Paulownia coreana is a medicinal, edible and industrial plant with the largest leaf, and is native to Korea. We evaluated the reducing power activities, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities (RSAs), nitrite scavenging activities (NSAs) and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation RSAs by solvent extraction of P. coreana bark by using 50℃ hot water and 25℃ methanol. The antioxidative effect of P. coreana bark extract on corn seed oil was evaluated using the Rancimat test. The extraction yields on dry weight basis with 15 folds of hot water and methanol were 23.88% and 5.30%, respectively; further the flavonoid content in the hot water extract was over 2.5 times more than that in the methanol extract. The DPPH RSA of the methanol extract was substantially higher than that of the water extract, whereas the NSA of the water extract was higher than that of the methanol extract at pH 1.2. The ABTS RSAs of the two extracts were almost the same as that of ascorbic acid and 2,6-ditertiarybutyl hydroxytoluene. The two extracts of P. coreana bark in this study were found to slightly improve the oxidation stability of corn seed oil.

Abstract
 1. Introduction
 2. Experimental
  2.1. Chemicals and preparation of the extract
  2.2. Determination of total polyphenol and flavonoidcontents
  2.3. Reducing power activity
  2.4. DPPH RSA
  2.5. Nitrite scavenging activity
  2.6. ABTS RSA
  2.7. Rancimat test
 3. Results and discussion
  3.1. Physicochemical properties of extracts
  3.2. Total polyphenol and flavonoid contents
  3.3. Reducing power
  3.4. DPPH RSA
  3.5. Nitrite scavenging activity
  3.6. ABTS RSA
  3.7. Determination of oxidation stability by Rancimattest
 4. Conclusion
 References

• Nam Gull Lee(Department of Food Science & Nutrition, Tongmyong University)
• Kap Seop Jeong(Department of Food Science & Nutrition, Tongmyong University) Corresponding author