Bixin (Annatto Apocarotenoid · E160b Food Colorant · Antioxidant · Photoprotective)

Compound	Bixin (cis-Bixin; methyl hydrogen 9-cis-6,6’-diapocarotene-6,6’-dioate)
Chemical class	Terpenoid — Carotenoid / Apocarotenoid (C25 irregular apocarotenoid; methyl ester)
CAS	6983-79-5
Primary source	Bixa orellana (annatto / achiote seed pericarp, 1–5% of seed weight)
Key applications	Food colorant (E160b); antioxidant; anti-inflammatory; antidiabetic preclinical; photoprotective
Claim strength	Moderate
Typical form	Annatto extract (bixin 3% and 5%); food-grade annatto oleoresin; bixin isolate
Buy from Herbuno	Bixin 5% Extract Powder | Standardized Bixa orellana → Bixin 3% Powder (Annatto Extract) | Standardized Bixa orellana →

Name origin: From Bixa (the annatto genus, from a native South American name for the plant). Bixin is a C25 apocarotenoid — unusually, it is an irregular carotenoid with 25 carbons rather than the standard 40-carbon carotenoid backbone. It is the methyl ester of norbixin (the free acid form). In the annatto seed pericarp, bixin accumulates at 1–5% of seed weight, making annatto the richest commercial source of any single carotenoid on earth. Upon saponification of bixin (removing the methyl ester), norbixin is produced — norbixin is water-soluble and is the form used in aqueous food applications, while bixin is oil-soluble and used in fat-based food applications. Traditional use: Annatto (achiote) has been used by indigenous peoples of Central and South America for millennia — as a body paint and cosmetic (the red seed pigment), food colouring, sunscreen, and traditional medicine for GI conditions, fevers, and skin disorders. Contemporary global use is primarily as a food colourant (E160b, annatto; widely used in cheese, butter, margarine, smoked fish, processed meats). Food additive status: Bixin/norbixin (annatto, E160b) is one of the most widely used natural food colorants globally — approved in the US (GRAS), EU (E160b), and almost all regulated food markets. Commercial source: Bixin 3% and 5% standardised annatto extract powder is available from Herbuno.

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Evidence for Bixin Applications

Antioxidant — carotenoid activity: Bixin is a potent singlet oxygen quencher and free radical scavenger, with ORAC values comparable to beta-carotene on a molar basis. Its conjugated polyene chain is responsible for antioxidant capacity. As an apocarotenoid, bixin does not convert to vitamin A (no provitamin A activity), making it relevant as a pure antioxidant without vitamin A toxicity concerns at higher doses. Claim strength: Moderate.

Photoprotective — traditional UV filter: Traditional indigenous use of annatto paste as a skin sunscreen (particularly among Amazonian peoples) is consistent with bixin’s UV absorption properties. Bixin absorbs in the UVA and UVB range. In vitro studies confirm photoprotective activity; some cosmetic formulations include bixin as a natural UV-absorbing colorant. Claim strength: Moderate (traditional; in vitro; no SPF RCTs).

Antidiabetic and anti-inflammatory (preclinical): Bixin activates PPAR-γ and α in adipose tissue models, improving insulin sensitivity and reducing adipose inflammation. In animal models of diabetes and metabolic syndrome, bixin reduces fasting glucose, improves lipid profiles, and reduces adipose tissue inflammation. No human clinical trials for metabolic applications have been completed. Claim strength: Moderate (animal; strong mechanistic).

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Frequently Asked Questions — Bixin

What is the difference between bixin and norbixin?
Bixin is the methyl ester form (oil-soluble, C25 apocarotenoid methyl ester). Norbixin is the free acid form (water-soluble) produced by saponification of bixin. Commercially: oil-soluble annatto preparations (for fat-based applications like cheddar cheese colouring, butter) use bixin; water-dispersible annatto preparations (for aqueous applications like processed meats, beverages) use norbixin as its water-soluble potassium or sodium salt. Both are E160b in the EU. The distinction matters for solubility in formulation — bixin for lipid-based matrices, norbixin for aqueous systems.

Why is cheddar cheese orange?
Annatto (bixin/norbixin) is the standard colorant used to produce cheddar cheese’s characteristic orange-yellow colour. Without annatto, cheddar would be pale cream-white. The colouring convention began in 17th-century England when farmers added annatto to butter and cheese to compensate for the paler colour of winter milk (lower beta-carotene from winter grass diet vs summer pasture). The practice became convention even though modern milk production no longer has the same seasonal variation. The orange colour of cheddar has no nutritional or flavour significance — it is purely aesthetic tradition maintained by consumer expectation.

Is annatto safe — are there allergy concerns?
Annatto (E160b) has been associated with urticaria, angio-oedema, and hypersensitivity reactions in a small number of individuals — more than other natural colorants. The rate of annatto-attributed adverse reactions is low in absolute terms but higher than for most other natural colorants, leading some paediatric allergy guidelines to flag annatto as a potential trigger in children with unexplained urticaria. Individuals with known reactions to any carotenoid-rich foods should be cautious. The reactions appear to be to bixin/norbixin specifically rather than to other annatto constituents.

Does annatto have provitamin A activity?
No — bixin is a C25 apocarotenoid that lacks the structural features required for provitamin A conversion (specifically the beta-ionone ring of beta-carotene). The enzymatic cleavage that converts beta-carotene to retinol (beta-carotene 15,15’-dioxygenase) does not act on bixin’s different structure. This distinguishes bixin from carrot-derived carotenoids and makes it relevant as a pure antioxidant colorant without vitamin A excess concerns at high supplemental doses.

Related compounds: Crocin, Fucoxanthin, Capsanthin, Beta-Carotene

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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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