Light-induced oxidation and isomerization of all-trans-β-cryptoxanthin in a model system

• A C30-HPLC method was used to separate cis-isomers and oxides of β-cryptoxanthin.
• A total of seven cis-isomers and two oxidation products were identified.
• Sum of 13- and 13′-cis-β-cryptoxanthin was the major cis-isomer formed.
• The formation of di-cis isomers might prefer in the present of iodine.

The oxidation and isomerization of all-trans-β-cryptoxanthin as affected by iodine-catalysed illumination and non-iodine-catalysed illumination were studied. Seven cis-isomers and two oxidation products were separated by HPLC method using a C30 column. The identification and structural elucidation of the compounds were determined by HPLC–DAD–APCI–MS. Five compounds were identified in details for the first time, namely, β-β-carotene-3-one, 5,6-epoxy-β-β-carotene-3-one, 13,15-di-cis-, 9,13-di-cis- and 9,9′-di-cis-β-cryptoxanthin. Sum of 13- and 13′-cis-β-cryptoxanthin was the major cis-isomer of β-cryptoxanthin formed, accounting for 59.0% and 30.6%, respectively. The formation of di-cis isomers may prefer in the present of iodine. 13,15-di-cis-β-cryptoxanthin was the major di-cis-isomer of the iodine-catalysed photo-isomerization.

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