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 Cav1.2 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 Cav1.2 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 ß-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.

Cardioprotective, hypotensive and toxicological studies of Populus ciliata (Wall. ex Royle).

Populus ciliata Wall ex. Royle has folkloric repute to treat various cardiovascular ailments and related disorders. The current study was designed to evaluate the toxic profile, cardioprotective and hypotensive effects of Populus ciliata (Wall. ex Royle). Populus ciliata crude ethanolic extract (Pc. Cr) and its aqueous (Pc. Aq) & organic (Pc. Dcm) fractions were tested on isolated aorta of rat and rabbit having intact and non-intact endothelium respectively. Pc. Cr & Pc. Aq relaxed the contractions induced by PE (1 µM)-induced and K+ (80 mM)-induced on aorta, possibly by mediating endothelium derived relaxing factor (EDRF) in intact endothelium and voltage dependent L-type calcium channels blocking (CCB) mechanism in non-intact endothelium. Pc. Cr showed anti-hypertensive & cardioprotective activity by decreasing force of contraction & heart rate on isolated rabbit paired atria and reduced blood pressure in anesthetized rat. Cardioprotective effect of Pc. Cr was assessed in isoproterenol induced acute myocardial infarction (AMI) and left ventricular hypertrophy (LVH) in Sprague Dawley rats. In LVH, Pc. Cr exerted positive effects by decreasing angiotensin II & renin and increasing cGMP & nitric oxide (NO) with reduced cardiac fibrosis, necrosis and cardiac cell size. In AMI, Pc. Cr responded effectively by decreasing cardiac markers creatinine kinase (CK), creatinine kinase myocardial band (CK-MB) and lactate dehydrogenase (LD) in blood associated with less edema and necrosis. Presence of catechin, vinallic acid, P-coumeric acid and quercitin identified through HPLC support the effectiveness of Pc. Cr in hypertension, AMI and LVH. Pc. Cr showed no significant adverse effects in Sprague Dawley albino rats after acute & sub-acute treatment in histopathological investigation. Extract of Populus ciliata showed vasorelaxant, hypotensive and cardioprotective effect in Sprague Dawley albino rats and white albino rabbit by mediating EDRF and voltage dependent L-type CCB mechanism respectively.

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.

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.

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.

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.

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.

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.

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.

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 (KATP) 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.

Vasorelaxant 4,5-seco-abietane diterpenoids with diverse 6/6/6, 6/6/7, and 6/6/8 architectures from Salvia prattii Hemsl.

Salpratins A-D (1-4), four new 4,5-seco-abietane diterpenoids, along with twelve known analogues, featuring diverse 6/6/6, 6/6/7, and 6/6/8 rings system, were isolated from Salvia prattii Hemsl. Particularly, salpratin A is the first example of 4,5;12,13-bis-seco-abietane diterpenoid features with a 5/6/6/6 ring system. Their structures were determined by analyses of comprehensive NMR and MS spectroscopic data and single-crystal X-ray diffractions. In addition, compounds 1, 3, 4, 6, 7, 8 and 14 showed potent vasorelaxant activity on endothelium-intact thoracic aorta rings precontracted with KCl.

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.

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.

Four new corynanthe-type alkaloids from the roots of Alstonia scholaris.

Four new corynanthe-type alkaloids, meloslines C-F (1-4), together with four known ones (5-8) were isolated from the roots of Alstonia scholaris. Their structures including absolute configurations were elucidated by extensive spectroscopic analysis and electronic circular dichroism (ECD) calculation. Compounds 1 and 2 exhibited potent vasorelaxant activity on endothelium-intact renal arteries precontracted with KCl.

Curcumane C and (±)-curcumane D, an unusual seco-cadinane sesquiterpenoid and a pair of unusual nor-bisabolane enantiomers with significant vasorelaxant activity from Curcuma longa.

A new seco-cadinane sesquiterpenoid (curcumane C, 1) and a pair of new nor-bisabolene enantiomers [(+)- and (-)-curcumane D, 2a and 2b] were isolated from C. longa. Compound 1 possesses an unusual 4,5-seco-cadinane skeleton with a tetrahydrophthalide moiety, while 2a and 2b contain an unusual 15-nor-bisabolene skeleton with a chromone core. All compounds exhibited significant vasorelaxant effects against KCl-induced contraction of rat aortic rings. Compound 1 also exhibited a vasorelaxant effect against phenylephrine-induced contraction of rat aortic rings. Meanwhile, compound 1 showed a stronger vasorelaxant effect in endothelium-intact rat aortic rings compared with endothelium-denuded rat aortic rings, indicating that vasodilation by 1 involved both endothelium-dependent and endothelium-independent pathways. Furthermore, compound 1 increased the NO content in human umbilical vein endothelial cells and its vasorelaxant effect could be attenuated by treatment with L-NAME, an endothelium NO synthase inhibitor. Thus, the underlying vasodilatory mechanisms of 1 may be mediated via abrogation of extracellular Ca2+ influx and regulation of NO release in vascular endothelial cells.