Free radical scavenging capacity as related to antioxidant activity and ginsenoside composition of Asian and North American ginseng extracts

Different Panax species derived from Asia (Panax ginseng C.A. Meyer) and North America (Panax quinquefolium L.) were extracted by methanol and evaluated for relative ginsenoside composition and antioxidant activities. Ginseng root contained a greater proportion of total ginsenoside compared to ginseng hair analyzed by high-performance liquid chromatography. North American ginseng root was characterized with undetectable ginsenoside Rf and greater Rb₁/Rb₂ than Asian ginseng root. Panax quinquefolium exhibited a relatively higher (P<0.05) affinity to scavenge free radical than panax ginseng using the 2,2-azobis (3-ethylbenzothine-6-thine-6-surfonic acid) radical model. In a bilayer lamella suspension oxidation model induced by peroxyl radicals, ginseng samples exhibited notable antioxidant activity. Specifically, however, the P. quinquefolium extracts delayed lipid peroxidation longer (P<0.05) than the P. ginseng extracts. Ginseng extracts from both Panax species protected human low-density lipoprotein against cupric ion-mediated oxidation. Similar protection was observed against peroxyl radical-induced supercoiled DNA breakage. A pure ginsenoside standard (e.g., Rb₁) produced similar results. The antioxidant activities of different ginseng species and specific plant parts include free radical scavenging and may be related to ginsenoside Rb₁/Rb₂ content.