Antihypertensive effect of mulberry leaf aqueous extract containing γ-aminobutyric acid in spontaneously hypertensive rats

We hypothesised that mulberry leaves (ML) exert their antihypertensive effect through γ-aminobutyric acid (GABA) and that the antihypertensive activity of ML extract would be comparable to GABA alone in spontaneously hypertensive rats (SHR). We found that single administration of a water extract from leaves of Morus alba L. (WEML) lowered systolic blood pressure (SBP) transiently in a dose-dependent manner. Interestingly, the SBP-lowering effect of WEML was significantly higher than after treatment with GABA alone. We further found that WEML strongly inhibited angiotensin I-converting enzyme (ACE) activity in vitro with an IC 50 value of 29.8 mg/ml. These results suggest that WEML has a transient antihypertensive effect in vivo that may involve a mechanism of ACE inhibition in addition to GABA.