Cardiovascular Effects of Plant Secondary Metabolites Norarmepavine, Coclaurine and Norcoclaurine
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1997-10-09Metadata
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Morales, M. A.
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Cardiovascular Effects of Plant Secondary Metabolites Norarmepavine, Coclaurine and Norcoclaurine
Abstract
Tbe cardiovascular etTeets of (±)-norannepavine, a benzylisoquinoline alkaloid of natural origin, have
been detennined on anaesthetized rats in vivo, on spontaneously beating atria and on aortic smooth
muscle. In aorta, the etTeets of (±)-coclaurine and (±)-norcoclaurine, benzylisoquinolines with a related
structure, were a1so compared.
(±)-Norarmepavine (10 mg/kg i.v.) decreased the mean arterial pressure and heart rate by 45% and
21 %, respectively. (±).Norannepavine (10-5_10-3 M) showed a negative chronotropic etTect on rat-iso·
lated atria, decreasing the spontaneous frequency by about 54%.
Aortic rings contracted with KCI 70 mM were relaxed in a concentration-dependent manner by (±).
norannepavine, (±)-coclaurine and (±)-norcoclaurine (10-6-10-3 M). The two earlier alkaloids exhibited
an efficacy similar to verapamil, relaxing the aortic rings by 100%. (±)-Norcoclaurine exhibited a lower
efficacy. These results point to the importance of methylation of these compounds. The rank order of
potency was: (±)·verapamil > (±)-norarmepavine > (±)-norcoclaurine > (±)-coclaurine.
The alkaloids shifted to the right the ealcium-dependent contraction eurves, denoting a calcium
antagonist-like etTect; however, only a 10-fold increment of (±)-noreoclaurine concentration produced an
equivalent etTect. Our results demonstrate the hypotensive and bradycardic properties of (±)-norannepavine.
It is proposed that this alkaloid could somehow modulate calcium entry, its intracellular release
or the calcium sensitivity of the cell eontractile-machinery, previously postulated for coclaurine. (±)Norcoclaurine
etTects reported here are not in agreement with the proposal of (±)-norcoclaurine as a calcium
channel activator or p.-adrenoceptor agonist.
Patrocinador
This study was supported by Grant 920291 of CONACYT, México and
Grant 8-3386/9212, DTI, University of Chile, under University of
Chile-IMSS 8inational Academical Agreement for Advance in
Pharmacology of Natural Products.
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PHYTOTHERAPY RESEARCH, VOL. 12, 103-109, 1998.
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