Phenolic Compounds in Field Horsetail (Equisetum arvense L.) as Natural Antioxidants

Abstract

In this paper, the study of antioxidant activity and phenolic composition of three different extracts (EtOAc, n-BuOH and H₂O) of field horsetail (Equisetum arvense L.) is presented. The antioxidant activity has been evaluated measuring the total reducing power (expressed by Ascorbate Equivalent Antioxidant Capacity - AEAC), inhibition of lipid peroxidation, and free radical scavenging capacity (RSC) towards 2,2-diphenyl-1- picrylhydrazyl (DPPH radical) and nitric oxide (NO), respectively. In addition, the total flavonoid content (TFC) and phenolic constituents of each extract have been determined. The results obtained show that the highest RSC regarding both DPPH and NO radicals is expressed by EtOAc extract (EC₅₀=2.37 μg/mL and EC₅₀=90.07 μg/mL, respectively), and the lowest by H₂O extract (EC₅₀=37.2 μg/mL and EC₅₀>333.33 μg/mL, respectively). n- BuOH extract showed the highest total reducing power (AEAC=13.40 μg/mL). Differences in the phenolic composition of examined extracts are found comparing the HPLC chemical profiles. Although, isoquercitrin is the main flavonoid in both EtOAc and n-BuOH extracts, a considerable amount of di-E-caffeoyl-meso-tartaric acid was presented in the n-BuOH extract. In H₂O extract high content of phenolic acids and low percentage of flavonoids were detected.