Complete 1H and 13C NMR assignments of six saponins from Sapindus trifoliatus

Complete H-1 and C-13 spectral assignments are reported for six saponins from the pericarp of Sapindus trifoliatus (Hindi name: Reetha) collected from Madhya Pradesh and Maharashtra, India, using only 1D and 2D NMR methods. The structures of the compounds were elucidated as hederagenin 3-O-(3-O-acetyl-beta-Dxylopyranosyl)-(1-3)-alpha-L-rhamnopyranosyl-(1-2)-alpha-L-ara- binopyranoside, hederagenin 3-O-(4-O-acetyl-beta-D-Xylopyranosyl)-(1-3)-alpha-L-rhamnopyranosyl-(1-2)-alpha-L-arabinop- yranoside, hederagenin 3-O-(3,4-O-diacetyL-beta-D-Xylopyranosyl)-(1-3)-alpha-L-rhamnopyranosyl-(1-2)-alpha-L-arabinopy- ranoside, hederagenin 3-O-(3,4-O-diacetyl-alpha-L-arabinopyranosyl)-(1-3)-a-L-rhamnopyranosyl-(1-2)-a-L-arabinop- yranoside, hederagenin 3-O-(alpha-D-Xylopyranosyl)-(1-3)-alpha-L-rhamnopyranosyl-(1-2)-alpha-L-arabinopyranoside and hederagenin 3-O-(alpha-L-arabinopyranosyl)-(1-3)-alpha-L-rhamnopyranosyl-(1-2)-alpha-L-arabinopyranoside. It is concluded that saponins of this complexity approach the limit of structural complexity, which can be solved by NMR alone, precisely and quickly. Copyright (c) 2005 John Wiley & Sons, Ltd.