A strategy for structure-activity relationship study on antioxidants in Echinops latifolius Tausch extracts by online HPLC-radical scavenging detection coupled with ESI-IT-TOF-M.

The antioxidant activity of caffeic acid compounds was significantly higher than that of flavonoids, implying that the antioxidant activity was related to the presence of hydroxyl groups, but not be facilitated by the number of hydroxyl groups. The antioxidant activity was associated with the existence of phenolic hydroxyl group [27]: compounds had the antioxidant activity by containing the phenolic hydroxyl group, while they had no antioxidant activity due to the lack of a phenolic hydroxyl structure. The antioxidant activity of caffeoylquinic acid compounds could be ranked as follows: 3,4-Dicaffeoylquinic acid > 1,5Dicaffeoylquinicacid > 3,5-Dicaffeoylquinic acid, indicating that the substitution position of caffeoyl on quinic acid had a greater influence on DPPH activity. [Extracted from the article]