Changes of Phenolic Acids and Antioxidant Activities in Diploid and Tetraploid Echinacea purpurea at Different Growth Stages

Abstract

Phenolic acids are the main active substances that contribute to the antioxidant activity of Echinacea purpurea (L.) Moench, Asteraceae. However, the effect of chromosome doubling and developmental growth stage on the phenolic acid accumulation and the antioxidant capabilities of E. purpurea has remained unclear. Our systematic studies indicate that the dry weight of tetraploid plants is significantly higher than that of diploid plants, leading to higher yields of cichoric acid, caffeic acid, chlorogenic acid, caftaric acid, and 1,5-dicaffeoyl quinic acid compared with diploid plants, at different growth stages. Cichoric acid and caftaric acid are the predominant compounds in diploid individuals. The period with the higher yields of cichoric acid and caftaric acid are coincided with that of total phenolic acids in four investigated organs (root, leaf, stem, and flower), which mostly observed during the flowering period (August). Furthermore, antioxidant activities in four different organs of tetraploid individuals were higher than those in diploid plants, at each growth stage. The changes in the antioxidant activity in different organs (flower, root, leaf, and stem) of diploid individuals were significantly and positively correlated with the trends in the content changes of total phenolic acids throughout different growth stages. Blooming time should be chosen as the best harvest time for both diploid and tetraploid plants, and the flowers and leaves may be used as raw materials for the extraction of total phenolic acids and development of antioxidant supplements to stimulate the immune system.