Formation Of Isomerized And Oxidised Products Of Oxygenated-carotenoids And Their Stability

Oxygenated-carotenoids have a varity of physiological functions,such as quenching free radicals,antioxidant and VA precursor.However,oxygenated-carotenoids are susceptible to oxidation and isomerization during light and heating conditions owing to the unstable of their chemical structures.To provide theoretical basis for the stability of oxygenated carotenoids in real food systems,this paper studied the oxidation and isomerization of oxygenated carotenoids in different model systems,analyzed chemical structures and stability of the forming compounds.The results are as follows:Methanol,MTBE and water as the mobile phase developed C30-HPLC-DAD-APCI-MS methods to analyze lutein and its isomers.Identification and structural elucidation of those isomers were based on comparing spectral data and order of elution to literatures.Peak area and injection volume of lutein showed a good linear relationship in the range of 2?150 ng.All-trans lutein generated 15-,13-/13'-,9-,9'-,7-,7'-mono-cis-isomer and 9,15-,13,15-,9,13-,9,9'-di-cis-lutein during iodine-catalyzed photo-isomerization.The simulation system with MCPBA produced many lutein epoxides,such as 5,6,5',6'-di-epoxy-3-hydroxy-?,?-carotene-3'-one,5,6-epoxy-3-hydroxy-?,?-carotene-3'-one,5,8-epoxy-3-hydroxy-?,?-carotene-3'-one and 3'-hydroxy-?,?-carotene-3-one.A signification degradation(P<0.05)of all-trans lutein was observed during both model systems.13/13'-?9-and 9'-cis-isomers were the most stable.While model system of photo-isomerization didn't detect di-cis isomers,and luetin was more stable.A method for determination of all-trans zeaxanthin and its stereoisomers by HPLC employing a C30 column was developed.Peak area and injection volume of lutein showed a good linear relationship in the range of 5?250 ng.Zeaxanthin generated the common mono-cis-isomers,13,15-,9,15-,9,13-and 9,9'-di-cis-zeaxanthin during iodine-catalyzed photo-isomerization,three di-cis-isomers were identified in details for the first time.The study of stability showed that a signification degradation(P<0.05)of all-trans zeaxanthin was observed during two treatments.For photo-isomerization without iodine,di-cis-isomers of zeaxanthin were not detected.And zeaxanthin was more stable during photo-isomerization.All-trans(3-cryptoxanthin generated the common 13+13'-,9-,9'-,15-mono-cis-isomer and ?,?-carotene-3-one,5,6-epoxy-?,?-carotene-3-one,13,15-,9,13-and,9'-di-cis-?-cryptoxanthin which were first detected during iodine-catalyzed photo-isomerization.The study of stability found that all-trans ?-cryptoxanthin had the same variation with lutein,zeaxanthin.13+13'-,9-and 9'-cis-isomer were the most stable,the same with zeaxanthin,?-cryptoxanthin was more stable in photo-isomerization.