Further Quinolizidine Derivatives as Antiarrhythmic Agents- 3

Fourteen quinolizidine derivatives, structurally related to the alkaloids lupinine and cytisine and previously studied for other pharmacological purposes, were presently tested for antiarrhythmic, and other cardiovascular effects on isolated guinea pig heart tissues in comparison to well-established reference drugs. According to their structures, the tested compounds are assembled into three subsets: (a) N-(quinolizidinyl-alkyl)-benzamides; (b) 2-(benzotriazol-2-yl)methyl-1-(quinolizidinyl)alkyl-benzimidazoles; (c) N-substituted cytisines. All compounds but two displayed antiarrhythmic activity that was potent for compounds 4, 1, 6, and 5 (in ascending order). The last compound (N-(3,4,5-trimethoxybenzoyl)aminohomolupinane) was outstanding, exhibiting a nanomolar potency (EC50 = 0.017 µM) for the increase in the threshold of ac-arrhythmia. The tested compounds shared strong negative inotropic activity; however, this does not compromise the value of their antiarrhythmic action. On the other hand, only moderate or modest negative chronotropic and vasorelaxant activities were commonly observed. Compound 5, which has high antiarrhythmic potency, a favorable cardiovascular profile, and is devoid of antihypertensive activity in spontaneously hypertensive rats, represents a lead worthy of further investigation.

Ethnobotanical Survey and Pharmacological Screening of Medicinal Plants Used as Antihypertensive in Sefrou Province (Middle-North of Morocco): Benefits and Challenges

Herbal medicine was used since the old time in the treatment of different types of diseases in Sefrou province, Morocco. However, few studies have been carried out to identify local medicinal flora and to scientifically document the knowledge of the traditional use of these medicinal plants by the population. This study aims to investigate the medicinal plants in Sefrou province, record their usage in folk medicine by the population and evaluate the hypotensive effect of selected plants using in vitro vascular activity. For that, an ethnobotanical survey was conducted among the Arabs and Amazighs population of Sefrou province from January 2017 to December 2018. The survey was conducted through oral interviews with a structured questionnaire. It covered those who knew and/or used plants for medicinal purposes, retailers, and wholesalers, and also included ecological repartition as well as the mode of administration. Then we selected some plants to evaluate the antihypertensive activity based on the in vitro bioassay. A total of 134 medicinal plants belonging to 52 families were identified; 61% are wild species, 49 (36%) are cultivated and 4 (3%) are cultivated as well as spontaneous. Medicinal plants used in Sefrou folk medicine have been investigated for their antihypertensive activity. They were selected based on their usage as cardiotonic, diuretics, and other uses related to the symptoms of hypertension. Most of the plants tested in this study were found to be more sensitive to relaxing contractions induced by noradrenaline. Out of 32 species examined, 14 (44%) showed more than 50% inhibition in isolated rat aortic rings, the vasorelaxant activity of these plants used for the screening was mostly inhibited by pre-treatment with N-ω-nitro-L-arginine (L-NOArg). The plants inventoried are alleged to be active against 104 therapeutic indications. Nine common symptoms are widely treated in indigenous pharmacopeia: gastrointestinal (19 plants), renal (27 plants), broncho-pulmonary system (7 plants), skin (13 species), diabetes (12 plants), cardiovascular (13 plants), eye, ear, nose, teeth, and throat diseases (5 plants); gynecological disorders (6 plants); rheumatism and gnawing pain (11 plants). 14% (19 species) of the plant inventoried are traded on a large scale and scope and more than 90 percent of the medicinal plants purchased from Sefrou go to big cities for export. The expansion of unregulated trade and commercial use of medicinal and aromatic plants poses a major threat to biodiversity in the region. Overall, people in Sefrou hold rich knowledge of herbal medicine. The vasorelaxant activity proved for the documented plants will provide a basis for other preclinical and clinical investigations.

Novel Labdane Diterpenes-Based Synthetic Derivatives: Identification of a Bifunctional Vasodilator That Inhibits CaV1.2 and Stimulates KCa1.1 Channels

Sesquiterpenes such as leucodin and the labdane-type diterpene manool are natural compounds endowed with remarkably in vitro vasorelaxant and in vivo hypotensive activities. Given their structural similarity with the sesquiterpene lactone (+)-sclareolide, this molecule was selected as a scaffold to develop novel vasoactive agents. Functional, electrophysiology, and molecular dynamics studies were performed. The opening of the five-member lactone ring in the (+)-sclareolide provided a series of labdane-based small molecules, promoting a significant in vitro vasorelaxant effect. Electrophysiology data identified 7 as a Ca_V1.2 channel blocker and a K_Ca1.1 channel stimulator. These activities were also confirmed in the intact vascular tissue. The significant antagonism caused by the Ca_V1.2 channel agonist Bay K 8644 suggested that 7 might interact with the dihydropyridine binding site. Docking and molecular dynamic simulations provided the molecular basis of the Ca_V1.2 channel blockade and K_Ca1.1 channel stimulation produced by 7. Finally, 7 reduced coronary perfusion pressure and heart rate, while prolonging conduction and refractoriness of the atrioventricular node, likely because of its Ca²⁺ antagonism. Taken together, these data indicate that the labdane scaffold represents a valuable starting point for the development of new vasorelaxant agents endowed with negative chronotropic properties and targeting key pathways involved in the pathophysiology of hypertension and ischemic cardiomyopathy.

Study of the Antihypertensive Effect of Laurus nobilis in Rats

AIMS

The study aimed to study the antihypertensive activity of Laurus nobilis.

BACKGROUND

Laurus nobilis L. is used to treat hypertension in Morocco.

OBJECTIVE

The study was designed to investigate the effect of the aqueous extract leaves of Laurus nobilis (AELN) on blood pressure.

MATERIALS AND METHODS

The antihypertensive and vasorelaxant activities of AELN were pharmacologically investigated in normotensive and L-NAME-induced hypertensive rats. Thereafter, blood pressure was evaluated, and the ex-vivo vasorelaxant activity of this extract was performed.

RESULTS

A considerable decrease in blood pressure parameters were observed in L-NAMEinduced hypertensive rats treated with AELN. The extract induced a vasorelaxant effect on the aorta precontracted with epinephrine or KCl by inhibiting extracellular Ca2+ entry.

CONCLUSION

The study demonstrates that Laurus nobilis aqueous extract exhibits potent antihypertensive and vasorelaxant activities via inhibiting Ca2+ entry.

Discovery of Three New Monoterpenoid Indole Alkaloids from the Leaves of Gardneria multiflora and Their Vasorelaxant and AChE Inhibitory Activities

Three novel monoterpenoid indole alkaloids gardflorine A (1), gardflorine B (2), and gardflorine C (3) were isolated from the leaves of Gardneria multiflora. Their structures, including absolute configurations, were established on the basis of spectroscopic methods (MS, UV, IR, 1D and 2D NMR) and circular dichroism experiments. All the compounds were evaluated for their vasorelaxant and acetylcholinesterase (AChE) inhibitory activities. Compound 1 exhibited potent vasorelaxant activity, with an EC50 value of 8.7 μM, and compounds 2 and 3 showed moderate acetylcholinesterase (AChE) inhibitory activities, with IC50 values of 26.8 and 29.2 μM, respectively.

Synthesis and characterization of new pyrazole-tetrazole derivatives as new vasorelaxant agents

The synthesis of new functionalized tetrazole-pyrazole compounds is reported. They were fully characterized by spectroscopy and spectrometry methods. The vasorelaxant potency of these molecules was also investigated. All compounds showed a good vasorelaxant activity but the Compound 6 "ethyl 1-((2-(3-bromopropyl)-2H-tetrazol-5-yl)methyl)-5-methyl-1H-pyrazole-3-carboxylate" seems to have the highest effect, which reached 70% at 10^-4 M concentration. This effect was partially endothelium-dependent; also, the vasorelaxant pattern of this compound was quite similar to that of the verapamil.

Pharmacological characterization of the cardiovascular effect of Nibethione: ex vivo, in vivo and in silico studies

OBJECTIVE

This work describes the vasorelaxant and antihypertensive effects and the mechanism of action on vascular smooth muscle cells of Nibethione, a synthetic thiazolidinedione derivative. Additionally, evidence of its cytotoxicity is assessed.

METHODS

Nibethione (NB) was synthesized, and its vasorelaxant effect and mechanism of action were assessed through ex vivo experiments. Molecular docking studies were used to predict the mode of interaction with L-type Ca²⁺ channel, and in vivo antihypertensive activity was assayed on spontaneously hypertensive rats (SHR). The cytotoxicity potential was evaluated in porcine aortic endothelial cells (PAECs) from primary explants.

KEY FINDINGS

Nibethione vasorelaxant effect was efficient on KCl (80 mm) and NE-contraction. This effect was deleteriously modified in the presence of potassium channel block drugs, while the maximal contraction induced with NE was significantly decreased by NB; the CaCl₂ -induced contraction was abolished entirely. In vivo experiments showed that NB decreased diastolic blood pressure in 20.3 % after its administration on SHR. The molecular docking showed that NB blocks L-type Ca²⁺ channel, and in vitro tests showed that NB did not produce cytotoxic activity on PAECs (IC₅₀ >1000 µm).

CONCLUSIONS

Nibethione showed in vivo antihypertensive and ex vivo vasorelaxant effects with implication of voltage-dependent L-type Ca²⁺ channel blocking, and this may contribute to the research of novel antihypertensive drugs.

Discovery of new phthalazinones as vasodilator agents and novel pharmacological tools to study calcium channels

AIM

Hydralazine has led to the synthesis of phthalazinone derivatives which induce vasorelaxation.

METHODS

A new series of 2-(aminoalkyl)-4-benzyl-2H-phthalazin-1-one derivatives has been synthesized to study their vasorelaxant activity.

RESULTS

At the highest-studied concentration, most of the new compounds relaxed the denuded aortic rings precontracted with phenylephrine by 72.9-85.7%. Compound 25 (C25) suppressed almost totally the contractile effects of phenylephrine, high KCl concentration, ionomycin and caffeine related to the activation of Ca²⁺ channels, whereas its inhibitory effect was reversed with high CaCl₂ concentrations.

CONCLUSION

Vasodilator effects of C25 appear to be due exclusively to the reversible blockage of different calcium channels. As broad range calcium channel blocker, C25 seems to be suitable as a pharmacological tool for calcium channel research.

Endothelium-independent vasorelaxant activity of Trachyspermum ammi essential oil on rat aorta

Several pharmacological activities of the essential oil of Trachyspermum ammi seeds (TAEO) have been previously studied. These include antitussive, antihypertensive, and antispasmodic effects. However, its action on isolated aorta has not yet been studied. This study was aimed to investigate the vasorelaxant activity of TAEO and characterize its mechanism of action. Extraction of TAEO was performed using Clevenger-type apparatus with the final content of 4.5% (v/w). To evaluate some probable mechanisms of action of TAEO, the action isometric tension was then measured in the aortic rings from Wistar rats which were precontracted with phenylephrine (PHE) (1 µM) or KCl (60 mM). The major constituents of TAEO included Thymol (38.1%), gamma-terpinene (33.3%), and p-cymene (23.1%), as was analyzed by GC-MS. The cumulative concentrations of TAEO reduced precontraction caused by PHE and KCl (p < 0.05) significantly, which was dose dependent. The vasorelaxation caused by TAEO was not influenced in the presence of methylene blue and L-NAME in the endothelium-intact and denuded aorta ring. The inhibitory effect of TAEO on the aortic rings precontracted with KCl and PHE was considerably reduced by nifedipine. These findings hypothesized that the vasorelaxation caused by TAEO is completely endothelium independent and the extracellular Ca²⁺ influx was also inhibited by TAEO.

Alkaloids and Phenolic Compounds from Sida rhombifolia L. (Malvaceae) and Vasorelaxant Activity of Two Indoquinoline Alkaloids

The follow-up of phytochemical and pharmacological studies of Sida rhombifolia L. (Malvaceae) aims to strengthen the chemosystematics and pharmacology of Sida genera and support the ethnopharmacological use of this species as hypotensive herb. The present work reports phytoconstituents isolated and identified from aerial parts of S. rhombifolia by using chromatographic and spectroscopic methods. The study led to the isolation of scopoletin (1), scoporone (2), ethoxy-ferulate (3), kaempferol (4), kaempferol-3-O-β-d-glycosyl-6''-α-d-rhamnose (5), quindolinone (6), 11-methoxy-quindoline (7), quindoline (8), and the cryptolepine salt (9). The alkaloids quindolinone (6) and cryptolepine salt (9) showed vasorelaxant activity in rodent isolated mesenteric arteries.