New steroidal glycosides from Dracaena marginata, Dracaena fragrans and Allium flavum

Abstract

Steroidal saponins are a class of glycosides occurring in many plant species. The aglycon part of these glycosides is constituted by a furostane or spirostane-type skeleton, rarely cholestane. These saponins are known for their interesting pharmacological activities such as antifungal, anti-ischemia, antispasmodic, cytotoxic, haemolytic [1 – 3], and anti-inflammatory properties [4]. The aim of our researches was the isolation and structural elucidation of the steroidal saponins from the biodiversity. In this context, the study of three plants species, Dracaena marginata, D. fragrans (Asparagaceae) and Allium flavum (Amaryllidaceae) led to isolation of twenty-one natural glycosides by column chromatography on Sephadex LH-20, medium pressure liquid chromatography and vacuum liquid chromatography on silica gel and reversed-phase RP-18 silica gel. The structures were elucidated by a detailed spectral analysis by 600 MHz 2D-NMR (COSY, TOCSY, ROESY/NOESY, HSQC, HMBC/HMQC), and mass spectrometry. Six new compounds were characterized as spirostane and furostane- type glycosides from D. marginata (1 – 3) and from A. flavum (4 – 6). The presence of a 4-O-sulfated arabinopyranosyl moiety in the oligosaccharide chain at C-1 of the steroid skeleton underlined the originality of the compounds of the two Dracaena species, and might represent a chemotaxonomic marker of the genus Dracena. The isolation and structure elucidation of the six new compounds will be presented.