Activity-guided isolation and identification of free radical-scavenging components from ethanolic extract of boneset (leaves of Eupatorium perfoliatum)

Abstract

Activity-directed fractionation and isolation procedures were used to identify the antioxidant components of Boneset (Eupatorium perfoliatum). Dried powdered leaves were extracted with ethanol and subsequently fractionated into light petroleum, chloroform, ethyl acetate, and n-butanol fractions. The ethyl acetate fraction, which showed the strongest antioxidant activity, reducing power and highest phenolic content, was subjected to Sephadex LH-20 chromatography followed by repetitive preparative TLC to afford protocatechuic acid as the major antioxidant constituent, together with small amounts of other antioxidants (hyperoside, quercetin and rutin). Similar treatment of the n-butanol fraction, the second most potent fraction, yielded predominantly rutin and a trace amount of hyperoside as active constituents. The identity of the compounds was established based on direct comparison of spectral data (UV, IR, 1D- and 2D-NMR and MS) with those of authentic samples and literature values.