| Alginate oligosaccharides(AOS) which is from marine plants can be extracted by chemical method or enzymolysis. It is composed of 2~20 hexuronic acids, having two monomeric unitsβ-D-mannuronic acid(M) and α-L-guluronic acid(G) linked by 1,4 bonds. Glyceollins, which are known as phytoalexins, can be synthesis in soybeans when they are exposed to exogenous stimulation. Studies have shown that AOS can be used as bio-elicitor to induce glyceollins accumulation in soybeans. In this paper, single degree of polymerization(DP) of AOS were purified, detected, and the capacity of inducing glyceollins accumulation in soybeans between these purified AOS was compared, the changes of nutrition in induced soybeans were studied.Single DP of AOS were purified from AOS mixture by Dowex1×8 c L- anion-exchange resin, atmospheric pressure, 50% acetic acid was used as mobile phase. The purification of the products recorded 98% which is confirmed by thin-layer chromatography(TLC) and high performance liquid chromatography(HPLC). The DP of the purified AOS were further analyzed by using the ultra high pressure liquid chromatography- tandem mass spectrometry(UPLC-ESI-MS). The results obtained from the UPLC-ESI-MS recorded DP 2~5.AOS with DP between 2~5 were used as elicitors upon glyceollins induction in soybeans. The existence of glyceollins was confirmed by UPLC-ESI-MS and the content of glyceollins was detected by HPLC. The quantities of glyceollins(mg/g dry weight) and their various levels of accumulation are 1.2339, 1.0611, 0.6494, 0.6373, 0.3472, and the corresponding elicitors used were alginate disaccharide, alginate pentasaccharide, alginate tetrasaccharide, alginate oligosaccharides mixture and alginate trisaccharide with the concentration of 1%, respectively. Alginate disaccharide seems to have the best eliciting activity among the six elicitors used in this study.The nutritional composition(isoflavonoids, amino acids, oligosaccharides and fatty acids) changes in soybean seeds induced by alginate oligosaccharides were explored in this study. Isoflavones, amino acids, oligosaccharides and fatty acids in induced soybeans changed dramatically. During the incubation period, glyceollins content was observed to have increased steadily from day 1 to day 5 having concentration of 0.01 mg?g-1dry weight at(1d) and 1.72 mg?g-1dry weight was recorded at 5d. Highest accumulations were recorded for coumestrol(664.8 μg?g-1 dry weight) and genistein(24.02 μg?g-1 dry weight) at 5d. While, daidzein decreased from 54.56 to 19.02 μg?g-1 dry weight respectively. Nutritional composition changes recorded during the five days study are as follow: total amino acids content in induced soybeans seeds increased from 39.38% to 43.45% during the incubation period, contents of threonine, methionine, lysine and some other essential amino acids were also observed to have increased. Amino acids content recorded in the non-induced soybean seeds during analysis also showed nutritional changes, but the changes were generally lower than the changes observed in the induced soybean seeds. The content of sucrose in induced soybean seeds decreased from 53.72 to 21.5 mg?g-1 dry weight, raffinose decreased totally at 3d, while stachyose decreased at 4d. In non-induced soybean seeds, sucrose decreased from 53.72 at(1d) to 23.09 mg?g-1 dry weight, little amount of raffinose and stachyose were also detected. The total fatty acids content in the induced soybean seeds decreased from 14.27% to 14.01% during analysis, while proportion of linoleic acid increased. |
PDF Full Text Request