Soy Saponins Research Articles

An Analytical Method for Soy Saponins by HPLC/ELSD

ABSTRACT: A high‐performance liquid chromatography/evaporative light scattering detection (HPLC/ELSD) method was developed to determine natural forms of soyasaponin B with (αg, βg, βa, γg, γya) and without (V, I, II, III, IV) 2,3‐dihydro‐2,5‐dihydroxy‐6‐methyl‐4H‐pyran‐4‐one (DDMP) in soybean. The coefficient of variance of intra‐day assays was < 9.51% and that of inter‐day assays was < 10.91%. The soyasaponin I was used as external standard for quantification of all soyasaponins because it was established that their ELSD signal responses were essentially the same under the specific operating conditions. The extraction conditions were optimized and the extract storage conditions were established for analysis of soyasaponin Bs in their natural state. The energy of activation of soyasaponin Pg was 40.76 kJ/mol. The recovery rates for soyasaponin I and II were 98.3% and 93.1%, respectively. The average of total soyasaponins content from 5 soybean samples was 3.37 μmol/g with ranges from 2.78 to 4.03 μmol/g. This method is simple and easy to use, and the sample preparation takes less time than existing methods.

Soy saponins and the anticancer effects of soybeans and soy-based foods.

While the cancer protective effect of soy-based diets has been the subject of numerous studies, the constituents of soy that may give rise to this effect remain elusive. Recent publications describing anticancer activity of crude and purified soybean saponins have sparked a renewed interest in these compounds. In this review, I summarize the epidemiological studies concerning the cancer protective effects of soy and the efforts to elucidate the constituents responsible for this effect. The recent reports of the anticancer activity of soy saponins is placed in context with reports of promising anticancer activity of structurally related non-dietary saponins from other legumes. While recent studies have demonstrated a direct effect of soy saponins on cancer cells, alternative mechanisms of cancer prevention by these agents are also discussed. It is concluded that the soy saponins may represent promising leads both in terms of elucidating the soy constituents involved in the cancer protective effect of soy as well as in the discovery of anticancer agents with novel mechanisms of action.

Antiproliferative crude soy saponin extract modulates the expression of IκBα, protein kinase C, and cyclooxygenase-2 in human colon cancer cells

Frequent consumption of soy and soy-based products is associated with reduced cancer incidence particularly for breast, colon, and prostate cancer. In this study, we examined the effect of crude soy saponin extract on PMA (phorbol 12-myristate 13-acetate)-induced inflammatory responses. Human adenocarinoma cells (HT-29) were treated with various concentrations of saponin extract for 72 h. Cell growth was measured at 24, 48 and 72 h of incubation, and the PMA-induced expressions of cyclooxygenase-2 (COX-2), protein kinase C (PKC), and IκBα were determined. The results indicate that crude saponin extract decreased cell growth in a dose- and time-dependent manner. Crude soy saponin extract suppressed the degradation of IκBα in PMA-stimulated cells, while COX-2 and PKC expressions were significantly down-regulated. These findings support the hypothesis that the soy saponins reduce the risk of colon tumorigenesis possibly by suppressing inflammatory responses.

Preliminary evidence that cholesterol improves growth and feed intake of soybean meal-based diets in aquaria studies with juvenile channel catfish, Ictalurus punctatus

Two feeding trials were conducted in aquaria to examine the effects of dietary soybean meal (SBM), purified soybean saponin and supplemental cholesterol concentrations on growth responses of channel catfish. In the first experiment, five dietary treatments were formulated to contain either 0%, 13.9%, 27.7%, 41.6% or 55.5% SBM which was added to the diets at the expense of soy protein concentrate (SPC) on an isonitrogenous basis. Each diet was fed to apparent satiation twice daily to triplicate groups of fish initially weighing 7.0 g/fish. At the end of the 8-week feeding trial, weight gain and feed intake (FI) in fish fed diets containing 0% or 13.9% SBM were significantly higher than in fish fed diets containing 27.7%, 41.6% or 55.5% SBM. Fish fed 27.7% dietary SBM exhibited significantly higher weight gain and feed intake compared with fish fed 41.6% or 55.5% dietary SBM. No significant differences were detected in feed efficiency (FE) or survival among fish fed any of the dietary treatments. In the second experiment, five dietary treatments were formulated to contain various concentrations of SBM (0% and 55.5%), supplemental cholesterol (0% and 1.0%) and purified soybean saponin (0% and 0.26%) to determine whether cholesterol could alleviate the deleterious effects of high dietary SBM concentrations. Each diet was fed to apparent satiation twice daily to triplicate groups of channel catfish initially weighing 9.7 g/fish. At the end of the 8-week feeding trial, weight gain, FI and FE were not significantly different between fish fed the purified control diet and fish fed the SBM-based diet (55.5% SBM) supplemented with 1.0% cholesterol. Fish fed the SBM-based diet containing 1.0% supplemental cholesterol exhibited significantly higher growth rate and FI compared with fish fed the SBM-based diet containing no supplemental cholesterol. Weight gain and FI in fish fed the diets containing purified soybean saponin were not significantly different than in fish fed the purified control diet, indicating that soy saponin was not responsible for reduced feed consumption in fish fed high dietary SBM concentrations. Results of this research indicated that 1.0% supplemental cholesterol may improve growth responses in juvenile channel catfish fed SBM-based diets and that soybean saponin was not responsible for reduced FI in fish fed high dietary SBM concentrations.

Soy Protein Reduces Paraquat-Induced Oxidative Stress in Rats

The effect of soy protein, soy isoflavones and saponins on paraquat (PQ)-induced oxidative stress was investigated in rats. Rats were fed experimental diets containing casein (CAS), soy protein (SPI), and casein with soy isoflavones and saponins (CAS + IS). The diets were supplemented or not with 0.025% paraquat (CAS + PQ, SPI + PQ, and CAS + IS + PQ). The protective effects of soy protein, soy isoflavones, and saponins on paraquat-induced oxidative stress were examined. Ingestion of soy protein generally mitigated the lung enlargement (P = 0.076), loss of body weight (P = 0.051) and oxidation of liver lipid (P = 0.043) and glutathione (P = 0.035) induced by paraquat, although soy isoflavones and saponins did not. To determine whether soy protein exerted its antioxidative effects by preventing paraquat absorption from digestive organs, rats were fed CAS or SPI diets and orally administered a 12.5 g/L paraquat solution. Plasma, urine, and fecal paraquat concentrations did not differ between the two groups, indicating that soy protein did not prevent paraquat absorption. The present study suggests that intake of soy protein itself, but not soy isoflavones and saponins, reduces paraquat-induced oxidative stress in rats, although this effect was not due to reduced absorption of paraquat from digestive organs.

Isoflavone Aglycone–Rich Extract without Soy Protein Attenuates Atherosclerosis Development in Cholesterol-Fed Rabbits

The antiatherogenic effect of soy protein with intact isoflavones is well established, but the effects of isoflavones without soy protein have not been determined. We investigated the antiatherogenic effect of an isoflavone aglycone-rich extract (containing 429.4 mg/g isoflavone aglycones) without soy protein from fermented soy in cholesterol-fed rabbits. We fed 12-wk-old New Zealand white male rabbits diets containing 1 g/100 g cholesterol with 0, 0.33 or 1 g/100 g isoflavone aglycones for 8 wk. We also fed the rabbits a diet containing 1 g/100 g cholesterol with 1.09 g/100 g soy saponin-rich extract, a component other than isoflavone aglycones in the isoflavone aglycone-rich extract. Controls did not consume cholesterol, isoflavone aglycones or saponins. The isoflavone aglycone- and saponin-rich extracts did not affect the serum lipid profile of cholesterol-fed rabbits. The serum concentration of daidzein in its conjugated form was significantly higher in the high isoflavone group than in the low isoflavone group. The level of cholesteryl ester hydroperoxide (ChE-OOH) induced by CuSO(4) in plasma in the high isoflavone group was significantly less than that in the cholesterol group, and the ChE-OOH levels of LDL in the low and high isoflavone groups were significantly less than those in the cholesterol group. The ChE-OOH levels in plasma and LDL in the saponin group did not differ from the cholesterol group. In the aortic arch, the cholesterol concentration was significantly lower in the high isoflavone group, and malondialdehyde concentration was significantly lower in the low and high isoflavone groups compared with the cholesterol group; however these concentrations in the saponin group did not differ from those in the cholesterol group. The atherosclerotic lesion area of the aortic arch was significantly lower in the isoflavone groups (26.3% lower in the low isoflavone group and 36.9% lower in the high isoflavone group) than in the cholesterol group. The lesion areas were not different in the soy saponin and cholesterol groups. Immunohistochemical analysis revealed fewer oxidized LDL-positive macrophage-derived foam cells in atherosclerotic lesions in the aortic arch of isoflavone groups compared with that of the cholesterol group. These results suggest that the antioxidative action of isoflavones and their antioxidative metabolites inhibit the oxidation of LDL, thereby exerting an antiatherosclerotic effect.

Effects of soy protein and saponins on serum, tissue and feces steroids in rat

Four groups of rats were fed, for 45 days, one of the following semipurified diets containing sucrose 55% (w/w) and (a) casein 25%, (b) casein 24%, saponins (from Saponaria officinalis) 1%, (c) isolated soy protein 25%, (d) soy protein 24%, saponins 1%. The soy protein diet, compared to the casein one, produced an increase in the fecal excretion of neutral sterols on the 29th and 42nd days, without any modification in the liver, aorta and serum cholesterol concentrations. The effect of soy protein cannot be attributed to its saponin content but other substances associated to soy protein may interfere. With the casein diet, added saponins increased the fecal excretion of neutral sterols and bile acids and decreased liver and aorta cholesterol levels. Serum cholesterol was found unchanged. The effects of saponins were suppressed or greatly reduced with the soy protein diet. These results could be explained by binding of the sterols in insoluble forms.

Physiological aspects of host specificity in the Bruchidae—IV. Developmental incompatibility of soybeans for Callosobruchus

The developmental incompatibility of soybeans for Callosobruchus chinensis L. is partly attributed to the presence of soybean saponins. Larvae of Callosobruchus do not hydrolyse saponins in vitro. Higher animals which do so are known to be unaffected by physiological levels of these glycosides. These saponins may therefore be regarded as specific metabolic defence mechanisms of the soybean evolved against insects. All the known protease inhibitors in soybeans, and also urease, have no apparent effect on the development of this beetle nor do the constituents of soy saponins—their sapogenins and sugars. Saponin fraction c and urease are ovipositional attractants of Callosobruchus. The attractance of arabinose and deterrence of sapogenins for oviposition is of theoretical interest.