Antioxidant properties of a North American ginseng extract

A North American ginseng extract (NAGE) containing known principle ginsenos ides for Panax quinquefolius was assayed for metal chelation, affinity to s cavenge DPPH-stable free radical, and peroxyl (LOO .) and hydroxyl (. OH) f ree radicals for the purpose of characterizing mechanisms of antioxidant ac tivity. Dissociation constants (Kd) for NAGE to bind transition metals were in the order of Fe2+ > Cu2+ > Fe3+ and corresponded to the affinity to inh ibit metal induced lipid peroxidation. In a metal-free linoleic acid emulsi on, NAGE exhibited a significant (p less than or equal to 0.05) concentrati on (0.01-10 mg/mL) dependent mitigation of lipid oxidation as assessed by t he ammonium thiocyanate method. Similar results were obtained when NAGE was incubated in a methyl linoleate emulsion containing haemoglobin catalyst a nd assessed by an oxygen electrode. NAGE also showed strong DPPH radical sc avenging activity up to a concentration of 1.6 mg/mL (r(2) = 0.996). Simila r results were obtained for scavenging of both site-specific and non site-s pecific . OH, using the deoxyribose assay method. Moreover, NAGE effectivel y inhibited the non site-specific DNA strand breakage caused by Fenton agen ts, and suppressed the Fenton induced oxidation of a 66 Kd soluble protein obtained from mouse brain over a concentration range of 2-40 mg/mL. These r esults indicate that NAGE exhibits effective antioxidant activity in both l ipid and aqueous mediums by both chelation of metal ions and scavenging of free radicals.