Isolation and structural elucidation of the major genuine soybean saponin

HPLC profile analysis of oleanene-glucuronides in several edible beans

HPLC analysis and yield of oleanene-glucuronide (OG) was done on some commercially available edible beans: seeds of Glycine max, Glycine max cv. Kuromame, Phaseolus vulgaris cv. Torosuku, Phaseolus vulgaris cv. Toramame, Phaseolus vulgaris cv. Taishokintoki, Phaseolus coccineus cv. Ooshirobana, Phaseolus coccineus cv. Murasakihanamame, Vigna unguiculata cv. Chuguro, Vigna angularis cv. Dainagon, Arachis hypogaea, Pisum sativum, and Vicia faba. All the beans listed above have OG, though in varying the amounts. Furthermore the HPLC profiles of beans belonging to the same genus were very similar except for that of the Vigna genus. There was no great difference of the HPLC profiles with respect to the cultivated varieties. The structures of the major OGs in each type of beans were identified as soyasaponins I (1) and V (2), and phaseoside I (3) (Phaseolus vulgaris and P. coccineus); 1 and soyasaponin II (4) (Glycine max); 1 and 2 (Vigna unguiculata); 1 (Pisum sativum, Arachis hypogaea and Vicia faba). In contrast, those in Dainagon (Vigna angularis cv. Dainagon) were identified as azukisaponins II (5) and VI (6).

A preliminary study on the effect of germination on saponin content and composition of lentils and chick peas

Two cultivars of chick peas (Cicer arietinum) and one cultivar of lentils (Lens culinaris) were subjected to germination in the dark for 6 days at 20 degrees C. Soyasaponin VI, also known as soyasaponin beta g, a DDMP- (2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one-) conjugated form of soyasaponin I, was the only saponin detected in both the unprocessed and germinated seed. No significant changes in saponin content were observed for chick peas or lentils after a 6-day germination.

Saponins conjugated with 2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one from Phaseolus coccineus

From the hypocotyl of scarlet runner bean (Phaseolus coccineus), a new 2,3-dihydro-2,5,-dihydroxy-6-methyl-4H-pyran-4-one conjugated saponin, named soyasaponin alpha a, was isolated together with two known saponins, soyasaponin alpha g and beta g. Their structures were elucidated by 1H NMR and 13C NMR spectroscopy and chemical techniques.

Implications of antinutritional components in soybean foods

There are a number of components present in soybeans that exert a negative impact on the nutritional quality of the protein. Among those factors that are destroyed by heat treatment are the protease inhibitors and lectins. Protease inhibitors exert their antinutritional effect by causing pancreatic hypertrophy/hyperplasia, which ultimately results in an inhibition of growth. The lectin, by virtue of its ability to bind to glycoprotein receptors on the epithelial cells lining the intestinal mucosa, inhibits growth by interfering with the absorption of nutrients. Of lesser significance are the antinutritional effects produced by relatively heat stable factors, such as goitrogens, tannins, phytoestrogens, flatus-producing oligosaccharides, phytate, and saponins. Other diverse but ill-defined factors appear to increase the requirements for vitamins A, B12, D, and E. The processing of soybeans under severe alkaline conditions leads to the formation of lysinoalanine, which has been shown to damage the kidneys of rats. This is not generally true, however, for edible soy protein that has been produced under milder alkaline conditions. Also meriting consideration is the allergenic response that may sometimes occur in humans, as well as calves and piglets, on dietary exposure to soybeans.

Genetic and chemical polymorphisms of saponins in soybean seed

The variation in saponin composition in soybean seeds is explained by different combinations of five genes controlling the utilization of soyasapogenol glycosides as substrates. The function of these genes is variety-specific and organ-specific. Phenotypes of over 1000 soybeans were classified into eight saponin types, and the frequency of phenotypes was different between the cultivated [Glycine max (L.) Merr.] and the wild soybean (G. soja Sieb. & Zucc.). The AaBc saponin type predominated in G. soja (58.4% of test collections), but was only found in 0.3% of G. max. Four unidentified arabinoside saponins were detected in the seeds of the AaBc type soybeans. The mode of inheritance of saponin types is explained by a combination of co-dominant, dominant and recessive acting genes. The combined chemical and genetic data show that the directed manipulation of soybean saponin composition is a possibility for the future.