Phenolic constituents and antioxidant activity of an extract of Anthurium versicolor leaves

Fractionation of a methanolic extract of the leaves of Anthurium versicolor has resulted in the isolation of two main fractions, I and II. Both the extract and the fractions were assayed for their radical-scavenging activity by means of an in vitro test (bleaching of the stable 1,1-diphenyl-2-picrylhydrazyl radical) and showed a significant radical-scavenging effect. Subsequent chromatographic fractionation of the most active fraction, II, has led to the isolation and characterization, as major constituents, of four new flavone glycosides, acacetin 6-C-[alpha -L-rhamnopyranosyl-(1 -->3)-beta -D-glucopyranoside] (1), acacetin 6-C-[beta -D-xylopyranosyl-(1 -->6)- beta -D-glucopyranoside] (2), acacetin 6-C-[beta -D-apiofuranosyl-(1 -->3)-beta -D-glucopyranoside] (3), and acacetin 8-C-[alpha -L-rhamnopyranosyl-(1 -->3)-beta -D-glucopyranoside] (4), as well as vitexin (apigenin-8-C-beta -D-glucopyranoside) and rosmarinic acid. The structures of 1-4 were determined using spectroscopic methods.