Antioxidant phenolic constituents from Fagopyrum dibotrys.

Fagopyrum dibotrys (D. Don.) Hara. is an erect perennial Polygonaceous herb. In China, its rhizome was used as folk medicine for the treatment of lung diseases, dysentery and rheumatism. The crude aqueous acetone extract from the rhizomes of this plant exhibited high antioxidant activity (SC50 = 10.95 microg/mL) in 1,1-diphenyl-2-picryldydrazyl (DPPH) radical scavenging assay. Detailed chemical investigation on the extract led to the isolation of two new phenols (1 and 2), together with 14 known antioxidant phenolic compounds (3-16). Their structures were determined by detailed spectroscopic analysis. The two new compounds were characterized as 3-methyl-gossypetin 8-O-beta-D-glucopyranoside (1) and 1,3,6'-tri-p-coumaroyl-6-feruloyl sucrose (diboside A, 2). The radical scavenging activity of all the isolated compounds was also described.