M. Meckes et al., The effects of chrysin and pinostrobin, two flavonoids isolated from Teloxys graveolens leaves, on isolated guinea-pig ileum, PHYTOMED, 5(6), 1998, pp. 459-463
The pharmacological effects of pinostrobin and chrysin obtained from the ae
rial parts of Teloxys graveolens (Chenopodiaceae) were evaluated using isol
ated in vitro guinea-pig ileal smooth muscle. Both flavonoids inhibited the
contractions evoked by high concentrations of potassium. The potency of th
e relaxant effect was determined by measuring the capacity of each product
in reducing the phasic and the slower sustained tonic contractile responses
induced by depolarization with 60 mM K+. Concentrations up to 5 x 10(-7) M
of pinostrobin and 1 x 10(-7) M of chrysin induced a non-competitive depre
ssion of responses to Ca2+ in ileum preparations bathed in a Ca2+-free, hig
h K+ medium. Both compounds produced a rightward displacement of the concen
tration-response curves to Ca2+ with a concentration-depend ant increase of
EC50 and a decrease of the maximal response. Examination of the inhibitory
effect produced by these flavonoids on the phasic component of contractile
response evoked with K+ and on the contraction induced with caffeine, led
to propose a different intracellular mechanism of action used by these comp
ounds.
The results obtained led us to conclude that the previously detected relaxa
nt effect of Teloxys graveolens crude extract is due in part, to the presen
ce of chrysin and pinostrobin, which inhibit intestinal smooth muscle contr
actions by means of a calcium-mediated mechanism. Since the modulation of c
alcium fluxes in the mucosal epithelium may play a role in antidiarrheal dr
ug action, the observed effects in vitro could in the same way explain the
popular use of the plant for the treatment of diarrhea.