We have shown that Protease N treated Royal Jelly (ProRJ) and peptides from ProRJ (Ile-Tyr (IY), Val-Tyr (VY), Ile-Val-Tyr (IVY)) inhibited angiotensin I-converting enzyme (ACE) activity and they have an antihypertensive effect in repeated oral administration for 28 d on spontaneously hypertensive rats (SHR). We investigated the contributive ratio of these peptides in ProRJ for antihypertensive effect in single oral administration on SHR. In single oral administration of each peptide and peptides mixture (MIX; IY, VY and IVY) at doses of 0.5, 1 and 10 mg/kg, systolic blood pressure (SBP) of SHR was reduced dose-dependently. This antihypertensive effect was held for 8 h. These results suggest that peptides contributed to the antihypertensive effect of ProRJ. And the contributive ratio of MIX in ProRJ for antihypertensive effect was computed to be about 38%. Therefore it is considered that intake of peptides, as a functional food would be beneficial for improving blood pressure in people with hypertension.

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Protease digested royal jelly (ProRJ) proved to inhibit angiotensin I converting enzyme (ACE) activity in vitro.And we have demonstrated that peptides isolated from ProRJ (Ile-Tyr (IY), Val-Tyr (VY)) also inhibited ACE activity.We examined an antihypertensive effect of RJ, ProRJ and RJ peptides (IY and VY) on spontaneously hypertensive rat (SHR). In chronic oral administration of ProRJ and RJ at the dose of 10 mg/kg/day for 28 days, the systolic blood pressure (SBP) of SHR was significantly decreased against the control.The blood pressure of normotensive rat (Wistar Kyoto rat) did not changed on the repeated administration of ProRJ.In repeated oral administration of RJ peptides at the dose of 10mg/kg/day for 28 days, SBP was significantly reduced against the control. These results suggest that the hypotensive effect of ProRJ is correlated with ACE inhibitory activity of RJ peptides, and ProRJ would be beneficial for improving blood pressure in hypertension.