Tensioactive Compounds from the Aquatic Plant Ranunculus fluitans L. (Ranunculaceae)

In the search for the cause for the formation of persistent foam in the Rhine River below the Rhine Fall at Schaffhausen, an investigation of the tensioactive principles from the aquatic plant Ranunculus fluitans L. (Ranunculaceae) was carried out. Two new (see 1 and 2) and four known bisdesmosidic triterpene saponins (see 4 – 6) were isolated along with the two known diacylglycerol galactosides 7 and 8. The saponin structures were established by the identification of the aglycon and sugar moieties by HPLC and chiral capillary zone electrophoresis (CZE), ion-spray LC/MS and extensive 1- and 2D homo- and heteronuclear NMR spectroscopy. The structures of the new oleanane-type saponins were identified as 3-O-[β-D-glucopyranosyl-(1→3)-α-L-arabinopyranosyl]-28-O-[α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl]hederagenin (1) and 3-O-[β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl]oleanolic acid [α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl] ester (2). LC/MS Studies of tensioactive fractions revealed the presence of additional glycoglycerolipids.