Vasorelaxant Activity of (2S)-Sakuranetin and Other Flavonoids Isolated from the Green Propolis of the Caatinga Mimosa tenuiflora

Some in vitro and in vivo evidence is consistent with the cardiovascular beneficial activity of propolis. As the single actors responsible for this effect have never been identified, an in-depth investigation of flavonoids isolated from the green propolis of the Caatinga Mimosa tenuiflora was performed and their mechanism of action was described. A comprehensive electrophysiology, functional, and molecular docking approach was applied. Most flavanones and flavones were effective CaV1.2 channel blockers with a potency order of (2S)-sakuranetin > eriodictyol-7,3'-methyl ether > quercetin 3-methyl ether > 5,4'-dihydroxy-6,7-dimethoxyflavanone > santin > axillarin > penduletin > kumatakenin, ermanin and viscosine being weak or modest stimulators. Except for eriodictyol 5-O-methyl ether, all the flavonoids were also effective spasmolytic agents of vascular rings, kumatakenin and viscosine also showing an endothelium-dependent activity. (2S)-Sakuranetin also stimulated KCa1.1 channels both in single myocytes and vascular rings. In silico analysis provided interesting insights into the mode of action of (2S)-sakuranetin within both CaV1.2 and KCa1.1 channels. The green propolis of the Caatinga Mimosa tenuiflora is a valuable source of multi-target vasoactive flavonoids: this evidence reinforces its nutraceutical value in the cardiovascular disease prevention arena.

The new quinazoline derivative (N2-methyl-N4-[(thiophen-2-yl)methyl]quinazoline-2,4-diamine) vasodilates isolated mesenteric arteries through endothelium-independent mechanisms and has acute hypotensive effects in Wistar rats

During the screening of new N2,N4-disubstituted quinazoline 2,4-diamines as phosphodiesterase-5 inhibitors and pulmonary artery vasodilators, one N2-methyl-N4-[(thiophen-2-yl)methyl]quinazoline-2,4-diamine (compound 8) presented a greater selectivity for systemic than pulmonary vasculature. The present study aimed to characterize its vasorelaxant and hypotensive effects in Wistar rats. Vasorelaxant effects of compound 8 and underlying mechanisms were evaluated on isolated mesenteric arteries. Acute hypotensive effect was evaluated in anesthetized rats. Additionally, cell viability and cytochrome P450 (CYP) activities were studied in rat isolated hepatocytes. Nifedipine was used as a comparator. Compound 8 induced a strong vasorelaxant effect, similar to nifedipine. This was unaffected by endothelium removal but was decreased by inhibitors of guanylate cyclase (ODQ) and KCa channel (iberiotoxin). Compound 8 enhanced sodium nitroprusside-induced relaxation, but inhibited vasoconstriction evoked by α1-adrenergic receptor activation and extracellular Ca2+ influx via receptor-operated Ca2+ channels. Acute intravenous infusion of compound 8 (0.05 and 0.1 mg/kg) produced hypotension. It showed similar potency to nifedipine for lowering diastolic and mean arterial blood pressure, but less so for the effect on systolic blood pressure. Compound 8 had no effect on hepatocyte viability and CYP activities except at high concentration (10 μM) at which a weak inhibitory effect on CYP1A and 3A was observed. In conclusion, this study identified a N2-methyl-N4-[(thiophen-2-yl)methyl]quinazoline-2,4-diamine with a potent vasodilator effect on resistance vessels, leading to an acute hypotensive effect and a low risk of liver toxicity or drug-drug interactions. These vascular effects were mediated mainly through sGC/cGMP pathway, opening of KCa channels, and inhibition of calcium entry.

Vascular relaxing effect of Hydrocotyle umbellata L. is mediated by blocking of l-type Ca2+ channels

ETHNOPHARMACOLOGICAL RELEVANCE

Hydrocotyle umbellata L. is a medicinal herb for the treatment of some health problems including hypertension, according to traditional medicine. Even so, its vascular effects and the pharmacological action mechanisms have not been analyzed.

AIM OF THE STUDY

This experiment aimed to analyze the effects of hydroalcoholic extract of Hydrocotyle umbellata L. (HEHU) on isolated vessels and verify the interaction of hibalactone (chemical marker) against Ca_v1.2 channels using molecular docking.

MATERIALS AND METHODS

Vascular reactivity experiments were performed using rat aortas with (E⁺) or without endothelium (E^-) in an isolated organ bath. Computational molecular docking approaches were used to show the direct effect on L-type Ca²⁺ Channels.

RESULTS

HEHU (0-560 μg/mL) induced relaxation of the pre-contracted arteries in a concentration-dependent manner. The maximum effect was higher in E⁺ (76.8 ± 4.1%) as compared to E^- (47.3 ± 5.5%). Pre-treatment of E⁺ arteries with L-NAME or ODQ reduced the relaxation to similar level of E^- arteries. The treatment of arteries with MDL-12,330 A, diclofenac, propranolol and atropine did not change the relaxation induced by HEHU. The contraction caused by internal Ca²⁺ release induced by caffeine was reduced after HEHU treatment. Moreover, the HEHU also impaired the contraction induced by Ca²⁺ influx stimulated with phenylephrine or high KCl. The docking study demonstrated the effectiveness of hibalactone in blocking the Ca_v1.2 channel.

CONCLUSIONS

These findings show that HEHU induces vascular relaxation which is potentiated (but not dependent) by endothelial cells. Blocking of Ca²⁺ influx seems to be the main mechanism for the vascular effects of HEHU.

The mechanisms of calcium mobilization by procyanidins, flavonols and flavonoids from Cecropia glaziovii Sneth in pulmonary endothelial cell cultures endorse its popular use as vasodilator phytomedicine

The hypotensive and antihypertensive activities of the aqueous extract (AE) and butanolic fraction (ButF) isolated from Cecropia glaziovii Sneth have been demonstrated in previous studies in animal models. This study aimed to evaluate the molecular mechanism of action responsible for the vasodilatory effect of procyanidins, flavanols, and flavonoids found in C. glaziovii in endothelial cell culture. For this purpose, we analyzed the effect of procyanidin B2 and B3 compounds, catechin, epicatechin, orientin, isoorientin, and isovitexin in the mobilization of Ca2+ in rat endothelial cell cultures. Parallel associations with different antagonists were examined by considering the following in vivo hypotensive mechanisms: blockage of L-type calcium channels, action on β-2 adrenergic receptors, and vasodilation via the nitric oxide pathway. All measurements of calcium mobilization were carried out by using the fluorescence measurement methodology in a Flexstation M3 spectrophotometer. The results indicate that some of the compounds have mixed actions, acting through different calcium mobilization pathways. The mobilization induced by such compounds significantly decreased when they were incubated with their corresponding antagonists. Taken together, our data suggest that the beneficial effects seen with the popular use of Cecropia glaziovii Sneth in pathological conditions, such as systemic arterial hypertension, seem to be related to the plant's hypotensive effect, very probably promoted by the actions of flavonols, flavonoids, and procyanidins, by different pathways of calcium mobilization.

Activation of cholinergic pathway induced vasodilation in rat aorta using aqueous and methanolic leaf extracts of Gynura procumbens

Gynura procumbens (GP) is a herbal medicinal plant of South-East Asian origin, popularly recognised as 'Sambung nyawa'. The plant has been used traditionally to treat various diseases including hypertension. The anti-hypertensive activity of this plant has also been scientifically proven both in vivo and in vitro yet the investigation on its mechanisms of actions remains limited. Our previous study has demonstrated the vasodilatory action of both aqueous and methanol GP extracts possibly via activation of the cholinergic pathway and that kaempferol 3-O-rutinoside is the active ingredient responsible in mediating this effect. Hence, in this study we further confirm the involvement of the cholinergic pathway by using several pharmacological interventions, focusing on the downstream mechanism of this pathway. Our results showed that in the presence of endothelium, GP extracts induced vasodilation via activation of the muscarinic M3 receptors. However, in the absence of endothelium, GP mediated vasodilation possibly via stimulation of other muscarinic receptors and/or involvement of nicotinic receptors, a speculation that needs further investigations. GP-induced relaxation was markedly inhibited by nitric oxide (NO) blocker, L-NAME, suggesting that GP elicited ACh endothelium-dependent relaxation by producing NO in rat aortic rings. In conclusion, these data demonstrate that the vasodilatory effect of GP extracts appears to be mediated via cholinergic pathway.

Endothelium-independent vasorelaxant effect of Asphodelus tenuifolius Cav. via inhibition of myosin light chain kinase activity in the porcine coronary artery

ETHNOPHARMACOLOGICAL RELEVANCE

Asphodelus tenuifolius Cav. (Asphodelaceae), a wild, terrestrial, annual stemless herb, is widely used in traditional medicine for the treatment of hypertension, diabetes, atherosclerosis and circulatory problems. A previous research study from our laboratory revealed that A. tenuifolius has beneficial effects in reducing blood pressure and improves aortic endothelial dysfunction in chronically glucose fed rats. Despite the fact that A. tenuifolius reduces blood pressure and improves endothelial function in vivo, there are no detailed studies about its possible mechanism of action.

AIM OF THE STUDY

This study was designed to provide pharmacological basis and mechanism of action for the traditional use of A. tenuifolius in hypertension and circulatory problems. We explored the vasorelaxant effect of A. tenuifolius and its underlying vasorelaxation mechanism in porcine coronary artery rings.

MATERIALS AND METHODS

Aqueous methanolic crude extract of A. tenuifolius was prepared by maceration process and then activity guided fractionation was carried out by using different polarity based solvents. Phytochemical studies were carried out using LC-DAD-MS. Segments of porcine distal coronary artery were set up in a wire myograph for isometric force measurements. Extract/fractions of A. tenuifolius seeds were tested for vasodilator activity by measurement of changes in tone after pre-contraction with the thromboxane mimetic U46619 in the presence or absence of inhibitors of intracellular signaling cascades.

RESULTS

Crude extract/fractions of A. tenuifolius produced dose dependent endothelium independent vasorelaxant response in coronary rings, whereas, the butanol fraction of A. tenuifolius (BS-AT) produced the largest relaxation response with 100% relaxation at 1 mg/ml, therefore the mechanism of relaxation of this fraction was determined. The relaxation to BS-AT was unaffected by removal of the endothelium, pre-contraction with KCl, or the presence of the non-selective potassium channel blocker tetraethylammonium, indicating that the relaxation was endothelium-independent, and does not involve activation of potassium channels. BS-AT (1 mg/ml) inhibited the contractile response to calcium,the L-type calcium channel activator BAY K8664,and ionomycin, indicating that it inhibits calcium-induced contractions. The relaxation response to BS-AT was attenuated in the absence of extracellular calcium. However, relaxations to BS-AT were also reduced after deletion of calcium from intracellular stores with cyclopiazonic acid. Incubation with 1 mg/ml BS-AT also inhibited phosphorylation of myosin light chains in homogenates of coronary artery.

CONCLUSION

The butanol extract of Asphodelus tenuifolius produces a large endothelium-independent relaxation of the porcine coronary artery through inhibition of calcium-induced contractions. The effect appears to be downstream of calcium influx, possibly through inhibition of myosin light chain kinase. This study supports previous studies demonstrating that A. tenuifolius reduces blood pressure. Future studies will aim to determine the active compounds underlying this response.

Mammalian Arginase Inhibitory Activity of Methanolic Extracts and Isolated Compounds from Cyperus Species

Polyphenolic enriched extracts from two species of Cyperus, Cyperus glomeratus and Cyperus thunbergii, possess mammalian arginase inhibitory capacities, with the percentage inhibition ranging from 80% to 95% at 100 µg/mL and 40% to 64% at 10 µg/mL. Phytochemical investigation of these species led to the isolation and identification of two new natural stilbene oligomers named thunbergin A-B (1–2), together with three other stilbenes, trans-resveratrol (3), trans-scirpusin A (4), trans-cyperusphenol A (6), and two flavonoids, aureusidin (5) and luteolin (7), which were isolated for the first time from C.thunbergii and C. glomeratus. Structures were established on the basis of the spectroscopic data from MS and NMR experiments. The arginase inhibitory activity of compounds 1–7 was evaluated through an in vitro arginase inhibitory assay using purified liver bovine arginase. As a result, five compounds (1, 4–7) showed significant inhibition of arginase, with IC₅₀ values between 17.6 and 60.6 µM, in the range of those of the natural arginase inhibitor piceatannol (12.6 µM). In addition, methanolic extract from Cyperus thunbergii exhibited an endothelium and NO-dependent vasorelaxant effect on thoracic aortic rings from rats and improved endothelial dysfunction in an adjuvant-induced arthritis rat model.

Ethnopharmacological basis for folkloric claims of Anagallis arvensis Linn. (Scarlet Pimpernel) as prokinetic, spasmolytic and hypotensive in province of Punjab, Pakistan

ETHNOPHARMACOLOGICAL RELEVANCE

The conventional naturopaths of Punjab Province (Pakistan) have trivial usage of Anagallis arvensis Linn.(Primulaceae) for cure of diarrhea, constipation, asthma as well as hypertension.

AIM

Present research was focused to discover comprehensive mechanism of spasmogenic, spasmolytic, bronchorelaxant and hypotensive folkloric usage of Anagallis arvensis Linn..

METHODOLOGY

The crude extract of Anagallis arvensis Linn. (Aa.Cr) & its (aqueous & organic) portions tested in-vitro on isolated jejunum, ileum, trachea, aorta, paired atria preparations as well as in-vivo in mice & normotensive anaesthetized rats. The responses have been noted by transducers (isotonic & isometric) coupled to Power Lab.

RESULT

Anagallis arvensis Linn. (Aa.Cr; crude aqueous-alcoholic extract) produced contractile action at low concentrations but relaxant action was observed by increasing concentrations on spontaneous contractions of isolated jejunum of rabbit. But, pre-treatment of tissue with atropine prior extract caused suppression of contractile effect indicating presence of cholinergic muscarinic response of Aa.Cr. It also triggered relaxation of high Potassium -stimulated contractions of jejunum with subsequent non-parallel right move in Ca++ CRCs. Moreover, Aa.Cr relaxed carbachol - & high Potassium - stimulated contractions in trachea of rabbit but observed relaxant effect was powerful against CCh (1 μM)- stimulated contractions with rightside parallel move of CCh-curves succeeded by non-parallel move, like Dicyclomine, having dual activities. The Aa.Cr also showed relaxant result on Phenylephrine and High Potassium -prompted contractions in endothelium intact aorta. The fractionation revealed segregations of contractile & relaxant effects in relevant aqueous & organic portions. The Intravenous administration of Aa.Cr to ketamine-diazepam anaesthetized normo-tensive albino rats resulted in decreased MABP, SBP & DBP. The Aa.Cr applied negative (-) inotropic & chronotropic action on paired atria. The Aa.Cr also exhibited anti-diarrheal action in mice against castor oil prompted diarrhea and also mitigated distance covered by charcoal meal in gastrointestinal tract in a manner comparable with loperamide.

CONCLUSION

These results revealed presence of CCB and selective muscarinic agonist activity in Aa.Cr, hence validating folkloric practice of Anagallis arvensis Linn. in diarrhea, constipation, asthma & hypertension.

Antihypertensive and vasorelaxant mode of action of the ethanol-soluble extract from Tagetes lucida Cav. aerial parts and its main bioactive metabolites

ETHNOPHARMACOLOGICAL RELEVANCE

Tagetes lucida Cav. commonly known as "yauhtli" or "pericón" is used in Mexican traditional medicine for the treatment of anxiety, depressant diseases, pain, hypertension, among others.

AIM

To evaluate the antihypertensive and vasorelaxant modes of action of a crude ethanolic extract from T. lucida aerial parts and to isolate the bioactive compounds.

MATERIALS AND METHODS

Ethanolic extract was tested in an in vivo assay in SHR rats by intragastric administration at 10 and 100 mg/kg dosages, to measure and to compare hemodynamic parameters like diastolic and systolic blood pressure and heart rate. Also, extract (3.03-1000 μg/ml), fractions (3.03-1000 μg/ml) and pure isolated compounds (1.75-550 μM) were evaluated on isolated aortic rings contracted with noradrenaline (0.1 μM) to determine their vasorelaxant effect and extract-mode of action.

RESULTS

Ethanolic extract of T. lucida lowered systolic and diastolic blood pressure on SHR rats without heart rate modification (P > 0.05). Moreover, the extract showed concentration-dependent relaxant effect in a partially endothelium-dependent manner (P < 0.05), through NO/cGMP system activation and calcium channel blockade. 6,7,8-trimethoxycoumarin (1), 6,7-dimethoxycoumarin (2), and 7-methoxycoumarin (3) from T. lucida are the main bioactive compounds of the extract and showed significant vasorelaxant activity.

CONCLUSIONS

Results provide evidence and endorsed the antihypertensive properties attributed to T. lucida in traditional medicine, which is produced by vasorelaxant effect mainly through multitarget NO/cGMP system activation and calcium channel blockade. Coumarin derivatives 1, 2 and 3 are the responsible of the vasorelaxant activity.

Diphlorethohydroxycarmalol Isolated from Ishige okamurae Exerts Vasodilatory Effects via Calcium Signaling and PI3K/Akt/eNOS Pathway

Nitric oxide (NO) is released by endothelial cells in the blood vessel wall to enhance vasodilation. Marine polyphenols are known to have protective effects against vascular dysfunction and hypertension. The present study is the first to investigate how diphlorethohydroxycarmalol (DPHC) isolated from Ishige okamurae affects calcium levels, resulting in enhanced vasodilation. We examined calcium modulation with the well-known receptors, acetylcholine receptor (AchR) and vascular endothelial growth factor 2 (VEGFR2), which are related to NO formation, and further confirmed the vasodilatory effect of DPHC. We confirmed that DPHC stimulated NO production by increasing calcium levels and endothelial nitric oxide synthase (eNOS) expression. DPHC affected AchR and VEGFR2 expression, thereby influencing transient calcium intake. Specific antagonists, atropine and SU5416, were used to verify our findings. Furthermore, based on the results of in vivo experiments, we treated Tg(flk:EGFP) transgenic zebrafish with DPHC to confirm its vasodilatory effect. In conclusion, the present study showed that DPHC modulated calcium transit through AchR and VEGFR2, increasing endothelial-dependent NO production. Thus, DPHC, a natural marine component, can efficiently ameliorate cardiovascular diseases by improving vascular function.

Chuanxiongdiolides R4 and R5, phthalide dimers with a complex polycyclic skeleton from the aerial parts of Ligusticum chuanxiong and their vasodilator activity

Chuanxiongdiolides R4-R6 (1-3), three novel phthalide dimers featuring two classes of unreported monomeric units (ligustilide/senkyunolide A and ligustilide/neocnidilide) with an unprecedented linkage style (3a,7'/7a,7'a), were isolated from the aerial parts of Ligusticum chuanxiong, together with three pairs of enantiomeric phthalide dimers [(-)/(+)-4a/4b, 5a/5b, and 6a/6b]. The bioassays revealed that compounds 1, 3, 4, 5, and 6 showed significant vasodilation effects, and the mechanism may be attributed to Cav1.2 activation blockade. Based on the established compounds library, the structure activity relationship of the phthalides was proposed. Our findings afford possible leads for developing new vasodilator against cardiovascular and cerebrovascular diseases such as hypertension and ischemic stroke.

Vasorelaxant and Antihypertensive Effects of Mentha pulegium L. in Rats: An In vitro and In vivo Approach

Aims The aim of the study was to investigate the effect of aqueous aerial part extract of Mentha pulegium L. (Pennyrile) (MPAE) on arterial pressure parameters in rats.

BACKGROUND

Mentha pulegium is a medicinal plant used to treat hypertension in the Moroccon population.

METHODS

In the current study, MPAE was prepared and its antihypertensive activity was pharmacologically investigated. L-NAME-hypertensive and normotensive rats received MPAE (180 and 300 mg/kg) orally for six hours for acute experiment and during seven days for the sub-chronic treatment. Thereafter, systolic, diastolic, mean arterial blood pressure and heart rate were evaluated. In the in vitro experiment, isolated denuded and intact thoracic aortic rings were suspended in a tissue bath system and the tension changes were recorded.

RESULTS

A fall in blood pressure was observed in L-NAME-induced hypertensive treated with MPAE. The extract also produced a dose-dependent relaxation of aorta pre-contracted with NE and KCl. The study showed that the vasorelaxant ability of MPAE seems to be exerted through the blockage of extracellular Ca2+ entry.

CONCLUSION

The results demonstrate that the extract of pennyrile exhibits antihypertensive activity. In addition, the effect may be, at least in part, due to the dilation of blood vessels via blockage of Ca2+ channels.

Study on vascular mechanisms underlying the hypotensive effect of Sorghum halepense (L.) Pers

Sorghum halepense L (Poaceae), ordinarily it is known as Johnson grass and locally as baru. This study was designed to find the vascular mechanisms underlying the hypotensive activity of S. halepense. In this study, effect of S. halepense seed extract/fractions on various blood pressure parameters were evaluated in normal and fructose induced hypertensive rats by invasive technique. Possible underlying hypotensive mechanism of active fraction was determined by using various pharmacological inhibitors. S. halepense extract/fractions vasorelaxant effect were also evaluated on rat aorta rings in organ bath and various intracellular signaling pathway inhibitors were used for determination of underlying mechanisms. S. halepense extract/fractions produced blood pressure lowering effect with most significant effect by its aqueous soluble fraction at dose of 10mg/kg. This effect was attenuated by pretreatment of atropine. Aqueous soluble fraction produced endothelium dependent vasorelaxation in rat aortic rings that was inhibited by pretreatment of atropine after phenylephrine induced contraction. The vasorelaxant effect of aqueous soluble fraction was attenuated by potassium channel blockers and also produced inhibitory effect on calcium entry through calcium channels. It also suppressed phenylephrine induced contraction like verapamil. By HPLC analysis found vanillic acid and naringinin in it. In conclusion, aqueous soluble fraction of S.halepense possess phytoconstituents which may be responsible for hypotensive and vasorelaxant effect of Sorghum halepense.

Vascular activity of infusion and fractions of Cymbopogon citratus (DC) Stapf. in human arteries

ETHNOPHARMACOLOGICAL RELEVANCE

Cymbopogon citratus (DC.) Stapf has been traditionally used mainly for inflammatory diseases and hypertension. However, the mechanisms underlying its vascular activity remain to be fully characterized and the fractions responsible for its cardiovascular activity are still unknown.

AIM OF THE STUDY

In this study, we aimed to assess the vascular activity of Cymbopogon citratus in human arteries and to study the role of cyclooxygenase in its vasorelaxant effects.

MATERIALS AND METHODS

Vascular effects of leaves infusion and three fractions (phenolic acids, flavonoids and tannins) were studied using distal segments of human internal thoracic arteries harvested from patients undergoing coronary revascularization, which were mounted as rings in tissue organ baths and maintained at 37 °C in Krebs Henseleit buffer. The effect on basal vascular tone, the effect on the noradrenaline-induced contraction and the vasorelaxant effects were assessed. The role of cyclooxygenase was evaluated with indomethacin.

RESULTS

Our results showed a mild effect on the basal vessel tone of the infusion. A significant inhibition on the adrenergic-mediated vasoconstriction was observed for the infusion (0.0002 mg/mL) and the flavonoid fraction (0.2 mg/mL), despite a potentiation was observed in some conditions. A vasorelaxant effect was observed for both the infusion (6.46% of maximal relaxation) and the tannin fraction (26.91% of maximal relaxation, P < 0.05 vs. infusion). Incubation with indomethacin (10 μM) elicited a decrease in the vasorelaxation to the infusion (P < 0.05).

CONCLUSIONS

These results suggest that cyclooxygenase may be involved in the vasorelaxation to the infusion of Cymbopogon citratus and that tannins are the compound fraction mainly responsible for this vasorelaxation.

The Possible Role of the Nitroso-Sulfide Signaling Pathway in the Vasomotoric Effect of Garlic Juice

The beneficial cardiovascular effects of garlic have been reported in numerous studies. The major bioactive properties of garlic are related to organic sulfides. This study aimed to investigate whether garlic juice works exclusively due to its sulfur compounds or rather via the formation of new products of the nitroso-sulfide signaling pathway. Changes in isometric tension were measured on the precontracted aortic rings of adult normotensive Wistar rats. We evaluated NO-donor (S-nitrosoglutathione, GSNO)-induced vasorelaxation and compare it with effects of hydrogen sulfide (H₂S)/GSNO and garlic/GSNO. Incubation with garlic juice increased the maximal GSNO-induced relaxation and markedly changed the character of the relaxant response. Although incubation with an H₂S donor enhanced the maximal vasorelaxant response of GSNO, neither the absolute nor the relative relaxation changed over time. The mixture of GSNO with an H₂S donor evoked a response similar to GSNO-induced relaxation after incubation with garlic juice. This relaxation of the H₂S and GSNO mixture was soluble guanylyl cyclase (sGC) dependent, partially reduced by HNO scavenger and it was adenosine triphosphate-sensitive potassium channels (K_ATP) independent. In this study, we demonstrate for the first time the suggestion that H₂S itself is probably not the crucial bioactive compound of garlic juice but rather potentiates the production of new signaling molecules during the GSNO-H₂S interaction.

Centaurium Erythraea Extracts Exert Vascular Effects through Endothelium- and Fibroblast-dependent Pathways

Centaurium erythraea is a plant used in traditional medicine for several cardiovascular disorders, namely hypertension, but there is no scientific evidence able to provide a molecular basis for its claimed antihypertensive effects. After a preliminary screen of extracts obtained from sequential extraction of C. erythraea aerial parts, effects of the methanolic fraction (MFCE) on changes in perfusion pressure of isolated rat mesenteric vascular bed (MVB) and in rat cardiac fibroblasts proliferation were investigated, gathering information on the mechanisms involved in endothelium-dependent effects and their dependence on a pro-proliferative stimulus. The HPLC-DAD determination of the phenolics content of MFCE revealed the presence of 22 phenolic compounds. MFCE reduced (63.3 ± 3.9%; n = 4) perfusion pressure in MVB and almost completely abrogated the Ang II-induced increase in cardiac fibroblasts proliferation. Reduction of the perfusion pressure caused by MFCE was endothelium-dependent and occurred in parallel with an increase in NO release. These effects were inhibited by muscarinic receptor antagonists, by L-NAME (a NO synthase inhibitor), and by ODQ (a soluble guanylate cyclase inhibitor). Experiments revealed that effects required the involvement of K⁺ channels, being inhibited by tetraethylamonium (TEA; a Ca²⁺ activated K⁺ channels inhibitor) and by glibenclamide (an ATP-sensitive K⁺ channels inhibitor). In conclusion, extracts from C. erythraea, particularly the compounds present in the MFCE, induce endothelium-dependent vasodilation and prevent fibroblast proliferation induced by angiotensin II, which can account for the claimed antihypertensive effects of C. erythraea in traditional medicine.

Cryptostrobin and catechin isolated from Eugenia mattosii D. Legrand leaves induce endothelium-dependent and independent relaxation in spontaneously hypertensive rat aorta

BACKGROUND

Considering the therapeutic potential of phenolic compounds, the purpose of the present study was to investigate the mechanisms involved in the relaxation induced by cryptostrobin and catechin, isolated from Eugenia mattosii D. Legrand leaves, in the aorta of spontaneously hypertensive rats (SHR).

METHODS

The thoracic aorta was isolated from SHR and kept in the organ bath system by recording contractile or relaxant responses.

RESULTS

The addition of cumulative concentrations of cryptostrobin and catechin induced endothelium-dependent and-independent relaxation in aorta rings from SHR, as well as both compounds were effective in reducing phenylephrine-induced contraction. Pretreatment of aortic rings with Nω-nitro-l-arginine methylester (L-NAME, an inhibitor of nitric oxide synthase) or 1H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, an inhibitor of soluble guanylate cyclase), resulted in a significant change of relaxant effect induced by catechin, and a slight influence on cryptostrobin-induced relaxation. Muscarinic receptor and potassium channels are involved in catechin-induced relaxation as assessed using atropine (a muscarinic receptor antagonist), tetraethylammonium (a non-selective K+ channel blocker) and glibenclamide (an ATP-sensitive K+ channel blocker). Conversely, cryptostrobin, but not catechin, blunted the contraction induced by the addition of phenylephrine in a calcium-free solution. Besides that, cryptostrobin attenuated the contraction of rat aorta rings induced by internal Ca2+ release and external Ca2+ influx.

CONCLUSIONS

These findings indicated that cryptostrobin and catechin alter vascular smooth muscle reactivity, and this effect may be involved, at least in part, by enhancing the endothelium NO/cGMP pathway and potassium channels activation. In addition, cryptostrobin reduced the phenylephrine, KCl and CaCl2-induced contractions in a calcium-free solution.

8-methoxysmyrindiol from Gerbera piloselloides (L.) Cass. and its vasodilation effects on isolated rat mesenteric arteries

Gerbera piloselloides (L.) Cass. (Compositae) possesses various biological effects. It is used as an oriental remedy for relieving cough and resolving phlegm. The present study is to investigate the vasodilation effects of Gerbera piloselloides on isolated rat mesenteric arteries (MAs) and the potential mechanism. Different organic extracts of Gerbera piloselloides were tested, and an HPLC-UV-FD-based analytical method was established to identify the active constituents. The principal components, namely, 8-MOP (8-methoxypsoralan) and 8-MSD (8-methoxysmyrindiol), were found to be predominant in the extracts of petroleum ether and dichloroform, which showed stronger vasodilation activities. 8-MSD was isolated from Gerbera piloselloides by silica gel column chromatography coupled with a Waters 2545 high throughput autopurification system, and its vasodilation effects were explored by an assay of tension on rat MA rings. The results suggest that 8-MSD induces vascular relaxation in rat MAs via an endothelium-dependent mechanism involving the Kir channel, which enables Ca²⁺ entry in the cell and activates production of NO. The present research indicates that 8-MSD may be therapeutically useful as an anti-hypertension agent and to potentially treat cardiovascular and gastrointestinal diseases.

Live Imaging and Analysis of Vasoactive Properties of Drugs Using an in-ovo Chicken Embryo Model: Replacing and Reducing Animal Testing

Vasodilation occurs as a result of the relaxation of the smooth muscle cells present in the walls of blood vessels. Various suitable models are available for the analysis of the vasoactive properties of drugs with therapeutic applications. But all these models have limitations, such as ethical issues and high cost. The purpose of this study is to develop an alternative model for studying the vasoactive properties of drugs using an in-ovo chicken embryo model. In the preliminary experiment, we used a well-known vasoconstrictor (adrenaline) and a vasodilator (spermine NoNoate) in the chick embryo area vasculosa and evaluated their concentration-response curve. Adrenaline (10 µM) and spermine NoNoate (10 µM) were administered in different arteries and veins and different positions of the right vitelline artery of the chick embryo. Results showed the middle of the vessel bed of the right vitelline artery having the best vasoactive effect compared to others. Finally, anti-hypertensive drugs, calcium channel blockers, and NOS agonists were administered in the chick embryo area vasculosa to validate the model. Results demonstrate that the chick embryo area vasculosa can be an alternative, robust, and unique in-ovo model for screening of anti-hypertensive drugs in real time.

Development and validation of bioanalytical liquid chromatography-tandem mass spectrometry method for the estimation of pentoxifylline in human plasma: Application for a comparative pharmacokinetic study

A method for bioanalysis of pentoxifylline in human plasma was developed using liquid chromatography-tandem mass spectrometry, which is simple, specific, and sensitive. Pentoxifylline D5 was used as the internal standard. Employing only 100 µl of human plasma, processing was done with solid-phase extraction technique. The analyte and the internal standard were separated from endogenous components on Ace phenyl column using a mixture of 5 mM ammonium acetate buffer and high performance liquid chromatography grade acetonitrile (60:40, v/v) as mobile phase at a flow rate of 1 ml/min. The linearity of the method was in the range of 3-1200 ng/ml with r² > 0.99. Positive ion MRM mode was used for the detection of the analyte and the internal standard. The method was validated as per the US Food and Drug Administration guidelines and the results were within the acceptance limits. The proposed method was applied for comparative pharmacokinetic study of pentoxifylline after oral administration of 400 and 600 mg tablets to South Indian male subjects under fed conditions.

Vasorelaxant and Antihypertensive Effects That Are Dependent on the Endothelial NO System Exhibited by Rice Bran-Derived Tripeptide

We recently identified a novel, potent antihypertensive peptide, Leu-Arg-Ala (LRA; minimum effective dose = 0.25 mg/kg), from rice bran protein. In this study, we found that LRA potently relaxed mesenteric arteries isolated from spontaneously hypertensive rats (SHRs) (EC₅₀ = 0.1 μM). In contrast, the vasorelaxant activity of each amino acid that constitutes the LRA tripeptide was remarkably attenuated. The LRA-induced vasorelaxant activity was inhibited by N(G)-nitro-l-arginine methyl ester (L-NAME; NO synthase [NOS] inhibitor) but not by an antagonist of bradykinin B2 and Mas receptors or by a phosphoinositide 3-kinase inhibitor. The antihypertensive effect induced after the oral administration of LRA was inhibited by L-NAME. LRA also induced the phosphorylation of endothelial NOS in human umbilical vein endothelial cells. Taken together, LRA may exhibit antihypertensive effects via NO-mediated vasorelaxation. LRA is the first example of a NO-dependent vasorelaxant peptide identified from rice bran protein.

Tambulin is a major active compound of a methanolic extract of fruits of Zanthoxylum armatum DC causing endothelium-independent relaxations in porcine coronary artery rings via the cyclic AMP and cyclic GMP relaxing pathways

BACKGROUND

Zanthoxylum armatum DC (Z. armatum), belonging to Rutaceae family, has been traditionally used for the treatment of various diseases such as hypertension, abdominal pain, headache, fever, high altitude sickness, diarrhea, dysentery, and as a tonic, condiment, and an anthelmintic treatment.

HYPOTHESIS

The present study aims to evaluate the vasorelaxant effect of a methanolic extract of the fruits of Z. armatum, isolate the active components and characterize the underlying mechanism.

STUDY DESIGN

A methanolic extract of fruits of Z. armatum was prepared and its vasorelaxant effect was studied using porcine coronary artery rings. Thereafter, the methanolic extract was analyzed, and a major compound was isolated and its structure elucidated (tambulin). Different pharmacological tools were used to characterize the vasorelaxant effect of tambulin.

RESULTS

The methanolic extract and the isolated tambulin caused similar endothelium-independent relaxations of porcine coronary artery rings with and without endothelium indicating a direct relaxing effect at the vascular smooth muscle. Tambulin did not affect the relaxation curves to the endothelium-dependent vasodilators, bradykinin and the calcium ionophore A23187 in rings with endothelium. Tambulin (1 µM) slightly but significantly shifted leftwards the concentration-relaxation curve to the endothelium-independent vasodilators, sodium nitroprusside (SNP), forskolin (FC) and isoproterenol but not those to soluble guanylyl cyclase activators (YC-1 and BAY 41-2272) and K⁺ channel openers (levcromakalim and 1-EBIO). Pretreatment with tambulin inhibited, in a concentration-dependent manner, contractions to KCl, serotonin (5-HT), CaCl₂ and U46619 in coronary artery rings without endothelium. Both the protein kinase A (H-89, 10 µM) and the protein kinase G (Rp-8-br-cyclic GMPS, 30 µM) inhibitors significantly reduced relaxations to tambulin in coronary artery rings without endothelium.

CONCLUSION

The present findings indicate that tambulin isolated from Z. armatum (fruits) is a major active principle inducing vasorelaxation through a direct effect at the vascular smooth muscle and involving both the cyclic AMP and/or cyclic GMP relaxing pathways.

Vascular mechanisms underlying the hypotensive effect of Rumex acetosa

CONTEXT

Rumex acetosa L. (Polygonaceae) is well known in traditional medicine for its therapeutic efficacy as an antihypertensive.

OBJECTIVE

The study investigates antihypertensive potential of crude methanol extract (Ra.Cr) and fractions of Rumex acetosa in normotensive and hypertensive rat models and probes the underlying vascular mechanisms.

MATERIALS AND METHODS

Ra.Cr and its fractions were tested in vivo on normotensive and hypertensive Sprague-Dawley rats under anaesthesia for blood pressure lowering effect. In vitro experiments on rat and Oryctolagus cuniculus rabbit aortae were employed to probe the underlying vasorelaxant mechanism.

RESULTS

In normotensive rats under anaesthesia, Ra.Cr caused fall in MAP (40 mmHg) at 50 mg/kg with % fall of 27.88 ± 4.55. Among the fractions tested, aqueous fraction was more potent at the dose of 50 mg/kg with % fall of 45.63 ± 2.84. In hypertensive rats under similar conditions, extract and fractions showed antihypertensive effect at same doses while aqueous fraction being more potent, exhibited 68.53 ± 4.45% fall in MAP (70 mmHg). In isolated rat aortic rings precontracted with phenylephrine (PE), Ra.Cr and fractions induced endothelium-dependent vasorelaxation, which was partially blocked in presence of l-NAME, indomethacin and atropine. In isolated rabbit aortic rings pre-contracted with PE and K⁺-(80 mM), Ra.Cr induced vasorelaxation and shifted Ca²⁺ concentration-response curves to the right and suppressed PE peak formation, similar to verapamil, in Ca²⁺-free medium.

DISCUSSION AND CONCLUSIONS

The data indicate that l-NAME and atropine-sensitive endothelial-derived NO and COX enzyme inhibitors and Ca²⁺ entry blocking-mediated vasodilator effect of the extract explain its antihypertensive potential.

Vasodilator Activity of Compounds Isolated from Plants Used in Mexican Traditional Medicine

Arterial hypertension is one of the main risk factors in the development of cardiovascular diseases. Therefore, it is important to look for new drugs to treat hypertension. In this study, we carried out the screening of 19 compounds (triterpenes, diterpenes, sesquiterpenes, lignans, and flavonoids) isolated from 10 plants used in Mexican traditional medicine to determine whether they elicited vascular smooth muscle relaxation and, therefore, could represent novel anti-hypertension drug candidates. The vasorelaxant activity of these compounds was evaluated on the isolated rat aorta assay and the results obtained from this evaluation showed that three compounds induced a significant vasodilatory effect: meso-dihydroguaiaretic acid [half maximal effective concentration (EC₅₀), 49.9 ± 11.2 µM; maximum effect (Emax), 99.8 ± 2.7%]; corosolic acid (EC₅₀, 108.9 ± 6.7 µM; Emax, 96.4 ± 4.2%); and 5,8,4′-trihydroxy-3,7-dimethoxyflavone (EC₅₀, 122.3 ± 7.6 µM; Emax, 99.5 ± 5.4%). Subsequently, involvement of the NO/cyclic guanosine monophosphate (cGMP) and H₂S/ATP-sensitive potassium channel (K_ATP) pathways on the vasodilator activity of these compounds was assessed. The results derived from this analysis showed that the activation of both pathways contributes to the vasorelaxant effect of corosolic acid. On the other hand, the vasodilator effect of meso-dihydroguaiaretic acid and 5,8,4′-trihydroxy-3,7-dimethoxyflavone, partly involves stimulation of the NO/cGMP pathway. However, these compounds also showed an important endothelium-independent vasorelaxant effect, whose mechanism of action remains to be clarified. This study indicates that meso-dihydroguaiaretic acid, corosolic acid, and 5,8,4′-trihydroxy-3,7-dimethoxyflavone could be used as lead compounds for the synthesis of new derivatives with a higher potency to be developed as drugs for the prevention and treatment of cardiovascular diseases.

Pharmacological validation of the folkloric uses of Cyperus rotundus L. in different ailments: An in vivo and in vitro research

In vivo and in vitro research study was conducted on Cyperus rotundus to evaluate the sound mechanistic background in the treatment of gastrointestinal, bronchial and vascular disorders as well as in pain, emesis, pyrexia and bacterial infections. Results showed that crude extract of Cyperus rotundus (Cr.Cr) exhibited the dose-dependent spasmolytic effect in rabbit jejunum by inhibiting the spontaneous and K+ (80 mM)-induced contractions. Pretreatment of tissue with Cr. Cr caused the rightward shift of calcium concentration response curves, similar to verapamil. Cr. Cr also caused the relaxation of K+(80 mM)- and carbachol (1 µM)-induced contractions of trachea preparations, similar to that of verapamil. Moreover, Cr. Cr also relaxed the contraction induced by the K+ (80 mM) and phenylephrine (1 µM) of aorta preparations. Data show that C. rotundus possess the spasmolytic, bronchodilator and vasodilator activities possibly through calcium channels blockade; validating its folkloric use in diarrhea, dyspepsia, bronchitis, asthma and hypertension in addition to antibacterial, antiemetic, antipyretic and analgesic activities.

Characterization of Vasorelaxant Principles from the Needles of Pinus morrisonicola Hayata

Pinus morrisonicola Hayata, usually called Taiwan five-leaf pine (5LP), is an endemic species in Taiwan and is traditionally used to relieve hypertension symptoms and improve cardiovascular function. In this study, the needle extract of 5LP was fractionated and analyzed by LC/MS/MS to search for possible antihypertensive candidates. In addition, bioassay-guided purification of the bioactive components was performed by Ca²⁺ fluorescent signal (Fluo 4-AM) assays. Two dihydrobenzofuran lignans, pinumorrisonide A (1) and icariside E4 (2), and one acylated flavonoid glycoside, kaempferol 3-O-α-(6‴-p-coumaroylglucosyl-β-1,4-rhamnoside) (3) were characterized from the active fractions. The structure of a new compound 1 was established on the basis of 2D NMR spectroscopic and mass spectrometric analyses, and the known compounds 2 and 3 were identified by comparison of their physical and spectroscopic data with those reported in the literature. The purified compounds 1–3 exhibited significant inhibition of Ca²⁺ fluorescence with IC₅₀ values of 0.71, 0.36, and 0.20 mM, respectively. A mechanism study showed that these compounds showed vasorelaxant effects by blocking the voltage-operated Ca²⁺ channel (VOCC) and inhibiting Ca²⁺ influx to the cytoplasmic. These results suggested that 5LP and the three characterized components could be promising antihypertensive candidates for the use as VOCC blockers.

Vasorelaxant properties of Vernonia amygdalina ethanol extract and its possible mechanism

CONTEXT

Vernonia amygdalina Del. (VA) (Asteraceae) is commonly used to treat hypertension in Malaysia.

OBJECTIVE

This study investigates the vasorelaxant mechanism of VA ethanol extract (VAE) and analyzes its tri-step FTIR spectroscopy fingerprint.

MATERIALS AND METHODS

Dried VA leaves were extracted with ethanol through maceration and concentrated using rotary evaporator before freeze-dried. The vasorelaxant activity and the underlying mechanisms of VAE using the cumulative concentration (0.01-2.55 mg/mL at 20-min intervals) were evaluated on aortic rings isolated from Sprague Dawley rats in the presence of antagonists.

RESULTS

The tri-step FTIR spectroscopy showed that VAE contains alkaloids, flavonoids, and saponins. VAE caused the relaxation of pre-contracted aortic rings in the presence and absence of endothelium with EC₅₀ of 0.057 ± 0.006 and 0.430 ± 0.196 mg/mL, respectively. In the presence of Nω-nitro-l-arginine methyl ester (EC₅₀ 0.971 ± 0.459 mg/mL), methylene blue (EC₅₀ 1.203 ± 0.426 mg/mL), indomethacin (EC₅₀ 2.128 ± 1.218 mg/mL), atropine (EC₅₀ 0.470 ± 0.325 mg/mL), and propranolol (EC₅₀ 0.314 ± 0.032 mg/mL), relaxation stimulated by VAE was significantly reduced. VAE acted on potassium channels, with its vasorelaxation effects significantly reduced by tetraethylammonium, 4-aminopyridine, barium chloride, and glibenclamide (EC₅₀ 0.548 ± 0.184, 0.158 ± 0.012, 0.847 ± 0.342, and 0.304 ± 0.075 mg/mL, respectively). VAE was also found to be active in reducing Ca²⁺ released from the sarcoplasmic reticulum and blocking calcium channels.

CONCLUSIONS

The vasorelaxation effect of VAE involves upregulation of NO/cGMP and PGI₂ signalling pathways, and modulation of calcium/potassium channels, and muscarinic and β₂-adrenergic receptor levels.

Bioactive Natural Product and Superacid Chemistry for Lead Compound Identification: A Case Study of Selective hCA III and L-Type Ca2+ Current Inhibitors for Hypotensive Agent Discovery

Dodoneine (Ddn) is one of the active compounds identified from Agelanthusdodoneifolius, which is a medicinal plant used in African pharmacopeia and traditional medicine for the treatment of hypertension. In the context of a scientific program aiming at discovering new hypotensive agents through the original combination of natural product discovery and superacid chemistry diversification, and after evidencing dodoneine's vasorelaxant effect on rat aorta, superacid modifications allowed us to generate original analogues which showed selective human carbonic anhydrase III (hCA III) and L-type Ca²⁺ current inhibition. These derivatives can now be considered as new lead compounds for vasorelaxant therapeutics targeting these two proteins.

A New Ajmaline-type Alkaloid from the Roots of Rauvolfia serpentina

A new ajmaline-type alkaloid, 21-Ο-methylisoajmaline (1), together with twenty-one known compounds, a mixture of β-sitosterol (2) and stigmasterol (3), reserpinine (4); tetrahydroalstonine (5), reserpine (6), venoterpine (7), yohimbine (8), 6'-O-(3,4,5-trimethoxybenzoyl)glomeratose A (9), isoajmaline (10), 3-epi-α-yohimbine (11), methyl 3,4,5-trimethoxy-trans-cinnamate (12), a mixture of β-sitosterol 3-Ο-β-D-glucopyranoside (13) and stigmasterol 3-Ο-β-D- glucopyranoside (14), rescidine (15), 7-deoxyloganic acid (16), ajmaline (17), suaveoline (18), (+)-tetraphyllicine (19), loganic acid (20), 3-hydroxysarpagine (21), and sarpagine (22), were isolated from the roots of Rauvolla serpentina. Their structures were elucidated by spectroscopic data analysis and comparison with literature data. Compounds 11, 12 and 15 were for the first time identified from the genus Rauvolfla and 5, 7, 11, 12, 15, 18 and 22 were found from R. sepentina for the first time. Compound 11 showed moderate anticholinesterase activity with IC₅₀ value of 15.58 μM, whereas 6 exhibited strong vasorelaxant activity with the EC₅₀ value of 0.05 μM.

Vasorelaxant and cardiovascular properties of the essential oil of Pogostemon elsholtzioides

ETHNOBOTANICAL RELEVANCE

Pogostemon elsholtzioides Benth. (Lamiaceae) is an aromatic shrub, endemic to eastern Himalaya region. The leaves are used for treating goiter and high blood pressure (BP) by indigenous people in Arunachal Pradesh, India. Young leaves are used as vegetable and leaf decoction is also used for cough, cold and headache by some indigenous communities in Northeast India.

AIM OF THE STUDY

This species is used for treating hypertension and the genus Pogostemon is rich in essential oil. Therefore, the present study was aimed at investigation of the chemical constituents, vasorelaxant and cardiovascular effects of the essential oil of P. elsholtzioides.

MATERIALS AND METHODS

P. elsholtzioides was collected from Pasighat, Arunachal Pradesh, India and essential oil was extracted from shade dried leaves. Essential oil was analyzed by GC-FID and GC-MS and the volatile constituents were identified. Vasorelaxant and cardiovascular properties of the essential oil were studied against phenylephrine induced contraction in isolated endothelium intact aortic preparations and by measuring systolic and diastolic BP, mean arterial pressure (MAP) and heart rate (HR) after carotid artery cannulation in Wistar rats.

RESULTS

The essential oil was rich in sesquiterpenes and curzerene, benzophenone, α-cadinol and germacrone were major constituents. The essential oil exhibited significant vasodilation effect in phenylephrine induced contracted aortic rings. Vasorelaxant effect of the essential oil was also observed both in the presence and absence of Nitro-L-arginine methyl ester against phenylephrine-contracted aortic rings. It also induced reduction of systolic and diastolic BP, MAP and HR.

CONCLUSIONS

Essential oil of P. elsholtzioides exhibited significant vasorelaxant effect against endothelium intact aortic preparation mediated through nitric oxide dependent pathway and also reduced BP. However, further study is needed to screen the role of calcium ions in both intracellular and extracellular pathway.

Chemical composition, vasorelaxant, antioxidant and antiplatelet effects of essential oil of Artemisia campestris L. from Oriental Morocco

BACKGROUND

Artemisia campestris L. (Asteraceae) is a medicinal herb traditionally used to treat hypertension and many other diseases. Hence, this study is aimed to analyze the essential oil of A. campestris L (AcEO) and to investigate the antiplatelet, antioxidant effects and the mechanisms of its vasorelaxant effect.

METHODS

The chemical composition of AcEO was elucidated using GC/MS analysis. Then, the antioxidant effect was tested on DPPH radical scavenging and on the prevention of β-carotene bleaching. The antiplatelet effect was performed on the presence of the platelet agonists: thrombin and ADP. The mechanism of action of the vasorelaxant effect was studied by using the cellular blockers specified to explore the involvement of NO/GC pathway and in the presence of calcium channels blockers and potassium channels blockers.

RESULTS

AcEO is predominated by the volatiles: spathulenol, ß-eudesmol and p-cymene. The maximal antioxidant effect was obtained with the dose 2 mg/ml of AcEO. The dose 1 mg/ml of AcEO showed a maximum antiplatelet effect of, respectively 49.73% ±9.54 and 48.20% ±8.49 on thrombin and ADP. The vasorelaxation seems not to be mediated via NOS/GC pathway neither via the potassium channels. However, pretreatment with calcium channels blockers attenuated this effect, suggesting that the vasorelaxation is mediated via inhibition of L-type Ca²⁺ channels and the activation of SERCA pumps of reticulum plasma.

CONCLUSION

This study confirms the antioxidant, antiplatelet and vasorelaxant effects of A.campestris L essential oil. However, the antihypertensive use of this oil should be further confirmed by the chemical fractionation and subsequent bio-guided assays.

Chemical composition, vasorelaxant, antioxidant and antiplatelet effects of essential oil of Artemisia campestris L. from Oriental Morocco

BACKGROUND

Artemisia campestris L. (Asteraceae) is a medicinal herb traditionally used to treat hypertension and many other diseases. Hence, this study is aimed to analyze the essential oil of A. campestris L (AcEO) and to investigate the antiplatelet, antioxidant effects and the mechanisms of its vasorelaxant effect.

METHODS

The chemical composition of AcEO was elucidated using GC/MS analysis. Then, the antioxidant effect was tested on DPPH radical scavenging and on the prevention of β-carotene bleaching. The antiplatelet effect was performed on the presence of the platelet agonists: thrombin and ADP. The mechanism of action of the vasorelaxant effect was studied by using the cellular blockers specified to explore the involvement of NO/GC pathway and in the presence of calcium channels blockers and potassium channels blockers.

RESULTS

AcEO is predominated by the volatiles: spathulenol, ß-eudesmol and p-cymene. The maximal antioxidant effect was obtained with the dose 2 mg/ml of AcEO. The dose 1 mg/ml of AcEO showed a maximum antiplatelet effect of, respectively 49.73% ±9.54 and 48.20% ±8.49 on thrombin and ADP. The vasorelaxation seems not to be mediated via NOS/GC pathway neither via the potassium channels. However, pretreatment with calcium channels blockers attenuated this effect, suggesting that the vasorelaxation is mediated via inhibition of L-type Ca2+ channels and the activation of SERCA pumps of reticulum plasma.

CONCLUSION

This study confirms the antioxidant, antiplatelet and vasorelaxant effects of A.campestris L essential oil. However, the antihypertensive use of this oil should be further confirmed by the chemical fractionation and subsequent bio-guided assays.

The Hydroalcoholic Extract of Leaves of Mandevilla moricandiana Induces NO-Mediated Vascular Relaxation

Natural products extracted from plants represent a valuable source of new bioactive substances. Many studies describe the potential of plant products for the treatment of cardiovascular diseases. Species of the Mandevilla genus have been studied for their biological activities, mainly as antioxidant, anti-inflammatory, and vasorelaxant. However, the phytochemical and pharmacological profiles of Mandevilla moricandiana have not been investigated yet. The aim of this study was to evaluate the vasodilator effect of the hydroalcoholic extract of the leaves of M. moricandiana, as well as its chemical profile. Chemical analysis and quantification of major compounds were performed by HPLC analysis. Total flavonoid content was quantified based on rutin equivalents, and major compounds were identified based on HPLC-DAD-MS analysis. M. moricandiana leaf extract-induced vasodilation was investigated in rat aortic rings precontracted with phenylephrine. The total flavonoids were quantified as 3.25 ± 0.11 % w/w of the hydroalcoholic leaf extract, and HPLC-DAD-MS allowed for the identification of luteolin and quercetin glycosides. The maximal relaxant effect of the hydroalcoholic leaf extract was 86.07 ± 1.68 % at a concentration of 30 µg/mL (p < 0.05; n = 6). The concentration of hydroalcoholic extract of the leaves of M. moricandiana necessary to reduce phenylephrine-induced contractions of the endothelium-intact aorta by 50 % was 0.82 ± 0.10 µg/mL. M. moricandiana leaf extract-induced vasodilation was abolished in aortas pretreated with NG-nitro-L-arginine methyl ester and 1H-[1,2,4]oxadiazolo-[4,3-α]quinoxalin-1-one. In addition, diphenhydramine partially inhibited the effect of the hydroalcoholic extract of the leaves of M. moricandiana. Thus, M. moricandiana-induced relaxation depends on the endothelium and on the activation of the nitric oxide/cyclic GMP pathway, with the involvement of endothelial histamine H₁ receptors. Luteolin and quercetin glycosides seem to contribute to the extract activity.

Airways and vascular smooth muscles relaxant activities of Gaultheria trichophylla

The aim of this experimental work was to explore the potential pharmacological activities of Gaultheria trichophylla Royle in hyperactive respiratory and vascular conditions. Gaultheria trichophylla was extracted with solvents, phytochemical detection tests were performed, and rabbit trachea and aorta strips were used to evaluate its effects on airways and vascular smooth muscles. Qualitative phytochemical tests showed the presence of flavonoids, alkaloids, anthraquinones, saponins, terpenoids, and condensed tannins. The methanol extract caused inhibition (EC₅₀ values of 3.12 mg/mL) of carbachol (1 μM) and partial relaxation of K⁺(80 mM) caused contractions in tracheal strips. The chloroform extract was comparatively more potent against carbachol than K+ induced contraction with EC₅₀ values of 0.64 and 2.26 mg/mL, respectively. However, the n-hexane extract showed more potency against K⁺ than cabachol induced contractions, as in case with verapamil, with EC₅₀ values of 0.61 and 6.58 mg/mL, respectively. In isolated prepared trachea, the extracts displaced the carbachol concentration response curves and maximum response was suppressed. In rabbit aorta preparations, methanol and n-hexane extracts partially relaxed phenylephrine (1 μM) and K⁺ induced vasoconstrictions. However, the chloroform extract inhibited phenylephrine induced contractions and exhibited a vasoconstrictor effect at lower concentrations and a relaxant effect at higher concentrations against K⁺ precontractions. The data indicates that, in addition to others, the extracts of G .trichophylla possess verapamil like Ca⁺⁺ channel blocking components which explain the possible role of this plant in respiratory and vascular conditions.

Delonix regia Leaf Extract (DRLE): A Potential Therapeutic Agent for Cardioprotection

Delonix regia (Boj. Ex. Hook) is a flowering plant in the pea family found in tropical areas and its leaves are used informally to treat diseases in folk medicine. However, the cardioprotective effects in this plant are still unclear. In this study, we found that the Delonix regia leaf extract (DRLE) (400 mg/kg/d) can reduce the mortality rate in an isoproterenol (ISO)-induced heart injury and hypertrophy mouse model. Decreased serum levels of creatine phosphokinase, LDH, GOT, TNF-alpha and increased nitric oxide levels were found in DRLE-treated ISO-injured mice. In the in vitro study, the porcine coronary artery exhibited vasodilation effect induced by DRLE in a dose-dependent manner. In the DRLE toxic test, overdose of DRLE showed the high safety in normal mice and may have the ability to remove the metabolic wastes in blood. In conclusion, we demonstrated for the first time that DRLE has the cardioprotective effects by activating the vasodilation through NO pathway and preventing the myocyte injury via inhibition of TNF-alpha pathway. We suggest that DRLE may act as a promising novel herbal medicine for cardioprotection.

Anti-cholinergic and Ca2+-antagonist mechanisms explain the pharmacological basis for folkloric use of Sisymbrium irio Linn. in gastrointestinal, airways and vascular system ailments

ETHNOPHARMACOLOGICAL RELEVANCE

Seeds of Sisymbrium irio Linn has been used traditionally in different regions of Pakistan for the treatment of gastrointestinal, airways and vascular system ailments. To insight the pharmacological basis, in vitro study was conducted in order to validate its folkloric uses.

MATERIAL AND METHODS

70% aqueous-methanolic extract of seeds from S. irio (Si.MEs) was tested on isolated rabbit aorta, jejunum and trachea strip hanged in tissue bath having physiological solutions aerated with carbogen and their responses were measured and recorded via Power Lab.

RESULTS

The Si.MEs exhibited the transient spasmogenic effect (0.01-1.0mg/mL) on spontaneous jejunum contractions, followed by the spasmolytic effect. The addition of atropine resulted in blocking in spasmogenic effect while the spasmolytic effect was originated, suggesting the presence of an antimuscarinic effect. Likewise verapamil, Si.MEs (0.03-5mg/mL) repressed the high concentration K⁺(80mM)-induced contraction and also drifted the Ca²⁺ concentration-response curves toward right (0.3-3.0mg/mL), possibly signifying the Ca²⁺ channel blockade. Furthermore, Si.MEs exhibited nonspecific relaxant effect on carbachol (1µM)- and high concentration K⁺(80mM)-induced tracheal contractions in a way comparable to dicyclomine, suggesting the coexistence of Ca²⁺-antagonistic and/or antimuscarinic properties. Additionally, Si.MEs also relaxed the phenylephrine(1µM)- and high concentration K⁺(80mM)-induced aortic contraction (0.01-3mg/mL), suggesting blockade of Ca²⁺ channel. Moreover, oral administration of Si.MEs, as high as 6g per kg, did not produce lethality among the treated groups of mice.

CONCLUSIONS

Aqueous-methanolic extract of seeds from S. irio (Si.MEs) exhibited the bronchodilator and gut modulator (spasmogenic and spasmolytic) activities, probably through dual blockade of muscarinic receptors and Ca²⁺ channels, whereas, vasodilator effect may be due to Ca²⁺ channels blockade.

Vasorelaxant mode of action of dichloromethane-soluble extract from Agastache mexicana and its main bioactive compounds

CONTEXT

Agastache mexicana (Kunth) Lint & Epling (Lamiaceae) is a plant used in Mexican traditional medicine for the treatment of hypertension, anxiety and so on.

OBJECTIVE

To determine the vasorelaxant effect and functional mode of action of dichloromethane-soluble extract from A. mexicana (DEAm) and isolate the constituents responsible for the pharmacological activity.

MATERIALS AND METHODS

Extracts were prepared from the aerial parts of A. mexicana (225.6 g) by successive maceration with hexane, dichloromethane and methanol (three times for 72 h at room temperature), respectively. DEAm (0.01-1000 μg/mL), fractions (at 174.27 μg/mL), acacetin and ursolic acid (UA) (0.5-500 μM) were evaluated to determine their vasorelaxant effect on ex vivo rat aorta ring model. In vivo UA antihypertensive action was determined on spontaneously hypertensive rats.

RESULTS AND DISCUSSION

DEAm induced a significant vasorelaxant effect in concentration-dependent and endothelium-independent manners (EC₅₀=174.276 ± 5.98 μg/mL) by a calcium channel blockade and potassium channel opening. Bio-guided fractionation allowed to isolate acacetin (112 mg), UA (2.830 g), acacetin/oleanolic acid (OA) (M1) (155 mg) and acacetin/OA/UA (M2) (1.382 g) mixtures, which also showed significant vasodilation. UA significantly diminished diastolic (80 mmHg) and systolic blood pressure (120 mmHg), but heart rate was not modified.

CONCLUSION

DEAm produced significant vasorelaxant action by myogenic control cation. The presence of acacetin, OA and UA into the extract was substantial for the relaxant activity of DEAm. In vivo antihypertensive action of UA corroborates the use of A. mexicana as an antihypertensive agent on Mexican folk medicine.

Allanblackia floribunda Oliv.: An aphrodisiac plant with vasorelaxant properties

ETHNOPHARMACOLOGICAL RELEVANCE

Allanblackia floribunda Oliv. is one of the most commonly used medicinal plant in Cameroon. The stem bark of the plant is traditionally used for its aphrodisiac and antihypertensive properties.

AIM OF THE STUDY

To validate the traditional uses of Allanblackia floribunda stem bark ethanol extract through the evaluation of their aphrodisiac and vasorelaxant properties.

MATERIALS AND METHODS

The extract's ability to increase sexual desire and the frequencies of erection (mount), intromission and prolonged latency of ejaculation were studied on adult male rats. The vasodilator effect was investigated using isolated rat aorta rings. Tests were conducted using fractions obtained by reverse phase column-chromatography (CC), after the acquisition of the HPLC fingerprint of the ethanol extract, resulted the most active in previous studies.

RESULTS

The CC allowed the isolation of five fractions whose aphrodisiac and vasodilator activities were tested and compared with those of the whole extract. Four compounds were identified and characterized, three of them, Fukugiside, Morelloflavone and Volkensiflavone, are secondary metabolites known to be in Allanblackia floribunda; the fourth, Spicataside, is a biflavonoid glycoside known to be present in the genus Garcinia but never found neither in Allanblackia floribunda nor in Allanblackia genus. The crude ethanolic extract (CEE) induced a relaxation on aorta rings with EC₅₀=11±2μg/mL and Morelloflavone displayed a similar activity with EC₅₀=42±6μg/mL; for all the other compounds only the vasodilation % at the maximum concentration assessable (90μg/mL) was determined: 30±8 (Fukugiside), 24±6 (Spicataside), 33±4 (Morelloflavone+Volkensiflavone), 47±1 (Volkensiflavone). Regarding the activity on male sexual behaviour, only CEE and Fukugiside showed activity in the 9 parameters evaluated.

CONCLUSIONS

These results may support the traditional uses of Allanblackia floribunda as aphrodisiac plant with antihypertensive properties suggesting the phytocomplex as responsible for the claimed activity.

Hydroalcoholic extract and pure compounds from Senecio nutans Sch. Bip (Compositae) induce vasodilation in rat aorta through endothelium-dependent and independent mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

Senecio nutans Sch. Bip. (Compositae) is an endemic plant of South America, and is used in herbal medicine in Andean communities for treating acute mountain sickness. Currently, the direct effects of hydroalcoholic extract of S. nutans (HAE S. nutans) or its isolated compounds on the vascular system are not well described. The aim of this study was to determine the effects and mechanism of action of S. nutans on vascular function in healthy rats.

MATERIAL AND METHODS

Seven compounds were isolated from the HAE S. nutans, and their structures were characterized using spectroscopic techniques as 1D and 2D NMR, and mass spectrometry. Vascular reactivity experiments were carried out in rat aorta. S. nutans-dependent vasodilation and phenylephrine-dependent contraction were measured in endothelium-intact and endothelium-denuded aortic rings of male rats.

RESULTS

Seven pure compounds were isolate from HAE S. nutans, but two pure compounds showed significant vasodilation in rat aorta: 4-hydroxy-3-(3-methyl-2-butenyl)acetophenone (compound E) and 5-acetyl-6-hydroxy-2-isopropenyl-2,3-dihydrobenzofurane (compound G). Although HAE S. nutans induced vasodilation in absence of endothelium, the vasodilation in intact aorta, via NO, was higher. HAE S. nutans reduced calcium-dependent contraction in endothelium-intact, but not in endothelium-denuded aortic rings.

CONCLUSION

HAE S. nutans and its isolated compounds caused vasodilation in rat aorta in absence of endothelium, suggesting its vasodilator properties is endothelium-dependent (NO) and or independent, and may involve a modulation of the calcium channels. This result is of clinical interest as potential therapy control of blood pressure.

Two new phenolic compounds from the seeds of Machilus yunnanensis

Chemical constituents investigation on the seeds of Machilus yunnanensis led to two new phenolic compounds 8-O-acetyl-phenylethanoid-4-O-β-D-glucopyranoside (1) and (E)-2,3-bis(4-hydroxyphenyl)acrylaldehyde (2), together with 16 known compounds. Their structures were elucidated on the basis of spectroscopic data analysis (IR, MS, 1D, and 2D NMR). Meanwhile, compounds 1-3, 6-13, 17, and 18 were evaluated for vasorelaxant effects on the rat endothelium-intact thoracic aorta rings precontracted with phenylephrine (PE) or KCl. The bioassay results showed that compound 17 had significant vasorelaxant effect on the endothelium-intact thoracic aorta rings precontracted with KCl.

Antihypertensive activity of 80% methanol seed extract of Calpurnia aurea (Ait.) Benth. subsp. aurea (Fabaceae) is mediated through calcium antagonism induced vasodilation

ETHNOPHARMACOLOGICAL RELEVANCE

Calpurnia aurea (Ait.) Benth. subsp. aurea (CASA) (Fabaceae) seeds are used to treat hypertension in Ethiopian folklore medicine, particularly by Shinasha, Agew-awi and Amhara people in northwest Ethiopia. However, the claim has so far not been substantiated scientifically.

AIM OF THE STUDY

The study was conducted to evaluate the antihypertensive activity of 80% methanol extract of CASA in animal model of hypertension as well as its vasorelaxant effect and possible underlying mechanisms in isolated guinea pig aorta.

MATERIAL AND METHODS

Hypotensive and antihypertensive effect of CASA extract was determined in vivo through the intravenous (iv) route in normotensive and hypertensive anesthetized rats using 2-kidney-1-clip (2K1C) rat model. Ex vivo, guinea pig thoracic aortic rings were isolated and suspended in organ bath, and the vasodepressor effects as well as the mechanism of action of the extract were studied by means of isometric tension recording experiments.

RESULTS

The blood pressure fell dose-dependently and significantly in renal hypertensive and normotensive rats following i.v. administration, suggesting that the hydroalcoholic extract possesses hypotensive and antihypertensive effects. The extract also caused a dose-dependent relaxation of aorta pre-contracted with KCl at a concentration of 5-250mg/L, with a maximum relaxation of 92.1% achieved at 250mg/L. The relaxation mechanism was found to be independent of the muscarinic receptors, histamine receptors, ATP dependent K(+) channels, cyclooxygenase enzymes, cGMP/NO pathway and the endothelium system. The extract caused rightward shift of the Ca(++) dose-response curves, similar to that caused by verapamil, indicating that it produced vasorelaxation by inhibiting extracellular Ca(2+) influx.

CONCLUSIONS

The findings demonstrate that the plant is endowed with antihypertensive effect, providing evidence for its traditional use. The effect may be, at least in part, due to dilation of blood vessels through blockage of Ca(2+) channels.

In vitro vasorelaxation mechanisms of Isoapiole extracted from Lemonfragrant Angelica Root on rat thoracic aorta

ETHNOPHARMCOLOGICAL RELEVANCE

Lemonfragrant Angelica (Ostericum citriodorum (Hance) C. Q. Yuan & Shan) is a traditional Chinese herb for treatment of angina pectoris, stomach pain and abdominal pain. However, its active components and mechanisms of action were not well understood.

AIMS OF THE STUDY

In this study, we investigated whether the isoapiole extracted from Lemonfragrant Angelica Root (LAR) could directly stimulate the production of nitric oxide (NO) in vascular endothelial cells (VECs) and lead to the vascular relaxation

MATERIALS AND METHODS

Vascular activity experiments were performed in aortic rings isolated from Wistar rats using standard muscle bath procedures. Isoapiole was added with different concentrations (0.75, 2.5, 5μg/mL), and vessel relaxation of rat aortic rings pre-contracted with norepinephrine (NE) or potassium chloride was recorded. NO release from aortic rings exposed to isoapiole (5μg/mL) was measured by Griess method. The endothelial nitric oxide synthase (eNOS) expression in primary human umbilical vein endothelial cells (HUVECs) incubated with isoapiole was determined using Western blot and microplate reader assay. Classical receptor antagonists, channel and enzymatic inhibitors were used to check the mechanisms involved.

RESULTS

Isoapiole (0.75, 2.5, 5μg/mL) inhibited norepinephrine-induced contraction in endothelium-intact rat aortic rings. However, a very weak relaxation of aortic rings was obtained in endothelium-denuded preparations. Isoapiole (0.75, 2.5, 5μg/mL) did not have vascular relaxative effect on neither endothelium-intact nor endothelium-denuded aortas pre-contracted with KCl (60mmol/L). The vasorelaxation effect of isoapiole on rat aortic rings was attenuated by the eNOS inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME). This result suggested that suggested that the isoapiole action was at least partially mediated by promoting eNOS expression. It was further found that isoapiole (5μg/mL) increased NO production in isolated rat thoracic aorta rings. Isoapiole increased eNOS expression leading to NO production in HUVECs.

CONCLUSION

Isoapiole stimulates NO production in the endothelium, leading to vascular dilatation.

Role of Nitric Oxide and Hydrogen Sulfide in the Vasodilator Effect of Ursolic Acid and Uvaol from Black Cherry Prunus serotina Fruits

The present research aimed to isolate the non-polar secondary metabolites that produce the vasodilator effects induced by the dichloromethane extract of Prunus serotina (P. serotina) fruits and to determine whether the NO/cGMP and the H2S/KATP channel pathways are involved in their mechanism of action. A bioactivity-directed fractionation of the dichloromethane extract of P. serotina fruits led to the isolation of ursolic acid and uvaol as the main non-polar vasodilator compounds. These compounds showed significant relaxant effect on rat aortic rings in an endothelium- and concentration-dependent manner, which was inhibited by NG-nitro-L-arginine methyl ester (L-NAME), DL-propargylglycine (PAG) and glibenclamide (Gli). Additionally, both triterpenes increased NO and H2S production in aortic tissue. Molecular docking studies showed that ursolic acid and uvaol are able to bind to endothelial NOS and CSE with high affinity for residues that form the oligomeric interface of both enzymes. These results suggest that the vasodilator effect produced by ursolic acid and uvaol contained in P. serotina fruits, involves activation of the NO/cGMP and H2S/KATP channel pathways, possibly through direct activation of NOS and CSE.

Role of AMP-activated Protein Kinase in NO- and EDHF-mediated Endothelium-dependent Relaxations to Red Wine Polyphenols

BACKGROUND

Several epidemiological studies have shown that regular consumption of moderate amounts of wine, in particular red wine, is associated with a decreased total mortality due, in part, to a reduced risk of cardiovascular diseases. The protective effect has been attributable to polyphenols, which are potent vasodilators and have anti-thrombotic properties. Polyphenols have been shown to induce pronounced endothelium-dependent relaxations of arteries by causing the redox-sensitive PI3-kinase-dependent formation of nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF). The aim of the present study was to determine the role of the AMP-activated protein kinase (AMPK) in the red wine polyphenols (RWPs)-induced endothelial formation of NO and EDHF.

METHODS AND RESULTS

Vascular reactivity was assessed in organ chambers. Cultured porcine coronary artery endothelial cells porcine coronary artery segements were used to study the phosphorylation level of endothelial NO synthase (eNOS) at serine 1177, and AMPK at the Threonine 172 by Western blot analysis and immunohistochemical staining. RWPs caused endothelium-dependent relaxations in rings from rat aorta and mesenteric artery, and in those from porcine coronary artery. NO-mediated relaxations to RWPs as assessed in the presence of indomethacin and charybdotoxin plus apamin, were inhibited by compound C (an inhibitor of AMPK). Compound C also reduced EDHF-mediated relaxations as assessed in the presence of indomethacin and N(G)-nitro L-arginine. In contrast, compound C did not affect endothelium-dependent relaxations to acetylcholine and those to sodium nitroprusside. Moreover, RWPs induced the phosphorylation of AMPK at threonine 172 and eNOS at serine 1177 in endothelial cells; these responses were inhibited by compound C.

CONCLUSION

The present findings indicate that RWPs cause both NO and EDHF-mediated relaxations in several types of isolated arteries and that these effects are dependent on the activation of the AMP-activated protein kinase pathway.

Dihydrogoniothalamin, an Endothelium and NO-Dependent Vasodilator Drug Isolated from Aniba panurensis

Dihydrogoniothalamin is a styrylpyrone isolated from the leaves of Aniba panurensis. The present work aimed at investigating the vasorelaxant activity of dihydrogoniothalamin and its underlying mechanism of action in the rat aorta. Dihydrogoniothalamin (0.01-100 µM) induced a concentration-dependent vasodilatation of aortas precontracted with phenylephrine. Endothelium removal or pretreatment of the preparation with NG nitro-L-arginine-methyl-ester abolished the vasodilator response for dihydrogoniothalamin. Pretreatment with calmidazolium did not affect the vasodilator response of dihydrogoniothalamin. On the other hand, wortmannin, a nonselective inhibitor of phosphatidylinositol 3-kinases, and protein kinase B inhibitor IV significantly shifted the concentration-response curve of dihydrogoniothalamin to the right and reduced its maximal effect. A nonselective antagonist of estrogen receptors, ICI 182,780, and a selective antagonist of estrogen receptor α, methyl-piperidino-pyrazole, were able to reduce the relaxation induced by dihydrogoniothalamin, but no effect was observed in the presence of the selective antagonists of estrogen receptor β and G protein-coupled receptor 30, 4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-3-yl]phenol (PHTPP), and G-15, respectively. Dihydrogoniothalamin also increased the phosphorylation of the activation sites of endothelial nitric oxide synthase and protein kinase B. The present results led us to conclude that dihydrogoniothalamin is a vasodilator drug acting in an endothelium- and nitric oxide-dependent manner through a mechanism involving the activation of nitric oxide synthase via the phosphatidylinositol 3-kinase/protein kinase B pathway, partially by stimulation of estrogen receptor α.

Isolation and bioactivity of diterpenoids from the roots of Salvia grandifolia

A phytochemical investigation of root extracts of Salvia grandifolia led to isolation of six previously unreported diterpenoids, grandifolias A-F, along with eight known compounds. The structures of grandifolias A-F were primarily established by extensive 1D and 2D NMR spectroscopic analyses, as well as HRESIMS data. Their absolute configurations were assigned by their calculated and experimental electronic circular dichroism spectra or by X-ray diffraction analysis. All of the diterpenoids were evaluated for their vasorelaxant effects. Grandifolia B and isograndifoliol both exhibited dose-dependent vasorelaxant effects on rat aortic rings, preconstricted by KCl or norepinephrine, with EC50 values of 36.36-74.51μg/mL.

Chemical composition and pharmacological properties of the essential oils obtained seasonally from Lippia thymoides

CONTEXT

Lippia thymoides Mart. & Schauer (Verbenaceae) is used in folk medicine to treat wounds, fever, bronchitis, rheumatism, headaches, and weakness.

OBJECTIVE

This study determinates the chemical composition of essential oils from L. thymoides, obtained at during each of the four seasons and correlates with pharmacological properties.

MATERIALS AND METHODS

Essential oils were obtained by hydrodistillation and analyzed by gas chromatography coupled to mass spectroscopy (GC-MS). Antioxidant activity was determined by DPPH free radical scavenging and β-carotene bleaching methods. The antimicrobial assays were performed by minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) methods. Isolated rat aorta and uterus, and guinea-pig trachea were utilized to evaluate relaxant potential in pre-contracted smooth muscle.

RESULTS AND DISCUSSION

Essential oils from leaves of L. thymoides had the sesquiterpene β-caryophyllene (17.22-26.27%) as the major constituent followed by borneol (4.45-7.36%), camphor (3.22-8.61%), camphene (2.64-5.66%), and germacrene D (4.72-6.18%). In vitro assays showed that these essential oils do not have antioxidant activity, have antimicrobial selectivity to Gram-positive bacteria Staphylococcus aureus (MIC = 0.004 mg/mL and MMC = 0.26-10.19 mg/mL) and Micrococcus luteus (MIC = 0.03 mg/mL and MMC = 8.43 mg/mL), relax isolated rat aorta (EC50 = 305-544 μg/mL, with endothelium; and EC50 = 150-283 μg/mL, without endothelium), and uterus (EC50 = 74-257 μg/mL), and minor potency, isolated guinea-pig trachea.

CONCLUSIONS

Lippia thymoides is a source of natural products of pharmaceutical interest, being necessary additional studies to determine the substances involved in the biological activities.

Gallic acid isolated from Spirogyra sp. improves cardiovascular disease through a vasorelaxant and antihypertensive effect

In this study, we investigated the vasorelaxant and antihypertensive effects of gallic acid (GA), a polyphenol isolated from the green alga Spirogyra sp., to assess its suitability as a therapeutic for cardiovascular diseases (CVDs). We examined the effect of GA on endothelium-dependent vasorelaxation in human umbilical vein endothelial cells (HUVECs). GA increased nitric oxide (NO) levels by increasing phosphorylation of endothelial nitric oxide synthase (eNOS), and its effect on NO production was attenuated by pretreatment with the eNOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). We also investigated its antihypertensive effect by examining GA-mediated inhibition of angiotensin-I converting enzyme (ACE). GA inhibited ACE with a half-maximal inhibitory concentration (IC50) value of 37.38 ± 0.39 μg/ml. In silico simulations revealed that GA binds to the active site of ACE (PDB: 1O86) with a binding energy of -270.487 kcal/mol. Furthermore, GA clearly reduced blood pressure in spontaneously hypertensive rats (SHR) to an extent comparable to captopril. These results suggest that GA isolated from Spirogyra sp. exerts multiple therapeutic effects and has potential as a CVD treatment.

Hispidacine, an unusual 8,4'-oxyneolignan-alkaloid with vasorelaxant activity, and hispiloscine, an antiproliferative phenanthroindolizidine alkaloid, from Ficus hispida Linn

Hispidacine, an 8,4'-oxyneolignan featuring incorporation of an unusual 2-hydroxyethylamine moiety at C-7, and hispiloscine, a phenanthroindolizidine alkaloid, were isolated from the stem-bark and leaves of the Malaysian Ficus hispida Linn. Their structures were established by spectroscopic analysis. Hispidacine induced a moderate vasorelaxant activity in rat isolated aorta, while hispiloscine showed appreciable antiproliferative activities against MDA-MB-231, MCF-7, A549, HCT-116 and MRC-5 cell lines.

Vascular L-type Ca²⁺ channel blocking activity of sulfur-containing indole alkaloids from Glycosmis petelotii

In the search for novel natural compounds endowed with potential antihypertensive activity, a new sulfur-containing indole alkaloid, N-demethylglypetelotine (2), and its known analogue glypetelotine (1), were isolated from the leaves of Glycosmis petelotii. Their structures were established on the basis of spectroscopic evidence. The two alkaloids were assessed for vasorelaxing activity on rat aorta rings and for L-type Ba(2+) current [I(Ba(L))] blocking activity on single myocytes isolated from rat tail artery. Both glypetelotine and N-demethylglypetelotine inhibited phenylephrine-induced contraction with IC50 values of 20 and 50 μM, respectively. The presence of endothelium did not modify their spasmolytic effect. Neither glypetelotine nor N-demethylglypetelotine affected Ca(2+) release from the sarcoplasmic reticulum induced by phenylephrine. The spasmolytic effect of glypetelotine increased with membrane depolarization. In the presence of 60 mM K(+), both compounds inhibited, in a concentration-dependent manner, the contraction induced by cumulative addition of Ca(2+), this inhibition being inversely related to Ca(2+) concentration. Glypetelotine and, less efficiently N-demethylglypetelotine, inhibited I(Ba(L)), the former compound also affecting I(Ba(L)) kinetics. In conclusion, glypetelotine is a novel vasorelaxing agent which antagonizes L-type Ca(2+) channels.