Muhammad Nabeel Ghayur

Ginger lowers blood pressure through blockade of voltage-dependent calcium channels

Ginger (Zingiber officinale Roscoe), a well-known spice plant, has been used traditionally in a wide variety of ailments including hypertension. We report here the cardiovascular effects of ginger under controlled experimental conditions. The crude extract of ginger (Zo.Cr) induced a dose-dependent (0.3-3 mg/kg) fall in the arterial blood pressure of anesthetized rats. In guinea pig paired atria, Zo.Cr exhibited a cardiodepressant activity on the rate and force of spontaneous contractions. In rabbit thoracic aorta preparation, Zo.Cr relaxed the phenylephrine-induced vascular contraction at a dose 10 times higher than that required against K+ (80 mM)-induced contraction. Ca2+ channel-blocking (CCB) activity was confirmed when Zo.Cr shifted the Ca2+ dose-response curves to the right similar to the effect of verapamil. It also inhibited the phenylephrine (1 μM) control peaks in normal-Ca2+ and Ca2+-free solution, indicating that it acts at both the membrane-bound and the intracellular Ca2+ channels. When tested in endothelium-intact rat aorta, it again relaxed the K+-induced contraction at a dose 14 times less than that required for relaxing the PE-induced contraction. The vasodilator effect of Zo.Cr was endothelium-independent because it was not blocked by L-NAME (0.1 mM) or atropine (1 μM) and also was reproduced in the endothelium-denuded preparations at the same dose range. These data indicate that the blood pressure-lowering effect of ginger is mediated through blockade of voltage-dependent calcium channels.

Pharmacological basis for the medicinal use of ginger in gastrointestinal disorders.

Ginger (rhizome of Zingiber officinale) has been widely used for centuries in gastrointestinal disorders, particularly dyspepsia, but its precise mode of action has yet to be elucidated. This study was undertaken to study the prokinetic action of ginger and its possible mechanism of action. Prokinetic activity of ginger extract (Zo.Cr) was confirmed in an in vivo test when it enhanced the intestinal travel of charcoal meal in mice. This propulsive effect of the extract, similar to that of carbachol, was blocked in atropine-pretreated mice, a standard cholinergic antagonist. Likewise, Zo.Cr showed an atropine-sensitive dose-dependent spasmogenic effect in vitro as well as in isolated rat and mouse stomach fundus tissues. In atropinized tissue, it showed spasmolytic activity as shown by the inhibition of 5-HT- and K+-induced contractions. A spasmolytic effect was also observed in other gut preparations either as noncompetitive inhibition of agonist dose–response curves, inhibition of high K+(80 mM)-induced contractions, or displacement of Ca2+ dose–response curves to the right, indicating a calcium antagonist effect. Phytochemical analysis revealed the presence of saponins, flavonoids, and alkaloids in the crude extract. These data indicate that Zo.Cr contains a cholinergic, spasmogenic component evident in stomach fundus preparations which provides a sound mechanistic insight for the prokinetic action of ginger. In addition, the presence of a spasmolytic constituent(s) of the calcium antagonist type may explain its use in hyperactive states of gut like colic and diarrhea.

Gastrointestinal, selective airways and urinary bladder relaxant effects of Hyoscyamus niger are mediated through dual blockade of muscarinic receptors and Ca2+ channels.

This study describes the spasmolytic, antidiarrhoeal, antisecretory, bronchodilatory and urinary bladder relaxant properties of Hyoscyamus niger to rationalize some of its medicinal uses. The crude extract of H. niger seeds (Hn.Cr) caused a complete concentration‐dependent relaxation of spontaneous contractions of rabbit jejunum, similar to that caused by verapamil, whereas atropine produced partial inhibition. Hn.Cr inhibited contractions induced by carbachol (1 μm) and K+ (80 mm) in a pattern similar to that of dicyclomine, but different from verapamil and atropine. Hn.Cr shifted the Ca2+ concentration–response curves to the right, similar to that caused by verapamil and dicyclomine, suggesting a Ca2+ channel‐blocking mechanism in addition to an anticholinergic effect. In the guinea‐pig ileum, Hn.Cr produced a rightward parallel shift of the acetylcholine curves, followed by a non‐parallel shift with suppression of the maximum response at a higher concentration, similar to that caused by dicyclomine, but different from that of verapamil and atropine. Hn.Cr exhibited antidiarrhoeal and antisecretory effects against castor oil‐induced diarrhoea and intestinal fluid accumulation in mice. In guinea‐pig trachea and rabbit urinary bladder tissues, Hn.Cr caused relaxation of carbachol (1 μm) and K+ (80 mm) induced contractions at around 10 and 25 times lower concentrations than in gut, respectively, and shifted carbachol curves to the right. Only the organic fractions of the extract had a Ca2+ antagonist effect, whereas both organic and aqueous fractions had anticholinergic effect. A constituent, β‐sitosterol exhibited Ca2+ channel‐blocking action. These results suggest that the antispasmodic effect of H. niger is mediated through a combination of anticholinergic and Ca2+ antagonist mechanisms. The relaxant effects of Hn.Cr occur at much lower concentrations in the trachea and bladder. This study offers explanations for the medicinal use of H. niger in treating gastrointestinal and respiratory disorders and bladder hyperactivity.

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 naturo-paths 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 Ca2+ dose-response curve. Similar results were observed with verapamil, a standard Ca2+ 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 uM) and K+-induced contractions in a similar fashion. In PE-contracted, endothelium-intact aorta, this vasodilator effect was partially blocked by Ncùnitro-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 Ca2+ 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.

Species differences in the prokinetic effects of ginger

This study describes the prokinetic actions of the aqueous extract of ginger (Zingiber officinale). Ginger extract (Zo.Cr), which tested positive for saponins, terpenes, phenols, flavonoids and alkaloids, showed a spasmogenic effect in isolated guinea-pig ileum with 8–50 times more potency than in rabbit jejunum and ileum and rat stomach fundus and ileum. Spasmogenicity in all the gut preparations except in guinea-pig ileum was atropine-sensitive. Zo.Cr exhibited a stimulant effect in vivo in mice and enhanced the intestinal transit of charcoal meal. A spasmolytic effect, mediated via Ca2 +  antagonist activity, was also exhibited by Zo.Cr, reflected in terms of inhibition of spontaneous contractions, K+ (80 mM)-induced contractions and displacement of Ca2 +  dose–response curves. The ginger pure compounds (6-shogaol, 6-gingerol, 8-gingerol and 10-gingerol) also exhibited a spasmolytic activity, which reduced with the increasing size of the side chain in their chemical structures. The study showed that the aqueous extract of ginger exhibits species-specific spasmogenicity in gut tissues of rabbit and rat (muscarinic-type) while through an uncharacterized pathway in guinea-pig ileum, along with a dormant relaxant effect, mediated via the blockade of voltage-dependent Ca2 +  channels.

Muscarinic, Ca++ antagonist and specific butyrylcholinesterase inhibitory activity of dried ginger extract might explain its use in dementia

Ginger rhizome (Zingiber officinale) has been used for centuries to treat dementia in South Asia. This study was undertaken to possibly justify its use. A 70% aqueous/methanolic extract of dried ginger (Zo.Cr) was used. Zo.Cr tested positive for the presence of terpenoids, flavonoids, secondary amines, phenols, alkaloids and saponins. When tested on isolated rat stomach fundus, Zo.Cr showed a spasmogenic effect (0.03–5.00 mg mL−1); it relaxed the tissue at concentrations ≥5 mg mL−1. The stimulant effect was resistant to blockade by hexamethonium and methysergide, but sensitive to atropine, indicating activity via muscarinic receptors. In atropinized (0.1 μM) preparations, Zo.Cr (0.3–3.0 mg mL−1) relaxed high K+ (80 mm)‐induced contractions, indicating Ca++ antagonism in addition to the muscarinic effect. This possible Ca++ antagonist activity was investigated in Ca++‐free conditions, with the inhibitory effect of the extract tested against contractions induced by externally administered Ca++. Zo.Cr (0.1–0.3 mg mL−1), similar to verapamil (0.03–0.10 μm), shifted the contractions induced by externally administered Ca++ to the right, thus suggesting an inhibitory interaction between Zo.Cr and voltage‐operated Ca++ channels. Zo.Cr (0.1–3.0 μg mL−1) also potentiated acetylcholine peak responses in stomach fundus, similar to physostigmine, a cholinesterase inhibitor. Zo.Cr, in an in‐vitro assay, showed specific inhibition of butyrylcholinesterase (BuChE) rather than acetylcholinesterase enzyme. Different pure compounds of ginger also showed spasmolytic activity in stomach fundus, with 6‐gingerol being the most potent. 6‐Gingerol also showed a specific anti‐BuChE effect. This study shows a unique combination of muscarinic, possible Ca++ antagonist and BuChE inhibitory activities of dried ginger, indicating its benefit in dementia, including Alzheimers disease.

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 Krebs 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 Nω‐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.

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.

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 EC50 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. Copyright

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 μM) and aminophylline (10 μM) pretreatment. In rabbit thoracic aorta, Ss.Cr dose-dependently (0.1–3 mg/mL) relaxed the high K+ (80 mM) and phenylephrine (PE, 1 μM)-induced contractions, indicating a possible Ca++ channel blocking (CCB) effect. When tested against PE (1 μM) control peaks in normal Ca++ and Ca++-free Krebs solution, Ss.Cr exhibited dose-dependent (0.1–3 mg/mL) inhibition, being more potent in relaxing the PE responses in Ca++-free Krebs 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.