Triterpenoids and saponins

Triterpenoid compounds are derived from a precursor, squalene, which was first isolated from shark liver (Bruneton 1995). They have similar configurations to steroids (found in plants and animals) whose C27 skeletons are also derived from squalene. According to convention, the rings are labelled A-D (or E if present) and the carbons are numbered as shown on the diagram. 

The triterpenoids are a large and diverse group made up of several subclasses  

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FIG. 4 Structure of representative saponins found in soybeans (triterpenoid) and eggplant (steroid). The R group represents one or more carbohydrate linkages that may contain rhamnose, xylose, arabinose, galactose, glucose, or glucuronic acid. 

Six isoprene units combine to give a molecular formula C30H4g for the triterpenes. Their derivatives - the triterpenoids - include sterols (found in all plant and animal cells), steroids (many hormones) and saponins (important plant products). 

Durantanins I (28), II (29), and III (30), the triterpenoid-type saponins, are allelochemicals from Duranta repent L.16... 

Figure 12 Triterpenoid and steroid skeletons common in plants and structures of some saponins.

Subsequent to the isolation of the dammarane-type triterpenoid glycosides jujuboside B (112), hodulosides I-V (113-117), hovenoside I, and saponins C2, E, and H (122-125) as sweetness inhibitors from the leaves of Hovenia dulcis Thunb. var. tomentella Makino [139], hodulosides VII-X (118-121) were isolated as sweetness-inhibitory agents [140]. Hodulosides I (113) and II (114) have hovenolactone (151) as their aglycone which is the same compoimd as in saponins E (124) and H (125). Hodulosides Ill-V and VII-X (115-121) are based on two different danunarane-type aglycone structures, however [139,140]. The sweetness-inhibitory potencies of hodulosides are shown in Table 2. The sweetness-inhibitory potency of hoduloside X (121) was not determined [140]. 

During the almost 20-years of research on Astragalus sapogenins and saponins, more than 40 species firom this genus have been studied and above 40 triterpenoid sapogenins and up to 130 saponins have been isolated and identified until now, and for some of them the biological activity has also been studied. 

B-lymphocytes. The gastrointestinal irritant properties of phytolaccinic acid and related triterpenoid glycosides (saponins) cause diarrhea and severe vomiting. 

Yang C-R, Li X-C (1996) Bioactive Triterpenoid and Steroid Saponins from Medicinal Plants in Southwest China. Adv Exp Med Biol 404 225... 

Several branched pentamers with terminal 6-deoxyhexose units have been reported, some having been synthesized and some isolated from natural sources. P-D-Fuc-(1 2)-p-D-Qui-(1 4)-[ 3-0-Me-P-D-Qui]-p-D-Xyl-(l- 4)-p-D-Qui has been isolated as a carbohydrate component of different triterpenoid starfish saponins, and saponins from Quillaja saponaria have yielded P-D-Api-(1 3)-P-D-Xyl-(l- 4)-[p-D-Glc-(1 3)]-a-L-Rha-(1 2)-D-Fuc. " ... 

Phytochemistry The aboveground parts contain saponins, up to 0.1 % alkaloids (especially smimovine), coumarins, tannins, flavonoids (0.9 % in stems, up to 4.9 % in leaves), vitamins C, E and P, and carotene. The roots contain triterpenoids, alkaloids, coumarins, and saponins (Khalmatov 1964 Svechnikova et al. 1983 Gan et al. 1986a, b). 

Phytochemistry The plant contains organic acids (tartaric, citric, and malic), essential oil, diterpenoids (phytol), triterpenoids, steroids, saponins, alkaloids, choline, vitamin C, carotene, phenylcarbonic acids (rosmarinic acid), tannins, cou-marins, flavonoids, cardiac glycosides, carbohydrates and anthocyanins (cyanin and pelargonin Akopov 1990 Plant Resources of the USSR 1991). 

When macerated plant material or plant extracts containing saponins is shaken with water, a thick stable foam usually results (Hostettmann et al, 1991). This is the basis of a simple, reasonably specific test for the general presence of these compounds. Saponins also are detected by the Lieber-mann-Burchard test, which is useful for distinguishing between triterpenoid and steroidal saponins (Chandel and Ras-togi, 1980). 

Oleszek, W., Kapusta I., and Stochmal, A. 2008. TLC of triterpenoids (including saponins), in Thin Layer Chromatography in Phytochemistry, Waksmundzka-Hajnos, M., Sherma, J., and Kowalska, T., Eds., CRC Press/Taylor Francis Group, Boca Raton, FL, Chapter 20. 

Rao AV, Gurftnkel DM (2000) The bioactivity of saponins triterpenoid and steroidal glycosides. Drug Metab Dmg Interact 17 211-235... 

Liao LP, Li SL, Li P (2005) Simultaneous determination of seven triterpenoids and triterpenoid saponins in Folium llicis Purputeae by high performance liquid chromatography coupled with evaporative light scattering detection. J Sep Sci 28 2061-2066... 

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