Determination of phenolic compounds and their antioxidant activity in Erigeron acris L. extracts and pharmaceutical formulation by flow injection analysis with inhibited chemiluminescent detection

It was found that the chemiluminescence (CL) produced from the reaction of luminol with iodine in the alkaline medium was strongly inhibited by plant phenolic compounds. Based on this finding, a new flow injection CL method was developed for the determination of caffeic acid and 6′-caffeoylerigeroside. The latter compound was isolated for the first time from Erigeron acris L. herb. The method was simple, rapid and sensitive with a detection limit of 4 × 10−3 ng mL−1 (caffeic acid) and 0.18 ng mL−1 (6′-caffeoylerigeroside), linear range of 0.1–1.5 ng mL−1 (caffeic acid) and 1–200 ng mL−1 (6′-caffeoylerigeroside), relative standard deviation of 3.3% for 10 measurements of 0.45 ng mL−1 caffeic acid and 2.9% for 40 ng mL−1 6′-caffeoylerigeroside. This method was successfully applied to determine the content of phenolic compounds/antioxidant activity of E. acris L. extracts and phenolic acids content in pharmaceutical formulation. A possible mechanism of the inhibition of the proposed CL system was discussed.