Effect of tamari soy sauce cake on blood pressure in spontaneously hypertensive rats

The effect of tamari soy sauce cake (tamari cake) on blood pressure in spontaneously hypertensive rats (SHR) was examined. The SHRs were fed an experimental diet for 28 days and their systolic blood pressures were measured by the tail cuff method. The rats fed diets containing desalted tamari cake at a level of 10% and 20% showed a significantly lower blood pressure compared to the control group (tamari cake free). The preparation of ACE inhibitory fractions (FI and FII) from tamari cake utilized alkali extraction, followed by chromatography on Diaion AMP 01 and Toyopearl HW-50F. The concentrations of FI and FII producing 50% inhibition of ACE activity were 0.99 and 0.19 mg/ml, respectively. Single dose oral administration of FII (0.03 g/kg of rat weight) in SHRs showed a significant reduction in systolic blood pressure of 19.8 mmHg at 24h after administration. These results suggest that FII lowered systolic blood pressure by suppressing ACE activity.