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Caracasandiamide, a second hypotensive agent isolated from Verbesina caracasana, is the cyclobutane dimer (truxinic type) of the previously reported 1-[(3,4-dimethoxycinnamoyl)amino]-4-[(3-methyl-2-butenyl)guanidino]butane (caracasanamide) (Delle Monache, G.; et al. BioMed. Chem. Lett. 1992, 25, 415−418). The structure was confirmed by synthesis starting from β-truxinic acid obtained by photoaddition of 3,4-dimethoxycinnamic acid. The dimer was coupled with 2 mol of prenylagmatine to give caracasandiamide in satisfactory yield. By contrast, the direct photodimerization of caracasanamide was unsuccessful. Caracasandiamide, assayed by the iv route in anesthetized rats at doses ranging from 50 to 3200 μg/kg of body weight, was found to have no appreciable effect on heart rate. At lower doses, the drug stimulates breathing and increases cardiac inotropism, stroke volume, and cardiac output, thus augmenting blood pressure and aortic flow. At higher doses, caracasandiamide depresses breathing likely through central neurogenic mechanisms (not involved in the cardiovascular effects), continues to stimulate cardiac inotropism, and induces, by reducing peripheral vascular resistance, arterial hypotension with reduction of both aortic flow and stroke volume. These cardiovascular effects appear to involve complex interactions at the level of the peripheral β1-, β2-, and α2-adrenoreceptor-dependent as well as M2- and M4-cholinergic receptor-dependent transductional pathways both in cardiovascular myocells and at the level of the postganglionic sympathetic endings (with reserpine- and guanethidine-like mechanisms). The cardiovascular effects of caracasandiamide, different from those of caracasanamide, do not depend on significant actions on the central nervous system and on baroreflex pathways. In a similar manner and more effective than caracasanamide, caracasandiamide may be considered a hypotensive and antihypertensive drug. It is devoid of some of the negative side effects, e.g., reflex tachycardia and decreased cardiac inotropism, which are shown by the majority of the most common antihypertensive and vasodilator drugs.

A new 6a-hydroxylated pterocarpan, named hildecarpin, has been isolated from the healthy roots of Tephrosia hildebrandtii.It has been assigned the structure (—)-3,6a-dihydroxy-2-methoxy-8,9-methylenedioxypterocarpan on the basis of its spectroscopic data, optical rotation and chemical transformations. Hildecarpin has exhibited insect antifeedant activity against the legume pod-borer Maruca testulalis, an important pest of the cowpea (Vigna unguiculata), and antifungal activity against Cladosporium cucumerinum.This finding suggests that the pterocarpan phytoalexins formed as a result of microbial infection of the cowpea plant may constitute a basis for induced resistance in the plant against M. testulalis. Un nouveau 6a-hydroxylpterocarpan nommé hildecarpin, a été isolé des racines du Tephrosia hildebrandtii.On lui a donné la structure (—)-3,6a-dihydroxy-2-methoxy-8,9-methylenedioxypterocarpan en se basant sur ses valeurs spectroscopiques, sa rotation optique, et ses transformations chimiques. Hildecarpin a montre une activité antiparasitaire contre le rongeur de gousse de legume Maruca testulalisun important insecte nuisible au petit pois (cowpea) Vigna unguiculata, et une activité antimycosique contre Cladosporium cocumerinum.Cette découverte suggère que les phytoalexins du pterocarpan formés à la suite d’une infection microbienne de la plante de petit pois (cowpea) pourrait constituer une base de resistance induite dans la plante contre M. testulalis.

The relationship between the chemical structure and the cyclic adenosine monophosphate phosphodiesterase inhibitory activity was studied regarding forty-eight flavones, thirty-five flavanones, and six isoflavones by using the 13C NMR chemical shift averaged over all aromatic carbons in a compound. The average value of potent 13C chemical shifts over the aromatic carbons active flavonoids (IC500.6–20.0×10-5M/L) are within the range from d 133.5 to d 135.7, but those of the inactive flavonoids and the weak active flavonoids are not within this range. This means that the averaged 13C chemical shift becomes an “index” for testing the inhibitory activity. Further, the above relationship was proposed as a means for conveniently determining the inhibitory activity.