Cichoric acid content and antioxidant activity of commercially available Echinacea herbal medicinal products

Echinacea spp. are very well known medicinal plants with immunomodulatory activity. The purpose of this study was to investigate the phenolic content (cichoric acid and total phenol) and the antioxidant activity of seven medicinal products with Echinacea purpurea (L.) Moench commercially available in Croatia. The content of total phenolics was determined spectrophotometrically with Folin Ciocalteu reagent, while the content of cichoric acid was established by using isocratic RP-HPLC. Antioxidant activity was established using the following techniques: radical scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical, reducing power and β-carotene-linoleic acid assay. The cichoric acid content varied greatly in products with a maximum of 1.6% (w/V) as well as the content of total phenols (0.03–16mg/mL). In all the in vitro analyses the extracts demonstrated marked antioxidant activities. The activity in the reducing power assay correlated very well with the content of total phenols (r2=0,995, P<0.0001), while the activity in the other assays did not correlate neither with the amount of cichoric acid nor with that of total phenolics. It seems that some other substances might be responsible for the activity of the investigated preparations in those assays. The results suggest that cichoric acid, as unstable phenolic compound characteristic for E. purpurea products vary as expected. On the other hand, the total phenolic and antioxidant activity of investigated products are greatly influenced by other ingredients of products.