Sarcorucinine-D Inhibits Cholinesterases and Calcium Channels: Molecular Dynamics Simulation and In Vitro Mechanistic Investigations.

Acetylcholinesterase (AChE) inhibitors and calcium channel blockers are considered effective therapies for Alzheimer's disease. AChE plays an essential role in the nervous system by catalyzing the hydrolysis of the neurotransmitter acetylcholine. In this study, the inhibition of the enzyme AChE by Sarcorucinine-D, a pregnane type steroidal alkaloid, was investigated with experimental enzyme kinetics and molecular dynamics (MD) simulation techniques. Kinetics studies showed that Sarcorucinine-D inhibits two cholinesterases-AChE and butyrylcholinesterase (BChE)-noncompetitively, with Ki values of 103.3 and 4.66 µM, respectively. In silico ligand-protein docking and MD simulation studies conducted on AChE predicted that Sarcorucinine-D interacted via hydrophobic interactions and hydrogen bonds with the residues of the active-site gorge of AChE. Sarcorucinine-D was able to relax contractility concentration-dependently in the intestinal smooth muscles of jejunum obtained from rabbits. Not only was the spontaneous spasmogenicity inhibited, but it also suppressed K+-mediated spasmogenicity, indicating an effect via the inhibition of voltage-dependent Ca2+ channels. Sarcorucinine-D could be considered a potential lead molecule based on its properties as a noncompetitive AChE inhibitor and a Ca2+ channel blocker.

Intestinal, airway, and cardiovascular relaxant activities of thymoquinone.

Thymoquinone (TQ) is a bioactive component found in many medicinal herbs. In this study, we report the smooth and cardiac muscle relaxant activities of this compound. TQ concentration dependently suppressed spontaneously contracting rabbit jejunum while also relaxed high K(+)-(80 mM) induced contractions in jejunum and guinea-pig ileum, indicating activity at voltage-operated Ca(++) channels (VOCC). Further, TQ displaced Ca(++) concentration-response curves, obtained in a Ca(++)-free environment, to the right, showing blockade of VOCC. Similar activity was observed with verapamil, a standard VOCC blocker. TQ also exhibited nonadrenergic relaxation of agonist-induced contractions in guinea-pig trachea. When tested in fluo-4-loaded mouse lung slices, TQ inhibited ACh-induced airway narrowing and Ca(++) signalling in airway smooth muscle cells. In endothelium-intact and endothelium-denuded rat aorta, TQ inhibited high K(+)-induced contractions at significantly lower concentrations than phenylephrine-(PE-) (1 microM) induced contractions. Relaxation of PE-induced contractions was resistant to blockade by L-NAME and atropine. In guinea-pig atria, TQ showed noncholinergic relaxation of atrial force and rate of contractions. These data suggest smooth and cardiac muscle relaxant activity of TQ possibly mediated, in part, via blockade of VOCC. The results also justify the use of TQ containing plants in related health disorders like colic, diarrhoea, cough, and asthma.

Trigonella foenum-graecum Methanolic Extract on Isolated Smooth Muscles and Acetylcholinesterase Enzyme: An In Vitro and Mechanistic In Silico Investigation.

Results: When tested on the baseline of isolated tissues, Tfg.Cr was devoid of any activity (stimulant or relaxant) till 10 mg/ml. This is an interesting finding, keeping in mind that the fenugreek seeds are used to alleviate constipation and diarrhoea. When Tfg.Cr was tried for any potential AChE inhibitory activity, it did show an inhibitory effect in increasing concentrations (47-380 µg/ml). This inhibitory effect was comparable to the effect produced by a standard AChE inhibitor physostigmine. One of the known fenugreek constituents, diosgenin, was also tested, and it also showed an AChE inhibitory effect in a concentration-dependent manner (11-190 µg/ml). Interaction between diosgenin and AChE was further investigated by molecular docking and molecular dynamics simulations for 100 ns, which showed that diosgenin interacted with the active-site gorge of AChE through hydrophobic, pi-pi stacking, and hydrogen bonds with various amino acids of the AChE enzyme. Conclusion: The results show that the fenugreek extract does not possess any GI stimulant or relaxant activity even though it is used traditionally in GI motility disorders. The extract and diosgenin could inhibit the AChE enzyme pointing towards their benefit to enhance the memory.

Pharmacological basis for the medicinal use of psyllium husk (Ispaghula) in constipation and diarrhea.

BACKGROUND: The objective of this study was to determine the pharmacological basis of the medicinal use of psyllium husk (Ispaghula) in gastrointestinal motility disorders. METHODS: In-vivo studies were conducted on mice, and isolated rabbit jejunum and guinea-pig ileum were used in in-vitro experiments. RESULTS: The crude extract of Ispaghula (Po.Cr) had a laxative effect in mice at 100 and 300 mg/kg, which was partially sensitive to atropine or SB203186 (5-HT(4) antagonist). At higher doses (500 and 1,000 mg/kg), Po.Cr had antisecretory and antidiarrheal activity. In guinea-pig ileum, Po.Cr (1-10 mg/ml) had a stimulatory effect, which was partially sensitive to atropine or SB203186. In rabbit jejunum, Po.Cr had a partially atropine-sensitive stimulatory effect followed by relaxation at 10 mg/ml. The relaxation was inhibited by the presence of L-NAME, a nitric oxide (NO) synthase inhibitor, or methylene blue, a guanylyl cyclase inhibitor. Similarly, the relaxant effect of Po.Cr on K(+) (80 mM)-induced contractions, was attenuated in the presence of L-NAME or methylene blue. Activity-directed fractionation of Po.Cr revealed that the gut stimulatory and inhibitory constituents were widely distributed in the aqueous and organic fractions. CONCLUSION: This study demonstrates that Ispaghula has a gut-stimulatory effect, mediated partially by muscarinic and 5-HT(4) receptor activation, which may complement the laxative effect of its fiber content, and a gut-inhibitory activity possibly mediated by blockade of Ca(2+) channels and activation of NO-cyclic guanosine monophosphate pathways. This may explain its medicinal use in diarrhea. It is, perhaps, also intended by nature to offset an excessive stimulant effect.

Identification of antiplatelet and acetylcholinesterase inhibitory constituents in betel nut.

OBJECTIVE: To investigate the possible mechanism and the compound(s) responsible for the antiplatelet and acetylcholinesterase (AChE) inhibitory effects of Areca catechu crude extract (Ac.Cr). METHODS: Aqueous-methanol (70%) was used for extraction of plant material (betel nut). Antiplatelet activity was measured in human platelet-rich plasma by using a Lumi-aggregometer while anti-AChE activity was measured spectrophotometrically in vitro. In an attempt to find the responsible compound(s) in betel nut for antiplatelet and anti-AChE activities, different commercially available betel nut compounds were tested. RESULTS: Ac.Cr inhibited platelet aggregation induced by arachidonic acid (AA), adenosine diphosphate (ADP), platelet-activating factor (PAF), epinephrine and Ca(2+)-ionophore. Ac.Cr was the most potent in inhibiting ADP- and Ca(2+)-ionophore-induced aggregation. In the AChE assay, Ac.Cr showed significant AChE inhibitory activity with almost complete inhibition of the enzyme. Out of the tested compounds, none of the compounds in betel nut showed any antiplatelet effect except for catechin that was the most potent against epinephrine-induced aggregation. Catechin was significantly less potent than Ac.Cr, indicating a presence of additional compound(s) with antiplatelet activity. For the AChE inhibitory effect, only tannic acid, gallic acid, diosgenin and isoguvacine were found to be active, whereby tannic acid was more potent than Ac.Cr. CONCLUSION: This study shows the possible antiplatelet and AChE inhibitory potential of betel nut while further studies are needed to confirm and identify more compounds in betel nut for these actions.

Potential Adverse Consequences of Combination Therapy with Gabapentin and Pregabalin.

Gabapentinoids comprise the medications gabapentin and pregabalin. These were designed to not only look chemically like the central inhibitory neurotransmitter gamma-aminobutyric acid (GABA) but also act like it. The prototype gabapentin was primarily introduced to be used as antiepileptic medication. Today, both chemicals are not only utilized as adjunct antiepileptics in focal (aware and impaired awareness) seizures but are also used in several neuropathic pain conditions and other clinical indications. Their use has skyrocketed in the past few years and this has brought forward more instances of adverse effects and errors in prescribing practices. We describe here a case of a female patient with a history of diabetes, diabetic neuropathy, and hypertension being prescribed both gabapentin and pregabalin concomitantly which led to adverse effects like drowsiness, dizziness, fatigue, and ataxia. Once the patient medication profile was revisited, the pharmacy staff was able to identify the therapeutic duplications (gabapentin and pregabalin). The physician was contacted and pregabalin was discontinued. This led to the disappearance of the adverse effects. The dose of the existing gabapentin was increased to control the symptoms of diabetic neuropathy. This report sheds light on the importance of responsible prescribing, efficient checking of medication profiles on the level of dispensing pharmacies, and timely follow-up to patients to keep the patients safe and their medical conditions under check.

Spasmolytic Effect of Grewia asiatica Fruit Extract on Isolated Smooth Muscles is Mediated via Multiple Pathways.

BACKGROUND: Grewia asiatica Linn, or phalsa, is a commonly consumed fruit in Pakistan. The fruit is employed in the traditional medicine practice of Pakistan as a smooth muscle relaxant in different gastrointestinal (GI) and cardiovascular diseases. In this investigation, we show the antispasmodic and vasorelaxant actions of Grewia asiatica fruit extract. METHODS: A 70% methanolic crude extract of the plant material was prepared (Ga.Cr). Different isolated GI tissue preparations and endothelium-intact aortas from rats were utilized to observe the pharmacological actions of the extract. RESULTS: Ga.Cr, in increasing concentrations, inhibited the spontaneously contracting rabbit jejunum. In an effort to determine the mechanism of this relaxant action, contractions were induced in jejunum and ileum tissues with K+ (80 mM). Ga.Cr was able to only partially inhibit these induced contractions indicating that the mechanism might not be completely through a blockade of Ca2+ channels (CCB). When tested on low K+-(25 mM) sustained contractions, Ga.Cr cumulatively suppressed these contractions (0.1-10 mg/ml), indicating an opening of K+ channels (KCO) as the mechanism. Cromakalim, a standard KCO, was also more specific in blocking low K+-induced contractions. For the effect in aorta tissues, Ga.Cr suppressed the agonist-induced contractions from 0.3 mg/ml to 10 mg/ml. Upon challenge with L-NAME, a nitric oxide (NO) blocker, the extract response curve shifted right, indicating vasodilation was mediated via endothelial NO. CONCLUSION: This study shows that GI antispasmodic and vasodilator activities of Ga.Cr may be mediated via a KCO mechanism in the GI tract and through the release of NO from vascular endothelium.

Science across borders: 5th annual natural health product research conference-march 26-29, 2008, toronto, Canada.

Canada is experiencing a growing interest in the use of alternative therapies and products particularly natural health products (NHP). In 1997, Canadians spent around C$ 2 billion on NHP. In an attempt to catch with this popularity of NHP use, Canadian researchers and administrators from academia, industry and government jointly established the Natural Health Product Research Society of Canada (NHPRS). Since its formation, NHPRS has been organizing an annual meeting which brings together world renowned researchers and experts in the area of NHP research. For 2008, the annual NHPRS meeting took place in Toronto from the 26th to 29th of March with a focus on 'Science Across Borders: Global Natural Health Products Research'. The scientific program was spread into three days of plenary lectures and oral presentations. The different sessions containing these talks were on: ethnobotany around the world; chemical analysis of NHP; product standards and quality control; ethnomedicine; novel analytical approaches; systemic research, nutrisciences and molecular medicine; and drug development from NHP. The meeting proved to be a great success in terms of the speakers that were invited and based on the data that was presented which highlighted recent research taking place in the field of NHP not only in Canada but from many parts of the world.

Antidiarrhoeal and spasmolytic activities of the methanolic crude extract of Alstonia scholaris L. are mediated through calcium channel blockade.

This study was aimed to provide a pharmacological basis to the medicinal use of Alstonia scholaris as an antidiarrhoeal and antispasmodic by using in vivo and in vitro techniques. In the in vivo study the crude extract of Alstonia scholaris (As.Cr), which tested positive for the presence of alkaloids, provided 31-84% protection against castor oil-induced diarrhoea in mice at 100-1000 mg/kg doses, similar to loperamide. In isolated rabbit jejunum preparation, the As.Cr caused inhibition of spontaneous and high K(+) (80 mm)-induced contractions, with respective EC(50) values of 1.04 (0.73-1.48) and 1.02 mg/mL (0.56-1.84; 95% CI), thus showing spasmolytic activity mediated possibly through calcium channel blockade (CCB). The CCB activity was further confirmed when pretreatment of the tissue with the As.Cr (0.3-1 mg/mL) caused a rightward shift in the Ca(++) concentration-response curves similar to verapamil, a standard calcium channel blocker. Loperamide also inhibited spontaneous and high K(+) precontractions as well as shifted the Ca(++) CRCs to the right. These results indicate that the crude extract of Alstonia scholaris possesses antidiarrhoeal and spasmolytic effects, mediated possibly through the presence of CCB-like constituent(s) and this study provides a mechanistic base for its medicinal use in diarrhoea and colic.

Antispasmodic, bronchodilator and vasodilator activities of (+)-catechin, a naturally occurring flavonoid.

Catechin is a well-known flavonoid found in many food plants and often utilized by naturopaths for the symptomatic treatment of several gastrointestinal, respiratory and vascular diseases. Our aim was to explore the biological basis for the medicinal use of this flavonoid by investigating whether catechin exhibits any pharmacological activity on smooth muscle preparations. We found that catechin dose-dependently relaxes both spontaneous and high K(+) (80 mM)-induced contraction in rabbit jejunum, showing specificity for the latter by causing a right-ward shift in the Ca(2+) dose-response curve. Similar results were observed with verapamil, a standard Ca(2+) channel blocker (CCB). Catechin also inhibited high K(+)-induced contraction in intact smooth muscle preparations from rat stomach fundus, guinea-pig ileum and guinea-pig trachea. In rat aorta, catechin inhibited phenylephrine (PE, 1 microM) and K(+)-induced contractions in a similar fashion. In PE-contracted, endothelium-intact aorta, this vasodilator effect was partially blocked by Nomega-nitro-L-arginine methyl ester and atropine, indicating activity at cholinergic receptors and possibly a CCB effect at higher doses of catechin. In guinea-pig atria catechin was found inactive. These data suggest that catechin may possess Ca(2+) antagonist activity--in addition to an endothelium-dependent relaxant component in blood vessels--thus providing a pharmacological basis for the efficacy of catechin in hyperexcitability disorders of gastrointestinal, respiratory and vascular smooth muscle.

Radish seed extract mediates its cardiovascular inhibitory effects via muscarinic receptor activation.

In this study, we describe the hypotensive, cardio-modulatory and endothelium-dependent vasodilator actions of Raphanus sativus (radish) seed crude extract in an attempt to provide scientific basis for its traditional use in hypertension. The plant extract (Rs.Cr) was prepared in distilled water and was subjected to phytochemical screening using standard analytical procedures. In vivo blood pressure was monitored in anaesthetized normotensive rats. Isolated tissue preparations were suspended in tissue baths containing Kreb's solution while acute toxicity study was performed in mice for 24 h. Rs.Cr tested positive for the presence of saponins, flavonoids, tannins, phenols and alkaloids and caused a dose-dependent (0.1-3 mg/kg) fall in blood pressure and heart rate of rats that was mediated via an atropine-sensitive pathway. In isolated guinea-pig atria, Rs.Cr showed dose-dependent (0.03-3.0 mg/mL) inhibition of force and rate of contractions. In the atropine-treated tissues, the inhibitory effect was abolished and a cardiac stimulant effect was unmasked which was resistant to adrenergic and serotonergic receptor blockade. In the endothelium-intact rat aorta, Rs.Cr inhibited phenylephrine-induced contractions, which was blocked by atropine and Nomega-Nitro-L-arginine methyl ester hydrochloride while was also absent in the endothelium-denuded preparations. The extract was safe in mice up to the dose of 10 g/kg. The study shows that the cardiovascular inhibitory effects of the plant are mediated through activation of muscarinic receptors thus possibly justifying its use in hypertension.

In vivo anthelmintic activity of ginger against gastrointestinal nematodes of sheep.

This paper describes the anthelmintic activity of Zingiber officinale Roscoe (family Zingiberaceae) rhizome, commonly known as ginger, to justify its traditional use in veterinary medicine. Crude powder (CP) and crude aqueous extract (CAE) of dried ginger (1-3 g/kg) were administered to sheep naturally infected with mixed species of gastrointestinal nematodes. Both CP and CAE exhibited a dose- and a time-dependent anthelmintic effect with respective maximum reduction of 25.6% and 66.6% in eggs per gram (EPG) of faeces on day 10 of post-treatment. Levamisole (7.5 mg/kg), a standard anthelmintic agent, exhibited 99.2% reduction in EPG. This study shows that ginger possesses in vivo anthelmintic activity in sheep thus justifying the age-old traditional use of this plant in helminth infestation.

Studies on cardio-suppressant, vasodilator and tracheal relaxant effects of Sarcococca saligna.

Sarcococca saligna is a shrub that is traditionally used for its medicinal properties in Pakistan. In this study we report the cardio-suppressant, vasodilator and tracheal relaxant activities of the aqueous-methanolic extract (Ss.Cr) of the plant. Ss.Cr, that tested positive for the presence of saponins, flavonoids, tannins, phenols, and alkaloids, exhibited a dose-dependent (0.3-5 mg/mL) negative inotropic and chronotropic effect on the isolated guinea-pig atrium which was resistant to atropine (1 microM) and aminophylline (10 microM) pretreatment. In rabbit thoracic aorta, Ss.Cr dose-dependently (0.1-3 mg/mL) relaxed the high K+ (80 mM) and phenylephrine (PE, 1 microM)-induced contractions, indicating a possible Ca++ channel blocking (CCB) effect. When tested against PE (1 microM) control peaks in normal Ca++ and Ca++-free Kreb's solution, Ss.Cr exhibited dose-dependent (0.1-3 mg/mL) inhibition, being more potent in relaxing the PE responses in Ca++-free Kreb's solution, thus indicating specific blockade of Ca++ release from the intracellular stores. Ss.Cr also relaxed the agonist-induced contractions in: a) rat aorta irrespective of the presence of endothelium or nitric oxide synthase inhibitor L-NAME and b) rabbit and guinea-pig tracheal strips. The data shows that Ss.Cr possesses possible Ca++ channel blocking activity which might be responsible for its observed cardio-suppressant, vasodilator and tracheal relaxant effects though more tests are required to confirm this Ca++ channel blocking effect.

Synthesis and smooth muscle-selective relaxant activity of a piperidine analogue: 1-(4'-fluorophenacyl)-4-hydroxy-4-phenyl-piperidinium chloride.

The antispasmodic and vasodilator activities of a newly synthesized piperidine derivative (1-(4'-fluorophenacyl)-4-hydroxy-4-phenyl-piperidinium chloride) were studied in vitro. The test compound exhibited a dose-dependent relaxant effect on the spontaneous and K+ (75 mM)-induced contractions of isolated rabbit jejunum with respective EC50 values of 0.01 mM (0.01-0.02, 95% Cl) and 0.30 mM (0.17-0.56). The Ca++ channel blocking (CCB) activity was confirmed when the test compound (0.1-0.2 mM) shifted the Ca++ dose-response curves to the right, similar to that produced by verapamil (0.1-1.0 microM), a standard CCB. In the isolated rabbit aorta, the test compound showed a dose-dependent vasodilator effect on K+ (75 mM)-induced contractions with an EC50 value of 0.08 mM (0.02-0.26) while also suppressed the norepinephrine (1 microM) control peak responses with EC50 value of 0.08 mM (0.05-0.13, n=5). When tested in Langendorff perfused rabbit heart preparation, the test compound exhibited a negligible inhibitory effect on the rate or force of atrial and ventricular contractions when tested up to 5 mM. The results show smooth muscle-selective relaxant effect of the test compound on intestinal and vascular preparations mediated possibly via blockade of voltage and receptor-operated Ca++ channels.

In vivo anthelmintic activity of Butea monosperma against Trichostrongylid nematodes in sheep.

Seeds of Butea monosperma administered as crude powder (CP) at doses of 1, 2 and 3 g/kg to sheep naturally infected with mixed species of gastrointestinal nematodes exhibited a dose and a time-dependent anthelmintic effect. The maximum reduction of 78.4% in eggs per gram of feces (EPG) was recorded on day 10 after treatment with 3 g/kg. Levamisole (7.5 mg/kg), a standard anthelmintic agent, exhibited 99.1% reduction in EPG.

Acidosis-induced relaxation of human internal mammary artery is due to activation of ATP-sensitive potassium channels.

Metabolic acidosis is associated with various clinical situations including diabetes mellitus and renal diseases. The aim of this study was to investigate the effects of acidosis on the resting as well as precontracted human left internal mammary artery. The vessels were obtained from the patients undergoing coronary artery bypass grafting surgery at The Aga Khan University Hospital, Karachi. Left internal mammary artery was cut into rings and isometric tension recording experiments were performed. Decrease in pH of the bathing solution from 7.4 to 6.8 had no effect on the resting tension of left internal mammary artery, whereas, acidic pH markedly relaxed the contractions to 24.8 mM KCl and 300 nM phenylephrine. Interestingly, when the KCl- or phenylephrine-contracted rings were treated with 3 microM glibenclamide; an inhibitor of ATP-sensitive potassium (K(ATP)) channels, the relaxant effect of acidosis was abolished. Similarly, acidosis failed to cause relaxation of 100 nM endothelin-1-induced contraction in Ca2+-free bathing solution or in the presence of a voltage-dependent Ca2+ channel inhibitor, verapamil (10 microM), whereas, endothelin-1-induced contraction was attenuated by acidosis in Ca2+-containing normal solution. From all these data, it is concluded that under the acidic pH conditions, opening of K(ATP) channels occurs; resulting in the hyperpolarization, decrease in Ca2+ influx via voltage-dependent Ca2+ channels and subsequent relaxation of human left internal mammary artery.

Pharmacological basis for the use of turmeric in gastrointestinal and respiratory disorders.

This study was carried out to provide scientific basis for the medicinal use of turmeric (Curcuma longa) in gastrointestinal and respiratory disorders. The crude extract of turmeric (Cl.Cr), relaxed the spontaneous and K+ (80 mM)-induced contractions in isolated rabbit jejunum as well as shifted the CaCl2 concentration-response curves. In rabbit tracheal preparation, Cl.Cr inhibited carbachol and K(+)-induced contractions. In anesthetized rats, Cl.Cr produced variable responses on blood pressure with a mixture of weak hypertensive and hypotensive actions. In rabbit aorta, Cl.Cr caused a weak vasoconstrictor and a vasodilator effect on K+ and phenylephrine-induced contractions. In guinea-pig atria, Cl.Cr inhibited spontaneous rate and force of contractions at 14-24 times higher concentrations. Activity directed fractionation revealed that the vasodilator and vasoconstrictor activities are widely distributed in the plant with no clear separation into the polar or non-polar fractions. When used for comparison, both curcumin and verapamil caused similar inhibitory effects in all smooth muscle preparations with relatively more effect against K(+)-induced contractions and that both were devoid of any vasoconstrictor effect and curcumin had no effect on atria. These data suggest that the inhibitory effects of Cl.Cr are mediated primarily through calcium channel blockade, though additional mechanism cannot be ruled out and this study forms the basis for the traditional use of turmeric in hyperactive states of the gut and airways. Furthermore, curcumin, the main active principle, does not share all effects of turmeric.

Cardiovascular effects of ginger aqueous extract and its phenolic constituents are mediated through multiple pathways.

Ginger is a world known food plant which is equally reputed for its medicinal properties. We report here the hypotensive, endothelium-dependent and independent vasodilator and cardio-suppressant and stimulant effects of its aqueous extract (Zo.Cr). Zo.Cr, which tested positive for saponins, flavonoids, amines, alkaloids and terpenoids, induced a dose-dependent (3.0-10.0 mg/kg) fall in the arterial blood pressure (BP) of anaesthetized rats which was partially blocked by atropine (1 mg/kg). In isolated endothelium-intact rat aorta, Zo.Cr (0.01-5.0 mg/ml) relaxed the phenylephrine (1 microM)-induced contractions, effect partially blocked by atropine (1 microM). Zo.Cr inhibited the K+ (80 mM)-induced contractions and also shifted the Ca++ dose-response curves to the right, similar to verapamil, indicating Ca++ antagonist activity. An atropine-resistant and l-NAME-sensitive vasodilator activity was also noted from ginger phenolic constituents 6-, 8- and 10-gingerol, while 6-shogaol showed a mild vasodilator effect. In guinea-pig atria, Zo.Cr (0.1-5.0 mg/ml) inhibited the force and rate of atrial contractions. Pretreatment with atropine blocked the inhibitory effect and a stimulatory effect was unmasked which was resistant to propranolol and verapamil but sensitive to ryanodine, blocker of Ca++ release from intracellular stores. Later at doses >or=1.0 mg/ml, the extract completely suppressed the atrial tissue, effect resistant to glibenclamide, pyrilamine, aminophylline and L-NAME. These data indicate that the aqueous ginger extract lowers BP through a dual inhibitory effect mediated via stimulation of muscarinic receptors and blockade of Ca++ channels and this study provides sound mechanistic basis for the use of ginger in hypertension and palpitations.

Species differences in the gut stimulatory effects of radish seeds.

This study describes the gastrointestinal (GI) prokinetic effects of the aqueous extract of radish seeds (Rs.Cr). Rs.Cr, which tested positive for terpenes, flavonoids, phenols, alkaloids and saponins, showed a spasmogenic effect in isolated rabbit jejunum and ileum, rat stomach fundus and ileum, and guinea-pig ileum and jejunum. Rs.Cr was around 10 times more potent in the guinea-pig tissues and this effect was resistant to atropine, pyrilamine or SB203186 while the spasmogenic effect in the rat and rabbit tissues was atropine sensitive. The extract exhibited atropine-sensitive GI prokinetic and laxative effects in vivo in mice. In the atropinized rabbit jejunum, Rs.Cr produced a spasmolytic effect independent of Ca(++) or K(+) channels, adrenergic or opioid receptor involvement. Activity-directed fractionation of Rs.Cr yielded four fractions, all showing effects similar to that of the parent extract. Rs.Cr and its fractions were found to be non-lethal up to 10 g kg(-1) in mice for 24 h, except for the petroleum fraction, which showed 50% mortality at high doses. Some known radish compounds (spermine, spermidine, putrescine and sinigrin) were also tested and found to be devoid of any activity. The study shows species-specific spasmogenic effects of radish in rabbit, rat and mouse via muscarinic receptors but through an uncharacterized pathway in guinea-pig tissues. Additionally, a dormant relaxant effect was also seen, while the three polyamines and one glucosinolate from radish were found to be inactive, indicating that the compound(s) responsible for the activities reported remains to be isolated.

Contractile effect of radish and betel nut extracts on rabbit gallbladder.

Raphanus sativus (abbreviated in this paper as Rs.Cr) and Areca catechu (Ac.Cr), commonly known as radish and betel nut respectively, are traditionally used in South Asia for different gastrointestinal, gallbladder, and hepatic diseases. There has not been any study to see how they modulate gallbladder contractility. We selected isolated rabbit gallbladder tissue preparations, mounted them in tissue baths containing Krebs-Henseleit solution at 37°C, and then recorded the changes in baseline tone of the tissues upon administration of Rs.Cr and Ac.Cr. Both the extracts exhibited concentration-dependent stimulant effect on the baseline tone of gallbladder tissues, similar to carbachol, a muscarinic receptor agonist. The stimulant effect of the extract, as well as that of carbachol, was completely blocked in the presence of atropine, a muscarinic antagonist, indicating similarity in the mechanism of action of the extracts with carbachol. The result shows potential of these extracts to contract the gallbladder and to subsequently increase bile secretion, but this remains to be investigated in detail. This study justifies the traditional use of radish and betel nut in different gastrointestinal disorders.