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]

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