Erratum to: Evaluation of antioxidant potential of ethyl acetate fraction of Rosmarinus officinalis L. and its major components

Abstract

The solvent fractions of rosemary methanol extract were obtained by successive extraction with n-hexane, chloroform, ethyl acetate, butanol, and water. The ethyl acetate fraction (EAF) contained a remarkable amount of polyphenol and flavonoid as well as high levels of alkyl and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activity. The activity guided fractionation and repeated chromatographic separations over silica gel, RP C18, and Sephadex LH-20 led to isolation of six compounds from the EAF. 1H NMR, 13C NMR, 2D NMR, MS, and IR spectroscopies determined the compounds to be caffeic acid (1), rosmarinic acid (2), rosmarinic acid methyl ester (3), luteolin (4), apigenin (5), and hispidulin (6), and high-performance liquid chromatography quantification was used to determine concentrations in EAF. Among the six isolated compounds, rosmarinic acid methyl ester showed the highest scavenging activities against di(phenyl)-(2,4,6-trinitrophenyl) iminoazanium, alkyl and ABTS radicals. The EAF mixture, but not individual isolated compounds, shielded dermal fibroblast cells from H2O2-induced cytotoxicity at concentrations that encompass the SC50 of alkyl and ABTS radical. Therefore, our findings suggested for the first time that antioxidant capacity of the EAF mixture result in a synergistic effect on the antioxidant action.