Pharmacological studies on Hypericum perforatum fractions and constituents

Context:This study describes the antispasmodic, bronchodilator, and cardiovascular-modulatory activities of Hypericum perforatum Linn. (Hypericaceae) fractions and constituents. Aim of study:Pharmacological investigation of H. perforatum fractions and active principles. Materials and methods:H. perforatum extract fractions [petroleum spirit (HpPet), chloroform (HpCHCl3), ethyl acetate (HpEtAc), and aqueous (HpAq)] and its compounds (hyperforin, hypericin, and hyperoside) were studied in various isolated tissue preparations. Results:In rabbit jejunum, HpCHCl3, HpEtAc and HpAq, like papaverine, inhibited both spontaneous and K (80mM)-induced contractions at similar concentrations, whereas HpPet was relatively potent against K, as verapamil. All fractions caused rightward of Ca² concentration- response curves (CRCs), similar to verapamil. HpCHCl3, 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, HpCHCl3, 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 HpCHCl3, 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. Discussion and conclusion:Thus, all tested fractions of H. perforatum exhibit a combination of Ca² antagonist and phosphodiesterase-inhibition, except petroleum spirit which was devoid of later mechanism. The compounds tested showed only Ca² channel blocking effect.