ï¢-Carotene, a pro-vitamin A carotenoid, was reacted with oxygen in benzene
as solvent, in the dark. The products of oxidation were characterised by HPLC with a
UV photodiode detector and LC-MS, EI mode. The products identified were oxygencontaining
compounds of the type epoxides, aldehydes and ketones. ESR study of
retinyl- and ionyl-derivatives revealed that the secondary sites C7 and C9 were the most
reactive towards radical generation. Both the results of product analysis and the ESR
study enabled us to propose that the products of ï¢-carotene autoxidation were obtained
by a free radical mechanism involving initial formation of a biradical during the transto-
cis isomerisation at the 15,15' bond and attack by oxygen.
Keywords: Carotene, Carotenoids, Apo-carotenoids, ESR, Degradation, Autoxidation,
Free radicals.