Inhibition of angiotensin converting enzyme by lithospermic acid B isolated from Radix Salviae miltiorrhiza Bunge.

The roots of Salviae miltiorrhiza (RSM) have been traditionally used for treatment of hypertensive disease in China, Korea, and Japan. Bioassay guided fractionation and purification as assayed by angiotensin converting enzyme (ACE) inhibitory assay resulted in the isolation of lithospermic acid B (LSB) as an active principle. The ACE plasma activities were significantly inhibited by the addition of LSB in a dose-dependent manner of which IC50 value was 86 microg/ml (120 microM). Moreover, angiotensin I-induced contraction was markedly attenuated by prior exposure of endothelium-intact aortic rings to LSB. These results suggest that RSM-induced antihypertensive effect may be, at least in part, due to ACE inhibitory effect of LSB.