The DPPH radical scavenging activity of two flavonol glycosides obtained from ethanolic extracts of Aconitum napellus sp. lusitanicurn was studied. The results showed a high DPPH antiradical activity of compound 1 (quercetin 3-O-(6-transcaffeoyl)-beta-glucopyranosyl-(1 -> 2)-beta-glucopyranosyl-7-O-alpha-rhamnopyranoside) when compared with compound 2 (quercetin-3-sophoroside-7-rhamnopyranoside), rutin and ascorbic acid. The relationship between the caffeoyl and rhamnopyranoside groups in the flavonol glycosides structures and the DPPH antiradical activity was also discussed. (c) 2006 Elsevier B.V. All rights reserved.