Xanthophylls

Plant pigments are an important source of non-toxic compounds for use as food or cosmetic colouring agents. The coloured xanthophylls in capsicum are important sources of pigments that can replace carcinogenic synthetic dyes.


Xanthopylls are very similar to carotenes but often contain hydroxyl groups.
Cryptoxanthin, shown to the right, is an example of a xanthophyll.

β-carotene, shown on the left, is an example of a carotene.

Until now, the common method for extracting red pigments from dried fruit of Capsicum has used hexane as the extraction solvent. Current extraction processes are limiting in that the red pigment can only be recovered from American paprika varieties or other mild cultivars.

A study from the New Mexico State University presents a process for the efficient extraction of these pigments using a "green chemistry" method that generates an oleoresin from dried capsicum fruit with virtually the same xanthophyll composition as the hexane extraction method.

Reference
Richard D. Richins, Laura Hernandez, Barry Dungan, Shane Hambly, F. Omar Holguin, and Mary A. O'Connell. A 'Green' Extraction Protocol to Recover Red Pigments from Hot Capsicum Fruit. HortScience, 2010; 45: 1084-1087

Further Reading
Functional Groups
Empirical and Molecular Formula
Molecular Mass (Formula Weight)
Percentage Composition
Oxidation of Alcohols
Intermolecular Forces

Study Questions

1. Circle the hydroxyl group in cryptoxanthin.
2. Write the molecular formula for cryptoxanthin.
3. What is the empirical formula for cryptoxanthin?
4. What percentage by mass of carbon is present in cryptoxanthin?
5. Write the molecular formula for β-carotene.
6. What is the empirical formula for β-carotene?
7. What percentage by mass of hydrogen is present in β-carotene?
8. Which molecule, β-carotene or cryptoxanthin, would be the most polar? Explain your answer.
9. If you were given a solution that contained either cryptoxanthin or β-carotene, how might you be able to decide which of the compounds is present in the solution? Explain your answer.
10. If cryptoxanthin were to react with a strong oxidizing agent, what product(s) might you expect from the reaction? Explain your answer.