Abstract:

Objective: To study the interaction of five powerful antioxidant flavonoids isolated from Coreopsis tinctoria
Nutt. including marein, maritimetin, taxifolin, butein and okanin. Methods: The DPPH scavenging capacity was used as
the indicator of antioxidant activity, and Chou-Talalay method was used to analyze antioxidant interactions among these
flavonoids. Results: There was moderate synergistic antioxidant interaction between maritimetin and butein, and between
taxifolin and butein with weighed average combination index (CIwt) values of 0.824 and 0.749 for scavenging 1,1-diphenyl-
2-picrylhydrazyl (DPPH) free radical, respectively. In addition, the IC50 for maritimetin combined with butein was higher
than 1, and the CIwt value was less than 0.90, suggesting an obvious synergistic interaction. Nevertheless, a combination of
maritimetin, butein and taxifolin scavenged DPPH free radical with a CI value of higher than 1.0, indicating no synergistic
interaction among these three antioxidants. Conclusion: The structure and concentration of flavonoids from Coreopsis
tinctoria Nutt. can influence their antioxidant interaction.

Key words: flavonoids, antioxidant, Chou-Talalay method, interaction