We investigated the
antioxidant activities of some
phenolic acid derivatives on a cell free system and on cellular and enzymatic models involved in
inflammation. The stoichiometric
antioxidant activities of
phenolic acid derivatives were studied by measuring their capacity to scavenge the radical
cation 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (
ABTS(+)) and
reactive oxygen species (ROS) produced by stimulated neutrophils. The anticatalytic
antioxidant capacity of the molecules was evaluated on the activity of
myeloperoxidase (MPO), an
oxidant enzyme present in and released by the primary granules of neutrophils. The ROS produced by PMA-stimulated neutrophils were measured by
lucigenin-enhanced chemiluminescence (CL) and the potential interaction of the molecules with MPO was investigated without interferences due to medium by Specific Immuno-Extraction Followed by
Enzyme Detection (SIEFED). The
antioxidant activities of the phenolic compounds were correlated to their redox potentials measured by differential pulse voltammetry (DPV), and discussed in relation to their molecular structure. The ability of the phenolic molecules to scavenge
ABTS radicals and ROS derived from neutrophils was inversely correlated to their increased redox potential. The number of
hydroxyl groups (three) and their position (
catechol) were essential for their efficacy as stoichiometric
antioxidants or scavengers. On MPO activity, the inhibitory capacity of the molecules was not really correlated with their redox potential. Likewise, for the inhibition of MPO activity the number of
OH groups and mainly the elongation of the carboxylic group were essential, probably by facilitating the interaction with the active site or the structure of the
enzyme. The redox potential measurement, combined with
ABTS and CL techniques, seems to be a good technique to select stoichiometric
antioxidants but not anticatalytic ones, as seen for MPO, what rather involves a direct interaction with the
enzyme.