Studies on the vascular effects of the fractions and phenolic compounds isolated from Viscum album ssp album

Viscum album L. has been used in the indigenous system of medicine for trea tment of various diseases such as atherosclerosis and hypertension. In the literature, phenylpropan and flavonoid derivatives were suggested to play a role in the inhibition of cyclic adenosine monophosphate (cAMP)-phosphodie sterase (PDE) and a correlation was proposed between the in vitro inhibitio n of PDE and in vivo pharmacological activity. The Vascular effects of the phenolic compounds and subfractions isolated from n-butanolic fraction of V . album ssp. album were studied on noradrenaline-contracted rat aortic ring s. Isolated phenolic compounds (Syringin (VA-1), Coniferin (VA-9), 5,7-dime thoxy-flavanone-4'-O-[beta-D-apiofuranosyl(1 --> 2)]-beta-D-glucopyranoside (VA-4)) produced concentration-dependent contractions in rat aortic rings. Only one compound (Kalopanaxin D (VA-15)) displayed very slight relaxant r esponse. The weak concentration-dependent relaxing effect of the subfractio ns gave the idea that vasodilator activity were observed in the less polar subfractions. In addition, there was no clear correlation between the weak relaxant effects of subfractions and an inhibitory effect on cAMP-PDE. (C) 2000 Published by Elsevier Science Ireland Ltd. All rights reserved.