin is very low” ^{6Reference 6Pérez-Gálvez A et al. · 2003Incorporation of carotenoids from paprika oleoresin into human chylomicronsView study →}. A 12-week double-blind placebo-controlled study at 20 or 100 mg/day of paprika oleoresin reached the same wall from the other direction: β-cryptoxanthin and zeaxanthin accumulated dose-dependently in plasma while capsanthin was not detected before or during the treatment period ^{7Reference 7Umigai N et al. · 2018RCTSafety evaluation and plasma carotenoid accumulation in healthy adult subjects after 12 weeks of paprika oleoresin supplementation — a randomized double-blind placebo-controlled clinical trialView study →} — and capsanthin is present at roughly ten times capsorubin’s concentration.

Why. Two barriers stack. The xanthophylls are largely present as fatty-acid mono- and di-esters that must be hydrolysed before absorption ^{5,6Reference 5Hornero-Méndez D · 2000Xanthophyll esterification accompanying carotenoid overaccumulation in chromoplast of Capsicum annuum ripening fruits is a constitutive process and useful for ripeness indexView study →Reference 6Pérez-Gálvez A et al. · 2003Incorporation of carotenoids from paprika oleoresin into human chylomicronsView study →}, and the κ-end groups appear to make these particular pigments poor substrates for whatever selectivity operates at the enterocyte — free zeaxanthin and β-cryptoxanthin from the same oleoresin crossed fine ^{6Reference 6Pérez-Gálvez A et al. · 2003Incorporation of carotenoids from paprika oleoresin into human chylomicronsView study →}.

What has been tried. Formulation work has improved capsorubin’s in vitro bioaccessibility: a bovine serum albumin–dextran–gallic acid ternary conjugate emulsion reached 34%, and a sodium alginate emulsion 65% ^{23Reference 23Zhang D et al. · 2021Stability and bioaccessibility improvement of capsorubin using bovine serum albumin-dextran-gallic acid and sodium alginateView study →}. Encapsulation is a recurring theme across carotenoid colorants for exactly this reason ^{21Reference 21Rodriguez-Amaya DB et al. · 2023Comprehensive update on carotenoid colorants from plants and microalgae: challenges and advances from research laboratories to industryView study →}. But bioaccessibility in a simulated digestion is not plasma appearance in a person, and no human study has repeated the chylomicron measurement using an enhanced formulation.

Metabolism. There is no human ADME dataset. The one metabolic lead is the apocarotenoid apo-12’-capsorubinal, an oxidative cleavage product of capsorubin that is more biologically active than the parent in macrophage assays ^{15Reference 15Takatani N et al. · 2024Apo-12’-capsorubinal exhibits anti-inflammatory effects and activates nuclear factor erythroid 2-related factor 2 in RAW264.7 macrophagesView study →} — but its formation in humans has not been quantified.

Clinical Trials

There are no clinical trials of isolated capsorubin. The human record consists of two paprika-oleoresin/xanthophyll-mixture studies: a 12-week randomised double-blind safety and plasma-accumulation study (0/20/100 mg/day, n = 33, no adverse events, capsanthin undetectable in plasma) ^{7Reference 7Umigai N et al. · 2018RCTSafety evaluation and plasma carotenoid accumulation in healthy adult subjects after 12 weeks of paprika oleoresin supplementation — a randomized double-blind placebo-controlled clinical trialView study →}, and a 4-week randomised single-blind skin-moisture trial of a seven-xanthophyll paprika supplement ^{26Reference 26Yatsuhashi H et al. · 2022RCTEffects of oral supplementation with paprika xanthophylls on human skin moisture — a randomized single-blind parallel-group controlled trialView study →}. The single-dose chylomicron study is a mechanistic pharmacokinetic experiment rather than an efficacy trial ^{6Reference 6Pérez-Gálvez A et al. · 2003Incorporation of carotenoids from paprika oleoresin into human chylomicronsView study →}.

Last checked: July 2026.

Isolate vs. Plant Studies

Capsorubin sits awkwardly on this axis. The chemistry is genuine isolate work — the ROS reactivity, the radical-degradation ranking and the fibroblast UVB study all used purified capsorubin, in the last case with lutein as a comparator ^{8,9,11Reference 8Nishino A et al. · 2016Reaction of paprika carotenoids, capsanthin and capsorubin, with reactive oxygen speciesView study →Reference 9Pérez-Gálvez A · 2002Degradation of non-esterified and esterified xanthophylls by free radicalsView study →Reference 11Fernández-García E et al. · 2016Carotenoids exclusively synthesized in red pepper (capsanthin and capsorubin) protect human dermal fibroblasts against UVB induced DNA damageView study →}. That is a real strength for a molecule this minor, and it is why the antioxidant claims here can be stated at all.

Everything closer to a health outcome reverts to the mixture. The metabolic and anti-inflammatory work used “paprika pigments” as a blend, so the contribution of capsorubin versus capsanthin versus zeaxanthin is unresolved ^{13Reference 13Maeda H et al. · 2013Paprika pigments attenuate obesity-induced inflammation in 3T3-L1 adipocytesView study →}. The human skin trial used a seven-xanthophyll supplement ^{26Reference 26Yatsuhashi H et al. · 2022RCTEffects of oral supplementation with paprika xanthophylls on human skin moisture — a randomized single-blind parallel-group controlled trialView study →}. The 12-week supplementation study dosed whole oleoresin ^{7Reference 7Umigai N et al. · 2018RCTSafety evaluation and plasma carotenoid accumulation in healthy adult subjects after 12 weeks of paprika oleoresin supplementation — a randomized double-blind placebo-controlled clinical trialView study →}. And the review that summarises “paprika carotenoid” benefits treats capsanthin and capsorubin together throughout ^{12Reference 12Maeda H et al. · 2021Biological activities of paprika carotenoids, capsanthin and capsorubinView study →}.

There is a third category that is easy to miss: evidence borrowed sideways from capsanthin. Because capsanthin is ten times more abundant and better studied, most paprika-carotenoid claims in circulation are really capsanthin claims. They should not be transferred here. Where the two have been compared head to head the results diverge — capsorubin is the more oxidation-resistant ^{8,9Reference 8Nishino A et al. · 2016Reaction of paprika carotenoids, capsanthin and capsorubin, with reactive oxygen speciesView study →Reference 9Pérez-Gálvez A · 2002Degradation of non-esterified and esterified xanthophylls by free radicalsView study →}, capsanthin is the one reported to induce apoptosis in the MDR study ^{14Reference 14Molnár J et al. · 2004AnimalModulation of multidrug resistance and apoptosis of cancer cells by selected carotenoidsView study →} — so they are not interchangeable in either direction.

Its Role in Plants

Capsorubin is a chromoplast pigment of ripening fruit and, in one genus, of flowers. It is absent from green tissue: during pepper ripening the chloroplast pigments lutein and neoxanthin decline and disappear while β-carotene, antheraxanthin and violaxanthin rise and capsanthin, capsorubin, capsanthin-5,6-epoxide and cucurbitaxanthin A are synthesised de novo ^{4Reference 4Hornero-Méndez D et al. · 2000Carotenoid biosynthesis changes in five red pepper (Capsicum annuum L.) cultivars during ripeningView study →}.

The biosynthetic step is well characterised. Camara demonstrated the in vitro conversion of violaxanthin to capsorubin by a chromoplast-enriched fraction of Capsicum fruit in 1980 ^{2Reference 2Camara B · 1980In vitroCarotenoid biosynthesis: in vitro conversion of violaxanthin to capsorubin by a chromoplast enriched fraction of Capsicum fruitsView study →}; Bouvier and colleagues purified the responsible enzyme to homogeneity from C. annuum chromoplasts, showed it handled antheraxanthin and violaxanthin alike, named it capsanthin-capsorubin synthase, and cloned its cDNA — noting that the gene is expressed specifically during chromoplast development in fruits that accumulate ketocarotenoids, and not in mutants blocked at that step ^{1Reference 1Bouvier F et al. · 1994Xanthophyll biosynthesis in chromoplasts: isolation and molecular cloning of an enzyme catalyzing the conversion of 5,6-epoxycarotenoid into ketocarotenoidView study →}. CCS belongs to the lycopene cyclase family and functions as a flavoprotein with no net redox change, consistent with a rearrangement rather than an oxidation ^{30Reference 30Mialoundama AS et al. · 2010Characterization of plant carotenoid cyclases as members of the flavoprotein family functioning with no net redox changeView study →}.

Ecologically the function is the obvious one: colour. Deep red ripe fruit is a signal to seed dispersers, and in Lilium lancifolium the same two κ-xanthophylls produce the orange of the tepals — a pollinator signal rather than a fruit one ^{19Reference 19Jeknić Z et al. · 2012Cloning and functional characterization of a gene for capsanthin-capsorubin synthase from tiger lily (Lilium lancifolium Thunb. ‘Splendens’)View study →}. Zeaxanthin sits at the branch point controlling how much flux reaches the red pigments, which is why breeders track carotenoid ratios rather than totals when selecting for colour ^{4Reference 4Hornero-Méndez D et al. · 2000Carotenoid biosynthesis changes in five red pepper (Capsicum annuum L.) cultivars during ripeningView study →}.

Prevalence in Nature

Capsorubin is overwhelmingly a Capsicum molecule, but “exclusive to red pepper” — a phrase that appears even in paper titles ^{11Reference 11Fernández-García E et al. · 2016Carotenoids exclusively synthesized in red pepper (capsanthin and capsorubin) protect human dermal fibroblasts against UVB induced DNA damageView study →} — is not strictly accurate.

In ripe red paprika it accounts for about 3.2% of total carotenoids, with total carotenoids around 1.3 g/100 g dry weight ^{3Reference 3Deli J et al. · 2001Carotenoid composition in the fruits of red paprika (Capsicum annuum var. lycopersiciforme rubrum) during ripening; biosynthesis of carotenoids in red paprikaView study →}; in red bell pepper it is a minor carotenoid behind capsanthin, lutein, β-carotene and violaxanthin ^{25Reference 25de Azevedo-Meleiro CH · 2009Qualitative and quantitative differences in the carotenoid composition of yellow and red peppers determined by HPLC-DAD-MSView study →}; in a supercritical-CO2 extract of Senise pepper waste it was quantified at 0.38 mg/g against capsanthin’s 5.88 mg/g ^{22Reference 22Larocca V et al. · 2026Senise red pepper (Capsicum annuum L.) wastes as source of rich capsanthin extracts by supercritical CO2 extractionView study →}. It is generated de novo during ripening and is absent from green fruit ^{4Reference 4Hornero-Méndez D et al. · 2000Carotenoid biosynthesis changes in five red pepper (Capsicum annuum L.) cultivars during ripeningView study →}, and most of what is present is esterified ^{5Reference 5Hornero-Méndez D · 2000Xanthophyll esterification accompanying carotenoid overaccumulation in chromoplast of Capsicum annuum ripening fruits is a constitutive process and useful for ripeness indexView study →}. Yellow and orange peppers, which are blocked upstream, contain little or none — their profiles are dominated by violaxanthin and lutein ^{25Reference 25de Azevedo-Meleiro CH · 2009Qualitative and quantitative differences in the carotenoid composition of yellow and red peppers determined by HPLC-DAD-MSView study →}.

Outside the genus, two confirmed occurrences:

• Asparagus berries. HPLC of ripe and unripe Asparagus officinalis fruits identified capsanthin, capsorubin and capsanthin 5,6-epoxide alongside the usual xanthophylls ^{18Reference 18Deli J et al. · 2000Carotenoid composition in the fruits of Asparagus officinalisView study →}.
• Tiger lily tepals. The orange of Lilium lancifolium ‘Splendens’ flowers is due primarily to the accumulation of capsanthin and capsorubin, and the lily’s own CCS gene has been cloned and shown to make both pigments when expressed heterologously ^{19Reference 19Jeknić Z et al. · 2012Cloning and functional characterization of a gene for capsanthin-capsorubin synthase from tiger lily (Lilium lancifolium Thunb. ‘Splendens’)View study →}.

So the honest formulation is that capsorubin is near-exclusive to Capsicum among food plants, with scattered occurrences elsewhere in species that happen to express a CCS-type enzyme. That is still narrow enough to be diagnostically useful — but “found only in peppers” overstates it.

Major Natural Sources

Source	Part	Reported capsorubin	Reference
Red paprika (Capsicum annuum var. lycopersiciforme rubrum)	ripe fruit	3.2% of total carotenoids (total ~1.3 g/100 g dry wt)	3Reference 3Deli J et al. · 2001Carotenoid composition in the fruits of red paprika (Capsicum annuum var. lycopersiciforme rubrum) during ripening; biosynthesis of carotenoids in red paprikaView study →
Senise sweet pepper (C. annuum, PGI)	SC-CO2 extract of processing waste	0.38 mg/g extract (vs capsanthin 5.88 mg/g)	22Reference 22Larocca V et al. · 2026Senise red pepper (Capsicum annuum L.) wastes as source of rich capsanthin extracts by supercritical CO2 extractionView study →
Red bell pepper (C. annuum F1 Magali)	ripe fruit	present as a minor carotenoid; not quantified	25Reference 25de Azevedo-Meleiro CH · 2009Qualitative and quantitative differences in the carotenoid composition of yellow and red peppers determined by HPLC-DAD-MSView study →
Cayenne (C. annuum)	ripe fruit	present; no cultivar-specific figure located	—
Asparagus (Asparagus officinalis)	ripe and unripe berries	identified; not quantified	18Reference 18Deli J et al. · 2000Carotenoid composition in the fruits of Asparagus officinalisView study →
Tiger lily (Lilium lancifolium ‘Splendens’)	flower tepals	a primary pigment; not quantified	19Reference 19Jeknić Z et al. · 2012Cloning and functional characterization of a gene for capsanthin-capsorubin synthase from tiger lily (Lilium lancifolium Thunb. ‘Splendens’)View study →

Discovery & Synthesis

First isolation. Capsorubin belongs to the classical paprika-pigment chemistry of the 1920s–30s, when the red Capsicum carotenoids were separated and named — capsanthin first, capsorubin shortly after. We have not verified the primary isolation report against the original literature, so the attribution is left open here rather than stated as fact; the structural assignment of the κ,κ end groups came later, with modern spectroscopy.

Biosynthetic origin. Established in two steps: Camara showed a chromoplast-enriched fraction of Capsicum fruit converts violaxanthin to capsorubin in vitro (1980) ^{2Reference 2Camara B · 1980In vitroCarotenoid biosynthesis: in vitro conversion of violaxanthin to capsorubin by a chromoplast enriched fraction of Capsicum fruitsView study →}, and Bouvier and colleagues purified, characterised and cloned capsanthin-capsorubin synthase (1994), the single bifunctional enzyme responsible for both red pigments ^{1Reference 1Bouvier F et al. · 1994Xanthophyll biosynthesis in chromoplasts: isolation and molecular cloning of an enzyme catalyzing the conversion of 5,6-epoxycarotenoid into ketocarotenoidView study →}.

First total synthesis. Yamano and Ito, 2007 — a route to both capsanthin and capsorubin via a C15 cyclopentyl ketone built by Lewis-acid-promoted regio- and stereoselective rearrangement of an epoxy dienal, chemically reproducing the ring contraction that gives the κ-end group ^{17Reference 17Yamano Y · 2007Total synthesis of capsanthin and capsorubin using Lewis acid-promoted regio- and stereoselective rearrangement of tetrasubstituted epoxidesView study →}.

Manufacture today. There is no commercial synthesis and no commercial isolate. Capsorubin reaches the market only as a minority component of paprika oleoresin, extracted from Capsicum annuum fruit — increasingly by supercritical CO2 rather than organic solvents, and increasingly from processing by-products ^{21,22Reference 21Rodriguez-Amaya DB et al. · 2023Comprehensive update on carotenoid colorants from plants and microalgae: challenges and advances from research laboratories to industryView study →Reference 22Larocca V et al. · 2026Senise red pepper (Capsicum annuum L.) wastes as source of rich capsanthin extracts by supercritical CO2 extractionView study →}. Biotechnological routes are at proof-of-concept: CCS expression in E. coli, a purpose-designed microbial platform for plant chloroplast-derived enzymes producing capsanthin and capsorubin, and synthetic metabolic engineering in carrot germplasm yielding high-purity pigment ^{27,28Reference 27Chen H et al. · 2025Designing a microbial factory suited for plant chloroplast-derived enzymes to efficiently and green synthesize natural products: capsanthin and capsorubin as examplesView study →Reference 28Deng YJ et al. · 2024Generation of high purity capsanthin and capsorubin through synthetic metabolic engineering in carrot germplasmView study →}.

Patents: not yet researched.

Toxicity & Safety

Capsorubin carries a low flag. Three things support it: it is a component of an authorised food colour (E 160c) with a long history of dietary exposure through paprika and sweet pepper ^{20,21Reference 20EFSA Panel on Food Additives et al. · 2015Scientific opinion on the re-evaluation of paprika extract (E 160c) as a food additiveView study →Reference 21Rodriguez-Amaya DB et al. · 2023Comprehensive update on carotenoid colorants from plants and microalgae: challenges and advances from research laboratories to industryView study →}; a 12-week double-blind study of paprika oleoresin at 20 and 100 mg/day found no adverse events across blood biochemistry, haematology and urinalysis ^{7Reference 7Umigai N et al. · 2018RCTSafety evaluation and plasma carotenoid accumulation in healthy adult subjects after 12 weeks of paprika oleoresin supplementation — a randomized double-blind placebo-controlled clinical trialView study →}; and, bluntly, the molecule is barely absorbed, so systemic exposure from any realistic intake is minimal ^{6,7Reference 6Pérez-Gálvez A et al. · 2003Incorporation of carotenoids from paprika oleoresin into human chylomicronsView study →Reference 7Umigai N et al. · 2018RCTSafety evaluation and plasma carotenoid accumulation in healthy adult subjects after 12 weeks of paprika oleoresin supplementation — a randomized double-blind placebo-controlled clinical trialView study →}.

That said, “low toxicity” here means “no signal in a thin dataset”, not “thoroughly characterised”.

Safety at a Glance

✅ Low / no toxicity

• Long dietary history as a food pigment. Consumed in paprika, cayenne and sweet peppers, and authorised in the EU as part of paprika extract (E 160c).
• No adverse events in the one supplementation study. Paprika oleoresin at 20 or 100 mg/day for 12 weeks, with full safety bloods.
• Do not read pepper safety onto capsorubin, or vice versa. Cayenne’s real cautions — mucous-membrane and GI irritation — belong to capsaicin and the other capsaicinoids, not to the red pigments, which are non-pungent.
• No isolate toxicology package. No genotoxicity, repeat-dose, reproductive or drug-interaction data exist for pure capsorubin; the low badge rests on food use and the mixture study.

Full Safety and Interactions Detail

Regulatory position. The additive is defined as paprika extract, capsanthin, capsorubin (E 160c) and was re-evaluated by EFSA’s food additives panel in 2015 ^{20Reference 20EFSA Panel on Food Additives et al. · 2015Scientific opinion on the re-evaluation of paprika extract (E 160c) as a food additiveView study →}. Note that the additive is the extract, not the isolated pigment — paprika oleoresin also carries capsaicinoids unless specifically deodorised, which is the ingredient-level detail worth checking on any product, and the reason a colourant can occasionally taste of pepper.

Human tolerability data. The 12-week randomised double-blind placebo-controlled study (n = 33, 0/20/100 mg paprika oleoresin daily) reported no adverse events and no abnormalities in blood biochemistry, haematology or urine ^{7Reference 7Umigai N et al. · 2018RCTSafety evaluation and plasma carotenoid accumulation in healthy adult subjects after 12 weeks of paprika oleoresin supplementation — a randomized double-blind placebo-controlled clinical trialView study →}. The 4-week paprika xanthophyll skin trial reported no safety concerns, though it did record a small but statistically significant increase in facial brown stains in the paprika group — an unexplained finding in a cosmetic-endpoint study, not a toxicity signal, but worth noting rather than omitting ^{26Reference 26Yatsuhashi H et al. · 2022RCTEffects of oral supplementation with paprika xanthophylls on human skin moisture — a randomized single-blind parallel-group controlled trialView study →}.

Carotenodermia. Very high intakes of carotenoids generally can produce harmless yellow-orange skin discoloration. This is a class effect that in practice belongs to β-carotene and other well-absorbed carotenoids; given capsorubin’s negligible absorption ^{6,7Reference 6Pérez-Gálvez A et al. · 2003Incorporation of carotenoids from paprika oleoresin into human chylomicronsView study →Reference 7Umigai N et al. · 2018RCTSafety evaluation and plasma carotenoid accumulation in healthy adult subjects after 12 weeks of paprika oleoresin supplementation — a randomized double-blind placebo-controlled clinical trialView study →}, it is not a plausible contributor at any realistic intake.

Interactions. None documented. No CYP or transporter interaction study exists for capsorubin. The one transporter-adjacent finding is in vitro and points the other way — capsanthin and capsorubin increased rhodamine-123 accumulation ~30-fold in MDR-1-transfected cells, i.e. behaved as efflux-pump modulators in culture ^{14Reference 14Molnár J et al. · 2004AnimalModulation of multidrug resistance and apoptosis of cancer cells by selected carotenoidsView study →}. Whether that has any bearing on drug handling in a person is entirely unknown, and given the absorption data it is unlikely to be testable through diet.

Reproductive and developmental. No dedicated dataset exists for isolated capsorubin. Pregnancy and lactation decisions belong to the herb or product page where intake is actually decided, not to a molecule page for a pigment eaten in milligram quantities in food.

What is not known. Genotoxicity, repeat-dose toxicity, carcinogenicity and reproductive toxicity have not been assessed for the pure compound in the literature reviewed here. The low toxicity flag reflects food-additive status, dietary ubiquity, negligible absorption and an absence of signals — not a completed toxicological package.

Dosage

There is no established or meaningful human dose for capsorubin, and the pharmacokinetics are the reason: at the only oral dose ever measured in people, none of it reached the bloodstream ^{6Reference 6Pérez-Gálvez A et al. · 2003Incorporation of carotenoids from paprika oleoresin into human chylomicronsView study →}.

The most useful practical framing: eat the pepper, not the pigment. There is no capsorubin supplement, no isolate on the market, and no dose at which a human benefit has been shown. These are figures from published research and food-additive practice, not a personal recommendation.

References

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2. Camara B (1980). Carotenoid biosynthesis: in vitro conversion of violaxanthin to capsorubin by a chromoplast enriched fraction of Capsicum fruits. Biochemical and Biophysical Research Communications. https://pubmed.ncbi.nlm.nih.gov/7378074/
3. Deli J, Molnár P, Matus Z, Tóth G (2001). Carotenoid composition in the fruits of red paprika (Capsicum annuum var. lycopersiciforme rubrum) during ripening; biosynthesis of carotenoids in red paprika. Journal of Agricultural and Food Chemistry. https://pubmed.ncbi.nlm.nih.gov/11312889/
4. Hornero-Méndez D, Gómez-Ladrón de Guevara R, Mínguez-Mosquera MI (2000). Carotenoid biosynthesis changes in five red pepper (Capsicum annuum L.) cultivars during ripening. Cultivar selection for breeding. Journal of Agricultural and Food Chemistry. https://pubmed.ncbi.nlm.nih.gov/10995282/
5. Hornero-Méndez D, Mínguez-Mosquera MI (2000). Xanthophyll esterification accompanying carotenoid overaccumulation in chromoplast of Capsicum annuum ripening fruits is a constitutive process and useful for ripeness index. Journal of Agricultural and Food Chemistry. https://pubmed.ncbi.nlm.nih.gov/10820068/
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18. Deli J, Matus Z, Tóth G (2000). Carotenoid composition in the fruits of Asparagus officinalis. Journal of Agricultural and Food Chemistry. https://pubmed.ncbi.nlm.nih.gov/11032480/
19. Jeknić Z, Morré JT, Jeknić S, Jevremović S, Subotić A, Chen TH (2012). Cloning and functional characterization of a gene for capsanthin-capsorubin synthase from tiger lily (Lilium lancifolium Thunb. ‘Splendens’). Plant and Cell Physiology. https://pubmed.ncbi.nlm.nih.gov/23008421/
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21. Rodriguez-Amaya DB, Esquivel P, Meléndez-Martínez AJ (2023). Comprehensive update on carotenoid colorants from plants and microalgae: challenges and advances from research laboratories to industry. Foods. https://pubmed.ncbi.nlm.nih.gov/38002140/
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23. Zhang D, Wang S, Wang M, et al. (2021). Stability and bioaccessibility improvement of capsorubin using bovine serum albumin-dextran-gallic acid and sodium alginate. International Journal of Biological Macromolecules. https://pubmed.ncbi.nlm.nih.gov/33965493/
24. Shim YS, Kim KJ, Seo D, et al. (2013). Simultaneous determination of free capsorubin and capsanthin in red pepper powder using u-HPLC. Journal of AOAC International. https://pubmed.ncbi.nlm.nih.gov/23767359/
25. de Azevedo-Meleiro CH, Rodriguez-Amaya DB (2009). Qualitative and quantitative differences in the carotenoid composition of yellow and red peppers determined by HPLC-DAD-MS. Journal of Separation Science. https://pubmed.ncbi.nlm.nih.gov/19813226/
26. Yatsuhashi H, Takumi H, Terada Y, Kuriki T (2022). Effects of oral supplementation with paprika xanthophylls on human skin moisture — a randomized single-blind parallel-group controlled trial. Journal of Oleo Science. https://pubmed.ncbi.nlm.nih.gov/35387919/
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28. Deng YJ, et al. (2024). Generation of high purity capsanthin and capsorubin through synthetic metabolic engineering in carrot germplasm. Journal of Experimental Botany. https://pubmed.ncbi.nlm.nih.gov/39140865/
29. Pérez-Gálvez A, Rios JJ, Mínguez-Mosquera MI (2005). Thermal degradation products formed from carotenoids during a heat-induced degradation process of paprika oleoresins (Capsicum annuum L.). Journal of Agricultural and Food Chemistry. https://pubmed.ncbi.nlm.nih.gov/15941322/
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