Lycopene as the Most Efficient
Biological Carotenoid Singlet
Oxygen Quencher

This section is compiled by Frank M. Painter, D.C.
Send all comments or additions to:    Frankp@chiro.org

FROM:   Arch Biochem Biophys 1989 (Nov 1);   274 (2):   532–538

Di Mascio P, Kaiser S, Sies H

Institut fur Physiologische Chemie I,
Universitat Dusseldorf,
Federal Republic of Germany

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Lycopene, a biologically occurring carotenoid, exhibits the highest physical quenching rate constant with singlet oxygen (Kq = 31 X 109 M-l S-1), and its plasma level is slightly higher than that of -carotene (Kq = 14 X 109 M-1 S-l). This is of considerable general interest, since nutritional carotenoids, particularly -carotene, and other antioxidants such as a- tocopherol (Kq = 0.3 X 109 M-1 S-l) have been implicated in the defense against prooxidant states; epidemiological evidence reveals that such compounds exert a protective action against certain types of cancer. Also, albumin-bound bilirubin is a known singlet oxygen quencher (Kq = 3.2 X 109 M-l S-l). Interestingly, those compounds with low Kq values occur at higher plasma levels. When these differences are taken into account, the singlet oxygen quenching capacities of lycopene (0.7 M in plasma), -carotene (0.5 M in plasma), albumin-bound bilirubin (15 M in plasma), and a-tocopherol (22 M in plasma) are of comparable magnitude.

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