Studies On The Structure Identification Of Soyasaponins And Its Bioactivities

Soyasaponins (SS) are present in legumes and soybean is a primary dietary source of saponins. Recently, many researches on the structure, classification and bioactivities of SS have been reported. Some important biological properties of SS, including hyperlipidemia prevention, anticancer, immunoregulation, antioxidation, antimutagenicity and HIV infection inhibition, have been widely studied. However, few studies have been conducted to elucidate the molecular mechanisms of cancer cell growth inhibition and hyperlipidemia prevention by SS. In this paper, the structure of SS isolated and purified from Tianmen soybean was identified by high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI/MS~2), and some advanced technologies, such as confocal laser scanning microscopy (CLSM), flow cytometer (FCM) and RT-PCR and so on, were used to systematically study its bioactivities and corresponding mechanisms including anti-lipid peroxidation in vitro, antitumor activity both in vitro and in vivo and hyperlipidemia prevention.The main results are as follows:1 Isolation, purification and structure identification of SSThe optimum extraction conditions were that the powder of defatted soy was immersed in 80% alcohol solution in the ratio of 1:27 (W/V) and extracted by reflux for three times at 60°C with each time for 5 hours. The extracting rate of SS from the defatted soy powder was 2.58%. The extract was evaporated on a rotary evaporator to remove alcohol under vacuum at 50°C and then was extracted with n-BuOH-water (1:1, V/V) for two times. Then the n-BuOH fraction was collected and evaporated to dryness. The residue was dissolved in a mixture of MeOH and EtOAc (1:10, V/V) to produce precipitate at 4°C in a refrigerator overnight. The precipitate was collected by centrifugation and dissolved in water and then loaded onto a column packed with D101A macroporous resin. The column was washed with water to remove oligosaccharides and pigments at first, and then eluted with 30%-90% aqueous alcohol in gradient. Finally, three fractions of SS (SS-I, SS- II and SS-III) were obtained. Compared with the defatted soy powder, the yields of three fractions were 0.107%, 0.093% and 0.047% respectively.