Purification and Identification of a Novel Protein Isolated from Panax quinquefolium and Evaluation of its In vitro Antioxidant Properties

Objective: A novel protein was first purified from Panax quinquefolius L.（AGNP）, and in vitro antioxidant activities of AGNP were first studied in this work. Methods: AGNP was purified by Ion-exchange chromatography and Gel-filtration chromatography. The chemical characterizations of AGNP were tested by sodium dodecyl sulfate–polyacrylamide gel electrophoresis（SDS-PAGE）, high-pressure gel-filtration chromatography, MALDI-TOF-MS and HPLC. In vitro antioxidant effects were tested in simple antioxidant assay including 2,2-diphenylpicrylhydrazyl radical scavenging, superoxide radical（O2-） scavenging, hydroxyl radical（OH） scavenging, and ferric-reducing ability. Results: The results showed which the content of AGNP measured by Bradford method was 2.42 mg/m L and the subunit molecular weight of AGNP measured by sodium dodecyl sulfate–polyacrylamide gel electrophoresis（SDS-PAGE） was 15 kD. The AGNP molecular weight was 15, 114 Da both of SDS-PAGE and mass spectrum purity. The result of high-pressure gel-filtration chromatography demonstrated that the molecular weight of AGNP was 31,086 Da, which implied that AGNP was a homodimer. The in vitro Antioxidant results indicated that AGNP had obvious effects to remove the free radicals in vitro. Conclusion: In conclusion, AGNP had more powerful antioxidant capacity and it can be used as an effective natural antioxidant to alleviate oxidative stress.