Monodesmosidic oleanene-type saponins from kidney vetch (Anthyllis vulneraria L.) with hemolytic activity

Abstract

• Two saponins (anthylloside A and B) were isolated from Anthyllis vulneraria L. • First detection of saikosaponins in the legume (Fabaceae) family. • Saponin structures were assigned by 1D- and 2D-NMR and HR-ESI-MS experiments. • Anthylloside A exhibits strong hemolytic activity in a blood agar assay. Two undescribed monodesmosidic oleanene-type saponins, namely 3 β - O -{[ β -D-glucopyranosyl-(1→4)]- α -L-arabinopyranosyl}-saikogenin G ( 1 ) and 3 β -O-{[ β -D-glucopyranosyl-(1→4)]- α -L-arabinopyranosyl}-16-deoxysaikogenin F ( 2 ), named anthylloside A and B, have been isolated from an acetone-water extract from aerial parts of kidney vetch ( A. vulneraria L.). Isolation of 1 and 2 was achieved by solvent partition with EtOAc and subsequent repeated chromatographic purification. The structures of the isolated compounds were elucidated by spectrometric (HR-MS) and spectroscopic methods ( 1 H- and 13 C-NMR, UV, IR and CD), as well as GC–MS analysis of samples after 1 N HCl hydrolysis and subsequent derivatization. The configuration and conformation of both 1 and 2 were assigned by means of comprehensive 2D-NMR analyses including 1 H- 1 H−COSY, ROESY, decoupled g HSQC, g HMBC and selective 1D-TOCSY experiments. Moreover, 1 and 2 possess significant hemolytic activity, which was assessed in a blood agar assay and compared to that of three reference saponins.