Free radical scavenging capacity of carotenoids.

HERRERA, E.; MONTENEGRO M.A.; NAZARENO M. A.

Los Cocos, Córdoba,

Conferencia; 9a Conferencia Latinoamericana de Físicoquímica Orgánica.; 2007

UNC

Carotenoid pigments are widely spread in fruits and vegetables and they play an important protective role against many serious diseases such as cancer, macular degeneration heart diseases, and cataracts. This effect is owed to carotenoid capacity to scavenge reactive oxygen species (ROS) such as superoxide radical anion O2·-, hydroxyl radical HO· and peroxyl radicals ROO·  and to perform the quenching of a non radical species such as singlet oxygen 1O2, hence, they act effectively as antioxidants. A way of determination this antioxidant ability is by studying the intrinsic capacity of each compound to trap free radicals that is to say their Antiradical Activity. In this work, the scavenging capacity of a carotenoid series derived from b-carotene against the stable radical cation ABTS·+ was studied in an homogeneous organic medium as well as in an aqueous micelle medium. Radical was generated by reaction of ABTS [2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)] with potassium persulphate. The consumption of the radical ABTS·+ was monitored by registering the absorbance at 734 nm (micelles) and 752 nm (ethanol) as a function of the carotenoid concentration. The results obtained showed that the Antiradical Power (ARP) for the series of carotenoids studied decreases with the presence of polar functional groups (e.g. carbonyl and hydroxyl groups) onto the ring b-ionone, possibly due to their electron withdrawing effects, and with the decrease of the number of conjugated double bonds. For the whole series, smaller ARP values were observed in the aqueous micelle medium compared with those obtained in organic medium, which would be explained by secondary interactions of carotenoides with surfactant molecules in the micro-heterogeneous system.