Saponins from seeds of Zizyphus jujuba Mill. var. spinosa exhibit vasorelaxant effects on rat isolated aorta.

Aim: The vasorelaxant saponins jujuboside A(1), A1(2), B(3), and acetyljujuboside B(4) were isolated from 50% MeOH extracts of seeds of Zizyphus jujuba Mill. var. spinosa Hu ex H.F. Chou (Rhamnaceae), and their effects were studied using isolated rat aortic rings. Method: Dried jujube seeds were crushed and extracted with 50% MeOH, and the extracts were concentrated under reduced pressure. Vasorelaxant effects of this extracts were assessed on rat isolated aorta rings. The aorta rings were placed in a well‐oxygenated bath of modified Krebs–Henseleit solution and the mechanical tension was measured isometrically. Results: The crude extract was fractionated by chromatographic methods with the guidance of vasorelaxant activity, and four saponins (1~4) were isolated. These compounds were identified using nuclear magnetic resonance (NMR) studies. Compounds 1~4 showed slow relaxation activity against norepinephrine (NE)‐induced contractions of rat aorta with/without endothelium. Treatment with 1~4 did not significantly inhibit NE‐induced vasoconstrictions. Compounds 1~4 inhibited vasoconstriction induced by high‐concentration potassium (60 mM) and NE in the presence of nicardipine but did not affect phorbol 12‐myristate 13‐acetate‐induced vasoconstriction. Conclusion: These results suggest that inhibition of NE‐induced vasoconstriction by 1~4 is due to the inhibition of receptor‐operated Ca2+ channels and voltage‐dependent Ca2+ channels or inhibition of intracellular calcium modulations. [ABSTRACT FROM AUTHOR]