Pharmacological evaluation of N-methyl-actinodaphnine, a new vascular alpha-adrenoceptor antagonist, isolated from Illigera luzonensis

Interaction between α1B - and other α1 - and α2 -adrenoceptors in producing contractions of mouse spleen

We have investigated the interaction of α₁ - and α₂ -adrenoceptor subtypes in producing isometric contractions to NA in mouse whole spleen. The α₁ -adrenoceptor antagonist prazosin (10^-8 M) or the α₂ -adrenoceptor antagonist yohimbine (10^-6 M) alone produced only small shifts in NA potency in wild type (WT) mice, but the combination produced a large shift in NA potency. In spleen from α_1A/D -KO mice, the effects of prazosin and the combination of prazosin and yohimbine were similar to their effects in WT mice. Hence, in α_1A/D -KO mice, in which the only α₁ -adrenoceptor present is the α_1B -adrenoceptor, prazosin still antagonized contractions to NA. The α_1A -adrenoceptor antagonist RS100329 (3x10^-9 M) produced significant shifts in the effects of higher concentrations of NA (EC₅₀ and EC₇₅ levels) and the α_1D -adrenoceptor antagonist BMY7378 (3x10^-8 M) produced significant shifts in the effects of lower concentrations of NA (EC₂₅ and EC₅₀ levels). The effects of BMY7378 and RS00329 demonstrate α_1D -adrenoceptor and α_1A -adrenoceptor components, and suggest that the α_1B -adrenoceptor interacts with an α_1D -adrenoceptor, and to a lesser extent an α_1A -adrenoceptor, at low, and an α_1A -adrenoceptor at high, NA concentrations. This study demonstrates the complex interaction between α₁ - and α₂ -adrenoceptor subtypes in producing contractions of mouse spleen and may have general implications for α-adrenoceptor mediated control of smooth muscle.

Anti-inflammatory monoterpene esters from the stems of Illigera aromatica

Two new monoterpene esters illigerates F and G (1 and 2) together with 5 know compounds illigerate A (3), illigerate C (4), actinodaphnine (5), N-methylactinodaphnine(6) and N-methyllaurotetanine(7) were isolated from Illigera aromatica S. Z. Huang et S. L. Mo. Their structures were identified by extensive NMR data and by comparing with the known compounds. The anti-inflammatory activity of four monoterpenes (1 - 4) was evaluated by inhibiting nitric oxide (NO) production in lipopolysaccharide-activated murine macrophage RAW 264.7 cells and four monoterpenoids exhibited inhibitory effect with IC₅₀ values of 71.5 ± 7.3, 74.7 ± 5.6, 48.0 ± 7.4 and 65.1 ± 3.7 μM, respectively.

Phenols, Alkaloids and Terpenes from Medicinal Plants with Antihypertensive and Vasorelaxant Activities. A Review of Natural Products as Leads to Potential Therapeutic Agents

Numerous studies support the cardiovascular effects of medicinal plants. This review examines plants whose antihypertensive and vasorelaxant effects have been scientifically validated. Our study selected only chemically characterized plants whose mode of action had already been investigated. The aim of the paper is to provide a quick way to identify medicinal plants and their constituents with antihypertensive and vasorelaxant activities.

Anti-platelet aggregation and vasorelaxing effects of the constituents of the rhizomes of Zingiber officinale

In the present study, the chemical investigation of the bioactive fractions of the rhizomes of Zingiber officinale has resulted in the identification of twenty-nine compounds including one new compound, O-methyldehydrogingerol. Some of the isolates were subjected into the evaluation of their antiplatelet aggregation and vasorelaxing bioactivities. Among the tested compounds, [6]-gingerol and [6]-shogaol exhibited potent anti-platelet aggregation bioactivity. In addition, [10]-gingerol inhibited the Ca²⁺-dependent contractions in high K⁺ medium. According to the results in the present research, the bioactivity of ginger could be related to the anti-platelet aggregation and vasorelaxing mechanism.

Monoaminergic, Ion Channel and Enzyme Inhibitory Activities of Natural Aporphines, their Analogues and Derivatives

The aporphine alkaloids constitute the second-largest group of isoquinoline alkaloids. Nevertheless, only a relatively small number of natural aporphines and their derivatives have been studied from a pharmacological viewpoint. Here we review the pharmacological data available for these compounds as related to their dopaminergic, noradrenergic and serotonergic activities, and also some results pertaining to their effects on ion channels and enzymes.

Flavonoids and ent-labdane diterpenoids from Andrographis paniculata and their antiplatelet aggregatory and vasorelaxing effects

Two new flavones, designated as andropaniculosin A (1) and andropaniculoside A (2), and 30 known compounds were isolated as a result of detailed chemical examination on the whole plants of Andrographis paniculata. Their structures have been elucidated mainly by 1D and 2D NMR, and MS spectroscopic methods. Among them, four flavonoids showed potent inhibition of collagen, arachidonic acid, thrombin, and platelet activation factor induced platelet aggregation. Furthermore, a diterpenoid demonstrated moderate vasorelaxing effect in isolated rat thoracic aorta.

Saw palmetto extracts potently and noncompetitively inhibit human alpha1-adrenoceptors in vitro

BACKGROUND

We wanted to test whether phytotherapeutic agents used in the treatment of lower urinary tract symptoms have alpha1-adrenoceptor antagonistic properties in vitro.

METHODS

Preparations of beta-sitosterol and extracts of stinging nettle, medicinal pumpkin, and saw palmetto were obtained from several pharmaceutical companies. They were tested for their ability to inhibit [3H]tamsulosin binding to human prostatic alpha1-adrenoceptors and [3H]prazosin binding to cloned human alpha1A- and alpha1B-adrenoceptors. Inhibition of phenylephrine-stimulated [3H]inositol phosphate formation by cloned receptors was also investigated.

RESULTS

Up to the highest concentration which could be tested, preparations of beta-sitosterol, stinging nettle, and medicinal pumpkin were without consistent inhibitory effect in all assays. In contrast, all tested saw palmetto extracts inhibited radioligand binding to human alpha1-adrenoceptors and agonist-induced [3H]inositol phosphate formation. Saturation binding experiments in the presence of a single saw palmetto extract concentration indicated a noncompetitive antagonism. The relationship between active concentrations in vitro and recommended therapeutic doses for the saw palmetto extracts was slightly lower than that for several chemically defined alpha1-adrenoceptor antagonists.

CONCLUSIONS

Saw palmetto extracts have alpha1-adrenoceptor-inhibitory properties. If bioavailability and other pharmacokinetic properties of these ingredients are similar to those of the chemically defined alpha1-adrenoceptor antagonists, alpha1-adrenoceptor antagonism might be involved in the therapeutic effects of these extracts in patients with lower urinary tract symptoms suggestive of benign prostatic obstruction.

Antiplatelet effects of some aporphine and phenanthrene alkaloids in rabbits and man

Two aporphines (boldine and laurolitsine) and five phenanthrene alkaloids (litebamine, secoboldine, N-cyanosecoboldine, N-methylsecoglaucine and N-methylsecopredicentrine) were evaluated in-vitro for their ability to inhibit platelet aggregation. All seven alkaloids inhibited aggregation of rabbit platelets and inhibited the release of ATP induced by arachidonic acid and collagen in rabbit platelets. Those aggregations induced by platelet-activating factor (PAF), thrombin, U46619 and ADP were inhibited by the three N-substituted secoboldine derivatives only. Thromboxane B2 formation caused by arachidonic acid was also suppressed by these compounds. They did not affect the generation of [3H]inositol monophosphate caused by collagen, PAF and thrombin in the presence of indomethacin. Platelet cyclic AMP level was unaffected by litebamine, but was increased by N-methylsecoglaucine. Litebamine suppressed the secondary aggregation, but not the primary aggregation, induced by ADP and adrenaline in platelet-rich plasma from man, whereas N-methylsecoglaucine inhibited both primary and secondary aggregation. It is concluded that the antiplatelet effect of these seven aporphine and phenanthrene alkaloids is mainly a result of inhibition of thromboxane A2 formation; N-methylsecoglaucine has additional antiplatelet activity as a result of increasing the levels of platelet cyclic AMP.