Apocarotenals of Phenolic Carotenoids for Superior Antioxidant Activities.

A series of -phenolic carotenes with ortho- and meta-substitutions were respectively prepared utilizing the benzenesulfonyl protection method, which demonstrated the importance of the ring substituents on their effective conjugation, evaluated by their UV absorption values. The corresponding apo-12'-carotenals were devised to improve the conjugation effect of the -phenolic radical with the polyene chain by the conjugated aldehyde group. Apo-12'-carotenals and without -substituents exhibited superior antioxidant activities to their corresponding symmetrical carotenes as well as β-carotene and apo-12'-β-carotenal in 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging assays.