Vascular effects of Tanacetum vulgare L. leaf extract: in vitro pharmacological study

Aim of the study

Tanacetum vulgare L. (Asteraceae/Compositae) is principally used in traditional Moroccan medicine as antihypertensive remedy. The aim of the present study was to investigate the in vitro vascular activity of the aqueous extract of Tanacetum vulgare L.

Materials and Methods

The activity of Tanacetum vulgare L. extract was tested on contractile response of Wistar rat aorta to high KCl and noradrenaline and on endothelium-dependent relaxation evoked by acetylcholine.

Results

The addition of Tanacetum extract during the plateau phase of noradrenaline-evoked contraction produced a rapid relaxation that reached a maximum of 30% of the contraction and was suppressed by the NO synthase inhibitor N^G-nitro-l-arginine. At higher extract concentrations this rapid relaxation was followed by a slowly developing, N^G-nitro-l-arginine-resistant, relaxing effect. Tanacetum extract also depressed KCl-evoked contraction by 30% at maximum. This effect was abolished in the presence of N^G-nitro-l-arginine. The endothelium-dependent relaxation induced by acetylcholine was depressed in the presence of Tanacetum extract in the bathing solution.

Conclusion

:This study indicates that the aqueous extract of Tanacetum possesses NO-mediated and NO-independent vasorelaxing properties in vitro.     

Effect of aqueous extract of Ajuga iva supplementation on plasma lipid profile and tissue antioxidant status in rats fed a high-cholesterol diet

The present study was designed to explore the possible antioxidant and hypolipidemic effects of the aqueous extract of Ajuga iva (0.5% in the diet) in rats fed a high-cholesterol (1%) diet (HCD). The results indicated that the HCD-Ai versus HCD treatment led to many changes in biochemical parameters. They showed a decrease of plasma total cholesterol (TC) and VLDL-cholesterol but an increase of HDL(2)-cholesterol. The triacylglycerol contents were reduced in plasma and in VLDL. The lipid peroxidation determined by TBARS was decreased by 75% in plasma. TBARS in liver, heart and kidneys were highly reduced excepted in the adipose tissue. Ajuga iva treatment enhanced superoxide dismutase activity in liver and kidney. Glutathione reductase activity was lowered in adipose tissue but increased in liver and in kidney. A significant increase was noted in glutathione peroxidase activity in liver, heart and kidney but a low value in adipose tissue was observed. In conclusion, the present study demonstrates that in addition to its potent TG and TC-lowering effects, Ajuga iva is effective in improving the antioxidant status by reducing lipid peroxidation in plasma and tissues and enhancing the antioxidant enzymes in rats fed high-cholesterol diet. Furthermore, Ajuga iva may reduce intestinal cholesterol absorption.     

Nitric oxide-mediated endothelium-dependent relaxation of rat thoracic aorta induced by aqueous extract of red rice fermented with Monascus ruber

Vasodilatory effects of aqueous extract of red rice fermented with Monascus ruber IFO32318 were examined on the isolated rat aorta. The water phase of fermented rice with Monascus (WP/FRM, 0.1-10 mg/ml) caused a transient relaxation of the endothelium-intact rat aorta precontracted with norepinephrine (NE, 300 nM). The WP/FRM-induced relaxation was abolished by removal of endothelium or in the presence of N(G)-nitro-L-arginine (L-NNA, 10 microM), a nitric oxide (NO) synthase inhibitor. Neither atropine, a muscarinic receptor antagonist (10 microM), nor indomethacin, a cyclooxygenase inhibitor (10 microM), altered the WP/FRM-induced endothelium-dependent relaxation. gamma-Aminobutyric acid (GABA), one of the principle components of the extract, did not affect the muscle tension of the aorta with intact endothelium. In addition, WP/FRM increased the production of NO in primary cultured endothelial cells from human umbilical vein. The enhanced production of NO by WP/FRM was diminished by pretreatment with L-NNA (10 microM). In conclusion, WP/FRM induces relaxation of rat aorta by releasing NO from endothelium. There seem to be some unknown factor(s) other than acetylcholine (Ach) and GABA, in the aqueous extract of red rice, which stimulate vascular endothelial cells to produce and/or release NO leading to endothelium-dependent relaxation by WP/FRM.     

Effects of an aqueous extract of Terminalia arjuna on isolated rat atria and thoracic aorta

Terminalia arjuna (Combretaceae) is used traditionally in ayurveda, to treat a variety of cardiovascular disorders. The aims of this study were to characterize the positive inotropic effect of the aqueous extract of T. arjuna bark in isolated paced rat left atria and to study its effects on a vascular smooth muscle preparation, the rat thoracic aorta. The crude and semipurified aqueous extracts produced a positive inotropic effect of rat atria and the maximum contraction was comparable to that produced by isoprenaline. The positive inotropic effect of the extract was completely blocked by a β-adrenoceptor blocker, propranolol, and an uptake-1 blocker, cocaine. In precontracted aorta, the aqueous extract produced a contraction followed by relaxation. Propranolol did not block the relaxant effect of the aqueous extract. It is concluded that the positive inotropic effect of the aqueous extract was mediated via an action on β₁-adrenoceptors and was likely to be due to the release of noradrenaline from the sympathetic nerve endings. The vasorelaxant effect of the extract, however, was not mediated via an action on β₂ adrenoceptor.     

Effects of phenylpropanoid and iridoid glycosides on free radical-induced impairment of endothelium-dependent relaxation in rat aortic rings.

The protective effect of phenylpropanoid glycosides, forsythoside B and alyssonoside, and the iridoid glycoside lamiide, isolated from the aerial parts of Phlomis pungens var. pungens, against free radical-induced impairment of endothelium-dependent relaxation in isolated rat aorta was investigated. Aortic rings were exposed to free radicals by the electrolysis of the physiological bathing solution. Free radical-induced inhibition of the endothelium-dependent relaxation in response to acetylcholine was countered by incubation of the aortic rings before electrolysis with the aqueous extract (200 microg/ml), phenylpropanoid fraction (100 microg/ml) and iridoid fraction (150 microg/ml) of P. pungens var. pungens. Major components of the phenylpropanoid fraction forsythoside B and alyssonoside also prevented the inhibition of the acetylcholine response, at 10(-4) M concentration. However, the major component of iridoid fraction lamiide was found ineffective at the same concentration. The protective activity of phenylpropanoid glycosides against the free radical-induced impairment of endothelium-dependent relaxation may be related to their free radical scavenging property.     

Anti-hypertensive effects of the methanol/methylene chloride stem bark extract of Mammea africana in l-NAME-induced hypertensive rats

AIM OF THE STUDY: The methanol/methylene chloride (CH(3)OH/CH(2)Cl(2)) extract from the stem bark of Mammea africana was showed to possess vasodilating effect in the presence and the absence of N(omega)-nitro-l-arginine methyl ester (l-NAME). The present study was designed to evaluate the effects of the methanol/methylene chloride from the stem bark of Mammea africana. MATERIALS AND METHODS: The extract (200 mg/(kg day)) was administered orally in rats treated concurrently with l-NAME (40 mg/(kg day)). l-Arginine (100 mg/(kg day)) and captopril (20 mg/(kg day))were used as positive controls. Bodyweight, systolic arterial blood pressure and heart rate were measured weekly throughout the experiment period (28 days). At the end of treatment, animals were killed and the cardiac mass index evaluated. The aorta was used to evaluate the endothelium-dependant relaxation to carbachol. The aorta contraction induced by noradrenalin was also examined and expressed as a percentage of that induced by KCl. RESULTS: The extract neither affected the body weight nor the heart rate. The extract as captopril completely prevented the development of arterial hypertension. Both the substances failed to restore the endothelium-dependent vascular relaxation and increased the vascular contraction to norepinephrine in relation to KCl contraction. They also significantly reduced the left ventricular hypertrophy induced by l-NAME. CONCLUSION: These findings are in agreement with the traditional use of Mammea africana in the treatment of arterial hypertension and indicate that it may have a beneficial effect in patients with NO deficiency but will be unable to improve their endothelium-dependent vasorelaxation.     

Hypolipidemic effects of acute and sub-chronic administration of an aqueous extract of Ajuga iva L. whole plant in normal and diabetic rats

Diabetes is often accompanied by lipid abnormalities, which contribute significantly to cardiovascular (CV) morbidity and mortality in diabetic patients. The plant Ajuga iva (L.) Schreiber (Labiatea) is used in the treatment of diabetes in Moroccan folk medicine. Previously, we have demonstrated potent hypoglycemic activity and relatively non-toxic nature of a lyophilized aqueous extract of the whole plant (AI-extract) in normal (normoglycemic) and streptozotocin (STZ)-diabetic rats. In this study, we examined the AI-extract for its possible lipid-lowering activity in normal and STZ-diabetic rats. Taurine (TR) and glibenclamide (GLB) were used as reference substances. As shown previously, the AI-extract (10 mg/kg; oral) reduced plasma glucose levels after acute (single) and sub-chronic (3 weeks) dosing both in normal and diabetic rats. In normal rats, single and repeated oral administration of the AI-extract, at a dose of 10 mg/kg produced a small but significant decrease in plasma CHL levels (P<0.05). A single dose of the AI-extract did not produce a significant change in plasma TG, but sub-chronic dosing (for up to 21 days) caused a significant decrease in plasma TG (P<0.05). In STZ-diabetic rats, a single dose as well as repeated (3 weeks) treatment with the AI-extract produced a significant decrease in plasma CHL (P<0.01), and triglyceride (P<0.01) levels. The AI-extract also prevented weight loss in the diabetic animals. In summary, an aqueous extract of the Ajuga iva whole plant showed hypolipidemic activity, in addition to its hypoglycemic effect in normoglycemic and diabetic rats. In view of the hypoglycemic and hypolipidemic activity, and its relatively non-toxic nature (shown previously), Ajuga iva may be a candidate for development as an anti-diabetic agent in humans. Further studies are warranted to confirm our results and fractionate the AI-extract to isolate and identify the active principle(s), and to determine the exact mechanism(s) of action.     

芝麻素对代谢综合征大鼠主动脉内皮功能损伤的保护作用及机制

目的:观察芝麻素对代谢综合征大鼠主动脉内皮功能损伤的保护作用,探讨其可能机制。方法:高脂高糖诱导大鼠代谢综合征24周,于第9周开始连续口服芝麻素(120,60,30mg.kg^-1·d^-1)16周。测血压、血脂、血糖、血清过氧化氢和硝酸盐/亚硝酸盐含量;采用离体灌流系统,观察大鼠主动脉环对累积浓度去氧肾上腺素的收缩反应和对乙酰胆碱及硝普钠诱发的舒张反应;免疫组织化学法观察主动脉内皮型一氧化氮合酶(eNOS)表达和硝基酪氨酸(NT)含量。结果:芝麻素明显降低代谢综合征大鼠血压、血脂、血糖;提高主动脉环对乙酰胆碱诱导的舒张反应;上调主动脉eNOS表达,降低NT含量;升高血清硝酸盐/亚硝酸盐和减少过氧化氢含量。结论:芝麻素具有改善代谢综合征大鼠的内皮功能障碍,其机制可能与其降低氧自由基生成,上调主动脉eNOS表达,增加和(或)恢复NO的生物活性有关。     

Cardiovascular effects in rodents of the methanolic extract of the stem bark of Khaya senegalensis A. Juss

The methanolic bark extract of Khaya senegalensis was investigated for its effects on the cardiovascular system. The extract increased the blood pressure of chloralose anaesthetized rats. The increase in rate and force of contraction of isolated, spontaneous rabbit atria evoked by the extract were dose dependent and less pronounced than those produced by isoprenaline. The chronotropic effects of the extract and isoprenaline were antagonized by propranolol which also abolished the ionotropic effect of the extract and antagonized isoprenaline-induced inotrophy. The vasoconstrictor effect of the extract observed with isolated spiral strips of rabbit aorta was dose dependent, less potent than noradrenaline and was abolished by prazosin. These findings indicate that the hypertensive effect of the methanolic bark extract of K. senegalensis is partly due to the stimulation of β-receptors and α-adrenoceptors.     

Beneficial effect of aqueous garlic extract on the vascular reactivity of streptozotocin-diabetic rats

The present study evaluated the beneficial effect of aqueous extract of garlic (Allium sativum L.; 100mg/kg/day) on the alterations in vascular reactivity of streptozotocin-diabetic rats. After 8 weeks of treatment, thoracic aortic rings of rats were mounted in organ baths and contractile responses to phenylephrine and relaxant responses to acetylcholine and isosorbide dinitrate were assessed. Induction of diabetes significantly increased contractile responses to phenylephrine and impaired endothelium-dependent relaxations to acetylcholine in aortic rings, but did not change endothelium-independent relaxation to isosorbide dinitrate. Garlic administration significantly improved the impaired endothelium-dependent relaxations and decreased the enhanced contractile response to phenylephrine in diabetic rats. It is concluded that intraperitoneal administration of aqueous garlic extract can improve endothelial dysfunction in insulin-dependent model of uncontrolled diabetes.     

Arbutus unedo induces endothelium-dependent relaxation of the isolated rat aorta

Arbutus unedo L. (Ericaceae) is used in oriental Morocco to treat arterial hypertension. We studied its vasodilator effect and mechanisms of action in vitro. The root aqueous extract of Arbutus (0.25 mg/mL) produced a relaxation of noradrenaline-precontracted ring preparations of rat aorta with intact endothelium. Relaxation by Arbutus did not occur in specimens without endothelium and was inhibited by pretreatment with 100 microM N(G)-methyl-L-arginine (L-NMA), 10 microM methylene blue or 50 microM 1H-[1,2,4] oxadiazolo [4,3-a] quinoxaline-1-one (ODQ) but not by 10 microM atropine. These results suggest that Arbutus produces an endothelium-dependent relaxation of the isolated rat aorta which may be mediated mainly by a stimulation of the endothelial nitric oxide synthase by mechanisms other than activation of muscarinic receptors.     

Vasodilating properties of extracts from the leaves of Musanga cecropioides (R. Brown)

The mechanisms of action involved in the hypotensive properties of the aqueous extract of the leaves of Musanga cecropioides were investigated. The effect of the aqueous leaf extract of M. cecropioides, found to contain mostly saponins, flavonoids and procyanidins, was investigated on vascular smooth muscle and also in an in vivo direct invasive blood pressure study in both normotensive and hypertensive rats. The hypotensive or antihypertensive properties of the extracts appear to be due partly to a direct or indirect vasodilator effect and also to some alpha(1)- and beta(2)-adrenergic blocking effects. The extract also exhibited significant endothelium-dependent vascular smooth muscle relaxation, accounted for by the release of nitric oxide (NO), and induced significant angiotensin converting enzyme (ACE) inhibitory effects thereby supporting its vasodilator mechanism of action.     

Endothelium-dependent contraction of rat thoracic aorta induced by gallic acid

The vascular effect of a component of hydrolysable tannins, gallic acid, was examined in isolated rat thoracic aorta. Gallic acid exerted a contractile effect on the phenylephrine- or prostaglandin F(2/alpha)-precontracted endothelium-intact arteries. In endothelium-denuded arteries, the contractile response to-gallic acid was absent. Pretreatment with N(G)-nitro-L-arginine methyl ester (30 microM) abolished the gallic acid-induced contraction. Pretreatment with indomethacin (10 microM) or BQ610 (100 nM) had no observed effect. Pretreatment with gallic acid (1-10 microM) significantly attenuated the relaxation induced by acetylcholine, and that with 10 microM gallic acid also reduced the potency of sodium nitroprusside in the relaxation, without a reduction in efficacy, in endothelium-denuded arteries. These findings indicate that gallic acid induced endothelium-dependent contraction and strongly inhibited the endothelium-dependent relaxation rather than the endothelium-independent relaxation, probably through inhibition of endothelial nitric oxide (NO) production. Since NO plays an important role in vasodilative regulation and inflammatory disorders, these findings may also indicate that gallic acid interferes with the inflammatory responses.     

Antispasmodic property of the aqueous extract of Aristolochia albida Duch

The antispasmodic property of the underground parts of Aristolochia albida Duch (family: Aristolochiaceae) was evaluated. The evidence was provided by the aqueous extract of the plant's rhizome which exhibited significant relaxation of the spontaneous pendular contraction of isolated rabbit duodenum. The extract at moderate doses abolished acetylcholine (Ach), histamine and 5-hydroxytryptamine (5-HT) induced contractions on isolated rabbit duodenum and guinea-pig ileum. The effects of the extract mimicked antagonists (atropine, mepyramine and methysergide). Therefore, the extract evoked its antispasmodic actions by antagonism via muscarinic, histaminic and 5-HT receptors. © 1997 John Wiley & Sons, Ltd.     

Endothelium-dependent and direct relaxation induced by ethyl acetate extract from Flos Chrysanthemi in rat thoracic aorta

The aims of the present study were to investigate the vasoactive effects of ethyl acetate extract from Flos Chrysanthemi (FCE) and its mechanisms on the rat thoracic aorta. FCE (9.4-150 mg/L) caused a concentration-dependent relaxation on endothelium-intact rings precontracted with phenylephrine (PE, 10(-6)M) or a high level of K+ (6x10(-2)M). By removal of endothelium, the effect was not abolished but reduced significantly. N(G)-nitro-l-arginine methyl ester (l-NAME) (10(-4) M), methylene blue (10(-5) M) significantly inhibited the effect of FCE. Meanwhile, NO synthase of aorta in FCE group was markedly elevated versus the control. However, indomethacin did not influence FCE effect. SKF-525A combined with l-NAME had the same effect as l-NAME. Tetraethylammonium, BaCl2, 4-aminopyridine, 5-HD and propranolol also did not influence the vascular effect of FCE, but glibenclamide significantly attenuated its vasodilation. FCE did not reduce PE-induced transient contraction in Ca(2+)-free medium, but inhibited PE-induced contraction in K(+)-free solution or Ca2+ caused contraction after PE induced a stable contraction in Ca(2+)-free solution. It is concluded that FCE induced both endothelium-dependent and -independent relaxation. NO and cGMP-mediated pathway are likely involved in the endothelium-dependent relaxation, whereas inhibition of voltage-dependent Ca2+ channel, receptor-operate Ca2+ channel and activation of K(ATP) contribute in part to the endothelium-independent relaxation.     

Pharmacological investigation of Ocimum gratissimum in rodents.

The pharmacological activities were screened of aqueous extracts of Ocimum gratissimum in isolated rabbit jejunum (IRJ); rat stomach strip (RSS); and also its analgesic properties in mice. The extract caused a dose dependent inhibition of the rabbit jejunum spontaneous pendular movement. The blocking effect on acetylcholine induced contraction was non-competitive in the rat stomach strip since maximum contractions were suppressed and no parallel shift was observed in the curve. The result of the analgesic study showed that the extract evoked a prolongation of reaction time of 85% ( p < 0. 05) over 20 min observation time with no overt signs of toxicity. These results suggest the presence of analgesic and spasmolytic activities.     

Hypotensive effect of the hydroalcoholic extract from Jacaranda mimosaefolia leaves in rats

Hypothermic and cardiovascular activities of the methanol extract of Jacaranda mimosaefolia leaves were tested. To evaluate the hypotensive properties, anesthetized rats were used and temperature, blood pressure, and cardiac frequency were recorded. In addition, the in vitro effect produced by the extract on induced contraction with norepinephrine (NE) in rat aorta rings was evaluated. The extract produced a significant hypothermic effect with a maximum at 2 h, an effect which was accompanied by hypotension and low cardiac frequency, physiological conditions that were again re-established to the following 2 h. In isolated aorta preparations norepinephrine antagonistic effect was not correlated with the presence of Ca2+, pD2 for NE was modified by the extract, an effect that could explain a blockade of the adrenergic receptors.     

Effects of Crataegus microphylla on Vascular Dysfunction in Streptozotocin‐induced Diabetic Rats

Vascular dysfunction plays a key role in the pathogenesis of diabetic vascular disease. In this study, we aimed to investigate whether chronic in vivo treatment of Crataegus microphylla (CM) extract in diabetic rats induced with streptozotocin (STZ, intraperitoneal, 65 mg/kg) preserves vascular function and to evaluate whether the reduction of inducible nitric oxide synthase (iNOS), proinflammatory cytokines, and lipid peroxidation mediates its mechanisms of action. Starting at 4 weeks of diabetes, CM extract (100 mg/kg) was administrated to diabetic rats for 4 weeks. In aortic rings, relaxation to acetylcholine and vasoreactivity to noradrenaline were impaired, whereas aortic iNOS expression and plasma tumor necrosis factor‐α (TNF‐α) and interleukin‐6 (IL‐6), total nitrite–nitrate, and malondialdehite levels were increased in diabetic rats compared with controls. Chronic CM treatment significantly corrected all the above abnormalities in diabetic rats. In comparison, pretreatment of the aorta of diabetic rats with N‐[3(aminomethyl) benzyl]‐acetamidine, dihydrochloride (10^–5 M), a selective inhibitor of iNOS, produced a similar recovery in vascular reactivity. These results suggest that chronic in vivo treatment of CM preserves endothelium‐dependent relaxation and vascular contraction in STZ‐induced diabetes, possibly by reducing iNOS expression in the aorta and by decreasing plasma levels of TNF‐α and IL‐6 and by preventing lipid peroxidation. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects on rat uterine and aorta strip smooth muscle of Thymus leptophyllus extract

The diethylether extract from Thymus leptophyllus was found to be more active on uterine smooth muscle than on aorta strips. Rat uterus experiments with and without extracellular calcium, yielded similar IC₅₀ values. A non-specific mechanism for the relaxant activity can therefore be postulated. In rat aorta and in the presence of extracellular calcium the extract inhibited the contractile response induced by K⁺ depolarizing solution and had a less inhibitory effect on noradrenaline (NA) contraction. In a Ca²⁺-free solution the extract strongly reduced the Ca²⁺-release induced by NA, but it did not affect the transient contraction caused by caffeine (CAF).     

Scutellarin-induced endothelium-independent relaxation in rat aorta

Scutellarin is a flavonoid extracted from the traditional Chinese herb, Erigeron breviscapus Hand Mazz. In the present study, the vasorelaxant effects of scutellarin and the underlying mechanism were investigated in isolated rat aorta. Scutellarin (3, 10, 30, 100 microm) caused a dose-dependent relaxation in both endothelium-intact and endothelium-denuded rat aortic rings precontracted with noradrenaline bitartrate (IC(50) = 7.7 +/- 0.6 microm), but not with potassium chloride. Tetraethylammonium, glibenclamide, atropine, propranolol, indomethacin and N(G)-nitro-l-arginine methyl ester had no influence on the vasorelaxant effect of scutellarin, which further excluded the involvement of potassium channels, muscarinic receptor, nitric oxide pathway and prostaglandin in this effect. Pretreatment with scutellarin decreased the tonic phase, but not the phasic phase of the noradrenaline bitartrate induced tension increment. Scutellarin also alleviated Ca(2+)-induced vasoconstriction in Ca(2+)-depleted/noradrenaline bitartrate pretreated rings in the presence of voltage-dependent calcium channel blocker verapamil. The noradrenaline bitartrate evoked intracellular calcium increase was inhibited by scutellarin. Scutellarin had no effect on phorbol-12,13-diacetate induced contraction in a calcium-free bath solution. These results showed that scutellarin could relax thoracic artery rings in an endothelium-independent manner. The mechanism seems to be the inhibition of extracellular calcium influx independent of the voltage-dependent calcium channel.