Canarosine: a new guanidine alkaloid from Canavalia rosea with inhibitory activity on dopamine D1 receptors.

A new acyclic guanidine alkaloid, canarosine (1), together with five known compounds, beta-sitosterol (2), stigmasterol (3), daucosterol (4), epi-inositol 6-O-methyl ether (5), and rutin (6), were isolated from the aerial parts of Canavalia rosea. Their structures were established on the basis of their spectroscopic data. In the radioligand receptor binding assay, canarosine (1), at a concentration of 100 microg/ml, caused 91% inhibition of the dopamine D1 receptor binding with an IC50 value of 39.4 +/- 5.8 microM.