The triterpene group of compounds include sterols and triterpenes, which can accumulate as
glycosides (saponins) in extensive amounts in plants [16]. Saponins are glycosylated (aglycone =
sapogenin) secondary metabolites found in a variety of plant species [17]. Their surface-active
properties are what distinguish these compounds from other glycosides [16]. Due to the fact that some
of these saponins are the starting points for the semi-synthesis of steroidal drugs, these metabolites are
highly sought after by the pharmaceutical industry [18]. Saponins are classified according to their
aglycone skeleton. The first group consists of non-steroidal saponins, which are the most common and
occur mainly in the dicotyledonous angiosperms. The second group consists of the steroidal saponins
which are derived from the tetracyclic triterpenoids and isoprene units and are almost exclusively
present in monocotyledonous angiosperms. Some claim a third class called steroidal amines, which are
also referred to as steroidal alkaloids [7]. Steroidal saponins consist of a steroidal aglycone, a C27
spirostane skeleton which generally consists of a six-ring structure (Figure 1A). The hydroxyl-group in
the 26-position may be engaged in a glycosidic linkage so that the aglycone structure remains
pentacyclic (Figure 1B). This is referred to as a furostane skeleton. Triterpenoid saponins consist of a
triterpene aglycone, which consists of a C30 skeleton, compromising a pentacyclic structure (Figure 1C).