Radical scavenging and antimicrobial activity of horsetail (Equisetum arvense L.) extracts

Summary A reversed‐phase high performance liquid chromatography (RP‐HPLC) separation on C8 column and quantitative method were developed to analyse hydroxyl derivatives of benzoic and cinnamic acid and flavonoids in horsetail (Equisetum arvense L.) extracts. Total phenolic content of n‐butanol, ethyl acetate and water extracts, determined by the Folin‐Ciocalteu method, was 96.4, 26.4 and 15.4 mg g−1 of dry extracts, respectively. The antioxidative activity of horsetail extracts was tested by measuring their ability to scavenge stable 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and reactive hydroxyl radicals by electron spin resonance spectroscopy. The results demonstrated that the free radical scavenging activity (versus both DPPH and hydroxyl radicals) depended on the type and concentration of applied extracts; the highest DPPH (EC50 = 0.65 mg mL−1) and hydroxyl radical scavenging activities (EC50 = 0.74 mg mL−1) were obtained in the case of n‐butanol extract. The radical scavenging activity of extracts significantly correlated with total phenolic content. The antimicrobial tests showed that ethyl acetate and n‐butanol extracts inhibited the growth of tested bacteria.