The mechanism of vasorelaxation induced by ethanol extract of Sophora flavescens in rat aorta

Aim of the study

Sophora flavescens (SF) is a known medicinal herb for the treatment of cardiovascular symptoms associated with arrhythmia in China. However, the pharmacological action mechanisms involved have not been well studied. The aim of the present study was to define effects of roots of SF on the vascular tension and responsible mechanisms in rat thoracic aorta.

Materials and methods

Ethanol extract of the roots of SF (ESF) was examined for their vascular relaxant effect in isolated phenylephrine-precontracted rat thoracic aorta.

Results

ESF (0.1-100 μg/ml) induced relaxation of the phenylephrine-precontracted aortic rings in a concentration-dependent manner. Endothelium-denudation abolished the ESF-induced vasorelaxation. Pretreatment of the endothelium-intact aortic rings with l-NAME, an inhibitor of nitric oxide synthase, and ODQ, an inhibitor of soluble guanylyl cyclase (sGC), inhibited ESF-induced vasorelaxation. ESF increased cGMP levels of the aortic rings in a concentration-dependent manner and the effect was blocked by l-NAME and ODQ. Inhibition of K⁺ channels with glibenclamide and tetraethylammonium, cyclooxygenase inhibition with indomethacin, and β-adrenergic and muscarinic receptors blockade had no effect on the ESF-induced vasorelaxation.

Conclusion

These findings suggest that ESF relaxes vascular smooth muscle via endothelium-dependent NO-sGC-cGMP signaling pathway.     

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 (3–3000 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.     

HPLC测定五味子根茎叶中6种木脂素含量

目的: 比较五味子根茎叶6种木脂素含量的差异。 方法: 采用色谱柱Agilent TC-C₁₈(4.6 mm×250 mm,5 μm);流动相乙腈-水,梯度洗脱;检测波长 250 nm,流速 1 mL·min^-1,柱温 30℃。 结果: 野生五味子根茎叶总木脂素含量高于栽培品种,其根茎叶总木脂素含量差别挺大,其中根>主枝>侧枝>叶。 结论: 该方法稳定、可靠,能较好的对五味子根茎叶进行质量评价。     

Mechanisms of vasorelaxation induced by Ziziphora clinopodioides Lam. (Lamiaceae) extract in rat thoracic aorta

Aim of the study

Ziziphora clinopodioides Lam. (ZC) is widely used in Uyghur folk medicine for the treatment of hypertension diseases in Xinjiang, an autonomous region of China. To provide pharmacological basis for this traditional use, we explored the vasodilating effects of ZC and investigated the underlying mechanisms.

Materials and methods

Activity of hexane (ZCHE), dichloromethane (ZCDE) and aqueous (ZCAE) extracts of ZC were evaluated on isolated rat aortic rings pre-contracted with phenylephrine (PE) or high KCl. The mechanisms were evaluated on ZCDE, the most potent extract.

Results

ZCDE-induced relaxation in endothelium-intact aortic rings pre-contracted with phenylephrine (PE, 10⁻⁶ M) or high KCl (6 × 10⁻² M), with respective EC₅₀ values of 0.27 ± 0.03 and 0.34 ± 0.04 g/l. Mechanic removal of the endothelium did not significantly modify ZCDE-induced relaxation. In endothelium-denuded aorta pre-contracted with PE (10⁻⁶ M), the vasorelaxant effect of ZCDE was significantly decreased by 4-amino-pyridine (10⁻³ M), but not by glibenclamide (10⁻⁴ M), iberiotoxin (3 × 10⁻⁸ M) and thapsigargin (10⁻⁷ M). In Ca²⁺ free solution, ZCDE significantly inhibited extracellular Ca²⁺-induced contraction in high KCl and PE pre-contracted rings. Additionally ZDCE inhibited the intracellular Ca²⁺ release sensitive to PE (10⁻⁶ M).

Conclusions

The results demonstrate that ZDCE exhibits endothelium-independent vasodilating properties that are mediated by inhibition of extracellular Ca²⁺ influx through voltage- and receptor-operated Ca²⁺ channels (VDDCs and ROCCs), by inhibition of Ca²⁺ release from intracellular stores, and also by the opening of voltage-dependent K⁺ channels.     

Vasorelaxant and antihypertensive effect of Cocos nucifera Linn. endocarp on isolated rat thoracic aorta and DOCA salt-induced hypertensive rats

Ethnopharmacological relevance

The fruits of Cocos nucifera Linn. (Arecaceae) have long been used in traditional medicine for the treatment of cardio-metabolic disorders.

Aim of the study

To evaluate the ethanolic extract of Cocos nucifera Linn. endocarp (CNE) for its vasorelaxant activity on isolated rat aortic rings and antihypertensive effects in deoxycorticosterone acetate (DOCA) salt-induced hypertensive rats.

Materials and methods

Cocos nucifera Linn. endocarp was extracted with ethanol and characterized by HPLC. CNE was examined for its in vitro vascular relaxant effects in isolated norepinephrine, phenylephrine or potassium chloride pre-contracted aortic rings (both intact endothelium and denuded). In vivo anti-hypertensive studies were conducted in DOCA salt-induced uninephrectomized male Wistar rats.

Results

Removal of endothelium or pretreatment of aortic rings (intact endothelium) with l-NNA (10 μM) or ODQ (10 μM) followed by addition of contractile agonists prior to CNE significantly blocked the CNE-induced relaxation. Indomethacin (10 μM) and atropine (1 μM) partially blocked the relaxation, whereas glibenclamide (10 μM) did not alter it. CNE significantly reduced the mean systolic blood pressure in DOCA salt-induced hypertensive rats (from 185.3 ± 4.7 mmHg to 145.6 ± 6.1 mmHg). The activities observed were supported by the polyphenols, viz. chlorogenic acid, vanillic acid and ferulic acid identified in the extract.

Conclusions

These findings reveal that the vasorelaxant and antihypertensive effects of CNE, through nitric oxide production in a concentration and endothelium-dependent manner, is due to direct activation of nitric oxide/guanylate cyclase pathway, stimulation of muscarinic receptors and/or via cyclooxygenase pathway.     

Pentacyclic triterpenoids and ceramide mediate the vasorelaxant activity of Vitex cienkowskii via involvement of NO/cGMP pathway in isolated rat aortic rings

Ethnopharmacological relevance

Vitex cienkowskii Kotschy & Peyritsch is a deciduous tree, prescribed by Cameroonian traditional healers as one of the most popular plant widely used in many disorders including cardiovascular diseases. The preliminary pharmacological studies carried out on Vitex cienkowskii showed its vasorelaxant activities on guinea-pig aortic rings.

Aim of the study

The present work evaluated the vasorelaxant activity of extract and isolated compounds from Vitex cienkowskii.

Materials and methods

Rat aortic rings were used to evaluate the in vitro vascular effect of the extract. The antioxidant activity was determined by measuring the reduction of the free radical 1,1-diphenyl-1-picryl-hydrazyl (DPPH).

Results

Vitex cienkowskii induced significant relaxation in a concentration- and endothelium-dependent manner (EC₅₀ = 12.12 μg/ml, CH₂Cl₂-MeOH, 1:1) and did not produce a vasorelaxant effect on contraction evoked by KCl (60 mM). In order to determine its mode of action, Vitex cienkowskii-induced relaxant effect was evaluated in the presence of indomethacin (10 μM), L-NAME (100 μM), ODQ (1 μM) and SQ22356 (100 μM). Relaxation was significantly blocked by L-NAME and ODQ. These results indicate that Vitex cienkowskii-mediated relaxation is endothelium dependent, probably due to NO release, and the consequent activation of vascular smooth muscle soluble guanylate cyclase (sGC), a signal transduction enzyme that forms the second messenger cGMP. Bio-guided study of Vitex cienkowskii allowed the isolation of the known pentacyclic triterpenoids and a ceramide. It is the first report of salvin A, maslinic acid and a ceramide from Vitex cienkowskii. The activity induced by these compounds indicated that they may be partly responsible for the vasorelaxant effect of the plant extract.A dose of 40 mg/kg of CH₂Cl₂-MeOH (1:1) extract administered intravenously induced a decrease of mean arterial pressure but did not affect the heart rate. Moreover the plant extracts were found to be highly active in the DPPH radical scavenging assay.

Conclusion

Vitex cienkowskii extract possesses antioxidant property, vasorelaxing, and hypotensive effect linked to the endothelium related factors, where nitric oxide is involved.     

Water extract of Zanthoxylum piperitum induces vascular relaxation via endothelium-dependent NO-cGMP signaling

Aim of the study

The aim of the present study was to define the effects of extracts of leaves of Zanthoxylum piperitum (ZP) on the vascular tension and its mechanisms responsible in rat thoracic aortic rings.

Materials and methods

Methanol extract of ZP and aqueous fraction of the methanol extract (AZP) were examined for their vascular relaxant effects in isolated phenylephrine-precontracted aortic rings.

Results

Methanol extract of ZP and aqueous fraction of the methanol extract (AZP) induced relaxation of the phenylephrine-precontracted aortic rings in a concentration-dependent manner. Endothelium-denudation abolished the AZP-induced vasorelaxation. Pretreatment of the endothelium-intact aortic rings with N^G-nitro-l-arginine methylester (L-NAME) and 1H-[1,2,4]-oxadiazolo-[4,3-α]-quinoxalin-1-one (ODQ) inhibited the AZP-induced vasorelaxation. Inhibition of Ca²⁺ entry via L-type Ca²⁺ channels failed to block the AZP-induced vasorelaxation. Extracellular Ca²⁺ depletion slightly but significantly attenuated the AZP-induced vasorelaxation. Thapsigargin significantly attenuated the AZP-induced vasorelaxation. Further, Gd³⁺ and 2-aminoethyl diphenylborinate (2-APB), inhibitors of store-operated Ca²⁺ entry (SOCE), markedly attenuated the AZP-induced vasorelaxation. Also, wortmannin, an inhibitor of Akt, an upstream signaling molecule of eNOS, attenuated the AZP-induced vasorelaxation. AZP increased cGMP levels of the aortic rings in a concentration-dependent manner and the effect was blocked by L-NAME, ODQ, thapsigargin, Gd³⁺, 2-APB, and wortmannin. K⁺ channel inhibition with glibenclamide and tetraethylammonium, cyclooxygenase inhibition with indomethacin, and adrenergic and muscarinic receptors blockade had no effects on the AZP-induced vasorelaxation.

Conclusion

Taken together, the present study suggests that AZP relaxes vascular smooth muscle via endothelium-dependent activation of NO-cGMP signaling through the Akt- and SOCE-eNOS pathways.     

Effects of Schisandra chinensis Baillon (Schizandraceae) on lipopolysaccharide induced lung inflammation in mice

Aim of the study

This study was aimed to evaluate the neuroprotective and anti-aging activity of extracts in Caenorhabditis elegans from the roots and leaves of Damnacanthus officinarum Huang to provide the pharmacological basis in traditional medicine.

Materials and methods

Investigations on the neuroprotective and lifespan activity were carried out, which were observed by utilizing the following models: observing the worms’ chemosensory behavior test based on the aversion index in the assay plate, neuroprotective activity of nematode by evaluating the ASH neuron survival and lifespan test in C. elegans.

Results

It has been shown that the ethanol, n-butanol and aqueous extracts in the roots possessed significantly neuroprotective effect both in chemosensory behavior test and ASH neuron survival model. The same extracts in the leaves showed similar activities in two models, but have less potency revealing by the data. Four candidate extracts, possessing excellent neuroprotective activity, extend lifespan in C. elegans. The n-butanol extracts in the root part showed best efficacy among them.

Conclusion

The results show the n-butanol and aqueous extracts are the major pharmacological plant extracts. Moreover, the neuroprotective and lifespan-extension activity effects of root extracts are superior to leave extracts, supporting the traditional application of above-ground parts of DOH in treating various diseases associated with brain disorders and anti-aging.     

黄连对乙酰苯肼所致小鼠红细胞氧化性溶血的影响及作用机制

目的:观察黄连对小鼠红细胞氧化性溶血的影响并探讨相关机制。方法:采用乙酰苯肼(APH)诱导小鼠红细胞氧化性溶血模型,以伯氨喹啉为对照药,观察不同浓度的黄连对血浆游离血红蛋白、血清间接胆红素、全血网织红细胞、红细胞内脂质过氧化产物和抗氧化系统相关酶和蛋白以及全血总抗氧化能力的影响。结果:0.03 g.kg-1APH能引起正常小鼠血浆游离血红蛋白和血清间接胆红素含量及外周血网织红细胞数量显著升高,也能明显提高红细胞丙二醛(MDA)含量和降低红细胞超氧化物歧化酶(SOD)、6-磷酸葡萄糖脱氢酶(G6PD)活力、还原型谷胱甘肽(GSH)含量以及全血总抗氧化能力。0.058 g.kg-1伯氨喹啉能明显加重APH所引起的红细胞氧化性溶血和氧化系统破坏;0.6 g.kg-1黄连能明显降低血清间接胆红素含量,1.2 g.kg-1黄连尚能显著减少血浆游离血红蛋白量和全血网织红细胞数,同时明显降低红细胞MDA含量、增加SOD活力和GSH含量、提高全血总抗氧化能力。结论:黄连能一定程度减轻APH引起的小鼠红细胞氧化性溶血,其机制可能与降低脂质过氧化产物和提高红细胞抗氧化酶的量和能力有关。     

Vasodilatory effects of ethanol extract of Radix Paeoniae Rubra and its mechanism of action in the rat aorta

Ethnopharmacological relevance

Radix Paeoniae Rubra (RPR) is an important traditional Chinese medicine (TCM) commonly used in clinic for a long history in China. RPR is the radix of either Paeonia lactiflora Pall. or Paeonia veitchii Lynch. RPR has a wide variety of pharmacological actions such as anti-thrombus, anti-coagulation, and anti-atherosclerotic properties, protecting heart and liver. However, the mechanisms involved are to be defined.

Aim of the study

The aim of the present study was to define the effect of Paeonia lactiflora Pall. extracts on vascular tension and responsible mechanisms in rat thoracic aortic rings.

Materials and methods

Ethanol extract of Paeonia lactiflora Pall. (EPL) was examined for their vascular relaxant effects in isolated phenylephrine-precontracted rat thoracic aorta.

Results

EPL induced relaxation of the phenylephrine-precontracted aortic rings in a concentration-dependent manner. Vascular relaxation induced by EPL was significantly inhibited by removal of the endothelium or pretreatment of the rings with N^G-nitro-l-arginine methylester (l-NAME) or 1H-[1,2,4]-oxadiazolo-[4,3-α]-quinoxalin-1-one (ODQ). Extracellular Ca²⁺ depletion or diltiazem significantly attenuated EPL-induced vasorelaxation. Modulators of the store-operated Ca²⁺ entry (SOCE), thapsigargin, 2-aminoethyl diphenylborinate and Gd³⁺, and an inhibitor of Akt, wortmannin, markedly attenuated the EPL-induced vasorelaxation. Further, the EPL-induced vasorelaxation was significantly attenuated by pretreatment with tetraethylammonium, a non-selective K_Ca channels blocker, or glibenclamide, an ATP-sensitive K⁺ channels inhibitor, respectively. Inhibition of cyclooxygenases with indomethacin, and adrenergic and muscarinic receptors blockade had no effects on the EPL-induced vasorelaxation.

Conclusions

The present study suggests that EPL relaxes vascular smooth muscle via endothelium-dependent and Akt- and SOCE-eNOS-cGMP-mediated pathways through activation of both K_Ca and K_ATP channels and inhibition of L-type Ca²⁺ channels.     

Pharmacological mechanisms underlying the vascular activities of Loranthus ferrugineus Roxb. in rat thoracic aorta

Aim of the study

The present study was aimed to investigate the pharmacological basis for the use of Loranthus ferrugineus in hypertension.

Materials and methods

Loranthus ferrugineus methanol extract (LFME) was obtained using Soxhelt extractor and then successively fractionated using chloroform, ethyl acetate and n-butanol. The n-butanol fraction of LFME (NBF-LFME) was studied using isolated rat thoracic aorta.

Results

NBF-LFME (1.0 × 10⁻⁵ to 3.0 mg/ml) was found to be the most potent to concentration-dependently relax the endothelium-intact phenyephrine (PE, 1 μM)- and high K⁺ (80 mM)-precontracted rat aortic rings. Removal of the endothelium completely abolished the vascular relaxing properties of NBF-LFME. Pretreatment with atropine (1 μM), l-NAME (10 μM), indomethacin (10 μM) and methylene blue (10 μM) significantly blocked NBF-LFME-mediated relaxation. Endothelium-dependent and -independent relaxations induced by acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, were significantly enhanced in aortic rings pretreated with NBF-LFME when compared to those observed in control aortic rings. On the contrary, glibenclamide (10 μM), propranolol (1 μM) and prazosin (0.01 μM) did not alter NBF-LFME-induced relaxation.

Conclusions

The results suggest that NBF-LFME induced vascular relaxation by stimulating muscarinic receptors, activating the endothelium-derived nitric oxide-cGMP-relaxant pathway, promoting prostacyclin release and/or possibly through its ability to lengthen the released nitric oxide half-life. The present data further supports previous in vivo findings and explain the traditional use of Loranthus ferrugineus as an anti-hypertensive agent.     

Relaxant effects of Artemisia ludoviciana on isolated rat smooth muscle tissues

Ethnopharmacological relevance

Artemisia ludoviciana spp. mexicana (Willd. Ex.) Spring D.D. Keck (Asteraceae), known as “estafiate” is employed for the treatment of diarrhea, dysentery, parasites, abdominal pain, vomiting, stomach ache, and also as antispasmodic agent. The aim of the present study was to evaluate the relaxant effect of hexanic (HEAl), dichloromethanic (DEAl) and methanolic (MEAl) extracts on isolated trachea, ileum and aorta rat rings, and to establish the tracheo-relaxant mode of action of DEAl.

Materials and methods

All extracts were investigated based on their capacity of to inhibit the rat ileum spontaneous contraction, to relax contraction induced by noradrenaline (0.1 μM) on endothelium-intact and endothelium-denuded thoracic aorta rat rings, and also to inhibit contraction provoked by carbachol (1 μM) on rat trachea.

Results

Organic extracts had no spasmolytic action on ileum strips compared to positive control (papaverine, p < 0.05). On the other hand, all extracts induced a significant concentration- and partial endothelium-dependent vasorelaxant activity. Extracts also showed significant relaxant effect on pre-contracted tracheal tissue in a concentration-dependent manner. In last two experiments, DEAl was the most potent and efficient extract; however, it was less potent than papaverine and theophylline, used as positive controls (p < 0.05). In tracheal preparation, DEAl shifted to the right, in a parallel manner, the concentration-response curves induced by carbachol (p < 0.05). Also, DEAl induced a significant relaxant effect on the contraction produced by potassium chloride (KCl, 80 mM). Pre-incubation with 1-H-[1,2,4]-oxadiazolo-[4,3a]-quinoxalin-1-one (ODQ, 10 μM), indomethacin (10 μM), N_ω-nitro-l-arginine methyl ester (l-NAME, 10 μM), glibenclamide (10 μM) and 2-aminopyridine (2-AP, 100 μM) did not modify the DEAl-relaxant curves.

Conclusions

Functional experiments suggest that the most active extract, DEAl, induced its relaxant effect by possible muscarinic receptors antagonism and calcium channel blockade in tracheal rings. On the other hand, significant vasorelaxant activity showed by DEAl is partially endothelium-dependent. Finally, spasmolytic activity induced by the extracts in the rat ileum was not significant, which suggests that the antidiarrheic effect of the plant is related to antimicrobial and antiparasitic properties previously described.     

Inhibition of inducible nitric oxide production and iNOS protein expression in lipopolysaccharide-stimulated rat aorta and Raw 264.7 macrophages by ethanol extract of a Chinese herbal medicine formula (RCM-101) for allergic rhinitis

AIM OF THE STUDY: A Chinese herbal formula (RCM-101) has shown to be effective in reducing symptoms of seasonal allergic rhinitis (SAR) in a randomised, placebo-controlled clinical trial. The aim of this study is to investigate the effects of RCM-101 on the actions and synthesis of nitric oxide (NO). l-Arginine-induced endothelium-independent relaxations were studied in rat isolated aorta which was pre-treated with lipopolysaccharide (LPS). MATERIALS AND METHODS: NO production and inducible nitric oxide synthase (iNOS) protein expression were studied in LPS and interferon gamma-stimulated murine macrophages (Raw 264.7), measured by NO sensors and Western blotting. RESULTS: In rat aortic preparations, RCM-101 significantly inhibited endothelium-independent relaxations to l-arginine, but not affected those to sodium nitroprusside (SNP). In Raw 264.7 cells, RCM-101 and some of its individual ingredients (e.g., Radix glycyrrhizae, Radix bupleuri, Radix saposhnikoviae and Atractylodis rhizome macrocephalae) significantly inhibited the NO production and iNOS protein expression. CONCLUSIONS: The findings indicate that RCM-101 may inhibit inducible NO production by suppressing iNOS. In addition, its inhibitory action of iNOS is likely to be mediated by several key herbal ingredients.     

Potent relaxant effect of a Celastrus paniculatus extract in the rat and human ileum

Ethnopharmacological importance

Celastrus paniculatus Willd. (Celastraceae) is an Ayurvedic remedy used for the treatment of a number of diseases, including bowel spasms.

Aim of the study

To investigate the mode of the relaxing action of a methanolic extract prepared from the seeds of Celastrus paniculatus (CPE, 0.0001–10 μg/mL) in the rat ileum and to try to confirm on human tissues the intestinal pharmacological activity of the extract.

Materials and methods

The relaxant effect of CPE was studied in vitro by evaluating its effect on the spontaneous contractions of the isolated ileum.

Results

CPE exerted a tetrodotoxin- and ω-conotoxin-resistant inhibitory effect on rat ileum motility (IC₅₀: 0.24 ± 0.02 μg/mL; E_max: 99.0 ± 0.60%). The inhibitory effect was reduced by nifedipine but not by cyclopiazonic acid. Experiments with specific antagonists enabled us to exclude the involvement of the main endogenous spasmogenic (i.e. acetylcholine and tachykinins) and relaxing (noradrenaline, nitric oxide, ATP) compounds. CPE also relaxed the isolated human ileum (IC₅₀: 0.26 ± 0.02 μg/mL; E_max: 99.1 ± 0.46%).

Conclusion

It is concluded that (i) CPE exerted a powerful myogenic and L-type Ca²⁺-dependent relaxing effect in the isolated rat ileum and that (ii) the human ileum is sensitive to the inhibitory effect of CPE. If confirmed in vivo, our data could explain the traditional use of this herb in the treatment of intestinal spasms.     

Role of nitric oxide in the vasorelaxant and hypotensive effects of extracts and purified tannins from Geum japonicum

Crude extracts and three purified tannins from Geum japonicum Thunberg (Rosaceae) were examined for relaxant effects in isolated rat thoracic aorta and for hypotensive effects in anesthetized normotensive and hypertensive rats. The acetone extract and the butyl alcohol extract of Geum japonicum at a cumulative concentration of 30mug/ml potently relaxed phenylephrine-precontracted aortic rings by 73+/-5% and 80+/-7%, respectively, without affecting the resting tension of these vessels. Removal of the vascular endothelium, inhibition of nitric oxide (NO) synthase with N(omega)-nitro-l-arginine (l-NA) or inhibition of cGMP biosynthesis with methylene blue all abolished the vasorelaxant effects of the Geum japonicum extracts. Addition of l-arginine, the substrate for NO biosynthesis, reversed the inhibitory effects of l-NA. Similar vasorelaxant effects of 82+/-10%, 61+/-8% and 82+/-14%, were observed with the purified tannins, penta-O-galloyl-beta-glucoside, casuariin and 5-desgalloylstachyurin, respectively, at a cumulative concentration of 10muM. Intravenous injection of the butyl alcohol extract of Geum japonicum at a cumulative dose of 2.5mg/kg into both hypertensive and normotensive rats resulted in a marked reduction in the mean arterial blood pressure by 46+/-6% and 34+/-7%, respectively, which was abolished by prior injection of l-NA. Therefore, these results suggest that tannins may be responsible for the vasorelaxant and hypotensive effects of Geum japonicum, mediated via endogenous NO and subsequent cGMP formation. The data suggest that extracts of Geum japonicum may have potential use as new anti-hypertensive agents for lowering arterial blood pressure in hypertensive patients.     

Cochlospermum vitifolium induces vasorelaxant and antihypertensive effects mainly by activation of NO/cGMP signaling pathway

Aim of the study

Cochlospermum vitifolium is a medicinal plant used for the treatment of diabetes, hepatobilary and cardiovascular illnesses. The aim of current study was to determine the in vivo antihypertensive and in vitro functional vasorelaxant mechanism of methanol extract of Cochlospermum vitifolium (MECv) and naringenin (NG).

Materials and methods

Test material was assayed on rat isolated aorta rings test with- and without-endothelium to determine their vasorelaxant mechanism. Also, the in vivo antihypertensive effect was evaluated on spontaneously hypertensive rat (SHR) model. In addition, presence of NG into the extract was confirmed by reverse phase high performance liquid chromatography (RP-HPLC) analysis.

Results

MECv (120 mg/kg) and NG (50 and 160 mg/kg) showed acute antihypertensive effects on SHR when systolic and diastolic pressure were decreased at 1 h and 24 h after administration, respectively. Vasorelaxant effect of MECv and NG was shifted to the right when endothelium-intact aortic rings were pre-incubated with L-NAME (10 μM) and ODQ (1 μM). Also, NG relaxant curves were displaced to the right in the presence of tetraethylammonium (TEA, 1 mM) and 2-aminopyridine (2-AP, 100 μM) on endothelium-denuded aortic rings.

Conclusion

Experiments described above showed that MECv play an important role in hypertension regulation through NO synthesis and may be PGI₂ production and potassium channel activation on excessive endothelial dysfunction conditions. Unfortunately, presence of NG into the extract is not significant on bioactivity of the extract; however, this compound could be tested and evaluated as structural scaffold for future drug design for development of antihypertensive agents.     

Phytochemical study guided by the myorelaxant activity of the crude extract,fractions and constituent from stem bark of Hymenaea courbaril L.

Ethnopharmacological relevance

Hymenaea courbaril L. (Caesalpinoideae) is used in Brazilian folk medicine to treat anemia, kidney problems, sore throat and other dysfunctions of the respiratory system, such as bronchitis and asthma, although such properties are yet to be scientifically validated.

Aim of the study

In order to give a scientific basis to support the traditional use of Hymenaea courbaril, this study was designed to evaluate antioxidant, myorelaxant and anti-inflammatory properties of the ethanol extract from stem bark and its fractions. The myorelaxant effect of astilbin, a flavonoid isolated from the bioactive ethyl acetate fraction (EAF), has also been evaluated.

Material and methods

In the present study ethanol extract from stem bark (EEHC) and fractions were analyzed using bioassay-guided fractionation. The following activities were investigated: antioxidant by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, myorelaxant on rat tracheal smooth muscle, and anti-inflammatory using ovalbumin-induced leukocytosis and airway hyperresponsiveness in rats.

Results

The results of the present investigation show that the whole extract of Hymenaea courbaril and some of its fractions strongly scavenged DPPH radical. The extract showed myorelaxant activity on rat trachea, being EAF its highest efficient fraction. Bio-guided study allowed the isolation of astilbin, a well-known flavonoid. The activity induced by this compound indicates that it may be partly responsible for the myorelaxant effect of EAF. EAF reduced contractions that depended on divalent cation inflow through voltage-operated Ca²⁺ channels (VOCCs) or receptor-operated Ca²⁺ channels (ROCCs), but it was more potent to inhibit VOCC- than ROCC-dependent contraction induced by Ca²⁺ addition in ACh-enriched Ca²⁺-free medium. Oral pretreatment of antigen-challenged animals with EAF prevented airway hyperresponsiveness on KCl-induced contraction and reduced the number of total white cells, particularly eosinophils and neutrophils in bronchoalveolar lavage.

Conclusions

This study provided scientific basis that Hymenaea courbaril presents potential antioxidant, myorelaxant and anti-inflammatory actions, which support its use in folk medicine to treat inflammatory airway diseases.