Radical scavenger activity of phenylethanoid glycosides in FMLP stimulatedhuman polymorphonuclear leukocytes: Structure-activity relationships

Radical scavenger activities of 21 phenylethanoid glycosides, including 15 ester derivatives of caffeic, ferulic, vanillic and syringic acid as well a s 6 deacyl derivatives were determined by quantifying their effects on the production of reactive oxygen species (ROS) in a luminol-enhanced chemilumi nescence assay with formyl-methionyl-leucyl-phenylalanine (FMLP) stimulated human polymorphonuclear neutrophils (PMNs). All phenylethanoids acylated w ith phenolic acids showed strong antioxidant activity whereas the deacyl de rivatives were more than 30-fold less active. Therefore, the antioxidant ac tivity is mainly related to the number of aromatic methoxy and hydroxy grou ps and the structure of the acyl moiety (C-6-C-1 or C-6-C-3). In contrast, modification of the sugar chain or replacement of hydroxy groups by methoxy groups in the acyl or the phenylethanoid moiety is of minor importance. Th e position of the acyl moiety is without significance. Free caffeic, feruli c, vanillic and syringic acid are less active compared to the phenylethanoi d derivatives. This points to the importance of dissociation and lipophilic ity of these acids in a cellular test system.