Solvent effect in 1H NMR spectra of 3′‐hydroxy‐4′‐methoxy isoflavonoids from Astragalus membranaceus var. mongholicus

Abstract

Four 3′‐hydroxy‐4′‐methoxy‐isoflavonoids: calycosin‐7‐O‐β‐D‐glucopyranoside (1), calycosin (2), pratensein‐7‐O‐β‐D‐glucopyranoside (3), and pratensein (4) were isolated from Astragalus membranaceus var. mongholicus, among which compound 4 was obtained from this plant for the first time. The solvent effect obscuring ¹H signal patterns of B ring of compounds 1–4 was reported to avoid mis‐assignments. Previously reported NMR data of compounds 1 and 2 were corrected based on 1D and 2D NMR experiments. Copyright © 2006 John Wiley & Sons, Ltd.