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SECOND INTERNATIONAL SYMPOSIUM
ON THE ROLE OF SOY
IN PREVENTING AND TREATING CHRONIC DISEASESeptember 15-18, 1996
Brussells, Belgium
POSTER ABSTRACTSCHEMICAL STRUCTURE AND RADICAL SCAVENGING ACTIVITY OF SOYBEAN GLYCOSIDES
Yoshiki, Y.; Kahara T. Iida T, Okubo K. and Kanazawa T.
Dept. of Environmental Bioremediation, Graduate School of Agriculture, Tohoku University, Aobaku, Sendai, Japan 981
2nd Department of Internal Medicine, Hirosaki University School of Medicine, Hirosaki, Zaifucho, Hirosaki, Aomori, Japan 036
The soybeans (Glycine max L. Merr.) which have been used widely as food in China and Japan, contain about 2% glycosides. The composition and the structures of group B saponins in native soybean seeds were investigated. Five kinds of saponins named soyasaponins ag, bg, ba, ag and aa from soybean according to elution order from HPLC were isolated, and the structures were characterized as having a 2.3-dihydro-2.5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP) group attached by ether linkage to C-22 of the aglycones soyasaponin V, I, III and IV respectively. These DDMP saponins showed a superoxide dismutase-like activity resulting from the DDMP moiety by using hypoxanthine-XOD system. Furthermore, DDMP saponins had DPPH (1.1-diphenyl-2-picrylhydrazyl) radical scavenging activity. On the other hand, DDMP saponins effected as a pro-oxidant on the lipid peroxidation which is known to be a free radical chain reaction. Interetingly, they had the opposite effect, strong antioxidative effect, in the presence of antioxidant compounds such as phenolic compounds. Similar synergistic results were also obtained with superoxide and DPPH radical. The ionization potential and electron affinity of DDMP moiety which computed by the semi-empirical MNDO, were 8.38 and 1.16 respectively. The AMI conformation search of DDMP saponin cleaerly shows that the three types are conceivable as DDMP radical anion. Nine kinds of isoflavonoids from soybean were isolated and characterized. They were daizein, glycitin and genistein, acetylated daizein, glycitin and genistin and malonylated daizein, glycitin and genistein. The level and composition of daizein and genistin which are isoflavone glycosides of soybean cotyledon, varied tremendously not only by variety but also by year harvested and geographic location, even among the same variety. These glycosides also have showed the synergistic effect in the presence of gallic acid on the radical scavenging and antioxidative activity.
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