Study on the Antioxidant Activities of Crude Extracts from the Roots of Arnebia euchroma and Lithospermum erythrorhizon

Background/Purpose. To investigate the antioxidant activities and total polyphenol content in two Zicao species, Arnebia euchroma (AE) and Lithospermum erythrorhizon (LE). Methods. The antioxidant activities of aqueous and methanolic extracts of the roots of AE and LE were evaluated by Trolox equivalent antioxidant capacity (TEAC) assay, DPPH staining, free radical scavenging capacity and reducing power methods. We also analyzed the total content of phenolic compounds, flavonols, and flavonoids to investigate whether there is a correlation between content and antioxidant activity. Results. The Trolox equivalent antioxidant capacity and reducing power assays revealed that the methanol and water extracts of AE exhibited better antioxidant activity than those of LE. Methanol extracts of both species exhibited better antioxidant activity than water extracts. The order of antioxidant activity of the samples was AEM＞AEW≥LEM＞LEW. The DPPH radical scavenging test showed that AE exhibited greater capacity than LE to scavenge DPPH radicals. The order of scavenging ability was AEW＞AEM＞LEM＞LEW. The content of total polyphenols, flavonoids and flavonols was higher in the methanol extract than in the water extract of both species, although the content was higher in AE than in LE. Conclusion. This study provides evidence that the antioxidant activities of AE are greater than those of LE. Furthermore, the antioxidant activities of AE and LE are closely related to the total content of polyphenols, flavonoids and flavonols.