It can be concluded from the present study that the widely
distributed anthocyanidins and anthocyanins proved to be strong
radical scavengers against a variety of free radicals, i.e., DPPH, ABTS
and OH radicals where most of the anthocyanidins and anthocyanins
showed more scavenging activity than that of the wellknown
strong antioxidants trolox and catechol. Anthocyanidins
and anthocyanins scavenging activities were sensitive towards
the number and position of the hydroxyl and methoxy groups.
Compounds with a catechol structure in either ring A or B were
generally better hydrogen atom donors because of the stabilization
of the resulted radicals and the formation of stable quinone-like
products; besides, they were much stronger electron donors. The
presence of hydroxyl groups in positions 5, 7 and 40 only has little
effect on both hydrogen atom and electron donation activities,
while the presence of a 3-OH group improved both of these activities.
The importance of 3-OH group in hydrogen transfer reactions
suggests a 3-radical resonance through 5 or 7-OH group forming an
anthocyanin semiquinone radicals ending with a stable diketone,
similar to that observed for the catechol structure. On the other
Pg Pn Mv Cn Pt Dp
0
20
40
60
80
100
% Activity
Anthocyanidin
% DPPH
% ABTS
% OH
% FRAP
Pg-3-glu Pn-3-glu Mv-3-glu Cn-3-glu Pt-3-glu Dp-3-glu
0
20
40
60
80
100
% Activity
Anthocyanin
Fig. 4. Radical scavenging and reducing activities of some anthocyanidins and their
respective anthocyanins.