Saponins occur widely in plant species and exhibit a range of biological properties, both beneficial and deleterious. This review, which covers the literature to mid 1986, is concerned with their occurrence in plants and their effects when consumed by animals and man. After a short discussion on the nature, occurrence, and biosynthesis of saponins, during which the distinction between steroidal and triterpenoid saponins is made, the structures of saponins which have been identified in a variety of plants used as human foods, animal feedingstuffs, herbs, and flavorings are described. Many of these compounds have been characterized only during the last 2 decades, and modern techniques of isolation, purification, and structural elucidation are discussed. Particular consideration is given to mild chemical and enzymatic methods of hydrolysis and to recent developments in the application of NMR and soft ionization MS techniques to structural elucidation. Methods currently used for the quantitative analysis of saponins, sapogenols, and glycoalkaloids are critically considered; advances in the use of newer methods being emphasized. The levels of saponins in a variety of foods and food plants are discussed in the context of the methods used and factors affecting these levels, including genetic origin, agronomic, and processing variables, are indicated. Critical consideration is given to the biological effects of saponins in food which are very varied and dependent upon both the amount and chemical structure of the individual compounds. The properties considered include membranolytic effects, toxic and fungitoxic effects, adverse effects on animal growth and performance, and the important hypocholesterolemic effect. A final section deals briefly with the pharmacological effects of saponins from ginseng, since use of this plant is increasing in certain sections of western society as well as being traditional in the Orient.

The chemistry and biological significance of saponins in foods and feedingstuffs.

Sulfuric acid hydrolysis of steroidal glycosides of Amber fenugreek was studied by capillary gas chromatographic analysis of diosgenin [(25R)-spirost-5-en-3-ol] and isomeric spirostadiene artifacts from 100 mg samples of seed material. Following extraction with 80% ethanol, highest recoveries of diosgenin occurred when hydrolyses were conducted in sulfuric acid, prepared at 1 molar (M) concentration in water containing 60-80% 2-propanol. Compared to a previous method with aqueous hydrochloric acid, the selected conditions of hydrolysis at 100 degrees C for 2 h with sulfuric acid in 70% 2-propanol reduced diene formation but did not completely eliminate these artifacts. Extraction of steroidal saponins with various alcohol/water mixtures prior to sulfuric acid hydrolysis gave similar recoveries of diosgenin. Application of the quantitative method to experimental samples of Amber, Quatro, and ZT-5 fenugreek, using 10 mg subsamples of crushed seed that had been defatted with petroleum ether and dried at 60 degrees C, gave diosgenin levels of 0.55, 0.42, and 0.75%, respectively. Levels of smilagenin and sarsasapogenin were very low in hydrolyzed seed extracts from ZT-5, a Canadian breeder line of fenugreek.

Microdetermination of diosgenin from fenugreek (Trigonella foenum-graecum) seeds.

Mixtures of steroidal sapogenins isolated from the seed and combined aerial parts (foliage) of fenugreek (cultivar Amber) have been examined by capillary column gas chromatography with mass spectral and flame ionization detectors. Diosgenin [(25R)-spirost-5-en-3β-ol] was the major component in seed and foliage extracts hydrolyzed with hydrochloric acid. Yamogenin also appeared to be present. Tigogenin, neotigogenin, smilagenin, and sarsasapogenin were identified in the extracts. Dihydroxy steroidal sapogenins, tentatively identified as yuccagenin, gitogenin, and neogitogenin, were detected as minor components in hydrolyzed extracts from seed. A gas chromatographic method based on the use of an internal standard and a column of HP-5MS was developed to determine diosgenin in Amber fenugreek. Expressed on a dry weight basis, mean levels of diosgenin in seed were 0.54%. In field-grown foliage sampled during a season at 9, 15, and 19 weeks postseeding, diosgenin levels were 0.16, 0.07, and 0.07%, respectively....

Analysis of Steroidal Sapogenins from Amber Fenugreek (Trigonella foenum-graecum) by Capillary Gas Chromatography and Combined Gas Chromatography/Mass Spectrometry†

Potential allelopathic lupane triterpenes from bioactive fractions of melilotus messanensis

Bioproduction of diosgenin in callus cultures of Trigonella foenum-graecum L.

Changes in rotenone (R) and deguelin (D) concentrations were followed by thin-layer densitometry in the leaflets and other parts of two lines of Tephrosia vogelii Hook. f. In one line, relatively free of R, total leaflet D increased from 1.6 to 3.2 %. In the other line leaflet R increased with plant age from 0.3 to 1.1 %and leaflet D increased from 1.1 to 1.9 %. Rotenoid levels were higher in leaves formed later

Fontaine R. Earle

Papers

Rotenone and deguelin in Tephrosia vogelii at several stages of maturity

Screening seed of Trigonella and three related genera for diosgenin