Synthesis, biosimulation and pharmacological evaluation of benzimidazole derivatives with antihypertensive multitarget effect.

In this study, we synthesized a series of seven benzimidazole derivatives incorporating the structural acidic framework of angiotensin II (Ang II) type 1 receptor (AT1R) antagonists (ARA-II) employing a three-step reaction sequence. The chemical structures were confirmed by 1H NMR, 13C NMR and mass spectral data. Through biosimulation, compounds 1-7 were identified as computational safe hits, thus, best candidates underwent ex vivo testing against two distinct mechanisms implicated in hypertension: antagonism of the Ang II type 1 receptor and the blockade of calcium channel. Molecular docking studies helped to understand at the molecular level the dual vasorelaxant effects with the recognition sites of the AT1R and the L-type calcium channel. In an in vivo spontaneously hypertensive rat model (SHR), intraperitoneally administration of compound 1 at 20 mg/kg resulted in a 25 % reduction in systolic blood pressure, demonstrating both ex vivo vasorelaxant action and in vivo antihypertensive multitarget efficacy. ©2024 Elsevier.

Ex Vivo and In Silico Approaches of Tracheal Relaxation through Calcium Channel Blockade of 6-Aminoflavone and Its Toxicological Studies in Murine Models.

Asthma is a condition in which a person's airways become inflamed, narrowed, and produce greater amounts of mucus than normal. It can cause shortness of breath, chest pain, coughing, or wheezing. In some cases, symptoms may be exacerbated. Thus, the current study was designed to determine the mechanism of action of 6-aminoflavone (6-NH2F) in ex vivo experiments, as well as to determine its toxicity in acute and sub-chronic murine models. Tissues were pre-incubated with 6-NH2F, and concentration-response curves to carbachol-induced contraction were constructed. Therefore, tracheal rings pre-treated with glibenclamide, 2-aminopyridine, or isoproterenol were contracted with carbachol (1 µM), then 6-NH2F relaxation curves were obtained. In other sets of experiments, to explore the calcium channel role in the 6-NH2F relaxant action, tissues were contracted with KCl (80 mM), and 6-NH2F was cumulatively added to induce relaxation. On the other hand, tissues were pre-incubated with the test sample, and after that, CaCl2 concentration-response curves were developed. In this context, 6-NH2F induced significant relaxation in ex vivo assays, and the effect showed a non-competitive antagonism pattern. In addition, 6-NH2F significantly relaxed the contraction induced by KCl and CaCl2, suggesting a potential calcium channel blockade, which was corroborated by in silico molecular docking that was used to approximate the mode of interaction with the L-type Ca2+ channel, where 6-NH2F showed lower affinity energy when compared with nifedipine. Finally, toxicological studies revealed that 6-NH2F possesses pharmacological safety, since it did not produce any toxic effect in both acute and sub-acute murine models. In conclusion, 6-aminoflavone exerted significant relaxation through calcium channel blockade, and the compound seems to be safe.

Antihypertensive and vasorelaxant effect of leucodin and achillin isolated from Achillea millefolium through calcium channel blockade and NO production: In vivo, functional ex vivo and in silico studies.

ETHNOPHARMACOLOGICAL RELEVANCE: Achillea millefolium L. (Asteraceae), known as yarrow (milenrama), is a plant used in Mexican traditional medicine for the treatment of hypertension, diabetes, and related diseases. AIM: To determine the vasorelaxant and antihypertensive effect of A. millefollium and to isolate the main bioactive antihypertensive agents. MATERIALS AND METHODS: Organic (hexane, dichloromethane and methanol) and hydro-alcohol (Ethanol-H2O: 70:30) extracts obtained from flowers, leaves and stems were evaluated on isolated aorta rat rings with and without endothelium to determine their vasorelaxant effect. Hexane extract from flowers (HEAmF) was studied to evaluate its antihypertensive effect on spontaneously hypertensive rats (SHR). From HEAmF, bioactive compounds were obtained by bio-guided phytochemical separation through chromatography. RESULTS: Organic extracts showed the best vasorelaxant activity. Hexane extract from flowers was the most potent and efficient ex vivo vasorelaxant agent, showing significant decrease of systolic and diastolic blood pressure in SHR (p < 0.05). Phytochemical separation of HEAmF yielded two epimeric sesquiterpene lactones: leucodin (1) and achillin (2), the major components of the extract. Both 1 and 2 showed similar vasorelaxant action ex vivo (p < 0.05), and their effects where modified by L-NAME (10 µM, nitric oxide synthase inhibitor), by ODQ (1 µM, soluble guanylyl cyclase inhibitor), and also relaxed the contraction induced by KCl (80 mM). Finally, 1 and 2 intragastric administration (50 mg/kg) decreased systolic and diastolic blood pressure in SHR. CONCLUSIONS: Achillea millefolium showed antihypertensive and vasorelaxant effects, due mainly to leucodin and achillin (epimers). Both compounds showed antihypertensive activity by vasorelaxation putatively by endothelium-dependent NO release and cGMP increase, as well as by calcium channels blockade.

Tracheal relaxation through calcium channel blockade of Achillea millefolium hexanic extract and its main bioactive compounds.

ETHNOPHARMACOLOGICAL IMPORTANCE: Achillea millefolium L. (Asteraceae) is used for the treatment of respiratory diseases, diabetes, and hypertension. AIM: to explore its tracheal relaxant properties and clarify its functional mechanism of action on smooth muscle cells, which allow us to propose it as a potential anti-asthmatic drug. MATERIAL AND METHODS: organic and hydro-alcoholic extracts from A. millefolium were obtained by macerations, then their relaxing effect on ex vivo isolated rat trachea rings was determined. Most active extract (hexanic extract, EHAm) was studied to determine its functional mechanism of action using synergic, antagonist and inhibitor agents related with the contraction/relaxation process of the smooth muscle. Also, EHAm was subjected to bio-guided fractionation by open-column chromatography (on silica gel) using cyclohexane-EtOAc (80:20) in an isocratic way to isolate main bioactive compounds. RESULTS: organic and hydro-alcoholic extracts showed relaxant effect in a concentration-response dependent manner, being EHAm the most active. The functional mechanism of action indicates that EHAm induced a non-competitive antagonism to the muscarinic receptors ; in addition, the NO/cGMP pathway is involved in the relaxation process of the tracheal smooth muscle. However, the most important mechanism of action showed by EHAm was related with the calcium channel blockade influx into the smooth muscle cells. On the other hand, epimeric sesquiterpene lactones leucodin (1) and achillin (2) were isolated and purified, which are responsible for the observed smooth muscle relaxant activity of the extract. CONCLUSION: hexanic extract of A. millefollium induced a significant relaxant effect on tracheal rat rings by calcium channel blockade and NO release.

Hypoglycaemic and Antioxidant Effects of Propolis of Chihuahua in a Model of Experimental Diabetes.

Propolis is a bee-collected natural product that has been proven to have various bioactivities. This study tested the effects of a Mexican propolis on streptozotocin-induced diabetes mellitus in a murine model. The results showed that an ethanolic extract of propolis of Chihuahua (EEPCh) significantly inhibited increases in blood glucose and the loss of body weight in diabetic mice. EEPCh increased plasma insulin levels in STZ-diabetic mice, whereas, in untreated diabetic mice, there was no detection of insulin. EEPCh had a high antioxidant capacity (SA50 = 15.75 µg/mL), which was directly related to the concentrations of total phenols (314 mg GAE/g of extract) and flavonoids (6.25 mg QE/g of extract). In addition, increased activities of the enzymes superoxide dismutase, catalase, and glutathione peroxidase were observed in diabetic mice treated with EEPCh. Compounds such as pinocembrin, quercetin, naringin, naringenin, kaempferol, acacetin, luteolin, and chrysin were identified by HPLC-MS analysis. This investigation demonstrated that propolis of Chihuahua possesses hypoglycaemic and antioxidant activities and can alleviate symptoms of diabetes mellitus in mice. These effects may be directly related to the chemical composition of propolis, as most of the compounds identified in propolis are reportedly active in terms of the different parameters evaluated in this work.

Bioactivity of an antihypertensive peptide expressed in Chlamydomonas reinhardtii.

In this study, we developed a transplastomic C. reinhardtii strain that accumulates anti-hypertensive peptides. Tandem repeats of VLPVP peptide were included. PCR analysis confirmed the presence of the transgene in the modified strains. After in vitro digestion of biomass of a recombinant C. reinhardtii strain the VLVPV peptide was identified and quantified by HPLC. The highest expression line produced 0.292mg of recombinant protein per mg of freeze-dried biomass. Intragastric administration of the genetically modified strain to spontaneous hypertensive rats at a dose of 30mg/kg of body weight of recombinant protein significantly reduced systolic blood pressure. At the same dose, the recombinant protein exerts an ACE-inhibitory effect. This is the first study that indicates the potential of this microalga producing an antihypertensive peptide as a dietary supplement for hypertension patients.

Antidiabetic, antihyperlipidemic and anti-inflammatory effects of tilianin in streptozotocin-nicotinamide diabetic rats.

Flavonoids from medicinal plants have been used in traditional medicine to treat a variety of prevalent diseases. Flavones activate the signaling pathways promoting fuel metabolism and insulin sensitizing in hepatocytes and adipocytes, which suggests that flavones may have the potential to exert in vivo antidiabetic and antihyperlipidemic effects. Thus, the aim of the current study was to determine the antidiabetic, antihyperlipidemic and anti-inflammatory effects of tilianin in diabetic rats. Also, to understand the mechanism involved using in vitro 3T3-L1 cells and tissues from experimental animals treated with test samples through molecular profile studies. Non insulin-dependent diabetic mellitus (NIDDM) rats were treated over a short period (for 10 days) with 60mg/Kg/day of tilianin. After treatment, a biochemical blood profile was determined. Also, adipose and thoracic aortic tissues were used to determine pro-inflammatory profile, adiponectin and adhesion molecules by real-time PCR. In 3T3-L1 cells pretreated with tilianin (10µM), PPARα, PPARγ, GLUT4, FATP-1 and ACSL-1 mRNA expression were measured. In order to explain the potential PPARα interaction with tilianin, a docking study with PPARα was carried out. Thus, intragastric administration of tilianin and metformin induced a decrease in plasma glucose (GLU) in diabetic rats on day 6, and remained significantly lower until the end of the treatment; also blood triacylglycerides (TAG) and cholesterol (CHOL) (p<0.05) were diminished. Moreover, IL-1ß and IL-18 expression was significantly decreased in adipose tissue (p<0.05); meanwhile adiponectin was significantly overexpressed (p<0.05). Besides, ICAM-1 expression was significantly reduced in aortic tissue (p<0.05). In 3T3-L1 cells it was found that tilianin increased PPARα and ACSL1 mRNA levels (p<0.05). Finally, tilianin docking studies with PPARα showed polar interactions with Glu269, Tyr314, His 440 and Tyr464 residues. In conclusion, short-term tilianin treatment might exert its antidiabetic and antihyperlipidemic effect by modulating a pro-inflammatory profile, and increasing adiponectin expression. In addition, our results suggest the possible interaction of tilianin with PPARα.

Semisynthesis, ex vivo evaluation, and SAR studies of coumarin derivatives as potential antiasthmatic drugs.

Asthma is a chronic inflammatory disorder that causes contraction in the smooth muscle of the airway and blocking of airflow. Reversal the contractile process is a strategy for the search of new drugs that could be used for the treatment of asthma. This work reports the semisynthesis, ex vivo relaxing evaluation and SAR studies of a series of 18 coumarins. The results pointed that the ether derivatives 1-3, 7-9 and 13-15 showed the best activity (Emax = 100%), where compound 2 (42 µM) was the most potent, being 4-times more active than theophylline (positive control). The ether homologation (methyl, ethyl and propyl) in position 7 or positions 6 and 7 of coumarins lead to relaxing effect, meanwhile formation of esters generated less active compounds than ethers. The SAR analysis showed that it is necessary the presence of two small ether groups and the methyl group at position 4 (site 3) encourage biological activity through soft hydrophobic changes in the molecule, without drastically affecting the cLogP.

Tracheal relaxation of five medicinal plants used in Mexico for the treatment of several diseases.

OBJECTIVE: To assess the relaxant effect of several organic extracts obtained from Agastache mexicana (A. mexicana), Cochlospermum vitifolium (C. vitifolium), Cordia morelosana (C. morelosana), Lepechinia caulescens (L. caulescens) and Talauma mexicana (T. mexicana) used in Mexican traditional medicine for the treatment of several diseases. METHODS: Extracts were obtained by maceration at room temperature using hexane, dichloromethane and methanol for each plant material. The organic extracts were evaluated ex vivo to determine their relaxant activity on the contractions induced by carbachol (cholinergic receptor agonist, 1 µ mol/L) in isolated rat tracheal rings. RESULTS: A total of 15 extracts were evaluated (three for each species). All test samples showed significant relaxant effect, in a concentration-dependent manner, on the contractions induced by 1 µ mol/L carbachol, with exception of extracts from C. morelosana. Active extracts were less potent than theophylline [phosphodiesterase inhibitor, EC50: (28.79±0.82) µg/mL] that was used as positive control. Concentration-response curves revealed that the extracts with more significant effects were dichloromethanic extracts of T. mexicana [Emax: (103.03±3.32)% and EC50: (159.39±3.72) µg/mL) and C. vitifolium [Emax: (106.58±2.42)% and EC50: (219.54±7.61) µg/mL]. Finally, hexanic and dichloromethanic extracts from A. mexicana were fully effective but less potent than T. mexicana and C. vitifolium. CONCLUSIONS: Less polar extracts obtained from A. mexicana, T. mexicana and C. vitifolium exhibited greater relaxant effect on tracheal rat rings, which allows us to suggest them as sources for the isolation of bioactive molecules with potential therapeutic value in the treatment of asthma.

Experimental gestational diabetes mellitus induces blunted vasoconstriction and functional changes in the rat aorta.

Diabetic conditions increase vascular reactivity to angiotensin II in several studies but there are scarce reports on cardiovascular effects of hypercaloric diet (HD) induced gestational diabetes mellitus (GDM), so the objective of this work was to determine the effects of HD induced GDM on vascular responses. Angiotensin II as well as phenylephrine induced vascular contraction was tested in isolated aorta rings with and without endothelium from rats fed for 7 weeks (4 before and 3 weeks during pregnancy) with standard (SD) or hypercaloric (HD) diet. Also, protein expression of AT1R, AT2R, COX-1, COX-2, NOS-1, and NOS-3 and plasma glucose, insulin, and angiotensin II levels were measured. GDM impaired vasoconstrictor response (P < 0.05 versus SD) in intact (e+) but not in endothelium-free (e-) vessels. Losartan reduced GDM but not SD e- vasoconstriction (P < 0.01 versus SD). AT1R, AT2R, and COX-1 and COX-2 protein expression were significantly increased in GDM vessels (P < 0.05 versus SD). Results suggest an increased participation of endothelium vasodilator mediators, probably prostaglandins, as well as of AT2 vasodilator receptors as a compensatory mechanism for vasoconstrictor changes generated by experimental GDM. Considering the short term of rat pregnancy findings can reflect early stage GDM adaptations.

Antihyperglycemic and sub-chronic antidiabetic actions of morolic and moronic acids, in vitro and in silico inhibition of 11ß-HSD 1.

Morolic (1) and moronic (2) acids are the main constituents of acetonic extract from Phoradendron reichenbachianum (Loranthaceae), a medicinal plant used in Mexico for the treatment of diabetes. The aim of the current study was to establish the sub-acute antidiabetic and antihyperlipidemic effects of compounds 1 and 2 over non insulin-dependent diabetic rat model. Also, to determine the antihyperglycemic action on normoglycemic rats by oral glucose tolerance test. Daily-administered morolic (1) and moronic (2) acids (50 mg/kg) significantly lowered the blood glucose levels at 60% since first day until tenth day after treatment than untreated group (p<0.05). Moreover, analyzed blood samples obtained from diabetic rats indicated that both compounds diminished plasmatic concentration of cholesterol (CHO) and triglycerides (TG), returning them to normal levels (p<0.05). Also, pretreatment with 50 mg/kg of each compound induced significant antihyperglycemic effect after glucose and sucrose loading (2 g/kg) compared with control group (p<0.05). In vitro studies showed that compounds 1 and 2 induced inhibition of 11ß-HSD 1 activity at 10 µM. However, in silico analysis of the pentaclyclic triterpenic acids on 11ß-HSD 1 revealed that all compounds had high docking scores and important interactions with the catalytic site allowing them to inhibit 11ß-HSD 1 enzyme. In conclusion, morolic and moronic acids have shown sustained antidiabetic and antihyperglycemic action possibly mediated by an insulin sensitization with consequent changes of glucose, cholesterol and triglycerides, in part mediated by inhibition of 11ß-HSD 1 as indicated by in vitro and in silico studies.

Dose-dependent antihypertensive determination and toxicological studies of tilianin isolated from Agastache mexicana.

ETHNOPHARMACOLOGICAL RELEVANCE: Agastache mexicana is used in Mexican traditional medicine for the treatment of hypertension, anxiety and related diseases. AIM OF THE STUDY: Current work was developed to establish pharmacological/toxicological parameters of tilianin, a flavone extracted from Agastache mexicana in order to propose it for clinical trials. MATERIALS AND METHODS: Acute and sub-acute toxicology studies in Imprinting Control Region (ICR) mice and median effective dose (ED50) determination in conscious spontaneously hypertensive rats (SHR) were done. RESULTS: A median lethal dose (LD50) of 6624 mg/kg (6201, 7076) in mice and significant antihypertensive effect (ED50=53.51 mg/kg) in SHR were determined. Moreover, sub-acute oral administration of tilianin did not alter body weight, clinical chemistry parameters (alanine amino-transferase, aspartate amino-transferase, total cholesterol, high density lipoprotein, low density lipoprotein, triglycerides, glucose and insulin), and also did not induce any toxic or adverse effects on kidney, heart, liver, and lung functions. CONCLUSIONS: We have shown that tilianin, isolated from Agastache mexicana, was not toxic for rodents. Also, its antihypertensive effect was dose-dependent and ED50 (53.51 mg/kg) calculated was lesser than LD50 determined (6624 mg/kg), which suggest a wide range of pharmacology-toxicology patterns. Results support the hypothesis that tilianin must be investigated and developed for clinical trials as antihypertensive drug.

Antihyperglycemic effect and genotoxicity of Psittacanthus calyculatus extract in streptozotocin-induced diabetic rats / Efecto antihiperglicemico y genotoxico de extractos de Psittacanthus calyculatus en ratas diabeticas inducidas con streptozotocina

Psittacanthus calyculatus (DC.) G. Don (Lorantaceae) is known as “ingerto”. The aerial parts are used in the treatment of diabetes and hypertension. Methanolic extract was tested with streptozotocin-induced diabetic rats. Dose of 200 mg/Kg body weight for acute experiments, as well as 200 and 400 mg/Kg for semi-chronic bioassay were used. In both experiments extract produced significant hypoglycemic activity in streptozotocin-induced rats when compared with diabetic control (p 0.05). To study possible clastogenic effects of methanolic extract a mouse micronucleus test was performed (as part of the genetic toxicology trial). CD-1 white mice were administered with 200 and 400 mg/Kg of methanolic extract of P. calyculatus dissolved in water by intraperitoneal injection. The cytotoxic activity polychromatic erythrocytes/normochromatic erythrocytes (PCE/NCE) and the induction of micronuclei in peripheral blood erythrocytes (MNPCE) was recorded with sampling times of 24, 48 and 72, h after an exposure without killing of mice. The frequency of MNPCE in the circulating blood obtained from the tail of the mouse was statistically not significant compared with its negative control animals (time zero) and the PCE/NCE ratio showed evidences of light cytotoxic activity compared with its negative control animals (time zero). Thus, in this test, the methanolic extract of Psittacanthus calyculatus dissolved in water did not induce chromosomal damage resulting in micronucleus formation in peripheral blood erythrocytes and showed light cytotoxic activity.

En la zona del bajío mexicano la planta Psittacanthus calyculatus (DC.) G. Don (Lorantaceae) es conocida popularmente como “ingerto”. Las partes aéreas de este vegetal se utilizan para tratar enfermedades como la diabetes y la hipertensión. Se realizaron experimentos agudos y semi-crónicos en ratas diabéticas inducidas con estreptozotocina. El efecto hipoglucemiante del extracto metanólico se evaluó a dosis de 200 y 400 mg/Kg de peso. En ambos experimentos, el extracto redujo significativamente (p < 0.05) la glucemia en las ratas diabéticas. Para determinar los posibles efectos clastogénicos del extracto metanólico se administraron por vía intraperitoneal a ratones cepa CD-1 las dosis que mostraron actividad hipoglucemiante disueltas en agua y se llevó a cabo el bioensayo de micronúcleos en sangre periférica de ratón. La actividad citotóxica se determinó mediante el cálculo de la relación entre los eritrocitos policromáticos y los eritrocitos normocromáticos (PCE/NCE). La inducción de micronúcleos en eritrocitos de sangre periférica (MNPCE) fue el indicador de gentotoxicidad los cuales se midieron a las 24, 48 y 72 horas después de la administración del extracto. La frecuencia de micronúcleos en eritrocitos policromáticos no fue estadísticamente significativa con relación al control negativo (al tiempo 0) por lo tanto, el extracto no induce daño cromosómico. Asimismo la relación PCE/NCE mostró que el extracto metanólico fue ligeramente citotóxico a la dosis de 400 mg/Kg y a las 48 h posteriores a la administración.

Vasorelaxant activity of some structurally related triterpenic acids from Phoradendron reichenbachianum (Viscaceae) mainly by NO production: ex vivo and in silico studies.

The aim of the current study was to investigate the vasorelaxant activity of five structurally-related triterpenic acids namely ursolic (1), moronic (2), morolic (3), betulinic (4) and 3,4-seco-olean-18-ene-3,28-dioic (5) acids. The vasorelaxant effect of compounds 1-5 were determined on endothelium-denuded and endothelium-intact rat aortic rings pre-contracted with noradrenaline (0.1 µM). All compounds showed significant relaxant effect on endothelium-intact vessels in a concentration-dependent manner (p<0.05). Ursolic, moronic and betulinic acids were the most potent vasorelaxant agents with 11.7, 16.11 and 58.46 µM, respectively. Since vasorelaxation was blocked by L-NAME, while indomethacin did not inhibit the effect, endothelium-derived nitric oxide seems to be involved in triterpenic 2 and 3 mode of action. Compounds 1-5 were docked with a crystal structure of eNOS. Triterpenes 1-5 showed calculated affinity with eNOS in the C1 and C2 binding pockets, near the catalytic site; Ser248 and Asp480 are the residues that make hydrogen bonds with the triterpene compounds.

Relaxant effects of Artemisia ludoviciana on isolated rat smooth muscle tissues.

ETHNOPHARMACOLOGICAL RELEVANCE: Artemisia ludoviciana spp. mexicana (Willd. Ex.) Spring D.D. Keck (Asteraceae), known as "estafiate" is employed for the treatment of diarrhea, dysentery, parasites, abdominal pain, vomiting, stomach ache, and also as antispasmodic agent. The aim of the present study was to evaluate the relaxant effect of hexanic (HEAl), dichloromethanic (DEAl) and methanolic (MEAl) extracts on isolated trachea, ileum and aorta rat rings, and to establish the tracheo-relaxant mode of action of DEAl. MATERIALS AND METHODS: All extracts were investigated based on their capacity of to inhibit the rat ileum spontaneous contraction, to relax contraction induced by noradrenaline (0.1 µM) on endothelium-intact and endothelium-denuded thoracic aorta rat rings, and also to inhibit contraction provoked by carbachol (1 µM) on rat trachea. RESULTS: Organic extracts had no spasmolytic action on ileum strips compared to positive control (papaverine, p<0.05). On the other hand, all extracts induced a significant concentration- and partial endothelium-dependent vasorelaxant activity. Extracts also showed significant relaxant effect on pre-contracted tracheal tissue in a concentration-dependent manner. In last two experiments, DEAl was the most potent and efficient extract; however, it was less potent than papaverine and theophylline, used as positive controls (p<0.05). In tracheal preparation, DEAl shifted to the right, in a parallel manner, the concentration-response curves induced by carbachol (p<0.05). Also, DEAl induced a significant relaxant effect on the contraction produced by potassium chloride (KCl, 80 mM). Pre-incubation with 1-H-[1,2,4]-oxadiazolo-[4,3a]-quinoxalin-1-one (ODQ, 10 µM), indomethacin (10 µM), N(ω)-nitro-L-arginine methyl ester (L-NAME, 10 µM), glibenclamide (10 µM) and 2-aminopyridine (2-AP, 100 µM) did not modify the DEAl-relaxant curves. CONCLUSIONS: Functional experiments suggest that the most active extract, DEAl, induced its relaxant effect by possible muscarinic receptors antagonism and calcium channel blockade in tracheal rings. On the other hand, significant vasorelaxant activity showed by DEAl is partially endothelium-dependent. Finally, spasmolytic activity induced by the extracts in the rat ileum was not significant, which suggests that the antidiarrheic effect of the plant is related to antimicrobial and antiparasitic properties previously described.

Vasorelaxant effect of flavonoids through calmodulin inhibition: Ex vivo, in vitro, and in silico approaches.

In our search for potential antihypertensive agents, a series of structurally-related flavonoids was screened. Ex vivo and in vitro biological evaluations indicated that compounds 1-7 displayed an important vasorelaxant effect on the endothelium-intact (E(+)) and -denuded (E(-)) aortic rings test. Their in vitro anti-calmodulin (CaM) properties were determined by means of the inhibitory effect on the activation of the calmodulin-sensitive cAMP phosphodiesterase (PDE1) assay. Molecular modeling experiments were also performed in order to explore the probable binding site of 1-7 with CaM, and the results indicated that they could bind to the protein in the same pocket as trifluoperazine (TFP), a well-known CaM inhibitor.

Cochlospermum vitifolium induces vasorelaxant and antihypertensive effects mainly by activation of NO/cGMP signaling pathway.

AIM OF THE STUDY: Cochlospermum vitifolium is a medicinal plant used for the treatment of diabetes, hepatobilary and cardiovascular illnesses. The aim of current study was to determine the in vivo antihypertensive and in vitro functional vasorelaxant mechanism of methanol extract of Cochlospermum vitifolium (MECv) and naringenin (NG). MATERIALS AND METHODS: Test material was assayed on rat isolated aorta rings test with- and without-endothelium to determine their vasorelaxant mechanism. Also, the in vivo antihypertensive effect was evaluated on spontaneously hypertensive rat (SHR) model. In addition, presence of NG into the extract was confirmed by reverse phase high performance liquid chromatography (RP-HPLC) analysis. RESULTS: MECv (120 mg/kg) and NG (50 and 160 mg/kg) showed acute antihypertensive effects on SHR when systolic and diastolic pressure were decreased at 1 h and 24 h after administration, respectively. Vasorelaxant effect of MECv and NG was shifted to the right when endothelium-intact aortic rings were pre-incubated with L-NAME (10 microM) and ODQ (1 microM). Also, NG relaxant curves were displaced to the right in the presence of tetraethylammonium (TEA, 1 mM) and 2-aminopyridine (2-AP, 100 microM) on endothelium-denuded aortic rings. CONCLUSION: Experiments described above showed that MECv play an important role in hypertension regulation through NO synthesis and may be PGI(2) production and potassium channel activation on excessive endothelial dysfunction conditions. Unfortunately, presence of NG into the extract is not significant on bioactivity of the extract; however, this compound could be tested and evaluated as structural scaffold for future drug design for development of antihypertensive agents.

Synthesis, vasorelaxant activity and antihypertensive effect of benzo[d]imidazole derivatives.

A series of 1H-benzo[d]imidazole analogues of Pimobendan, substituted at position 5 with either -CF(3) or -NO(2), were synthesized using a short synthetic route. All the nitro derivatives were potent, and exhibited a concentration- and partial endothelium-dependent vasorelaxant effects, with EC(50)s <5microM. 2-Methoxy-4-[5-nitro-1H-benzo[d]imidazol-2-yl]phenol (compound 13) was the most potent derivative of the series, showing an EC(50) value of 1.81microM and E(max) of 91.7% for ex vivo relaxant response in intact aortic rings, resulting in a 2.5-fold higher activity compared to Pimobendan. The closely related 5-CF(3) analogue (compound 8), was 19 times less potent than 13. The antihypertensive activity of compound 13 was evaluated at doses of 25, 50 and 100mgkg(-1), using spontaneously hypertensive rats (SHR), showing a statistically significant dose-dependent effect.

Vasorelaxant and antihypertensive effects of methanolic extract from roots of Laelia anceps are mediated by calcium-channel antagonism.

RMELanc-induced relaxation in aortic rings precontracted with NE, 5-HT and KCl. It also reduced NE-induced transient contraction in Ca(2+)-free solution and inhibited contraction induced by increasing external calcium. Nevertheless, the vasorelaxant effect of RMELanc was not reduced by ODQ, 1-alprenolol, TEA, glibenclamide, and 2-AP. Oral administration of 100 mg/kg of RMELanc exhibited a significant decrease in systolic and diastolic blood pressures in SHR rats. HPLC analysis allowed us to detect the presence of 2,7-dihydroxy-3,4,9-trimethoxyphenantrene (1), which induced a significant relaxation effect. Therefore, our results suggest that RMELanc induces vasorelaxant and antihypertensive effects by blockade of Ca(2+) channels.

Antihypertensive and vasorelaxant effects of tilianin isolated from Agastache mexicana are mediated by NO/cGMP pathway and potassium channel opening.

Current investigation was undertaken to elucidate the mode of action of tilianin, isolated from Agastache mexicana, as a vasorelaxant agent on in vitro functional rat thoracic aorta test and to investigate the in vivo antihypertensive effect on spontaneously hypertensive rats (SHR). Tilianin (0.002-933 microM) induced significant relaxation in a concentration- and endothelium-dependent and -independent manners in aortic rings pre-contracted with noradrenaline (NA, 0.1 microM), and serotonin (5-HT, 100 microM). Effect was more significant (p < 0.05) in endothelium-intact (+E) aorta rings than when endothelium was removed(E). Pre-treatment with N-nitro-L-arginine methyl ester (L-NAME; 10 microM) or 1-H-[1,2,4]-oxadiazolo-[4,3a]-quinoxalin-1-one (ODQ, 1 microM) produced a significant change of the relaxant response and activity was markedly inhibited, but not by indomethacin (10 microM) or atropine (1 microM). Furthermore, tilianin (130 microM) provoked a significant displacement to the left in the relaxation curve induced by sodium nitroprusside (SNP; 0.32 nM to 0.1 microM). Moreover, tilianin induced significant in vitro NO overproduction (1.49 +/- 0.86 microM of nitrites/g of tissue) in rat aorta compared with vehicle (p < 0.05). In addition, pre-treatment with tetraethylammonium (TEA, 5 mM) and 2-aminopyridine (2-AP, 0.1 microM) shifted to the right the relaxant curve induced by tilianin (p < 0.05). Finally, a single oral administration of tilianin (50 mg/kg) exhibited a significant decrease in systolic and diastolic blood pressures (p < 0.05) in SHR model. Results indicate that tilianin mediates relaxation mainly by an endothelium-dependent manner,probably due to NO release, and also through an endothelium-independent pathway by opening K+ channels, both causing the antihypertensive effect.