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Bixin is an apocarotenoid found in annatto, a natural food coloring obtained from the seeds of the achiote tree (Bixa orellana). Annatto seeds contain about 5% pigments, which consist of 70-80% bixin.[2]

Skeletal formula
Ball-and-stick model
IUPAC name
(2E,4E,6E,8E,10E,12E,14E,16Z,18E)-20-methoxy-4,8,13,17-tetramethyl-20-oxoicosa-2,4,6,8,10,12,14,16,18-nonaenoic acid
Other names
cis-Bixin; α-Bixin; 9-cis-6,6'-Diapo-ψ,ψ-carotenedioic acid, 6-methyl ester
3D model (JSmol)
ECHA InfoCard 100.027.499
Molar mass 394.51 g·mol−1
Appearance Orange crystals
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oilHealth code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Bixin is chemically unstable when isolated and converts via isomerization into trans-bixin (β-bixin), the double-bond isomer.[1]

Bixin is soluble in fats and alcohols but insoluble in water. Upon exposure to alkali, the methyl ester is hydrolyzed to produce the dicarboxylic acid norbixin, a water-soluble derivative.

Chemical structure of trans-bixin
Ball-and-stick model of trans-bixin
Chemical structure of norbixin


  1. ^ a b Merck Index, 11th Edition, 1320
  2. ^ Executive Summary Bixin Archived July 21, 2011, at the Wayback Machine., National Toxicology Program