Abstract:
The vasodilator effect of eriodictyol (5,7,3′,4′ -tetrahydroxyflavanone), isolated previously from the medicinal plant Satureja obovata Lag., was studied in rat thoracic aorta
rings. Eriodictyol relaxed in a concentration-dependent manner the noradrenaline
(10-6 M) and KCl (80 mM) induced contractions.
The relaxant effect was more potent in noradrenaline precontracted preparations
(IC50 = 6.11 ± 0.2 × 10-5 M)
than in those precontracted with KCl (IC50 = 2.96 ± 0.1
× 10-4 M). Eriodictyol produced weakly concentration-dependent
inhibition of the phasic component induced by KCl and noradrenaline while
the inhibition of the tonic phase of these contractions was more pronounced.
These effects were endothelium independent. In addition, eriodictyol (10
-5 and 5 × 10-5 M) inhibited CaCl
2 cumulative concentration response curves. Eriodictyol weakly inhibited
the release of calcium from the sarcoplasmic reticulum and its contribution
to the relaxant effect seems to be slight. We have also observed the relaxant
effect of eriodictyol on phorbol-12-myristate-13-acetate (PMA) (10-7 M) induced contractions both in normal calcium (IC50
= 4.69 ± 0.3 × 10-5 M) and calcium-free
medium (IC50 = 3.74 ± 0.4 × 10-5 M).
Finally we studied the effects on protein kinase C (PKC) activity. This flavonoid
did not show any activity. These results suggest that the vasodilator effect
of eriodictyol in rat thoracic aorta could be partially related to the inhibition
of calcium influx or other enzymatic protein subsequent to activation of PKC
related to the activation of contractile proteins like myosin light chain
kinase (MLCK).
Key words:
Eriodictyol - flavonoid -
Satureja obovata
- Lamiaceae - rat aorta - vascular smooth muscle relaxant - PKC activity
