Flavonol triglycosides from Ornithopus compressus L. (Fabaceae)

Abstract

Five flavonoid glycosides were isolated from the aerial parts of Ornithopus compressus L., yellow serradella (Fabaceae). The structures of the isolated natural products were determined as kaempferol 3-O-(2,6-di-O-β-D-glucopyranosyl)-β-D-galactopyranoside (1), kaempferol 3-O-β-D-glucopyranosyl-(1→6)-[2-O-(2E)-feruloyl-β-glucopyranosyl]-(1→2)-β-D-galactopyranoside (2), quercetin 3-O-(2,6-di-O-β-D-glucopyranosyl)-β-D-galactopyranoside (3), quercetin 3-O-β-D-glucopyranosyl-(1→6)-[2-O-(2E)-feruloyl-β-glucopyranosyl]-(1→2)-β-D-galactopyranoside (4), and isorhamnetin 3-O-(2,6-di-O-β-D-glucopyranosyl)-β-D-galactopyranoside (5). While compounds 1 and 3 have been described previously, compounds 2, 4 and 5 represent formerly undescribed natural products. For structure elucidation UV, HRMS, and NMR (1H NMR, 13C NMR, H,H-COSY, HMBC, and HSQC) were employed. Absolute sugar configurations were confirmed using GLC–MS/MS after hydrolysis, octylation, and acetylation of the isolated compounds. Additionally, DPPH radical and ABTS radical cation scavenging activities as well as cytotoxic activities of the isolated compounds were assessed.