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.     

Metabolite profiling and chemopreventive bioactivity of plant extracts from Bidens pilosa

Bidens pilosa has been used as a folk medicine in various medications and as a popular ingredient in herb teas. Chemopreventive activities of crude and fractionated plant extracts of Bidens pilosa were evaluated in this study. Ethyl acetate and butanolic fractions, partitioned from the total crude extract of Bidens pilosa, exhibited significant scavenging free radical activity (IC(50) values approximately = with 14-17 microg/mL) comparable to that of alpha-tocopherol. Strong effects on the inhibition of LPS-mediated nitric oxide production in RAW 264.7 cells were also observed for the EA and BuOH fractions. Detectable cytotoxicity on RAW 264.7 cells, however, was observed for the EA fraction at a dose >100 microg/ml. The metabolite profile and major constituents of the BuOH fraction were studied and characterized using various spectroscopic analyses. A new compound, heptanyl 2-O-beta-xylofuranosyl-(1-->6)-beta-glucopyranoside (1), and eight phenolic compounds, namely quercetin 3-O-rabinobioside (2), quercetin 3-O-rutinoside (3), chlorogenic acid (4), 3,4-di-O-caffeoylquinic acid (5), 3,5-di-O-caffeoylquinic acid (6), 4,5-di-O-caffeoylquinic acid (7), jacein (8), centaurein (9) were for the first time isolated from Bidens pilosa. Compounds 2-7 are the major antioxidative constituents in the Bidens pilosa extract.     

Evaluation of in vivo antihypertensive and in vitro vasodepressor activities of the leaf extract of Syzygium guineense (Willd) D.C

The aim of this work was to evaluate the antihypertensive activity of the hydroalcohol extract of the leaves of Syzygium guineense (Willd) D.C. (Myrtaceae) in a 1-kidney-1-clip rat model and its vasorelaxant effect on isolated aorta. The extract reduced blood pressure in a dose and time dependent fashion. Following 3 days of treatment, single oral daily doses of 50, 100 and 150 mg/kg caused an overall reduction (p < 0.05) of systolic blood pressure by 6.9, 34.0 and 40.8 mmHg, respectively. The diastolic blood pressure was, however, significantly reduced (p < 0.05) by 100 mg/kg (10.3 mmHg) and 150 mg/kg (18.4 mmHg) doses only. The mean blood pressure was reduced by 5.0, 18.3 and 25.9 mmHg by the respective doses. The extract also caused a dose-dependent relaxation of aorta precontracted with KCl at a concentration of 5-70 mg/mL, with a maximum relaxation of 56.22% achieved at 70 mg/mL concentration. The relaxation mechanism was found to be independent of the endothelium system, muscarinic receptors, histamine receptors, ATP dependent K(+) channels, cyclooxygenase enzymes and cGMP/NO pathway. The findings suggest that the extract had an antihypertensive effect most likely caused by dilation of the blood vessels, a confirmation for the folkloric use of the plant.     

Hypotensive and spasmolytic activities of ethanolic extract of Capparis cartilaginea

An ethanolic extract of Capparis cartilaginea (CC) at a dose of 1–10 mg/kg caused a dose-dependent fall in blood pressure and heart rate in anaesthetized rats. These effects were not blocked by atropine (1 mg/kg) and pretreatment with CC did not alter the pressor response to norepinephrine, indicating that the cardiovascular effects of CC are independent of cholinergic or adrenergic receptor involvement. In spontaneously beating guinea-pig atria, CC induced a concentration-dependent (0.1–1 mg/mL) decrease in force and rate of atrial contractions. In rabbit thoracic aorta, CC caused inhibition of norepinephrine or K⁺-induced contractions. In guinea-pig ileum, CC (1 mg/mL) inhibited submaximal contractions induced by acetylcholine, histamine or 5-HT. Spontaneous contractions of rat uterus were also abolished when CC was added to the tissue bath at similar concentrations. These results suggest that the direct relaxant action of CC on myocardium and blood vessels may be responsible for its hypotensive and bradycardiac effects observed in the in vivo studies. Moreover, CC exhibits general spasmolytic activity in different smooth muscle preparations.     

Vascular action of the crude hydroalcoholic extract from Hymenaea martiana on the isolated rat and rabbit aorta

The present study investigates the effect of the hydroalcoholic extract (HE) from Hymenaea martiana (Leguminosae) on endothelium-dependent and independent relaxation responses induced by acetylcholine (ACh), histamine (His), calcium ionophore (A23187) and sodium nitroprusside in precontracted aortic rings from rat and rabbit. In addition, we have also evaluated the action of the HE on noradrenaline- (NA), angiotensin I-(AI) and AII-induced contractions in the rabbit aorta. The HE (0.25–0.5 mg/mL) inhibited in a concentration-dependent manner the relaxant response induced by ACh in rings of rabbit aorta and by His in rat aorta. Relaxation in response to A23187 was inhibited in rat but not in rabbit aortic rings. In contrast, the HE was completely ineffective against endothelium-independent relaxations caused/by sodium nitroprusside in rabbit aorta rings. The HE (0.5–1.0 mg/mL) significantly enhanced the maximal contractile responses induced by NA in rabbit aorta set up with the endothelium, but caused no effect in endothelium rubbed preparations. In addition, the HE (0.5 mg/mL) markedly antagonized the contractile responses elicited by AI, but caused only a slight effect on AII-induced contractile responses in rabbit aorta. These findings indicate that the active principle(s) present in the HE from the bark of Hymenaea martiana selectively inhibit the endothelium-dependent vasorelaxant responses caused by several substances in aortic rings from rat and rabbit, presumably by a mechanism related with endothelium-derived relaxation factor synthesis and/or inactivation. The HE also antagonized AI but not AII-induced contractions in rabbit aorta, suggesting some interference with the angiotensin converting enzyme.     

In vitro study of mutagenic potential of Bidens pilosa Linné and Mikania glomerata Sprengel using the comet and micronucleus assays

Teas of Bidens pilosa and Mikania glomerata are popularly consumed to medicinal ends. The capacity to induce DNA damages and mutagenic effects of these teas were evaluated, in vitro, on HTC cells, with comet assay and micronucleus test. The teas tested at various doses were prepared differently: infusion of Mikania glomerata (IM) and Bidens pilosa (IB), macerate of Mikania glomerata in 80% ethanol (MM80) and decoction of Bidens pilosa (DB). In IM and MM80, the quantity of coumarin was determined by high-performance liquid chromatography (HPLC) with UV detection. Methylmethanesulfonate was utilized as positive control, phosphate-buffered saline as negative control, 80% ethanol as solvent control and 2-aminoanthracene as drug metabolism control. The comet assay demonstrated genotoxic effects for both plants. The genotoxic potential of IB was upper than DB, showing dose-response. In the MN test, excepting IM 40 microL/mL, all treatments was not mutagenic. The effects did not show direct relation with cumarin quantity present in IM and MM80. The results demonstrated DNA damages at the highest concentrations of alcoholic macerate (10 and 20 microL/mL) and infusion of Mikania glomerata (20 and 40 microL/mL) and of Bidens pilosa infusion (40 microL/mL). Thus, both dose and preparation-form suggest caution in the phytotherapeutic use of these plants.     

Vasorelaxant effects of Brillantaisia nitens Lindau (Acanthaceae) extracts on isolated rat vascular smooth muscle

Brillantaisia nitens Lindau (Acanthaceae) is traditionally used in Cameroon for the treatment of many diseases including cardiovascular disorders. We have studied its vasorelaxant effects in rat vascular smooth muscle. In this study, aqueous, methylene chloride, methanol, and methylene chloride/methanol leaves extracts of Brillantaisia nitens were tested for their relaxing ability in vitro. Strips of rat aorta, with or without intact endothelium, were mounted in tissue baths, contracted with KCl (60mM) or norepinephrine (10(-4)M), and then exposed to the plant extracts. These extracts exhibited concentration-dependent vasorelaxations of norepinephrine-induced contractions of intact aortic strips. The EC(50) were 0.42+/-0.01mg/ml (aqueous extract), 0.63+/-0.02mg/ml (methylene chloride extract), 0.73+/-0.02mg/ml (methanol extract) and 0.36+/-0.02mg/ml (methylene chloride/methanol extract). The methylene chloride/methanol (CH(2)Cl(2)/CH(3)OH) extract was the most potent relaxing extract. It caused a concentration-dependent and endothelium-independent relaxation of the rat aortic strips contracted by KCl or norepinephrine. On the NE-induced contraction, its maximal relaxant activity (109%) due to the dose of 1.5mg/ml, was not significantly modified by the pretreatment of aortic strips with indomethacin (89%, P>0.05) or with l-NAME (103%, P>0.05). This suggests that the vasorelaxation elicited by CH(2)Cl(2)/CH(3)OH extract was not mediated via endothelium-derived prostacyclin or nitric oxide. In contrast, this relaxation was markedly reduced by tetraethylammonium, a blocker of non-selective K(+) channels and glibenclamide, a blocker of ATP-sensitive K(+) channels. The CH(2)Cl(2)/CH(3)OH extract significantly inhibited Ca(2+)-induced concentration-contraction and the Ca(2+) influx in aortic strips incubated with 60mM KCl. These results indicate that the vasorelaxant effect of the CH(2)Cl(2)/CH(3)OH extract of Brillantaisia nitens is due to an inhibition of Ca(2+) influx, possibly via the activation of ATP-sensitive K(+) channels.     

Selective modulatory effects of the essential oil of Croton zehntneri on isolated smooth muscle preparations of the guinea-pig

The effects of the essential oil of the plant Croton zehntneri (EOCz) in the concentration range 1–200 μg/mL were studied on the mechanical activity of various in vitro smooth muscle preparations of the guinea-pig. In isolated ileum EOCz induced a variable response such that in 57% of tissues basal tone was reduced (EC₅₀ 5 μg/mL) whereas the rest remained unaffected by the oil. In concentrations above 10 μg/mL EOCz induced spontaneous oscillatory contractions in all preparations. In contrast the basal tone of the aorta, portal vein and bladder remained unaltered by the oil. In the portal vein EOCz concentration-dependently inhibited the amplitude of spontaneous contractions (IC₅₀ 109 μg/mL) without reducing frequency, whereas in the bladder such activity was increased by the oil (EC₅₀ 44 μg/mL). In ileum precontracted with 60 mM KCl, EOCz induced a complete and concentration-dependent relaxation with an IC₅₀ value of approximately 26 μg/mL. In contrast EOCz did not relax KCl-induced tone in the aorta or bladder, whilst eliciting less than 20% relaxation of the precontracted portal vein. Thus our data show that EOCz exerts differential modulatory effects on the contractility of various smooth muscles of the guinea-pig. That EOCz appears to selectively relax intestinal smooth muscle may support its use in folk medicine as a gastrointestinal antispasmodic. © 1998 John Wiley & Sons, Ltd.     

Gastric antisecretory and antiulcer activities of an ethanolic extract of Bidens pilosa L. var. radiata Schult. Bip

Bidens pilosa var. radiata Schult. Bip. is used in folk medicine to treat stomach disorders including peptic ulcers. The ethanolic extract (0.5-2 g/kg) decreased the gastric juice volume, acid secretion, as well as pepsin secretion in pylorus ligated rats. B. pilosa extract showed antiulcer activity against indomethacin-induced gastric lesions. The extract effectively inhibited gastric haemorrhagic lesions induced by ethanol, and with an effective dose of 2 g/kg being more potent than sucralfate (400 mg/kg). In contrast, ranitidine (50 mg/kg) failed to reduce these lesions. These results indicate that B. pilosa ethanolic extract exerts a cytoprotective effect in addition to its gastric antisecretory activity that could be due, partly at least, to the presence of flavonoids of which quercetin was identified by HPLC.     

Evaluation of pharmacological activity of a crude hydroalcoholic extract from Jatropha elliptica

The pharmacological effect of the hydroalcoholic extract of Jatropha elliptica was analysed in in vivo and in vitro models. When given orally in mice, the extract showed a low acute toxicity (LD₅₀ 5 g/kg). In a dose of 0.5 or 1 g/kg p.o. the extract did not interfere with diuresis in the rat, but was found to be effective in blocking rat paw oedema induced by carrageenan and partially, serotonin-induced oedema. In the same dose, the extract failed to inhibit rat paw oedema induced by dextran and the increase of rat cutaneous vascular permeability caused by Bothrops Jararaca venom, dextran, histamine, PAF-acether and serotonin. Pre-incubation of the isolated rat uterus and guinea-pig ileum with the extract (0.2–0.8 mg/mL), produced a concentration-related and non-competitive inhibition of contractions induced by acetylcholine and bradykinin. However, the extract was about 2-fold more potent in inhibiting the contraction of both agonists in guinea-pig ileum than in rat uterine muscle. In rat aorta, the extract (50–100 μg/mL) caused a concentration-dependent inhibition of noradrenaline-evoked contractions, being about 5-fold more potent when compared to the IC₅₀ values obtained in rat uterus.     

Pharmacological studies on hypotensive and spasmolytic activities of pure compounds from Moringa oleifera

Bioassay directed fractionation of an ethanolic extract of Moringa oleifera (MO) leaves resulted in the isolation of four pure compounds, niazinin A (1), niazinin B (2), niazimicin (3) and niaziminin A + B (4 + 5). Intravenous administration of either one of the compounds (1–10 mg/kg) produced hypotensive and bradycardiac effects in anaesthetized rats. Pretreatment of the animals with atropine (1 mg/kg) completely abolished the hypotensive and bradycardiac effects of acetylcholine (ACh), whereas cardiovascular responses to the test compounds remained unaltered, ruling out the possible involvement of muscarinic receptor activation. In isolated guinea-pig atria all the compounds (50–150 μg/mL) produced negative inotropic and chronotropic effects. Each compound inhibited K⁺ -induced contractions in rabbit aorta as well as ileal contractions induced by ACh or histamine at similar concentrations. Spontaneous contractions of rat uterus were also inhibited equally by all compounds. These data indicate that the direct depressant action of these compounds exhibited on all the isolated preparations tested is probably responsible for its hypotensive and bradycardiac effects observed in vivo. Moreover, spasmolytic activity exhibited by the constituents of the plant provides a scientific basis for the traditional uses of the plant in gastrointestinal motility disorders.     

Effects of methanol, cyclohexane and methylene chloride extracts of Bidens pilosa on various gastric ulcer models in rats

Ethnobotanical studies have revealed that Bidens pilosa is used in the traditional management of wounds and chronic gastro-duodenal ulcers. This led us to screen the methanol, cyclohexane and methylene chloride extracts of the plant for anti-ulcerogenic activity using the HCl/ethanol gastric necrotizing solution. The methylene chloride extract, which showed the highest activity (100% inhibition) at a dose of 750 mg/kg compared with the methanol and cyclohexane extracts (41 and 46% inhibition, respectively), was further tested using the indomethacin-HCl/ethanol-, absolute ethanol- and pylorus ligation-induced ulcer methods. Pre-treatment with indomethacin significantly reduced the protective effect of the extract against HCl/ethanol solution to 31%. The extract had very little gastric mucosal protection against absolute ethanol (9.8% inhibition at 750 mg/kg) compared with the controls and neither reduced gastric acid secretion in vivo nor the acidity of gastric juice following in vitro incubation.     

Diuretic effect of the aqueous extract of Bidens odorata in the rat

The aerial part of Bidens odorata Cav., are used in Mexican Folk Medicine to treat renal diseases. The aim of this study is to measure the diuretic response to aqueous extract of this plant at doses of 41 and 166 mg/kg and to compare it with that induced by furosemide at 2 mg/kg. Aqueous extracts, furosemide or vehicle were administered orally to adult rats and the effects on sodium, potassium and water balance were assessed. Aqueous extracts at both doses and furosemide produced important and significant increments in urinary excretion of sodium, potassium and water in rats with respect to control group. This increase was dose dependent and aqueous extract at the highest dose induced a more marked sodium and water excretion than furosemide, potassium excretion increased but it was less than the one induced by furosemide. These results suggest that the aqueous extract of Bidens odorata induce diuretic response.     

Antispasmodic and hypotensive effects of Ferula asafoetida gum extract

The effects of Ferula asafoetida gum extract on the contractile responses of the isolated guinea-pig ileum induced by acetylcholine, histamine and KCl, and on the mean arterial blood pressure of rat were investigated. In the presence of extract (3 mg/ml), the average amplitude of spontaneous contractions of the isolated guinea-pig ileum was decreased to 54 +/- 7% of control. Exposure of the precontracted ileum by acetylcholine (10 microM) to Ferula asafoetida gum extract caused relaxation in a concentration-dependent manner. Similar relaxatory effect of the extract was observed on the precontracted ileum by histamine (10 microM) and KCl (28 mM). However, when the preparations were preincubated with indomethacin (100 nM) and different antagonists, such as propranolol (1 microM), atropine (100 nM), chlorpheniramine (25 nM) then were contracted with KCl, exposure to the extract (3 mg/ml) did not cause any relaxation. Furthermore, Ferula asafoetida gum extract (0.3-2.2 mg/100g body weight) significantly reduced the mean arterial blood pressure in anaesthetised rats. It might be concluded that the relaxant compounds in Ferula asafoetida gum extract interfere with a variety of muscarinic, adrenergic and histaminic receptor activities or with the mobilisation of calcium ions required for smooth muscle contraction non-specificly.     

Antileukemic activity of Bidens pilosa L. var. minor (Blume) Sherff and Houttuynia cordata Thunb.

To evaluate the anti-leukemic activity of Bidens pilosa L. var. minor (Blume) Sherff and Houttuynia cordata Thunb., cytotoxicity tests with an XTT-based colorimetric assay were used. Five leukemic cell lines, namely L1210, U937, K562, Raji and P3HR1, were cultured with hot water extracts of B. pilosa var. minor or H. cordata. Hot water extracts of B. pilosa var. minor inhibited these five leukemic cells with IC50s between 145 microg/ml and 586 microg/ml. The effect was greatest on four cell lines, namely L1210, P3MR1, Raji and K562, with IC50s below 200 microg/ml and a selective index of more than 5. Hot water extract of H. cordata inhibited these five leukemic cells with IC50s between 478 microg/ml and 662 microg/ml. The selective index was between 1.5 and 2.1. B. pilosa var. minor was more effective than H. cordata in inhibiting most of the leukemic cells in our study. We suggest that B. pilosa L. var. minor (Blume) Sherff may prove to be a useful medicinal plant for treating leukemia.     

Hystological and pharmacological study of Thymus piperella (L.)

Histological and pharmacological assays have been carried out with methanol, hexane, dichloromethane and butanol extracts of Thymus piperella (L.) leaves. All the extracts were considered innocuo in the toxicity test. Methanol and also hexane, dichlorometane and butanol fractions, inhibited significantly the contractions induced by acetylcholine in isolated rat ileum in a concentration-dependent manner and the hexane extract was the most potent. However, the methanol extract did not modify the contractile effect of noradrenaline and histamine on isolated rat aorta and guinea-pig trachea respectively at the assayed dose (10, 100, 200 microg/mL). These results contribute to explain in part the use of this plant in folk medicine. In addition, morphological and histological structures characteristic of this species have been described for the first time.     

Anti-Herpes simplex virus activity of Bidens pilosa and Houttuynia cordata

The present study evaluated the antiviral activity of Bidens pilosa L. var. minor (Blume) Sherff and Houttuynia cordata Thunb., using cytotoxicity test with XTT-based colorimetric assay. BCC-1/KMC cells were infected with herpes simplex virus (HSV) and then were cultured with hot water extract of B. pilosa (HWBP) or H. cordata (HWHC). Results showed that HWBP significantly inhibited the replication of HSV at a concentration of 100 microg/ml (11.9% for HSV-1, p < 0.01; 19.2% for HSV-2, p < 0.005), whereas HWHC had the same effect at a concentration of 250 microg/ml (10.2% for HSV-1, p < 0.05; 32.9% for HSV-2, p < 0.005). The ED50 of HSV type 1 (HSV-1) and HSV type 2 (HSV-2) for HWBP was 655.4 microg/ml and 960 microg/ml respectively, for HWHC it was 822.4 microg/ml and 362.5 microg/ml respectively. Both drugs had selective indexes above 1.04. H. cordata had better effect against HSV-2 than HSV-1, and had a low ED50 against HSV-2. We suggest that H. cordata might be a useful medicinal plant against infection of HSV-2.     

Differential antagonistic effect of hydroalcoholic extract from Hymenaea martiana hayne arzeik on kinin and other agonist-induced contractions of the isolated rat uterus and Guinea-pig ileum

This study was undertaken to evaluate the action of the hydroalcoholic extract (HE) from the bark of Hymenaea martiana on bradykinin (BK), lysyl-bradykinin (L-BK), acetylcholine (ACh), angiotensin II (AII), prostaglandin F_2a (PGF_2a), serotonin (5-HT), oxytocin (Ot) and histamine (His)-induced contractions of the isolated rat uterine muscle and guinea-pig ileum. The HE (50–200 μg/mL) added to the bath for 20 min caused a concentration-dependent rightward displacement of BK, L-BK and ACh-induced contractions in the rat uterus, allied to a discrete but significant reduction of maximal responses to the latter two agonists. By contrast, at the same range of concentrations the HE antagonized in a concentration-dependent but noncompetitive manner the contractions induced by AII, but only at high concentrations (200 μg/mL) it significantly inhibited contractions evoked by both PGF_2a and Ot, while contractile responses induced by 5-HT were not affected. In the guinea-pig ileum, the HE of H. martiana (50 and 100 μg/ml) caused a discrete rightward displacement of the BK and ACh concentration—response curves. Higher concentrations of the HE of H. martiana (200 μg/mL) caused a marked depression of BK and ACh-induced maximal responses. These findings show that the active principle(s) presents in the HE from the bark of H. martiana exhibits an interesting pharmacological profile against several neurotransmitter-induced contractions in nonvascular smooth muscles. Such actions may be relevant for supporting, at least in part, the use of this plant in folk medicine.     

Myorelaxant and antispasmodic effects of the essential oil of Alpinia speciosa on rat ileum

The effects of the essential oil of Alpinia speciosa Schum (EOAS) on rat ileum were studied. EOAS (0.1-600 microg/mL) reversibly relaxed ileal basal tonus. Submaximal contractions induced by 60 mM KCl or acetylcholine were concentration dependently inhibited by EOAS with similar IC(50) values ( approximately 44 and 48 microg/mL, respectively). These results show that EOAS possesses both relaxant and antispasmodic actions in the ileum.     

Vasodilator Effects of the Extract of the Leaves of Cistus populifolius on Rat Thoracic Aorta

The effects of different extracts of Cistus populifolius L. on smooth muscle were studied. The aqueous extract inhibited in a dose dependent manner the noradrenaline (NA) (10⁻⁹–1.03×10⁻⁶ MSC ) and CaCl₂ (2×10⁻⁴–1.28×10⁻² MSC )-induced contractions in rat thoracic aorta. Furthermore, this extract induced relaxant effects in rat aorta precontracted with NA (10⁻⁶ MSC ) and with K⁺ (80 mMSC ). Two different vasodilator responses were observed on NA-induced contractions: one an endothelium-dependent response abolished by methylene blue but not by indomethacin, and the other an endothelium-independent response unaffected by methylene blue and indomethacin similar to that obtained with a flavone, luteolin (10⁻⁵ MSC ). The search for active constituents included a bioactivity-directed fractionation of the lyophilized aqueous extract (LAE) using vascular reactivity experiments. Four different fractions (Cl₂CH₂, Me₂CO, MeOH, H₂O) were analysed at two different concentrations (1 and 2 mg (dry plant)/mL). The methanol fraction was the most active on NA precontracted vascular segments with endothelium, whereas the water fraction was the most active on segments without endothelium. These relaxant effects were less on K⁺ (80 mMSC )-induced contractions. Due to these results we suggest that this plant contains interesting hydrophilic compounds with strong pharmacological action. The endothelium-independent relaxant effect is probably related to flavonoid constituents. However we cannot relate the endothelium-dependent relaxation to known natural compounds in Cistus species. The presence of these constituents with relaxing properties on smooth muscle could account for the use of Cistus plant in traditional medicine.