Hydroxyl radical-scavenging property of secoisolariciresinol diglucoside (SDG) isolated from flax-seed

Recently there has been a moderate resurgence in the use of flax-seed in a variety of ways including bread. The scientific basis of its use is very limited. There is some claim for beneficial effects in cancer and lupus nephritis. These claims could be due to its ability to scavenge oxygen radicals. However, its antioxidant activity is not known. Recently a method has been developed to isolate secoisolariciresinol diglucoside (SDG) from defatted flax-seed in large quantity (patent pending). We investigated the ability of SDG to scavenge OH using high pressure liquid chromatography (HPLC) method. OH was generated by photolysis of H2O2 (1.25-10.0 mu moles/ml) with ultraviolet light and was trapped with salicylic acid which is hydroxylated to produce OH-adduct products 2,3-dihydroxybenzoic acid (DHBA) and 2,5 DHBA. H2O2 produced a concentration-dependent OH as estimated by 2,3-DHBA and 2,5-DHBA. A standard curve was constructed for known concentrations of 2,3-DHBA and 2,5-DHBA against corresponding area under the peaks which then was used for measurement of 2,3-DHBA and 2,5-DHBA generated by UV irradiation of H2O2 in the presence of salicylic acid. SDG in the concentration range of 25, 50, 100, 250, 500, 750, 1000 and 2000 mu g/ml (36.4, 72.8, 145.6, 364.0, 728.0, 1092.0, 1456.0 and 2912.0 mu M respectively) produced a concentration-dependent decrease in the formation of 2,3-DHBA and 2,5-DHBA, the inhibition being 4 and 4.65% respectively with 25 mu g/ml (36.4 mu M) and 82 and 74% respectively with 2000 mu g/ml (2912.0 mu M) The decrease in OH-adduct products was due to scavenging of OH and not by scavenging of formed 2,3-DHBA and 2,5-DHBA. SDG prevented the lipid peroxidation of liver homogenate in a concentration-dependent manner in the concentration range from 319.3-2554.4 mu M. These results suggest that SDG scavenges OH and therefore has an antioxidant activity.