F. Trigueiro et al., Endothelium-independent vasorelaxant effect of dioclein, a new flavonoid isolated from Dioclea grandiflora, in the rat aorta, J PHARM PHA, 52(11), 2000, pp. 1431-1434
We have investigated the endothelium-independent vasorelaxant effect of the
new flavonoid dioclein (5,2',5'-trihydroxy-6-7-dimethoxyflavanone) in the
rat aorta.
In endothelium-denuded vessels, dioclein induced a concentration-dependent
relaxation of aortic rings precontracted with noradrenaline (IC50 = 3.5 +/-
0.89 x 10(-4) M) and KCl (IC50 = 5.2 +/- 1.2 x 10(-4) M). In the absence o
f extracellular calcium, dioclein reduced the contraction induced by noradr
enaline (maximal reduction approximately 33%) but not that induced by caffe
ine. Dioclein also produced a concentration-dependent inhibition of the sus
tained contractions induced by the phorbol ester 12-O-tetradecanoyl phorbol
-13-acetate in normal (IC50 = 4.0 +/- 0.2 x 10(-4) M) and Ca2+-free solutio
n (IC50 = 4.0 +/- 0.3 x 10(-4) M).
The results indicate that the endothelium-independent vasorelaxant effect o
f dioclein may be explained by inhibition of contractions dependent on acti
vation of protein kinase C, voltage-dependent Ca2+ influx and on the releas
e of intracellular Ca2+ stores sensitive to noradrenaline.