Cinnamophilin, a novel thromboxane A2 receptor antagonist, isolated from Cinnamomum philippinense.
The pharmacological activity of cinnamophilin ((8R,8'S)-4,4'-dihydroxy-3,3'-dimethoxy-7-oxo-8,8'-neolignan), isolated from Cinnamomum philippinense, was studied in isolated rat aorta, guinea-pig trachea and rabbit platelets. Cinnamophilin was found to be a thromboxane A2 receptor blocking agent in these tissues as revealed by its competitive antagonism of the U-46619 (9,11-dideoxymethanoepoxy-9 alpha,11 alpha-prostaglandin F2 alpha)-induced contraction of rat aorta and guinea-pig trachea and aggregation of rabbit platelets with pA2 values of 7.3 +/- 0.2, 5.2 +/- 0.1 and 6.3 +/- 0.3, respectively. Protection against the irreversible vasoconstriction of rat aorta caused by U-46619 (0.05 microM) was obtained by cinnamophilin (10 microM) but not by caffeine (25 mM). Cinnamophilin (1-15 microM) also possessed voltage-dependent Ca2+ channel blocking action, judging from its antagonism of the high K+ (60 mM)- and Bay K 8644 (0.1 microM)-induced contraction in rat thoracic aorta. Cinnamophilin (30 microM) produced a slight relaxation of noradrenaline (3 microM)-induced tonic contractions, and this relaxing effect was abolished in the presence of nifedipine (1 microM). Nifedipine (10 microM) sufficient to inhibit high K(+)-induced contractions failed to attenuate the contractile response to U-46619. A high concentration of cinnamophilin (100 microM) did not affect the aortic contraction induced by endothelin-1, angiotensin II, carbachol or serotonin. Neither cAMP nor cGMP in rat aorta was increased by cinnamophilin. These results indicate that cinnamophilin is a selective thromboxane A2 receptor antagonist especially in rat aorta, and also possesses voltage-dependent Ca2+ channel blocking properties.
Yu
S M
SM
Department of Pharmacology, Chang Gung Medical College, Taiwan.
Ko
F N
FN
Wu
T S
TS
Lee
J Y
JY
Teng
C M
CM
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D005260:Female; D006139:Guaiacol / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D017705:Lignans / Q000302:isolation & purification / Q000494:pharmacology*; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D010946:Plants, Medicinal / Q000737:chemistry*; D010974:Platelet Aggregation / Q000187:drug effects; D011450:Prostaglandin Endoperoxides, Synthetic / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011817:Rabbits; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D017482:Receptors, Thromboxane / Q000037:antagonists & inhibitors*; D013624:Taiwan; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology
D002121:Calcium Channel Blockers; D017705:Lignans; D011450:Prostaglandin Endoperoxides, Synthetic; D017482:Receptors, Thromboxane; C088121:cinnamophilin; D013928:Thromboxane A2; D006139:Guaiacol; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000242:Cyclic AMP; D006152:Cyclic GMP