Bioavailability of Echinacea root powder phenolics in humans

Abstract

We hypothesized that Echinacea angustifolia, purpurea, and pallida root powder phenolics were metabolized and found in the body as caffeic acid (the main subunit of most of these phenolics). Healthy adult subjects, 6 female and 6 male received 4 g of each Echinacea root powder in a single dose, each dose separated by a one-week washout period in a randomized crossover design. Subjects were instructed to consume diets of minimal phenolic content for 2 days before dosing, and foods provided for all meals during the day of each feeding were low in phenolics. Phenolic contents of E. angustifolia, E. purpurea, and E. pallida were 49.6 μmol (mainly echinacoside), 41.2 μmol (mainly cichoric acid), and 41.0 μmol (mainly echinacoside and cichoric acid)/4 g, respectively. In subjects who consumed E. purpurea and E. pallida, cichoric acid and a smaller peak tentatively identified as caffeic acid, were detected in urine. The 24h urinary recovery of cichoric acid in subjects who consumed E. purpurea and E. pallida were 0.36 ± 0.25 and 0.34 ± 0.31 % of ingested dose, respectively. These results indicate a lack of any significant conversion of Echinacea phenolic acids into caffeic acid, and very low bioavailability of cichoric acid, such that is unlikely that this compound contributes much to the bioactivities of Echinacea. Funded by NIEHS Grant No. PO1 ES12020, Center for Research on Dietary Botanical Supplements, Iowa State University.