Acid-gastric antisecretory effect of the ethanolic extract from Arctium lappa L. root: role of H+, K+-ATPase, Ca2+ influx and the cholinergic pathway.

BACKGROUND: Arctium lappa L., popularly known as burdock, is a medicinal plant used worldwide. The antiulcer and gastric-acid antisecretory effects of ethanolic extract from roots of Arctium lappa (EET) were already demonstrated. However, the mechanism by which the extract reduces the gastric acid secretion remains unclear. Therefore, this study was designed to evaluate the antisecretory mode of action of EET. MATERIALS AND METHODS: The effects of EET on H+, K+-ATPase activity were verified in vitro, whereas the effects of the extract on cholinergic-, histaminergic- or gastrinergic-acid gastric stimulation were assessed in vivo on stimulated pylorus ligated rats. Moreover, ex vivo contractility studies on gastric muscle strips from rats were also employed. RESULTS: The incubation with EET (1000 µg/ml) partially inhibited H+, K+-ATPase activity, and the intraduodenal administration of EET (10 mg/kg) decreased the volume and acidity of gastric secretion stimulated by bethanechol, histamine, and pentagastrin. EET (100-1000 µg/ml) did not alter the gastric relaxation induced by histamine but decreased acetylcholine-induced contraction in gastric fundus strips. Interestingly, EET also reduced the increase in the gastric muscle tone induced by 40 mM KCl depolarizing solution, as well as the maximum contractile responses evoked by CaCl2 in Ca2+-free depolarizing solution, without impairing the effect of acetylcholine on fundus strips maintained in Ca2+ -free nutritive solution. CONCLUSION: Our results reinforce the gastric antisecretory properties of preparations obtained from Arctium lappa, and indicate that the mechanisms involved in EET antisecretory effects include a moderate reduction of the H+, K+-ATPase activity associated with inhibitory effects on calcium influx and of cholinergic pathways in the stomach muscle.

Hypotensive and diuretic effect of the butanolic soluble fraction of the hydroethanolic extract of bark of Scutia buxifolia Reissek in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Scutia buxifolia, a native tree popularly known as "coronilha", is widely used in Brazilian folk medicine for diuretic and anti-hypertensive purposes. AIM OF THE STUDY: We investigated the effects of a butanolic (BuOH) soluble fraction of the hydroethanolic extract (HESB) of bark of Scutia buxifolia on both blood pressure and urinary excretion of rats. The involvement of the nitric oxide/guanylate cyclase pathway in the hypotensive effect found was also explored. MATERIAL AND METHODS: We tested the effect of the BuOH soluble fraction of HESB on the mean arterial pressure (MAP) of anesthetized rats. The fraction was administered at doses of 1, 3 and 10mg/kg (i.v.) in normotensive rats during continuous infusion of vehicle (10 µl/min), or phenylephrine (4 µg/kg/min), or l-NAME (7 mg/kg/min), two approaches able to induce a sustained hypertensive state. In some experiments, a bolus injection of ODQ (2mg/kg) was administered in animals infused with phenylephrine before the administration of the BuOH soluble fraction of HESB. We also measured the effects of the BuOH soluble fraction on the MAP of spontaneously hypertensive rats (SHR). Separate groups of rats were treated orally with either HESB (10, 30 or 100mg/kg), or its BuOH soluble fraction (3, 10 or 30 mg/kg), and were subjected to measurement of diuresis and blood pressure. RESULTS: The BuOH soluble fraction of HESB (10mg/kg, i.v.) reduced the MAP of both phenylephrine-infused and SHR rats by 20.6 ± 6.0 and 41.8 ± 8.3 mm Hg, respectively. However, no hypotensive effect was found in normotensive animals infused with l-NAME, a non-selective inhibitor of nitric oxide synthase, or animals previously treated with the soluble guanylate cyclase inhibitor ODQ. The urinary excretion was increased by 70% at 6-8h after a single oral administration of the BuOH soluble fraction of HESB (10mg/kg), without change in urinary density, pH, or Na(+) and K(+) concentrations. In addition, MAP was lower 3h after the acute oral treatment with the BuOH soluble fraction (82.1 ± 3.8 mm Hg), compared with MAP of animals from the control group (97 ± 3.2 mm Hg). CONCLUSION: This study demonstrates that the BuOH soluble fraction of the hydroethanolic bark of Scutia buxifolia, which has its bark used in folk medicine for the treatment of hypertension mainly by its presumed diuretic properties, possesses both diuretic and hypotensive effects in rats, and that at least the hypotensive effect is fully dependent on activation of the nitric oxide/guanylate cyclase pathway.

Involvement of bradykinin and prostaglandins in the diuretic effects of Achillea millefolium L. (Asteraceae).

ETHNOPHARMACOLOGICAL RELEVANCE: Achillea millefolium L. (Asteraceae), popularly known as "mil-folhas", is well recognized and widely used in Brazilian folk medicine to treat heart and kidney disorders. Among its popularly described effects are diuretic and hypotensive actions. AIM OF THE STUDY: The diuretic activity of Achillea millefolium L. extracts and its semi-purified fractions, as well as the mechanisms involved, were evaluated in male Wistar rats. MATERIAL AND METHODS: An aqueous extract (AEAM, 125-500 mg/kg), hydroethanolic extract (HEAM, 30-300 mg/kg), dichloromethane subfractions (DCM-2, 10 and 30 mg/kg), or hydrochlorothiazide (10mg/kg), were orally administered and the animals were kept in metabolic cages for 8h for urine collection. To evaluate the involvement of bradykinin and prostaglandins in the diuretic action of Achillea millefolium, selected groups of rats received HOE-140 (1.5mg/kg, i.p.) or indomethacin (5mg/kg, p.o.), before treatment with a DCM-2 subfraction (30 mg/kg). The urinary volume, conductivity, pH, density and electrolyte excretion were measured. RESULTS: Similar to hydrochlorothiazide, both HEAM and DCM-2, but not AEAM, increased urinary volume and the excretion of Na(+) and K(+) when compared with the control group (vehicle). The diuretic effect of DCM-2 was abolished by HOE-140 (a bradykinin B2 receptor antagonist), as well as by indomethacin (a cyclooxygenase inhibitor). CONCLUSION: The present study reveals that extracts obtained from Achillea millefolium are able to effectively increase diuresis when orally administered in rats. This effect depends on both the activation of bradykinin B2 receptors and the activity of cyclooxygenases.

Endothelium-dependent and independent vasorelaxation induced by an n-butanolic fraction of bark of Scutia buxifolia Reiss (Rhamanaceae).

ETHNOPHARMACOLOGICAL RELEVANCE: Scutia buxifolia has been widely used in Brazilian folk medicine as an anti-hypertensive agent. We evaluated the vascular effects and mechanism involved in the relaxation of aorta induced by an n-butanolic fraction (BuOH) from Scutia buxifolia. MATERIALS AND METHODS: Rat aortic rings precontracted by phenylephrine (1 µM) were exposed to cumulative concentrations (3­3000 µg/ml) of crude extracts or fractions obtained from bark or leaves of Scutia buxifolia. Classical receptor antagonists, channel and enzymatic inhibitors were used to check the mechanisms involved. RESULTS: The crude extracts of both leaves and bark of Scutia buxifolia, as well as several fractions, were able to induce partial or total relaxation of rat aortic rings. The BuOH fraction of bark of Scutia buxifolia was the most potent in endothelium-intact (E+) preparations, and also induced a partial, but very significant relaxation in endothelium-denuded (E−) vessels. The non-selective nitric oxide synthase inhibitor L-NAME, as well as the soluble guanylate cyclase inhibitor ODQ, vanished the relaxation in E+. In E− preparations, K+ channel blockers, such as tetraethylammonium, glibenclamide, 4-aminopyridine, and the large-conductance calcium-activated K+ channel blocker iberiotoxin, were able to significantly reduce the maximum relaxation elicited by BuOH fraction. CONCLUSION: Our results demonstrated that BuOH fraction obtained from barks of Scutia buxifolia induced both endothelium-dependent and -independent relaxation in rat aortic rings. The endothelium-dependent relaxation is fully dependent on NO/cGMP system, while direct activation of K+ channels may explain, at least in part, the endothelium-independent relaxation induced by BuOH fraction of Scutia buxifolia.

Mechanisms underlying the diuretic effects of Tropaeolum majus L. extracts and its main component isoquercitrin.

ETHNOPHARMACOLOGICAL RELEVANCE: Previous studies have shown that the extracts obtained from Tropaeolum majus L., and its main compound isoquercitrin (ISQ), exhibit pronounced diuretic effects, supporting the ethnopharmacological use of this plant. The aim of this study was to evaluate the efficacy and mechanisms underlying the diuretic action of an ethanolic extract of Tropaeolum majus (HETM), its purified fraction (TMLR), and its main compound ISQ, in spontaneously hypertensive rats (SHR). MATERIALS AND METHODS: The diuretic effects of HETM (300mg/kg; p.o.), TMLR (100mg/kg; p.o.), and ISQ (10mg/kg; p.o.), were compared with classical diuretics in 7days repeated-dose treatment. The urinary volume, sodium, potassium, chloride, bicarbonate, conductivity, pH and density were estimated in the sample collected for 15h. The plasmatic concentration of sodium, potassium, urea, creatinine, aldosterone, vasopressin, nitrite and angiotensin converting enzyme (ACE) activity were measured in samples collected at the end of the experiment (seventh day). Using pharmacological antagonists or inhibitors, we determine the involvement of bradykinin, prostaglandin and nitric oxide (NO) in ISQ-induced diuresis. In addition, reactive oxygen species (ROS) and the activity of erythrocytary carbonic anhydrase and renal Na(+)/K(+)/ATPase were evaluated in vitro. RESULTS: HETM, TMLR and ISQ increased diuresis similarly to spironolactone and also presented K(+)-sparing effects. All groups presented both plasmatic aldosterone levels and ACE activity reduced. Previous treatment with HOE-140 (a B2-bradykinin receptor antagonist), or indomethacin (a cyclooxygenase inhibitor), or L-NAME (a NO synthase inhibitor), fully avoided the diuretic effect of ISQ. In addition, the 7days treatment with ISQ resulted in increased plasmatic levels of nitrite and reducing ROS production. Moreover, the renal Na(+)/K(+)/ATPase activity was significantly decreased by ISQ. CONCLUSION: Our results suggest that the mechanisms through ISQ and extracts of Tropaeolum majus increase diuresis in SHR rats are mainly related to ACE inhibition, increased bioavailability of bradykinin, PGI2, and nitric oxide, besides an inhibitory effect on Na(+)/K(+)-ATPase.

Hypotensive mechanism of the extracts and artemetin isolated from Achillea millefolium L. (Asteraceae) in rats.

Traditional uses of Achillea millefolium L. (Asteraceae) include the treatment of cardiovascular diseases. In the present study, we used anesthetized rats to assess the hypotensive effect of a hydroethanolic extract (HEAM), and its dichloromethane (DCM), ethyl acetate (EA), butanolic (BT), and dichloromethane-2 (DCM-2) fractions, besides the flavonoid artemetin, isolated from A. millefolium. The oral administration of HEAM (100-300 mg/kg), DCM (20mg/kg), DCM-2 (10-30 mg/kg), but not EA (10 mg/kg) and BT (50 mg/kg) fractions significantly reduced the mean arterial pressure (MAP) of normotensive rats. The phytochemical analysis by NMR (1)H of DCM and DCM-2 fractions revealed high amounts of artemetin, that was isolated and administered by either oral (1.5 mg/kg) or intravenous (0.15-1.5 mg/kg) routes in rats. This flavonoid was able to dose-dependently reduce the MAP, up to 11.47 ± 1.5 mmHg (1.5 mg/kg, i.v.). To investigate if artemetin-induced hypotension was related to angiotensin-converting enzyme inhibition, we evaluated the influence of this flavonoid on the vascular effects of both angiotensin I and bradykinin. Intravenous injection of artemetin (0.75 mg/kg) significantly reduced the hypertensive response to angiotensin I while increased the average length of bradykinin-induced hypotension. Artemetin (1.5 mg/kg, p.o.) was also able to reduce plasma (about 37%) and vascular (up to 63%) ACE activity in vitro, compared to control group. On the other hand, artemetin did not change angiotensin II-induced hypertension. Our study is the first showing the hypotensive effects induced by the extract and fractions obtained from A. millefollium. In addition, our results disclosed that this effect may be, at least in part, associated with high levels of artemetin and its ability to decrease angiotensin II generation in vivo, by ACE inhibition.

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 (12.5-100mg/kg) and intravenously treated with ISQ and KPF being later anesthetized with ketamine (100mg/kg) and xylazine (20mg/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 3h 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.

Diuretic and potassium-sparing effect of isoquercitrin-an active flavonoid of Tropaeolum majus L.

AIM OF THE STUDY: Previous studies have shown that the extracts obtained from Tropaeolum majus L. exhibit pronounced diuretic effects supporting the ethnopharmacological use of this plant as diuretic. In the present work, phytochemical investigation, guided by bio-assay in spontaneously hypertensive rats (SHR), was carried out in order to identify the compounds responsible for diuretic action. MATERIAL AND METHODS: Chromatographic fractionation of the hydroethanolic extract yielded an active fraction (TMLR) rich in isoquercitrin. TMLR (25-100mg/kg) and isoquercitrin (5-10mg/kg), as well the reference drug hydrochlorothiazide (10mg/kg) were orally administered in a single dose or daily for 7 days to SHR. The urine excretion rate, pH, density, conductivity and content of sodium (Na(+)) and potassium (K(+)) electrolytes were measured in the urine of saline-loaded animals. RESULTS: The urinary excretion rate was dose-dependently increased in both TMLR and isoquercitrin groups, as well as Na(+). Despite the changes in urinary excretion of electrolytes, the plasmatic levels of Na(+) and K(+) had not been changed. In addition, we did not find any evidence of renal toxicity or other adverse effects in these animals, even after prolonged treatment with TMLR or isoquercitrin. CONCLUSION: This research supports and extends the ethnomedicinal use of T. majus as diuretic. This activity seems to be associated to the presence of the flavonol isoquercitrin.

Standardized extract of Dicksonia sellowiana Presl. Hook (Dicksoniaceae) decreases oxidative damage in cultured endothelial cells and in rats.

AIMS: Aging and a variety of pathologies, including cancer, diabetes, cardiovascular and inflammatory diseases have been associated with reactive oxygen species (ROS), such as superoxide anion (O2·â»), hydroxyl radical (·OH) and hydrogen peroxide (H2O2) generation. Plant polyphenols bear radical scavenging/antioxidant activity. A phytomedicinal preparation obtained from aerial parts of Dicksonia sellowiana (Dicksoniaceae), a native plant from Central and South America, has been widely used in Brazil against asthma and presents beneficial effects in several other diseases, including cardiovascular disturbance. In this work, we investigated whether Dicksonia sellowiana, which is also known to contain high levels of polyphenols, presents antioxidant activity. METHODS: The antioxidant activity of the hydroalcoholic extract obtained from Dicksonia sellowiana leaves (HEDS) was investigated by in vitro and in vivo tests. RESULTS: HEDS (0.1-100 µg/mL) exhibited a strong scavenging activity against all reactive species tested (DPPH, O2·â»,·OH and H2O2; IC50=6.83±2.05, 11.6±5.4, 2.03±0.4, and 4.8±0.4 µg/mL, respectively). HEDS strongly protected endothelial cells against H2O2-induced oxidative stress by mechanisms other than increasing catalase activity. In addition, HEDS protected cell membrane from oxidative damage. HEDS, (20 and 40 mg/kg) inhibited lipid peroxidation in vivo (29.8% and 24.5%, respectively). CONCLUSIONS: According to our results, we can speculate that the traditional uses of Dicksonia sellowiana for cardiovascular diseases, asthma and skin diseases could be, at least in part, related to the potent antioxidant and endothelial protective activities of the plant.

In vivo assessment of safety and mechanisms underlying in vitro relaxation induced by Mikania laevigata Schultz Bip. ex Baker in the rat trachea.

Mikania laevigata, popularly known in Brazil as "guaco", is largely used in folk medicine against respiratory diseases. However, neither the assessment of the toxicity of "guaco" syrup (GS, used by humans) nor its efficacy or mechanisms of action has been properly investigated. Using in vitro procedures, we showed that the hydroalcoholic extract (HE) from Mikania laevigata induces a concentration-dependent relaxation of rat trachea which does not depend on epithelium-derived substances but involves changes in the cellular mobilization of calcium, perhaps due to a direct effect on membrane potassium channels. In addition, we assessed both oral and intraperitoneal acute toxicity, as well as the oral subchronic and chronic toxicity of GS containing controlled amounts of coumarin, the main biological marker of Mikania laevigata preparations used in humans. The calculated LD(50) of GS after intraperitoneal administration was 0.904 g/kg in mice (both sexes) and 0.967 and 0.548 g/kg in male and female rats, respectively. However, the LD(50) values of GS by the oral route were calculated to be up to 10 g/kg, in both male and female mice and rats. Repeated dose 28- or 90-day oral treatment with GS (75, 150 and 300 mg/kg) did not produce any disturbances in the hematological or biochemical parameters of either male or female rats, nor did it provide evidence of toxicity in the hepatic, renal or pancreatic systems. Besides the mechanistic findings, our results provide evidence of the safety of Mikania laevigata in rodents, even after subchronic and chronic administration, at least in relation to the evaluated parameters.

Safety and antiulcer efficacy studies of Achillea millefolium L. after chronic treatment in Wistar rats.

Achillea millefolium L. (Asteraceae), popularly known as yarrow, has been used in folk medicine to treat complaints such as inflammation, pain, wounds, hemorrhages and gastrointestinal disturbances. The aim of the present study was to assess the safety and efficacy of the aqueous extract (AE) of the plant after chronic exposure. Indeed, the AE was effective in protecting the gastric mucosa against acute gastric lesions induced by ethanol and indomethacin and in healing chronic gastric lesions induced by acetic acid with (ED(50)=32 mg/kg, p.o.). Safety studies were performed in female and male Wistar rats treated daily with AE (0.3-1.2 g/kg, p.o./day) or vehicle (water, 10 ml/kg/day) for 28 or 90 consecutive days. Satellite groups consisted of animals sacrificed 30 days after the end of these treatments. Clinical observations, body and organ weight measurements, gross autopsy, hematology, clinical biochemical and histopathological examinations were performed. Slight changes in liver weight, cholesterol, HDL-cholesterol and glucose were observed in male and female animals. These changes were not correlated with dose or time of exposure of the animals to the AE. Overall, the results show the antiulcer potential of the aerial parts of the Achillea millefolium which is accompanied by no signs of relevant toxicity even at very long chronic exposure.

Involvement of nitric oxide in the gastroprotective effects of an aqueous extract of Pfaffia glomerata (Spreng) Pedersen, Amaranthaceae, in rats.

The plants belonging to Pfaffia genus are used in folk medicine to treat gastric disturbances. This study examined the effects of an aqueous extract of Pfaffia glomerata (Spreng) Pedersen (AEP) on the gastrointestinal tract. Wistar rats were pretreated orally (p.o.) with the AEP (125, 250, 500 and 1000 mg.kg(-1)) before induction of ulcers by hypothermic restraint stress (HRS, 3 h restraint stress at 4 degrees C), ethanol (ET, 70%; 0.5 ml/animal; p.o.) or indomethacin (IND, 20 mg.kg(-1); s.c.). Control animals received water (C) or ranitidine (60 mg.kg(-1)) p.o. The AEP protected rats against HRS and ET-induced ulcers, but was not able to protect the gastric mucosa against IND-induced ulcers. When injected into the duodenal lumen, the AEP reduced total acidity and both basal and histamine-stimulated acid secretion in pylorus-ligated rats. In addition, gastric secretion from AEP-treated animals exhibited increased concentrations of nitrite and nitrate. Treatment of animals with L-NAME (120 mg.kg(-1), p.o.) prevented both the reduction of total acidity and the increase in NOx levels promoted by AEP treatment. In conclusion, AEP effectively protected the gastric mucosa and inhibited gastric acid secretion in rats, probably by involving the histaminergic pathway and an enhanced production of nitric oxide in the stomach.