BACKGROUND The O-(beta-hydroxyethyl)-rutosides (HRs) are a standard mixture of flavonoid-derivatives that have a clinico-pharmacological activity on peripheral circulation, particularly on the endothelial cells of veins and lymphatics. Flavonoids are believed to prevent the oxidative damage derived from radical oxidative species (ROS), like hydroxyl radicals (HO.) and hypochlorite (-OCl). The aim of the study was to investigate the stability and capability of HRs in toto and of their single components (7-mo-nohydroxy ethyl rutoside; 7,4'-dihydroxyethyl rutoside; 7,3',4'-trihydroxyethyl rutoside and the 7,5,3',4'-tetrahydroxyethyl rutoside) of scavenging ROS and other radicals generated by different oxidative systems, and also their anti-lipoperoxidative activity at mM concentrations (1.0-10.0 mM). METHODS The following oxidative systems have been employed: Fenton reaction for the hydro-xylation of l-tyrosine to l-DOPA and the peroxidation of arachidonic acid; photo-Fenton type reaction for the oxidation of toluene in the aqueous UV irradiated TiO2 system; the azocompound 2.2'-azobis(2, 4-dimethylvaleronitrile (AMVN) to produce peroxy radicals and the daily autoxidation of arachidonic acid. Analyses were performed by HPLC, HPLC-MS, GC-MS, and spectrophotometry. RESULTS At 5.0 mM concentration, HRs produced the following inhibitions: 63+/-5% of the overall formation of cresols, benzaldehyde, benzyl alcohol, and biphenyl induced by photo-Fenton reaction; 91.6+/-5% and 59+/-8% of the synthesis of l-DOPA induced by HO. generated by Fenton reaction; 45+/-7% and 52+/-6% of the oxidation of arachidonic acid induced by Fenton reaction and AMVN; 60+/-4% of the autoxidation of arachidonic acid. These effects were strictly concentration dependent. CONCLUSIONS At mM concentrations, HRs display a significant antilipoperoxidative activity due to their notable scanvenging activity against HO.; moreover these actions are concentration-dependent.