Bixin is an apocarotenoid

Apocarotenoid

Apocarotenoids are organic compounds which occur widely in living organisms. They are derived from carotenoids by oxidative cleavage,catalyzed by carotenoid oxygenases. Examples include the vitamin A retinoids retinal, retinoic acid, and retinol; and the plant hormone abscisic acid....

 found in annatto

Annatto

Annatto, sometimes called roucou or achiote, is a derivative of the achiote trees of tropical regions of the Americas, used to produce a yellow to orange food coloring and also as a flavoring...

, a natural food coloring

Food coloring

Food coloring is a substance, liquid or powder, that is added to food or drink to change its color. Food coloring is used both in commercial food production and in domestic cooking...

 obtained from the seeds of the achiote tree (Bixa orellana). Annatto seeds contain about 5% pigments, which consist of 70-80% bixin.

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

Bixin is soluble in fats but insoluble in water. Upon exposure to alkali

Alkali

In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...

, the methyl ester

Ester

Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

 is hydrolyzed

Hydrolysis

Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...

 to produce the dicarboxylic acid

Dicarboxylic acid

Dicarboxylic acids are organic compounds that contain two carboxylic acid functional groups. In molecular formulae for dicarboxylic acids, these groups are often written as HOOC-R-COOH, where R may be an alkyl, alkenyl, alkynyl, or aryl group...

norbixin, a water-soluble derivative.