B. Gestetner

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.

Structure of a saponin from lucerne (Medicago sativa)

Abstract The carbohydrate moiety of a highly toxic lucerne saponin was found to be a trisaccharide, which has been characterized as O -β- d -glucopyranosyl (1 → 6)-β- d -glucopyranosyl (1 → 3) β- d -glucopyranose by enzymatic hydrolysis, full and partial acid hydrolysis and gas chromatographic analysis of the methanolysis products of the methylated saponin. The results of enzymatic degradation of the saponin indicate a glycosidic bond between the carbohydrate moiety and the aglycone; analogy to other saponins and theoretical considerations point toward an attachment at C 3 of the aglycone.

Fungistatic activity of lucerne saponins and digitonin as related to sterols

Abstract The relationship between the growth inhibiting activity of saponins and the presence of sterols in fungi was studied. Spraying of mycelia with lucerne saponins or digitonin resulted in swift lysis of the hyphal tips of those fungi, which contain cholesterol in their cell membrane. The fungistatic activity of the saponins was found to be closely related to the relative amount of cholesterol in the found. Incorporation of exogenous cholesterol did not change the sensitivity of Pythium sp. PRL 2142 to lucerne saponins or digitonin. Similar experiments with M. laidlawii changed this organism from a tolerant to a highly sensitive one to digitonin but not to lucerne saponins, indicating that the growth inhibiting activity of saponins depends not only on the presence but also on the orientation of cholesterol in the cell membrane.

Medicagenic acid, the factor responsible for hemolytic activity of lucerne saponins

Die aus Wurzeln von Luzerne isolierten Saponine wirken stärker hämolytisch als diejenigen in den grünen Teilen dieser Pflanze. Die hämolytisch wirksameren Saponine sind reicher an Medicagensäure und es wird angenommen, dass diese für die hämolytische Wirkung der Saponine verantwortlich ist. Die Anwesenheit von 2 Carboxylgruppen in der Medicagensäure scheint für ihre hämolytische Wirkung von ausschlaggebender Bedeutung zu sein, da der Dimethylester dieser Säure nicht mehr hämolytisch wirkt.

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.

The effect of the carbohydrate moiety on biological activities of synthetic glycosides of medicagenic acid.

Synthetische Glycoside der Medicagensäure wirken fungistatisch und hämolytisch im gleichen Ausmass wie das natürliche Luzerne-Saponin und unbeeinflusst von der Natur des Zuckers in den Glycosiden. Der hämolytische Index der Medicagensäure ist geringer, die fungistatische Wirkung derselben aber etwas höher als diejenige der Glycoside, was mit der geringeren Wasserlöslichkeit der Medicagensäure erklärt werden kann.