Yeun-Chih Huang

A Highly Selective β1-adrenergic Blocker with Partial β2-agonist Activity Derived from Ferulic Acid, an Active Component of ligusticum wallichii Franch

Short-term injection of ferulinolol (0.1, 0.5, and 1.0 mg/kg, i.v.) produced dose-dependent bradycardia responses in pentobarbital-anesthetized Wistar rats, whereas it had no significant effects on the blood pressure. Ferulinolol markedly inhibited the tachycardia effects induced by (-)isoproterenol but did not show any blocking effect on the arterial pressor responses induced by (-)phenylephrine. These findings clearly suggested that ferulinolol had a beta-adrenergic blocking activity; nevertheless, it did not involve an alpha-adrenergic blocking action. In isolated guinea pig tissues, ferulinolol competitively antagonized (-)isoproterenol-induced positive inotropic and chronotropic effects of the atria and tracheal relaxation responses. The parallel shift to the right of the concentration-response curve of (-)isoproterenol suggested that ferulinolol was a beta-adrenoceptor-competitive antagonist. The apparent pA2 values for ferulinolol on right atria, left atria, and trachea were 7.62 +/- 0.05, 7.54 +/- 0.01, and 6.28 +/- 0.11, respectively. Ferulinolol was more potent on the atria than on tracheal tissues, demonstrating that it possessed beta1-adrenoceptor selectivity. The intrinsic sympathomimetic activity (ISA) of ferulinolol and propranolol were determined on isolated atria and trachea from reserpine-treated guinea pig. Propranolol caused significantly negative inotropic and chronotropic effects at > or =1 microM, whereas ferulinolol possessed fewer cardiodepressant activities than propranolol. In reserpine-treated tracheal strips, ferulinolol produced dose-dependent relaxant responses, but propranolol was without effectiveness. Preincubating the preparations with ICI 118,551 (0.1, 1.0, and 10 nM), a beta2-adrenoceptor antagonist, significantly shifted the concentration-relaxation curves of ferulinolol to a region of higher concentrations. These results implied that ferulinolol had a partial beta2-agonist activity. Further, binding characteristics of ferulinolol and various beta-adrenoceptor antagonists were evaluated in [3H]CGP-12177 binding to rat ventricular or lung membranes. The Ki values of ferulinolol, atenolol, metoprolol, and (-)propranolol were 103, 262, 123, and 0.23 nM, respectively, in ventricular membranes, and 2,412, 7,539, 2,186, and 0.72 nM, respectively, in lung membranes. In conclusion, ferulinolol was found to be a highly selective beta1-adrenoceptor antagonist with partial beta2-agonist activity but was devoid of alpha-adrenoceptor blocking action.

Vanidipinedilol : A vanilloid-based β-adrenoceptor blocker displaying Calcium entry blocking and vasorelaxant activities

Calcium channel and beta-adrenoceptor blockade have proved highly useful in antihypertensive therapy. Studies of the mechanisms of action of vanidipinedilol that combine these effects within a single molecule are described here. Intravenous injection of vanidipinedilol (0.1, 0.25, 0.5, 1.0, and 2.0 mg/kg) produced dose-dependent hypotensive and bradycardic responses, significantly different from nifedipine-induced (0.5 mg/kg, i.v.) hypotensive and reflex tachycardic effects in pentobarbital-anesthetized Wistar rats. A single oral administration of vanidipinedilol at doses of 10, 25, and 50 mg/kg dose-dependently reduced blood pressure with a decrease in heart rate in conscious spontaneously hypertensive rats (SHRs). In the isolated Wistar rat atrium, vanidipinedilol (10(-7), 10(-6), and 10(-5) M) competitively antagonized the (-)isoproterenol-induced positive chronotropic and inotropic effects and inhibited the increase in heart rate induced by Ca2+ (3.0-9.0 mM) in a concentration-dependent manner. The parallel shift to the right of the concentration-response curve of (-)isoproterenol and CaCl2 suggested that vanidipinedilol possessed beta-adrenoceptor-blocking and calcium entry-blocking activities. On tracheal strips of reserpinized guinea pig, cumulative doses of vanidipinedilol (10(-10) to 3x10(-6) M) produced dose-dependent relaxant responses. Preincubating the preparation with ICI 118,551 (10(-10), 10(-9), 10(-8) M), a beta2-adrenoceptor antagonist, shifted the vanidipinedilol concentration-relaxation curve significantly to a region of higher concentrations. These results implied that vanidipinedilol had a partial beta2-agonist activity. In the isolated thoracic aorta of rat, vanidipinedilol had a potent effect inhibiting high-K+-induced contractions. KCI-induced intracellular calcium changes of blood vessel smooth muscle cell (A7r5 cell lines) determined by laser cytometry also was decreased after administration of vanidipinedilol (10(-8), 10(-7), 10(-6) M). Furthermore, the binding characteristics of vanidipinedilol and various antagonists were evaluated in [3H]CGP-12177 binding to ventricle and lung and [3H]nitrendipine binding to cerebral cortex membranes in rats. The order of potency of beta1- and beta2-adrenoceptor antagonist activity against [3H]CGP-12177 binding was (-)propranolol (pKi, 8.59 for beta1 and 8.09 for beta2) > vanidipinedilol (pKi, 7.09 for beta1 and 6.64 for beta2) > atenolol (pKi, 6.58 for beta1 and 5.12 for beta2). The order of potency of calcium channel antagonist activity against [3H]nitrendipine binding was nifedipine (pKi, 9.36) > vanidipinedilol (pKi, 8.07). The ratio of beta1-adrenergic-blocking/calcium entry-blocking selectivity is 0.1 and indicated that vanidipinedilol revealed more in calcium entry-blocking than in beta-adrenergic-blocking activities. It has been suggested that vanidipinedilol-induced smooth muscle relaxation may involve decreased entry of Ca2+ and partial beta2-agonist activities. In conclusion, vanidipinedilol is a nonselective beta-adrenoceptor antagonist with calcium channel blocking and partial beta2-agonist associated vasorelaxant and tracheal relaxant activities. Particularly, the vasodilator effects of vanidipinedilol are attributed to a synergism of its calcium entry blocking and partial beta2-agonist activities in the blood vessel. A sustained bradycardic effect results from beta-adrenoceptor blocking and calcium entry blocking, which blunts the sympathetic activation-associated reflex tachycardia in the heart.

Eugenodilol : A third-generation β-adrenoceptor blocker, derived from eugenol, with α-adrenoceptor blocking and β2-Adrenoceptor agonist-associated vasorelaxant activities

: Eugenodilol, derived from natural eugenol, was first investigated with in vivo and in vitro models. In our in vivo study, eugenodilol (0.5, 1.0, and 1.5 mg/kg, i.v.) produced dose-dependent hypotensive and bradycardic responses in pentobarbital-anesthetized Wistar rats. Eugenodilol also inhibited the tachycardia and arterial pressor effects induced by (-)isoproterenol and phenylephrine, respectively. In our in vitro study, eugenodilol competitively antagonized (-)isoproterenol-induced positive inotropic and chronotropic effects and tracheal-relaxation responses on isolated guinea pig tissues in a concentration-dependent manner. The apparent pA2 values were 7.88+/-0.12 for right atria, 7.52+/-0.05 for left atria, and 7.33+/-0.15 for trachea, indicating that eugenodilol was a nonselective beta-adrenoceptor blocker. In thoracic aorta experiments, the apparent pA2 values of alpha-adrenoceptor blockade were 7.05+/-0.25 and 6.87+/-0.08 for eugenodilol and labetalol, respectively. In addition, eugenodilol produced cumulative relaxation responses on isolated guinea pig tracheal strips. The effects were competitively antagonized by ICI 118,551 (10(-8)-10(-6) M), a relatively selective beta2-adrenoceptor antagonist. In the radioligand-binding assay, the Ki values of [3H]CGP-12177 binding to rat ventricle and lung membranes were 9.72 and 48.29 nM, respectively, and the value of [3H]prazosin binding to rat brain membrane was 38.72 nM. These results further confirmed the alpha/beta-adrenoceptors-blocking activities of eugenodilol reported in the functional studies. We conclude that eugenodilol is a novel third-generation beta-adrenoceptor blocker with ancillary blocking activity at alpha-adrenoceptors and weak sympathomimetic activity at beta2-adrenoceptors.

Eugenolol : An eugenol-derived β-adrenoceptor blocker with partial β2-Agonist and calcium mobilization inhibition associated vasorelaxant activities

The β‐adrenoceptor blocking, vasorelaxant and hypotensive activities of eugenolol (1‐(isopropylamino)‐3‐[(4‐ allyl‐2‐methoxy‐)phenoxy]‐2‐propanol) were investigated under in vivo and in vitro conditions. In pentobarbital anesthetized rats, eugenolol (0.1, 0.5, 1.0 mg/kg, i.v.) produced a dose‐dependent hypotensive and bradycardia response. Eugenolol also inhibited the tachycardia effects induced by (–)isoproterenol, but did not block arterial pressor responses induced by phenylephrine. In isolated guinea pig tissues, eugenolol competitively antagonized the (–)isoproterenol‐induced positive inotropic and chronotropic effects and tracheal relaxation responses. The apparent pA2 values for eugenolol on right atria, left atria and trachea were 8.23 ± 0.04, 8.36 ± 0.13 and 8.18 ± 0.12, respectively. On tracheal strips of reserpinized guinea pig, cumulative doses of eugenolol (10–10–10–7 M) produced dose‐dependent relaxant responses. Preincubating the preparation with ICI 118,551 (10–8, 10–7, 10–6 M) shifted the eugenolol concentration‐relaxation curve significantly to a region of higher concentrations. Binding characteristics of eugenolol and propranolol were evaluated in [3H]dihydroalprenolol binding to pig ventricular membranes. The Ki values of eugenolol and propranolol were 18.1 ± 3.2 and 3.8 ± 0.5 nM, respectively. In guinea pig isolated thoracic aorta, eugenolol relaxed more potently the contractions induced by phenylephrine than those by high K+. The vasorelaxant effect of eugenolol on phenylephrine‐ or high K+‐induced contraction was not attenuated by TEA or Bay K 8644 pretreatment. Furthermore, eugenolol pretreatment had a greater inhibitory effect on phenylephrine induced phasic contraction than on tonic contraction. These results indicate that eugenolol exhibits non‐selective β‐blocking and vasorelaxant activity by inhibiting Ca2+ channels, receptor‐mediated Ca2+ mobilization and by its partial β2‐agonist activity. Drug Dev. Res. 40:239–250, 1997.

Ferulidilol: A vasodilatory and antioxidant adrenoceptor and calcium entry blocker, with ancillary β2‐agonist activity

Intravenous injection of ferulidilol (0.5, 1.0, 1.5 mg kg−1) produced dose‐dependent hypotensive and bradycardia responses in pentobarbital‐anesthetized Wistar rats. Ferulidilol competitively antagonized (‐)isoprenaline‐induced positive inotropic and chronotropic effects of the atria and tracheal relaxation responses on isolated guinea pig tissues. The parallel shift to the right of the concentration–response curve of (‐)isoprenaline suggested that ferulidilol was a β‐adrenoceptor antagonist. The apparent pA2 values were 8.04 ± 0.09 for the right atria, 8.03 ± 0.15 for the left atria, and 7.51 ± 0.06 for the trachea, respectively. Ferulidilol was more potent than labetalol. In thoracic aorta experiments, ferulidilol also produced a competitive antagonism of norepinephrine‐ and CaCl2‐induced contraction with pA2 and pKCa−1 values of 7.05 ± 0.03 and 6.04 ± 0.05, respectively. Ferulidilol produced cumulative relaxation responses on isolated tracheal strips from reserpine‐treated guinea pigs. The effects were competitively antagonized by ICI 118,551 (10−8–10−6 M), a relatively selective β2‐adrenoceptor antagonist. The results implied that ferulidilol had partial β2‐agonist activity. In the radioligand binding assay, ferulidilol produced dose‐dependent inhibition of [3H]CGP‐12177 binding to rat ventricle and lung membranes with Ki values of 3.40 and 17.94 nM, respectively. In addition, ferulidilol also antagonized [3H]prazosin and [3H]nitrendipine binding to rat brain membrane with Ki values of 32.48 and 305.01 nM, respectively. These results further confirmed the α/β and calcium entry blocking activities of ferulidilol described in functional studies. Furthermore, ferulidilol (10−8–10−5 M] inhibited lipid peroxidation induced by Fe2+ and ascorbic acid, indicating that it possesses the antioxidant activity inherent in ferulic acid. Our results demonstrate that ferulidilol is a new generation α/β‐adrenoceptor blocker with ancillary calcium entry blockade, partial β2‐agonist activities and additional antioxidant effects. Drug Dev. Res. 47:77–89, 1999.

A new aspect of view in synthesizing new type β-adrenoceptor blockers with ancillary antioxidant activities

A series of vanilloid-type beta-adrenoceptor blockers derived from antioxidant traditional Chinese herbal medicines were synthesized and tested for their antioxidant and adrenoceptor antagonistic activities. They all possessed significant beta-adrenoceptor blocking activities under in vitro experiments and radioligand binding assays. In addition, some compounds were further examined in in vivo tests and produced antagonist effects matching that of propranolol and labetalol by measurements of antagonism toward (-)isoproterenol-induced tachycardia and (-)phenylephrine-induced pressor responses in anesthetized rats. Furthermore, all of the compounds had antioxidant effects inherited from their original structures. In conclusion, compound 11 had the most potent beta-adrenoceptors blocking activity, 12 and 13 possessed high cardioselectivity, whereas 14, 15 and 16 possessed additional alpha-adrenoceptor blocking activity and 15 is the most effective antioxidant of all. The antioxidant activity may be due to their alpha and beta unsaturated side chain at position 1 and ortho-substituted methoxy moiety on 4-phenoxyethylamine.

Isoeugenodilol: A vasorelaxant α/β-adrenoceptor blocker with antioxidant activity

Isoeugenodilol, derived from isoeugenol, was investigated under in vivo and in vitro conditions. Isoeugenodilol (0.1, 0.5, 1.0, and 3.0 mg kg–1, i.v.) produced dose‐dependent hypotensive and bradycardia responses in pentobarbital‐anesthetized Wistar rats. Isoeugenodilol (0.5 mg kg–1, i.v.) also markedly inhibited both the tachycardia effects induced by (‐) isoproterenol and arterial pressor responses induced by phenylephrine. A single oral administration of isoeugenodilol at doses of 10, 30, and 100 mg kg–1 dose‐dependently reduced blood pressure, with a decrease in heart rate in conscious spontaneously hypertensive rats (SHRs). In the isolated Wistar rat right atria, left atria, and guinea pig tracheal strips, isoeugenodilol competitively antagonized the (‐) isoproterenol‐induced positive chronotropic effects, inotropic effects, and tracheal relaxation effects in a concentration‐dependent manner. The parallel shift to the right of the concentration–response curve of (‐) isoproterenol suggested that isoeugenodilol was a β1/β2‐adrenoceptor competitive antagonist. The apparent pA2 values were 7.33 ± 0.12 in the right atria, 7.80 ± 0.09 in the left atria, and 7.26 ± 0.11 in the trachea, indicating that isoeugenodilol was a nonselective β‐adrenoceptor blocker. In thoracic aorta experiments, isoeugenodilol also produced a competitive antagonism of norepinephrine‐induced contraction with a pA2 value of 7.47 ± 0.45. In isolated atria of reserpinized rats, cumulative additions of isoeugenodilol and propranolol produced significantly cardiodepressant responses at high concentrations (10–5 M) and were without intrinsic sympathomimetic activity (ISA). In isolated rat thoracic aorta, isoeugenodilol more potently relaxed the contractions induced by norepinephrine (3 × 10–6 M) than those by high K+ (75 mM). The vasorelaxant effects of isoeugenodilol on norepinephrine‐induced contractions were attenuated by pretreatment with tetraethylammonium (TEA) and glibenclamide, implying the involvement of K+ channel opening. In addition, isoeugenodilol inhibited norepinephrine‐induced biphasic contraction; it affected the fast phase significantly more than the slow phase. Furthermore, the binding characteristics of isoeugenodilol and various β‐adrenoceptor antagonists were evaluated in [3H]CGP‐12177 binding to rat ventricle and lung tissues and [3H]prazosin binding to brain membranes. The ranking order of inhibition for [3H]CGP‐12177 binding on β‐adrenoceptor was propranolol > labetalol > isoeugenodilol, and that for [3H]prazosin binding to α‐adrenoceptors was isoeugenodilol > labetalol. Furthermore, isoeugenodilol inhibited lipid peroxidation induced by Fe2+ and ascorbic acid with IC50 of 0.74 ± 0.03 mM, indicating that it possesses the antioxidant activity inherent in isoeugenol. In conclusion, isoeugenodilol was found to be a new generation α/β‐adrenoceptor antagonist with vasorelaxant activity by inhibiting Ca2+ channel, receptor‐mediated Ca2+ mobilization and by K+ channel opening, and to have additional potentially antioxidant effects. Drug Dev. Res. 51:29–42, 2000.

Lipid solubility of vasodilatory vanilloid-type β-blockers on the functional and binding activities of β-adrenoceptor subtypes

Abstract Various vanilloid-type β-adrenoceptor blockers were studied on guinea pig right atrium and trachea and rat colon. In addition, we also investigated their β1-, β2-, and β3-adrenoceptor binding affinities. All these β-adrenergic antagonists inhibited (−)isoproterenol-induced positive chronotropic effects of the right atrium and tracheal relaxation responses in a concentration-dependent manner. Some of these agents prevented the inhibition of rat colon spontaneous motility by (−)isoproterenol. Of the agents tested, we found that ferulidilol, eugenodilol, eugenolol, isoeugenolol, and ferulinolol, as well as propranolol and metoprolol, possessed β3-adrenoceptor blocking activities, others were nearly without effectiveness. Furthermore, the binding characteristics of vanilloid-type β-adrenergic antagonists were evaluated in [3H]CGP-12177, a β1/β2-adrenoceptor blocker and a β3-adrenoceptor agonist, binding to β1-, β2-, and β3-adrenoceptor sites in rat ventricle, lung, and interscapular brown adipose tissue (IBAT) membranes, respectively. Eugenodilol, eugenolol, metoprolol, isoeugenolol, and ferulinolol were less potent than both propranolol and ferulidilol in competing for the β3-adrenoceptor binding sites. From the results of in vitro functional and binding studies, we suggested that propranolol, ferulidilol, eugenodilol, eugenolol, metoprolol, isoeugenolol, and ferulinolol all possessed β3-adrenoceptor blocking activities. On the other hand, we also found that eugenodilol, eugenolol, metoprolol, isoeugenolol, and ferulinolol had a low lipid solubility in comparison with propranolol and ferulidilol. In conclusion, we proposed that β3-adrenoceptor antagonistic actions of these vanilloid-type β-blockers were positively correlated with their lipid solubility.

The Interference of Uptake of Thallium-201in Cultured RAT Myocardial Cells with Existence of Potassium Related Pharmaceuticals-A Preliminary Report

Thallium-201 myocardial perfusion imaging is wildly used to detect and assess the extent of jeopardized myocardial ischemia in the coronary artery disease and the viability of myocardium post infarction. In recent years, there has been a great deal of pharmacological development of blockers and openers of potassium channel. In this study, we will discuss the interference of uptake of thallium-201 ion in cultured neonatal rat myocytes with existence of a variety of pharmacological agents. The cultures of neonatal rat myocardial cells were incubated with different agents such as potassium chloride, sodium-potassium ATPase pump inhibitor (ouabain), cesium compound, variable potassium channel blockers (4 AP, TEA and glibenclamide) and their openers (minoxidil, and cromakalim). The radioactivity of intracellular thallium-201 that could enter rat myocardial cells was detected by gamma counter sixty minutes after thallium-201 was added. In this study we found that thallium and potassium ions behave in an analogous manner in cultured rat myocardial cells. Both 2.5 mM and 5 mM concentration of extracellular potassium ion significantly result in reduction of thallium-201 ion influx in rat myocardial cells. 0.5 mM ouabain, an inhibitor of sodium-potassium ATPase pump, reduced about 40% of influx of thallium-201 ion in cultured rat myocardial cells via active transport. Combination of both potassium ion and ouabain inhibit most of thallium-201 ions influx in myocardial cells, but it is not completely inhibited. Cesium, a potassium antagonist, also interferes with the uptake of thallium-201 in cultured rat myocytes in our study. The most interesting finding in our investigation is that potassium channel blockers such as TEA and glibenclamide, inhibit the influx of thallium-201 in myocytes. However, potassium channel openers have no overt effect on influx of thallium-201 in cultured rat myocytes. We indirectly observe about 60% of influx of thallium-201 ion into cultured rat myocardial cells via active sodium-potassium ATPase pump. Potassium, cesium and potassium channel blockers, such as TEA and glibenclamide, inhibited the different percentage of influx of thallium-201 in cultured rat myocardial cells in this study.