Pharmacological studies on Hypericum perforatum fractions and constituents

This study describes the antispasmodic, bronchodilator, and cardiovascular-modulatory activities of Hypericum perforatum Linn. (Hypericaceae) fractions and constituents.

Pharmacological investigation of H. perforatum fractions and active principles.

H. perforatum extract fractions [petroleum spirit (HpPet), chloroform (HpCHCl(3)), ethyl acetate (HpEtAc), and aqueous (HpAq)] and its compounds (hyperforin, hypericin, and hyperoside) were studied in various isolated tissue preparations.

In rabbit jejunum, HpCHCl(3), HpEtAc and HpAq, like papaverine, inhibited both spontaneous and K(+) (80 mM)-induced contractions at similar concentrations, whereas HpPet was relatively potent against K(+), as verapamil. All fractions caused rightward of Ca(2+) concentration-response curves (CRCs), similar to verapamil. HpCHCl(3), HpEtAc, and HpAq shifted isoprenaline-inhibitory CRCs to left, like papaverine, while HpPet was devoid of any such effect, as verapamil. In guinea-pig trachea, HpCHCl(3), HpEtAc, and HpAq equipotently relaxed carbachol and K(+)-induced contractions and shifted the isoprenaline-curves to the left, whereas HpPet was more effective against K(+), without potentiating isoprenaline effect. When tested in rabbit aorta, all fractions exhibited vasoconstrictor and vasodilator effects, except HpEtAc, which did not produce vasoconstriction. In guinea-pig atria HpCHCl(3), HpEtAc, and HpAq initially caused cardiac stimulation, followed by inhibition, similar to papaverine, whereas HpPet, like verapamil, caused only cardiac suppression. Hyperforin, hypericin, and hyperoside showed a similar pattern of spasmolytic effect to verapamil.

Thus, all tested fractions of H. perforatum exhibit a combination of Ca(2+) antagonist and phosphodiesterase-inhibition, except petroleum spirit which was devoid of later mechanism. The compounds tested showed only Ca(2+) channel blocking effect.