Phenolic constituents from Balanophora laxiflora with DPPH radical-scavenging activity.

Balanophora laxiflora HEMSL. (Balanophoraceae), a dioeciously parasitic plant, has been used as a tonic and for sobering up from drunk by the local people of Yunnan province, China. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay on the acetone extract of the fresh female plant of B. laxiflora displayed considerable radical-scavenging activity (SC(50)=16.4 microg/ml). Further purification of the extract led to the isolation of two new phenolic glycosides, balaxiflorins A and B (1 and 2, resp.), together with 17 known phenolic compounds including 3-phenylpropanoids, 3, 17-18, four lignans, 4-7, nine hydrolyzable tannins, 8-16, and gallic acid (19). Their structures were determined by detailed spectroscopic analysis. The free-radical-scavenging activity of the isolated compounds was examined by DPPH assay.