New steroidal saponins from Asparagus acutifolius

Asparagus acutifolius L. belongs to the Liliaceae family in which the steroidal saponins are fairly widespread. A survey of the literature showed that several Asparagus species have already been chemically studied and found to contain bioactive steroidal saponins. As part of our ongoing search for biologically active steroid saponins as potent antifungal agents [1–3] a phytochemical investigation of the roots of A. acutifolius has led to the isolation by several chromatographic steps on normal and reversed phase silica gel of three new steroidal glycosides. Their structures were determined by spectroscopic methods including 1D- and 2D-NMR (COSY, TOCSY, HSQC and HMBC) and FAB-MS as (25S)-3β,5β,22α-22-methoxyfurostan-3,26-diol 3-O-β-D-xylopyranosyl-(1→2)-[β-D-xylopyranosyl-(1→4)]-β-D-glucopyranosyl 26-O-β-D-glucopyranoside [1], (25S)-5β-spirostan-3β-ol 3-O-β-D-xylopyranosyl-(1→2)-[β-D-xylopyranosyl-(1→4)]-β-D-glucopyranoside [2] and (25S)-5β-spirostan-3β-17α-diol 3-O-β-D-xylopyranosyl-(1→2)-[β-D-xylopyranosyl-(1→4)]-β-D-glucopyranoside [3]. In addition, the antifungal activity of these compounds was tested against three human pathogenic yeasts (Candida albicans, C. glabrata and C. tropicalis). Spirostanol saponins presented antifungal activity with MICs values between 12.5 and 50µg/mL whereas furostanol compounds were inactive.

References: 1. Sautour, M. et al. (2004), Planta Med. 70: 90–92. 2. Sautour, M. et al. (2004), Chem. Pharm. Bull. 52: 1353–1355. 3. Sautour, M. et al. (2005), J. Nat. Prod. 68: 1489–1493.