Apparent Inhibitory Effect of Fermented Brown Rice on Salivary Amylase Activity Relative to That of Acarbose, Guava Leaf Tea and Nucleic Acid

Abstract

This study examined the apparent inhibitory effect of fermented brown rice （FBR） on amylase activity in human saliva. When diluted human saliva was made to react for 30 minutes with a substrate mixture of FBR and soluble starch, the amount of starch remaining was significantly higher than in the control where the substrate was a mixture of normal brown rice and soluble starch. Moreover, there was no difference in the amount of starch remaining between the FBR mixture substrate and a substrate of normal brown rice with added nucleic acid （DNA･RNA）. Furthermore, there was no evident difference in amylase activity between the saliva in the presence of FBR and that in the presence of nucleic acid. However, the salivary amylase activity in the presence of FBR was significantly lower than that in the control, or for saliva in the presence of normal brown rice. In addition, the Michaelis constant （Km value） for saliva in the presence of FBR did not differ from that in the presence of nucleic acid, and furthermore was significantly higher than that of the control and saliva in the presence of normal brown rice. Finally, Lineweaver-Burk plots showed that the type of inhibition was competitive in both cases. These results suggest that FBR competitively inhibits alpha-amylase activity in human saliva.