Angiotensin converting enzyme inhibitory phenylpropanoid glycosides from Clerodendron trichotomum

The stems of Clerodendron trichotomum have been traditionally used for treatment of hypertension in far East Asia including China, Korea, and Japan. Bioassay-guided fractionation and purification of the EtOAc-soluble extract of Clerodendron trichotomum afforded acteoside (1), leucosceptoside A (2), martynoside (3), acteoside isomer (4), and isomartynoside (5). The angiotensin converting Enzyme (ACE) activities were significantly inhibited by the addition of these phenylpropanoid glycosides (1-5) in a dose-dependent manner of which IC(50) values were 373+/-9.3 microg/ml, 423+/-18.8 microg/ml, 524+/-28.1 microg/ml, 376+/-15.6 microg/ml, 505+/-26.7 microg/ml, respectively. These results suggest that the antihypertensive effect of Clerodendron trichotomum may be, at least in part, due to ACE inhibitory effect of phenylpropanoid glycosides.