ACTIVITY AND LOCATION OF OLIVE OIL PHENOLIC ANTIOXIDANTS IN
LIPOSOMES
Fátima Paiva-Martinsa, Michael H. Gordon* , b and Paula Gameiroc
a
Centro de Investigação em Química, Departamento de Química, Faculdade de Ciências,
Universidade do Porto, Rua do Campo Alegre, nº 687, 4169-007 Porto, Portugal.Tel: 351-226082956/856 Fax: 351-22-6082959. E-mail: [email protected]
b
School of Food Biosciences, The University of Reading, Whiteknights PO Box 226, Reading
RG6 6AP, UK. Tel: 44-1189-316723. Fax: 44-1189-310080
E-mail: [email protected]
c
CEQUP, Departamento de Química, Faculdade de Ciências, Universidade do Porto, Rua do
Campo Alegre, nº 687, 4169-007 Porto, Portugal., Tel: 351-22-6082956/889 Fax: 351-226082959
E-mail: [email protected]
Key words: olive oil, phenols, antioxidants, liposomes, α-tocopherol.
The antioxidant activity of hydroxytyrosol, hydroxytyrosol acetate, oleuropein, 3,4dihydroxyphenylelenolic acid (3,4-DHPEA-EA) and 3,4-dihydroxyphenylelenolic acid
dialdehyde
(3,4-DHPEA-EDA)
towards
oxidation
initiated
by
2,2’-azobis(2amidinopropane)hydrochloride in a soybean phospholipid liposome system was studied. The
antioxidant activity of these olive oil phenols was similar and the duration of the lag phase was
almost twice that of α-tocopherol. Trolox® showed the worst antioxidant activity. However,
oxidation before the end of the lag phase was inhibited less effectively by the olive oil phenols
than by α-tocopherol and Trolox®. Synergistic effects were observed in the antioxidant activity
of combinations of α-tocopherol plus olive oil phenols both with and without ascorbic acid and
inhibition of oxidation prior to the end of the lag phase was improved by the combination of
antioxidants. Fluorescence anisotropy of probes and fluorescence quenching studies showed that
the olive oil phenols did not penetrate into the membrane, but their effectiveness as antioxidants
showed they were associated with the surface of the phospholipid bilayer.