Saponin Drugs

Most of the saponins of official saponin drugs are triterpene glycosides. Some drugs also or only contain steroid saponins.

Sugar residues may be linked via the OH group at C-3-OH of the aglycone (monodesmosidic saponins) or more rarely via two OH groups or a single OH group and a carboxyl group of the aglycone moiety (bisdesmosidic saponins).

Triterpene saponins. These saponins possess the oleanane or, more rarely, the ursane or dammarane ring system. Many have acidic properties, due to the presence of one or two carboxyl groups in the aglycone and/or sugar moiety. Other oxygen-containing groups may also be present in the sapogenin, e.g. −OH, −CH2OH or −CHO.

The carbohydrate moiety usually contains one to six monosaccharide units, the most common of these being glucose, galactose, rhamnose, arabinose, fucose, xylose, glucuronic and galacturonic acid. The horse chestnut saponins are partly esterified with aliphatic acids.

Most triterpene saponins possess hemolytic activity, which varies from strong to weak, depending on the substitution pattern.

Steroid saponins. The sapogenins of the steroid saponins are mostly spirostanols. Furostanol derivatives are usually converted into spirostanols during isolation procedures: these sapogenins do not carry carboxyl groups. Steroid saponins possess less sugar units than the triterpene saponins. In contrast to the monodesmosides, the bisdesmosidic furostanol glycosides exert no hemolytic activity.