Interaction of Gamma-Aminobutyric Acid and Ca(2+) on Phenolic Compounds Bioaccumulation in Soybean Sprouts under NaCl Stress

NaCl stress can enhance the accumulation of phenolic compounds in soybean during germination. In the present study, effects of gamma-aminobutyric acid (GABA) and Ca(2+) on the biosynthesis of phenolic compounds in soybean sprouts germinated with NaCl stress were investigated. Results showed that addition of Ca(2+) increased the content of total phenolics, phenolic acids, and isoflavonoids in soybean sprouts by ca. 15%, 7%, and 48%, respectively, through enhancing the activities of three key enzymes involved in the biosynthesis. On the other hand, addition of LaCl(3), a calcium channel blocker, inhibited the synthesis of phenolic compounds, indicating that Ca(2+) plays an important role in the synthesis of these compounds in soybean sprouts. Addition of GABA can increase the content of Ca(2+) in soybean sprouts by ca. 20% and alleviate the inhibition of LaCl(3) on phenolics biosynthesis in soybean sprouts. Similarly, addition of Ca(2+) can reverse the inhibition of 3-mercaptopropionate, an inhibitor of endogenous GABA synthesis, on the biosynthesis of phenolic compounds in soybean sprouts under NaCl stress. To conclude, both GABA and Ca(2+) can enhance the biosynthesis of phenolic compounds in soybean sprouts and there was an interaction between their effects on the promotion of phenolic compounds biosynthesis.