January 17, 2022
It’s a compliment to call me cheesy.
What molecule am I?
Image of Bixin 3D Image of Bixin

Bixin is a natural product found in the seeds of the achiote tree (Bixa orellana) that grows in Latin America, India, and East Africa. Like the carotenes, it contains nine conjugated double bonds, but with carboxyl groups rather than hexene rings at both ends.

Bixin is sometimes referred to as cis-bixin because of the lone (Z)-configuration of the second double bond from its ester terminus. When bixin is isolated, the thermodynamically unstable (Z)-bond isomerizes, coverting the molecule to all-trans-bixin.1 Both bixins are insoluble in water; but base hydrolysis of either produces the water-soluble diacid norbixin.2 All three molecules have vivid red-orange colors.

Indigenous peoples have long ground B. orellana seeds into a powder or paste called annatto, of which bixin is the principal ingredient. Annatto is used as a food colorant and flavoring agent; it is also extracted with hot water or oil to make liquids that are used for the same purposes. In modern times, annatto has become a commercial ingredient for coloring dairy products, margarine, baked goods, processed meats, and other foods.

Aqueous annatto extracts, which primarily contain norbixin, are frequently used to produce uniformly colored cheeses such as cheddars. Cheeses may have color inconsistencies from batch to batch because of multiple milk sources and seasonal variations in dairy-cow feed. January 20 is National Cheese Lovers Day, so as you slice your cheddar, be thankful for bixin and the achiote tree.

1. CAS Reg. No. 39937-23-0.
2. CAS Reg. No. 542-40-5.

Bixin hazard information

Hazard class*GHS code and hazard statement
Not a hazardous substance or mixture 

*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. 

Molecule of the future

4′-Fluorouridine1 (4′-FlU) is a ribonucleoside analogue that was first described in two 2014 patents. In December 2021, Richard K. Plemper and colleagues at Georgia State University (Atlanta), Texas Biomedical Research Institute (San Antonio), and Emory University (Atlanta) reported that administration of 4′-FlU inhibits respiratory viruses such as respiratory syncytial virus, a threat to pediatric and elderly patients, and the COVID-19 virus SARS-CoV-2.

Molecule of  the future

The advantage of 4′-FlU is that it is effective when taken orally once daily. Molnupiravir (formerly EIDD-2801), the only other oral COVID-19 medication in the pipeline (also codeveloped by Plemper), must be taken twice daily. The earliest effective treatment, remdesivir, must be injected.

1. CAS Reg. No. 1613589-24-4.

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Bixin fast facts

CAS Reg. No.6983-79-5
acid, 4,8,13,17-tetramethyl-,
1-methyl ester, (2E,4Z,6E,8E,10E,
Empirical formulaC25H30O4
Molar mass394.50 g/mol
AppearanceRed-orange crystals
Melting point198 °C
Water solubilityInsoluble
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