Caffeoyl Derivatives: Major Antioxidant Compounds of Some Wild Herbs of the Asteraceae Family

The polyphenolic composition and antioxidant activity of the aerial parts of 18 medicinal or food plants of the Asteraceae family were studied. Five main caffeoyl derivatives were determined individually by HPLC and compared with levels determined by colorimetry for total dihydroxycinnamic derivatives and total phenolics. The aim of this study was to assess the contribution of these constituents to the antioxidant activity of the herbs determined by DPPH radical scavenging tests. Significant correlations were found between total phenolic (R = 0.8904), total dihydroxycinnamic derivative (R = 0.8529) and total caffeoyl derivative (R = 0.7172) concentrations and the DPPH-scavenging ability of all herbs. The antioxidant activity of the main constituents, including chicoric acid (EC50 = 8.24 μmol/l) or 3,5dicaffeoylquinic acid (EC50 = 7.62 μmol/l), was very high compared to vitamin C (EC50 = 15.66 μmol/l). Thus, for each species, antioxidant activity mainly involves the major caffeoyl derivatives. The contribution to antioxidant activity were assessed as 48.92% for 3,5-dicaffeoylquinic acid in Tanacetum parthenium (30.08 g/kg), and 68.96% for chicoric acid in Taraxacum officinale (34.08 g/kg). The main caffeoyl derivatives among polyphenols can be considered as the major antioxidant compounds of the studied Asteraceae herbs.