Hypotensive Activity of Lannea coromandelica Bark Extract

An ethanol extract of Lannea coromandelica bark (ELC) showed hypotensive activity in anaesthetized dogs and rats. On intravenous administration (i.v.) at a dose range of 5–100 mg/kg in dogs and 1–25 mg/kg in rats it produced a mild to marked decrease in the arterial blood pressure in a dose dependent manner. The effect did not alter after cholingergic, histaminergic, adrenergic and ganglion receptor blockade. The hypotension was also unchanged in vagotomized and eviscerated dogs, whereas there was a slight increase in hypotension in the spinal preparation. It produced dose related decreases in heart rate, without any effect on respiratory rate.     

Cardiovascular effects of the South American medicinal plant Cecropia pachystachya (ambay) on rats

Cecropia pachystachya is used in South America for relieving cough and asthma. In Argentina it is known as "ambay" and grows in the neotropical forests (Ntr C.p.) and in temperate hilly regions (Tp C.p.). To evaluate their cardiovascular profile, the effect of extracts obtained from plants growing in the neotropical region as well as in temperate areas were compared by i.v. administration in normotensive rats. The following parameters were measured: blood pressure (BP) and heart rate (HR). The hypotensive effect was stronger for Ntr C.p., which aqueous extract decreased BP at doses between 90 and 300 mg lyophilised/kg until 46.2 +/- 12% of basal. The extract of Tp C.p. reduced BP to 86.1 +/- 11% of basal (p < 0.05 respect to Ntr C.p.) at 180 mg/kg, but increased HR at 90 and 180 mg/kg (until 133.6 +/- 10.8% of basal, p < 0.05) and produced death by respiratory paralysis at 320 mg/kg (about 3g dry leaves/kg). The hypotensive effects, but not the chronotropic ones, were attenuated by pretreatment with reserpine (5 mg/kg). The plant extracts had not diuretic activity by oral administration in conscious rats, nor produced vasodilation of perfused hindquarters arterial bed precontracted with high-[K] or 100 microM phenylephrine. The results suggest that neotropical ambay is more hypotensive than the one from the temperate hilly region. When it reaches plasma, it could produce hypotension (by central blockade of sympathic innervation of vessels) and tachycardia (by central cholinergic inhibition of heart), although it happens at doses higher than the oral ethnotherapeutic (about 340 mg dried leaves/kg).     

Hypotensive effect of aqueous saffron extract (Crocus sativus L.) and its constituents,safranal and crocin,in normotensive and hypertensive rats

In this study, the effects of saffron (Crocus sativus) stigma aqueous extract and two active constituents, crocin and safranal, were investigated on blood pressure of normotensive and desoxycorticosterone acetate‐induced hypertensive rats. Three doses of crocin (50, 100 and 200 mg/kg), safranal (0.25, 0.5 and 1 mg/kg) and the aqueous extract (2.5, 5 and 10 mg/kg) were administered intravenously in different groups of normotensive and hypertensive animals and their effects on mean arterial blood pressure (MABP) and heart rate (HR) were evaluated. The aqueous extract of saffron stigma, safranal and crocin reduced the MABP in normotensive and hypertensive anaesthetized rats in a dose‐dependent manner. For example, administrations of 10 mg/kg of aqueous extract, 1 mg/kg of safranal and 200 mg/kg of crocin caused 60 ± 8.7, 50 ± 5.2 and 51 ± 3.8 mmHg reductions in MABP, respectively. It can be concluded that the aqueous extract of saffron stigma has hypotensive properties which appear to be attributable, in part, to the actions of two major constitutes of this plant, crocin and safranal. It seems that safranal is more important than crocin for lowering down blood pressure of rats. Copyright © 2009 John Wiley & Sons, Ltd.     

Mechanisms of cardiovascular activity of Andrographis paniculata in the anaesthetized rat

The cardiovascular activities of crude water extract (WE) of Andrographis paniculata (Burm. f.) Nees (Acanthaceae), its three semi-purified ethyl acetate (FA), n-butanol (FB) and aqueous (FC) fractions, as well as andrographolide, a major plant constituent, were elucidated in anaesthetized Sprague-Dawley (SD) rats for the very first time. FA and andrographolide, which possesses multiple pharmacological activities, elicited no drop in mean arterial blood pressure (MAP), while WE, FB and FC produced a significant fall in MAP in a dose-dependent manner without significant decrease in heart rate. The ED₅₀ values for WE, FB and FC were 11.4, 5.0 and 8.6 mg/kg, respectively. These suggested that the hypotensive substance(s) of the crude water extract was concentrated in FB. Pharmacological antagonist studies were consequently only tested in FB (5 mg/kg). The hypotensive action of FB was not mediated through effects on the β-adrenoceptor, muscarinic cholinergic receptor and angiotensin-converting enzyme, for it was not affected by propranolol, atropine and captopril, respectively. However, it seems to work via α-adrenoceptors, autonomic ganglion and histaminergic receptors, since the hypotensive effect of FB was negated or attenuated in the presence of phentolamine, hexamethonium as well as pyrilamine and cimetidine.     

Saponins from the leaves of Musanga cecropioïdes (cecropiaceae) constitute a possible source of potent hypotensive principles

The aqueous leaf extract and saponins extracted from the aqueous leaf extract of Musanga cecropioïdes exhibited potent hypotensive effects in both normotensive and hypertensive rats. The intravenous administration (direct invasive blood pressure study technique) of 15–30 mg/kg body weight of the aqueous leaf extract produced a fall in blood pressure (BP) of 35%–57% in hypertensive rats and 27% in normotensive individuals. This BP fall was followed by a transient rise, while saponins extracted from the aqueous extract of the leaves of MC produced a fall in BP of 55% in hypertensive and 30% in normotensive rats. In the indirect (tail cuff) blood pressure study, the effect was also dose-dependent. The oral administration of 300 mg/kg body weight of the aqueous leaf extract produced a BP fall of over 30% by 12 h following extract administration while the saponins (0.02–0.8 mg/kg body weight) produced a fall of 10% to 53%.     

Antihypertensive effects of isoquercitrin and extracts from Tropaeolum majus L.: evidence for the inhibition of angiotensin converting enzyme

Aim of the study

Previous studies have shown that the extracts obtained from Tropaeolum majus L. exhibit pronounced diuretic properties. In the present study, we assessed whether the hypotensive and/or antihypertensive mechanism of hydroethanolic extract (HETM), semi-purified fraction (TMLR) obtained from T. majus and the flavonoids isoquercitrin (ISQ) and kaempferol (KPF) can be mediated by their interaction with angiotensin converting enzyme (ACE).

Methods and methods

Firstly, to evaluate changes in mean arterial pressure (MAP), different groups of normotensive and spontaneously hypertensive rats (SHR) were orally and intraduodenally treated with HETM (10-300 mg/kg) and TMLR (12.5-100 mg/kg) and intravenously treated with ISQ and KPF being later anesthetized with ketamine (100 mg/kg) and xylazine (20 mg/kg). The left femoral vein and the right carotid artery were isolated, and polyethylene catheters were inserted for ISQ and KPF (0.5-4 mg/kg) administration and blood pressure recording, respectively. The plasmatic ACE activity was evaluated to indirect fluorimetry, in serum samples after orally treatment with HETM, TMLR, ISQ and KPF.

Results

The oral administration of the HETM and its TMLR significantly reduced, in a dose-dependent manner, the MAP in both normotensive and SHR. In addition, these preparations significantly decreased the MAP for up to 3 h after the administration of the extract. Additionally, the intravenous administration of ISQ, but not KPF, decreased MAP in rats. Otherwise, neither the extracts nor ISQ affected the heart rate. The oral administration of the HETM, TMLR or ISQ reduced ACE activity in serum samples at 90 min after administration. Finally, the intravenous administration of ISQ caused a significant reduction in the hypertensive response to angiotensin I, but not angiotensin II in normotensive rats.

Conclusion

Our results show that the hypotensive effects caused by the HETM, as well as by its TMLR, may be associated with the high levels of the flavonoid ISQ found in this plant. In addition, ISQ-induced hypotension in rats is an event dependent on the inhibition of angiotensin II generation by ACE.     

Possible mechanisms of action of the neutral extract from Bidens pilosa L. leaves on the cardiovascular system of anaesthetized rats

The aim of this study was to investigate the hypotensive and cardiac effects of the neutral extract from Bidens pilosa leaves. Intravenous administration of the extract resulted in a biphasic dose-related hypotensive activity. In normotensive rats (NTR), B. pilosa decreased systolic blood pressure by 18.26%, 42.5% and 30% at doses of 10, 20 and 30 mg/kg, respectively. In spontaneously hypertensive rats (SHR), the decrease in systolic blood pressure was 25.77%, 38.96% and 28.64% at the above doses, respectively. These doses induced hypotension by 27%, 34.13% and 18.73% respectively in salt-loaded hypertensive rats. In NTR, B. pilosa reduced heart rate by 23.68% and 61.18% at doses of 20 and 30 mg/kg, respectively. The force of contraction of the heart was only affected at 30 mg/kg. The initial phase of hypotensive response was partially inhibited by atropine while propranolol increased this effect. These results suggest that B. pilosa exhibited its fi rst hypotensive effects by acting on the cardiac pump efficiency and secondly through vasodilation.     

Pharmacological basis for the empirical use of Eugenia uniflora L. (Myrtaceae) as antihypertensive.

The rational basis for the use of Eugenia uniflora L. (Myrtaceae) as antihypertensive in Northeastern Argentina was assessed in normotensive rats. Intraperitoneal administration of the aqueous crude extract (ACE) decreased blood pressure (BP) of normotensive rats dose-dependently until 47.1 +/- 8.2% of control. The effective-dose 50 was 3.1 +/- 0.4 mg dried leaves/kg (d.l./kg) (yielding of ACE: 17% w/w). To determine the origin of hypotensive activity. Alpha-adrenergic antagonistic and vasorelaxant ACE activities were tested. The dose-response curve for phenylephrine on BP was inhibited non-competitively until 80% of its maximal effect (at 8 mg d.l. ACE/kg). Perfusion pressure (PP) of rat hindquarters (previously vasoconstricted by high-K+) was decreased by ACE in a concentration-dependent manner until -32.3 +/- 11.5% of tonic contraction at 1.2 g d.l. ACE/100 ml. In addition, A.C.E demonstrated diuretic activity at a dose (120 mg d.l./kg) higher than the hypotensive one. It was almost as potent as amiloride, but while amiloride induced loss of Na+ and saving of K+, ACE induced decrease in Na+ excretion. The results suggest that the empirical use of Eugenia uniflora L. (Myrtaceae) is mostly due to a hypotensive effect mediated by a direct vasodilating activity, and to a weak diuretic effect that could be related to an increase in renal blood flow.     

Hypotensive activity and toxicology of constituents from root bark of Polyalthia longifolia var. pendula

A defatted extract of Polyalthia longifolia var. pendula root bark (PRB) in 50% methanol showed a significant ability to reduce blood pressure. It caused a 22% and 47% fall in mean arterial blood pressure (MABP) in rats at doses of 3 mg/kg and 30 mg/kg, respectively. Compounds purified from this extract include kolavenic acid (3), clerodane (1) and its isomer (2), liriodenine (4), lysicamine (5) and bisclerodane imide (6) and its isomer (7). Of these, only kolavenic acid produced a 22% fall in MABP, at a dose of 30 mg/kg. PRB showed a decrease in blood pressure of normotensive and egg yolk induced hypertensive rats. The LD50 of PRB was determined as 100 mg/kg in mice.     

Hypotensive effect of crude root extract of Solanum sisymbriifolium (Solanaceae) in normo- and hypertensive rats

The hypotensive effect of the crude hydroalcoholic extract from root of Solanum sisymbriifolium Lam. (Solanaceae) was investigated both in normotensive and hypertensive rats. The intravenous administration of the extract (50 and 100 mg/kg) produced a significant decrease in blood pressure in anaesthetized hypertensive (adrenal regeneration hypertension + deoxycorticosterone acetate (ARH + DOCA)) rats. Oral administration of the extract (10, 50, 100 and 250 mg/kg) also produced a dose-dependent hypotensive effect in conscious hypertensive animals. In anaesthetized normotensive rats, the extract (50 and 100 mg/kg, i.v.) also induced hypotension in a dose-dependent manner. Lastly, no significant effect on blood pressure was produced by the extract when administered orally (10, 50, 100, 250, 500 and 1000 mg/kg) to conscious normotensive rats.     

Cardiovascular effects of an extract from the roots of a shrub Elaeophorbia drupifera.

A crude extract was prepared from the roots of E. drupifera. Lethality studies in mice showed a dose-mortality relationship with an LD(50) of 145 mg/kg mice i.p. The extract (2-260 microg/kg. i.v.) was tested in graded doses on the blood pressure and heart rate of urethane anaesthetized rats. The results showed that the extract decreased both the blood pressure and heart rate in a dose-dependent manner. The maximum decrease in blood pressure (control, 78.3 +/- 6. 5 mmHg) and heart rate (control, 120.2 +/- 5.5 beats/min) produced by the extract was about 46.2% and 41.7% (% control), respectively. Blocking the beta adrenoceptors with propranolol (0.5 microg/kg. i.v. ) did not prevent the action of the extract on both the blood pressure and heart rate, suggesting that the extract was acting at a different site. This view was supported by the observation that the extract significantly depressed the increase in blood pressure and heart rate caused by bilateral occlusion of the common carotid artery. Also, the extract was found to prolong ACh-induced hypotension in the rats. In animals pretreated with atropine sulphate (0.2 mg/kg. i.v), the extract was less effective in depressing the blood pressure. However, this atropine antagonism was surmounted by raising the concentration of the extract. Finally, in vitro studies using isolated arterial strips revealed that the extract also had a relaxant effect on vascular smooth muscle. This relaxant effect was dose-dependent and was attenuated and/or abolished by phentolamine (0.5 microg/mL). Also, the extract relaxed aortic strips precontracted with noradrenaline (1 x 10(-7) mol L(-1)) but failed to relax strips precontracted with KCl (50 mmol/L). We conclude that the crude extract from the roots of E. drupifera probably contains acetylcholine-like agent(s) which interferes with the cholinergic mechanism, as well as catecholamine-like agent(s) exhibiting mainly alpha-adrenoceptor activity.     

Activation of nitric oxide signaling pathway mediates hypotensive effect of Muntingia calabura L. (Tiliaceae) leaf extract

The cardiovascular effect of the crude methanol extract from the leaf of Muntingia calabura L. (Tiliaceae) was investigated in the anesthetized rats. The crude methanol extract was sequentially fractionated to obtain the water-soluble extract (WSE). Intravenous administration of the WSE (10, 25, 50, 75 or 100 mg/kg) produced an initial followed by a delayed decrease in systemic arterial pressure (SAP) in a dose-dependent manner. The M. calabura-induced initial hypotension lasted for 10 min and the delayed depressor effect commenced after 90 min and lasted for at least 180 min post-injection. The same treatment, on the other hand, had no appreciable effect on heart rate (HR) or the blood gas/electrolytes concentrations. Both the initial and delayed hypotensive effects of WSE (50 mg/kg, i.v.) were significantly blocked by pre-treatment with a nonselective nitric oxide (NO) synthase (NOS) inhibitor, N(G)-nitro-L-arginine methyl ester ((L)-NAME, 0.325 mg/kg/min for 5 min) or a soluble guanylate cyclase (sGC) inhibitor, 1H-[1,2,4]oxadiazole[4,3-alpha]quinoxalin-1-one (ODQ, 0.2 mg/kg/min for 5 min). Moreover, whereas the initial depressor effect of WSE was inhibited by pre-treatment with a selective endothelial NOS (eNOS) inhibitor, N5-(1-Iminoethyl)-L-ornithine ((L)-NIO, 1 mg/kg/min for 5 min), the delayed hypotension was attenuated by a selective inducible NOS (iNOS) inhibitor, S-methylisothiourea (SMT, 0.5 mg/kg/min for 5 min). Administration of WSE also produced an elevation in plasma nitrate/nitrite concentration, as well as an increase in the expression of iNOS protein in the heart and thoracic aorta. These results indicate that WSE from the leaf of M. calabura elicited both a transient and delayed hypotensive effect via the production of NO. Furthermore, activation of NO/sGC/cGMP signaling pathway may mediate the M. calabura-induced hypotension.     

Effect of a diterpenoid from Salvia cinnabarina on arterial blood pressure in rats

The effect of a diterpenoid isolated from Salvia cinnabarina, 3,4-seicosopimar-4(18),7,15-triene-3-oic acid (SCB), on arterial blood pressure was evaluated in anaesthetized rats. Male Wistar rats, anaesthetized with urethane (sol. 10% p/v; 10 mL/kg), underwent surgery for continuous monitoring of arterial blood pressure. After preliminary experiments to evaluate the dose response (3, 10 and 30 mg/kg i.v.) of SCB, a dose of 3 mg/kg was chosen for all successive experiments. On different groups of rats treated with the ganglion-blocking agent chlorisondamine (2.5 mg/kg i.p.) the effect of SCB (3 mg/kg i.v.) was evaluated before and following an infusion of the nitric oxide synthase inhibitor L-NAME (0.3 mg/kg/min i.v.). Intravenous administration of SCB at doses of 3, 10 and 30 mg/kg led to a fall in mean arterial blood pressure (MABP) of 14.75 +/- 1.44 mmHg, 36.60 +/- 31.40 mmHg and 31.40 +/- 6.28 mmHg, respectively (n = 4-5), that was not modified by treatment of the rat with chlorisondamine nor with L-NAME. The results demonstrate a hypotensive effect of SCB - due to a peripheral mechanism but independent of endothelial nitric oxide release.     

Studies on antihypertensive and antispasmodic activities of methanol extract of Acacia nilotica pods

A methanol extract of Acacia nilotica pods (AN) caused a dose-dependent (3-30 mg/kg) fall in arterial blood pressure. Treatment of animals with atropine abolished the vasodilator response of acetylcholine (ACh), whereas the antihypertensive effect of the plant extract remained unaltered. Phentolamine (an alpha-adrenergic blocker) abolished the vasoconstrictor effect of norepinephrine (NE), whereas pretreatment of the animal with AN, did not modify the NE response. These results indicate that the antihypertensive effect of plant extract is independent of muscarinic receptor stimulation or adrenoceptor blockade. In the in vitro studies, AN produced a dose-dependent (0.3-3.0 mg/mL) inhibitory effect on force and rate of spontaneous contractions in guinea-pig paired atria. Similarly, it inhibited the spontaneous contraction of rabbit jejunum in a concentration-dependent (0.1-3.0 mg/mL) manner. AN also inhibited K(+)-induced contractions in rabbit jejunum at a similar concentration range, which suggests that the antispasmodic action of AN is mediated through calcium channel blockade, and this may also be responsible for the blood pressure lowering effect of AN, observed in the in vivo studies.     

Acute diuretic, natriuretic and hypotensive effects of a continuous perfusion of aqueous extract of Urtica dioica in the rat

This study was performed on anaesthetized male Wistar rats that received a continuous intravenous perfusion during 1.25 h of an aqueous extract of aerial parts of Urtica dioica L. (Urticaceae) at a low dose of 4 mg/kg/h or at a high dose of 24 mg/kg/h, or furosemide (control diuretic) at a dose of 2 mg/kg/h. As compared with a control period in each rat, the arterial blood pressure was reduced proportionally to the dose of the perfusion of the plant extract (15 and 38%, P<0.001, respectively). These effects were accompanied by a correlative increase of diuresis (11 and 84%, P<0. 001, respectively) and natriuresis (28 and 143%, P<0.001, respectively). In the rats perfused by furosemide, the arterial blood pressure was reduced by 28% (P<0.001). The diuresis and natriuresis were also increased proportionally in this case (85 and 155%, P<0.001, respectively). Nevertheless, the hypotensive action of U. dioica was reversible during the recovery periods in about 1 h with the lower dose of the plant extract and furosemide, while the effect of the higher dose was persistent, indicating a possible toxic effect. In conclusion, the results demonstrate an acute hypotensive action of U. dioica that indicates a direct effect on the cardiovascular system. Moreover, diuretic and natriuretic effects were also observed, suggesting an action on the renal function. Finally, the plant extract seems to have a toxic effect at the higher dose.     

Blood pressure depression by the fruit juice of Carica papaya (L.) in renal and DOCA-induced hypertension in the rat

A crude ethanol extract was prepared from the unripened fruit of Carica papaya. Lethality studies showed a dose-mortality relationship with an LD(50) of 325.2 mg/kg in mice administered i.p. Male albino Wistar rats were randomly divided into three batches (15 rats per batch)-renal, DOCA-salt hypertensives and normotensives. Each batch was further divided into three groups-the untreated, hydrallazine and extract treated groups. The mean arterial blood pressure (MAP) and the heart rate were measured in all groups. From the results, the basal (control) MAP were 93.8 +/- 4.5, 175.2 +/- 5. 1 and 181.3 +/- 6.2 mmHg in the normotensive, renal and DOCA-salt hypertensives, respectively. Both hydrallazine (200 microg/100 g i. v) and extract (20 mg/kg.i.v) produced a significant depression of MAP in all groups (p < 0.01 vs controls), but the extract produced about 28% more depression of MAP than hydrallazine in the hypertensive groups. In another group of rats, the extract failed to depress the MAP in rats pretreated with propranolol, but atropine and noradrenaline pretreatment did not prevent the action of the extract on blood pressure. In vitro studies using isolated rabbit arterial (aorta, renal and vertebral) strips showed that the extract (10 microg/mL) produced relaxation of vascular muscle tone which was, however, attenuated by phentolamine (0.5-1.5 microg/mL). It is concluded that the fruit juice of C. papaya probably contains antihypertensive agent(s) which exhibits mainly alpha-adrenoceptor activity.     

Cardiovascular effects of Tabernaemontana pandacaqui

Intravenous injection of ethanolic extracts of the stem, leaf and flower of Tabernaemontana pandacaqui caused hypotension in pentobarbital anesthetized rats. At high doses (100-300 mg/kg), the flower extract showed a transient hypertensive effect preceeding hypotensive activity. The effects of the extracts on the heart rate of anesthetized rats correlated well with the negative chronotropic and inotropic activity observed with isolated atrium. The hypotensive activity was not inhibited by antihistaminic and antimuscarinic agents. The extracts had no effect on the pressor effects induced by norepinephrine or dual carotid occlusion. These results suggest that the hypotensive action of the extracts is not mediated through histaminic and muscarinic receptors stimulation, alpha-adrenoceptor blockade or interference of sympathetic transmission.     

Pharmacological effects of Eugenia uniflora (Myrtaceae) aqueous crude extract on rat's heart

The effect of aqueous crude extract (ACE) of Eugenia uniflora L. (Myrtaceae) was studied on rat's perfused ventricles. This plant is used in South American traditional medicine as an antihypertensive and we already demonstrated previously its hypotensive properties. In this paper, maximal left intraventriclular pressure (P) of rat's hearts beating at 0.2 Hz firstly increased to 162.1+/-11.1% of basal value during 1-3 min of perfusing ACE 0.6%. Maximum rate of contraction (+P) also increased to duplicating +P/P ratio. Both types of effect were significantly decreased by either propranolol 0.35 microM, and pre-treatment with reserpine (5 mg/kg), suggesting that they were caused by a compound that releases cathecolamines with beta-adrenergic action. Nevertheless, after 20 min of perfusing ACE, ventricles decreased P to about 50% of their basal value, suggesting a negative-inotropic compound present in the extract. The perfusion of 1.2% ACE decreased P in a pressure-[Ca](o) curve (0.5-2 mM) in a non-competitive manner, suggesting that an irreversible Ca-blocking compound is also present in the extract. In summary, E. uniflora ACE has a dual effect on the heart related to its hypotensive action and is probably responsible for the therapeutic or adverse effects in patients under cardiac risk.     

The aqueous extract of Terminalia superba (Combretaceae) prevents glucose-induced hypertension in rats

Aim of the study

The stem bark of Terminalia superba (Combretaceae) (TS) is used in traditional Cameroonian medicine as antihypertensive remedy. The aim of this study was to investigate the hypotensive and the antihypertensive effects of the aqueous extract of the stem bark of Terminalia superba.

Materials and methods

Hypertension was obtained in rats by oral administration of 10% d-glucose for 3 weeks. The acute effects of Terminalia superba were studied on blood pressure (BP) and heart rate (HR) after intravenous administration in normotensive rats (NTR) and glucose hypertensive rats (GHR). The antihypertensive effects were studied after oral administration of the extract (50 and 100 mg/kg/day) or nifedipine (10 mg/kg/day) for 3 weeks. At the end of the experiment, BP and HR were measured and reduced glutathione (GSH), malondialdehyde (MDA) and superoxide dismutase (SOD) activity levels were measured in heart, aorta, liver and kidney.

Results

Intravenous administration of the aqueous extract of Terminalia superba induced a significant hypotensive response without any change in HR. The hypotensive effect of the extract was unaffected by atropine or propranolol but decreased by reserpine (5 mg/kg) and yohimbine (0.1 mg/kg). In addition, the oral administration of the extract significantly prevented the rise in BP in glucose-hypertensive rats. Finally, the treatment with plant extract significantly blunted the decrease in GSH and the increase in MDA levels associated with hypertension, and significantly prevents the increase in aortic SOD activity.

Conclusions

The present study demonstrates that the aqueous extract of the stem bark of Terminalia superba exhibits hypotensive and anti-hypertensive properties that are, at least in part, related to a withdrawal of sympathetic tone and to an improvement of the antioxidant status, respectively. Overall data validate the use of Terminalia superba as antihypertensive therapy in traditional medicine.     

A hypotensive procyanidin-glycoside from Rhamnus lycioides ssp. lycioides

A lyophilized hot water extract of the aerial parts of Rhamnus lycioides L. (Rhamnaceae) produced a lowering of systemic arterial blood pressure in normotensive anaesthetized Wistar rats. An activity-guided fractionation of the methanolic extract led to the isolation of a tetrameric procyanidin-glycoside which produced a clear dose-dependent hypotensive response (1.5-6 mg/kg i.v.). This principle was characterized using acid hydrolysis, thiolytic degradation and spectroscopic methods. It consisted of four flavanol units with a 2,3-cis configuration and with a O-beta-d-glucosylpyranoside function on the epicatechin terminal unit. The interflavan linkage was (4-8).