Studies on the constituents of Chenopodium quinoa seeds: Isolation and characterization of new triterpene saponins

Abstract

Six triterpenoid saponins were isolated from the edible grain quinoa, which is seeds of Chenopodium quinoa (Chenopodiaceae). Following are their structures: phytolaccagenic acid 3-O-[α-L-arabinopyranosyl-(1″→3′)-β-D-glucuronopy ranosyl]-28-O-β-D-glucopyranoside (1); phytolaccagenic acid 3-O-[β-D-glucopyranosyl-(1″→3′)-α-L-arabinopyrano syl]-28-O-β-D-glucopyranoside (2); phytolaccagenic acid 3-O-[β-D-glucopyranosyl-(1‴→3″)-β-D-xylopyranosyl -(1″→2′)-β-D-glucopyranosyl]-28-O-β-D-glucopyranos ide (3); phytolaccagenic acid 3-O-[β-D-glucopyranosyl-(1‴→2″)-β-D-glucopyranosy l-(1″→3′)-α-L-arabinopyranosyl]-28-O-β-D-glucopyr anoside (4); oleanolic acid 3-O-[α-L-arabinopyranosyl-(1″→3′)-β-D-glucuronopy ranosyl]-28-O-β-D-glucopyranoside (5); and oleanolic acid 3-O-[β-D-glucopyranosyl-(1″→3′)-α-L-arabinopyrano syl]-28-O-β-D-glucopyranoside (6). The oleanane-type saponins (5, 6)were isolated for the first time in this plant, two of the phytolaccagenane (1, 3) were new compounds and two (2, 4) were previously found in quinoa. The structures were characterized on the basis of hydrolysis and spectral evidence, including 1D-and 2-D NMR (HMQC and HMBC) and ESI-MS analyses.