Identification of products from canthaxanthin oxidation

• We examine the oxidation of canthaxanthin.
• Canthaxanthin oxidation gave 4-oxo-β-carotenals and 4-oxo-β-carotenones.
• We suggest that free radical mechanism is involved in the oxidation of canthaxanthin.

Canthaxanthin is a carotenoid that lacks pro-vitamin A activity but is known to have antioxidant activity. The products of its oxidation in oxygen were found to be mainly substituted apo-carotenals and apo-carotenones. The product profile resembles that obtained in the oxidation of β-carotene, except that with canthaxanthin these products are the 4-oxo-β-apo-carotenals and 4-oxo-β-apo-carotenones. Epoxides and diepoxides were clearly identified from β-carotene oxidation but in contrast, with canthaxanthin, apart from 5,6-epoxy-canthaxanthin, which was detected at the early stage of oxidation and minor quantities of 5,6-epoxy-β-ionone and 5,6-epoxy-4-oxo-β-apo-11-carotenal, no other epoxides were detected. The identities of these products lead us to suggest that the mechanism of canthaxanthin oxidation bears significant similarity to that of β-carotene.