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


OBJECTIVE
Pharmacological investigation of H. perforatum fractions and active principles.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Khan
Arif-ullah
AU
Department of Biological and Biomedical Sciences, Aga Khan University Medical College, Karachi-74800, Pakistan.
Gilani
Anwarul-Hassan
AH
Najeeb-ur-Rehman
D000818:Animals; D000873:Anthracenes; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000302:isolation & purification / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D020902:Hypericum / Q000737:chemistry*; D066298:In Vitro Techniques; D008297:Male; D010569:Perylene / Q000031:analogs & derivatives / Q000302:isolation & purification / Q000494:pharmacology; D010696:Phloroglucinol / Q000031:analogs & derivatives / Q000302:isolation & purification / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000302:isolation & purification / Q000494:pharmacology*; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology*; D011794:Quercetin / Q000031:analogs & derivatives / Q000302:isolation & purification / Q000494:pharmacology; D011817:Rabbits; D013729:Terpenes / Q000302:isolation & purification / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D000873:Anthracenes; D002121:Calcium Channel Blockers; D010726:Phosphodiesterase Inhibitors; D010936:Plant Extracts; D013729:Terpenes; D010569:Perylene; C004965:hypericin; C021304:hyperoside; D011794:Quercetin; D014700:Verapamil; D010696:Phloroglucinol; C001654:hyperforin; D002118:Calcium