The growth inhibition and the induction of apoptosis brought about by soyasaponins extracted from soy flour ( Glycine max (L.)) and concentrated for soyasapogenols A and B formed by hydrolysis were tested for cytoactivity in the human hepatocellular carcinoma cell line Hep-G2. Concentrated soyasapogenol A (SG-A) and soyasapogenol B (SG-B) extracts contained approximately 69.3% and 46.2% of their respective aglycones (soyasapogenols) assessed by HPLC and ESI-MS, while the soyasaponin extract (TS), derived from crude methanol extraction, did not contain any detectable amounts of SG-A or SG-B. An MTT viability assay showed that all three extracts had an effect on Hep-G2 proliferation in a dose-response manner with 72 h LC50 values of 0.594+/-0.021 mg/mL for TS, 0.052+/-0.011 mg/mL for SG-A, and 0.128+/-0.005 mg/mL for SG-B. Apoptotic cells were determined by flow cytometry cell cycle analysis and confocal laser scanning microscopy (CLSM). Cell cycle analysis indicated a significant ( P< 0.05) greater sub-G1 buildup of apoptotic cells at 24 h (25.63+/-2.1%) and 72 h (47.1+/-3.5%) for the SG-A extract compared to SG-B, whereas the TS extract produced only a minor buildup of sub-G1 cells. CLSM confirmed a morphological change of all treatments after 24 h, at the respective LC50 concentrations. These results show that the samples that contained mainly soyasapogenols A and B showed a greater ability to inhibit proliferation of cultured Hep-G2 when compared to a total soyasaponin extract that did not contain any soyasapogenols.
We studied the western lowland gorilla diet as a possible model for human nutrient requirements with implications for colonic function. Gorillas in the Central African Republic were identified as consuming over 200 species and varieties of plants and 100 species and varieties of fruit. Thirty-one of the most commonly consumed foods were collected and dried locally before shipping for macronutrient and fiber analysis. The mean macronutrient concentrations were (mean +/- SD, g/100 g dry basis) fat 0.5 +/- 0.4, protein 11.8 +/- 8.2, available carbohydrate 7.7 +/- 6.3 and dietary fiber 74.0 +/- 12.9. Assuming that the macronutrient profile of these foods was reflective of the whole gorilla diet and that dietary fiber contributed 6.28 kJ/g (1.5 kcal/g), then the gorilla diet would provide 810 kJ (194 kcal) metabolizable energy per 100 g dry weight. The macronutrient profile of this diet would be as follows: 2.5% energy as fat, 24.3% protein, 15.8% available carbohydrate, with potentially 57.3% of metabolizable energy from short-chain fatty acids (SCFA) derived from colonic fermentation of fiber. Gorillas would therefore obtain considerable energy through fiber fermentation. We suggest that humans also evolved consuming similar high foliage, high fiber diets, which were low in fat and dietary cholesterol. The macronutrient and fiber profile of the gorilla diet is one in which the colon is likely to play a major role in overall nutrition. Both the nutrient and fiber components of such a diet and the functional capacity of the hominoid colon may have important dietary implications for contemporary human health.
Soyasaponins are a group of complex and structural diverse oleanane triterpenoids found in soy (Glycine max) and other legumes. They are primarily classified into two main groups − group A and B − based on the attachment of sugar moieties at positions C-3 and C-22 of the ring structures. Group A soyasaponins are bidesmosidic, while group B soyasaponins are monodesmosidic. Group B soyasaponins are further classified into two subcategories known as 2,3-dihydro-2,5-dihydroxy-6 -methyl-4H-pyran-4-one (DDMP) and non-DDMP conjugated molecules. The preparation and purification of soyasaponin molecules is complicated by the presence of bioactive soy isoflavones, which often overlap with soyasaponin in polarity and must removed from extracts before biological assessment. Soyasaponin extracts, aglycones of group A and B and individual group B soyasaponins such as soyasaponin I have been reported to posses specific bioactive properties, such as in vitro anti-cancer properties by modulating the cell cycle and inducing apoptosis. The isolation, chemical characterization and detection strategies by HPLC and HPLC-MS are reviewed, along with the reported bioactive effects of soyasaponin extracts and individual molecules in cultured cancer cell experiments.
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