A. Bondi

A new isoflavone from soya beans

Abstract A new isoflavone was isolated from soya beans and shown to be 7,4′-dihydroxy, 6-methoxyisoflavone, for which the name glycitein is proposed.

Soya bean saponins—VII : A method for the determination of sapogenin and saponin contents in soya beans

Abstract A quantitative method has been devised for the determination of the saponin content in acid hydrolysates of soya beans, based on the use of a modified Lieberman-Burchard reagent and employing certain essential steps of purification from accompanying interfering materials. All five known soya sapogenins (soya sapogenols A, B, C, D and E) have been found to give the same colour yield per unit weight with this reagent. A 1:1 sapogenin:sugar ratio has been found to be typical for various soya bean saponin extracts prepared from different soya bean varieties, and has been used as a conversion factor of sapogenin into saponin content. The saponin content determined in six different soya bean varieties has been found to amount to ∼ 0·60 per cent of the defatted soya bean meal.

Interaction of lucerne saponins with sterols

Abstract The structural features of sterols, which enable them to interact with lucerne saponins, were studied. It was found that an intact steroid ring structure having the conformation of cholestanol, to which a side chain characteristic to cholesterol or phytosterols is attached, is essential for the formation of a sterol-saponin addition product. Unlike the complex formed between digitonin and cholesterol, these addition products are extremely unstable and their formation is not dependent on the presence of a 3-β-hydroxyl group. In addition products formed with cholesterol or 7-dehydrocholesterol an approximately 1:5 molar ratio exists between saponin and sterol, whereas in the case of other sterols this ratio is approximately 1:8. Although lucerne saponins readily form addition products with a variety of sterols, a preferential affinity to cholesterol and 7-dehydrocholesterol was found when the addition product was formed while cholesterol and one of the other sterols were present simultaneously in the reaction mixture. These preferential affinities were demonstrated also by bioassays conducted with the fungus Sclerotium rolfsii Sacc.

Interaction of alfalfa saponins with components of the erythrocyte membrane in hemolysis

Abstract The interactions of saponins with erythrocyte membrane components involved in the hemolytic mechanism were studied. It was found that the alfalfa saponin, medicagenic acid 3- β - O -triglucoside, forms interaction products of different stability with membrane cholesterol, proteins and phospholipids. The resulting structural changes affect only slightly the membranous enzyme activities examined. It is suggested that breakdown of the structure of the membrane stems from a combination of non-specific interactions of saponins with membrane proteins phospholipids and cholesterol leading consequently to hemolysis.

Soya bean saponins—VI : Composition of carbohydrate and aglycone moieties of soya bean saponin extract and of its fractions

Abstract A modified acid hydrolysis method, using sulphuric acid-water-dioxane for four hours results in no loss of the released monosaccharides, and has been used for the hydrolysis of total soya bean saponin extract and of four of its fractions. The sugar moieties of the extract and of its fractions has been shown by thin layer and paper chromatography to consist of glucose and xylose in addition to the previously reported galactose, arabinose, rhamnose and glucuronic acid. The quantitative determination of these sugars has been carried out by direct densitometric measurements of paper chromatograms stained with silver nitrate. The sapogenin composition of the aglycone moiety of the extract and of its fractions has been established by paper chromatography.

The effect of alfalfa saponins on growth and lysis of Physarum polycephalum.

The prelytic events associated with the interaction of saponins with Physarum polycephalum membrane components were studied. It was found that alfalfa saponins form interaction products with membranal sterols, proteins and phospholipids. The interaction of saponins with proteins affect also certain membranal enzymic activities such as NADH oxidase and Malate dehydrogenase. It is suggested that although the interaction of the saponin with sterols is much more specific than with other membranal components, the lysis of plasmodia of P. polycephalum should be attributed to a concerted attack on the various membrane constituents. In continuation of these interactions, the changes of permeability of plasmodia membrane were expressed by increment of inorganic sodium ions and water influx, traced by lysis, while no efflux of ions was observed.

Biosynthesis of triterpenoid sapogenols in soybean and alfalfa seedlings

Abstract By incubation of germinating soybeans with mevalonate-[2- 14 C] (MVA), radioactivity was incorporated into four sapogenols which were identified by TLC. Unequivocal evidence for the identity of three of the four sapogenols was provided by co-crystallization to constant specific radioactivity. The partition of incorporated radioactivity into lipid- and water-soluble fractions and the pattern of radioactivity of individual sapogenols varied with the mode of administering labeled substrates to soybean seedlings, such as incubation of germinating soybeans with MVA-[2- 14 C], immersion of roots into MVA-[2- 14 C] or foliar application of squalene-[ 14 C]. When alfalfa seedlings were incubated with MVA-[2- 14 C], about two-thirds of the radioactivity incorporated into the sapogenols was associated with medicagenic acid.