No abstract

The detailed 1H and 13C NMR assignments of the four known triterpenes 3β‐hydroxyurs‐12‐en‐28‐oic acid, 3‐oxo‐24‐methylenecycloartan, 3‐oxo‐11α‐hydroxy‐20(29)lupen and 29‐hydroxyfriedelin, isolated from three Brazilian plants, were achieved by 1D and 2D techniques such as DEPT, HETCOR, HMQC, HMBC, COSY and NOESY. Copyright © 2000 John Wiley & Sons, Ltd.

A new phenylcoumarone type trinorlignan, krametosan (1), along with the known norlignans, ratanhiaphenol I (2) and 2-(2'-hydroxy-4',6'-dimethoxyphenyl)-5-(E)-propenylbenzofuran (3), the lignan conocarpan (4) and dinorlignan decurrenal (5), were isolated from the CHCl3 extract of the roots of Krameria tomentosa. The structure of these compounds were elucidated by the spectroscopic methods.

In this work, we studied the effect of the norlignan 2-(2'-hydroxy-4',6'-dimethoxyphenyl)-5-[( E)-propenyl]benzofuran (DMPP) in the rat aorta. In aortic rings with intact endothelium, DMPP inhibited in a concentration-dependent manner the vasodilator effect produced by acetylcholine with an IC50 value of 31.2+/-6.3 microM. DMPP also inhibited basal nitric oxide production. In endothelium-denuded vessels DMPP was without effect whereas superoxide dismutase (SOD) was effective in potentiating responses to the NO donor SIN-1. Contractile effects of carbachol in guinea-pig ileum and trachea were unaffected by DMPP. It is concluded that DMPP inhibits the endothelium-dependent relaxation induced by acetylcholine in the rat aorta without affecting receptor or smooth muscle cells function. Decreased nitric oxide production by endothelial cells seems to be the mechanism involved in the inhibitory effect of DMPP.