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\u27s 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

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

Gut modulatory and antiplatelet activities of Viscum cruciatum

Viscum cruciatum Sieber (Viscaceae) is widely used in folk medicine for various gastrointestinal and inflammatory disorders. The crude extract of Viscum cruciatum (VCr), which tested positive for alkaloids, flavonoids, coumarins, saponins, sterols, tannins, and terpenes, caused concentration-dependent (0.01–3.0 mg/mL) relaxation of spontaneous and K+ (80 mM)-induced contractions of isolated rabbit jejunum, similar to that caused by verapamil. VCr shifted the Ca2+ concentration–response curves to the right with suppression of the maximum response, like verapamil. In guinea-pig ileum preparations, VCr caused atropine-sensitive spasmogenic effects. When tested for its effect on human platelets, VCr inhibited the adrenaline and adenosine 5′-diphosphate (ADP)-induced human platelet aggregation at the concentration range of 0.3–1.2 mg/mL. These observations indicate the presence of spasmogenic, spasmolytic, and antiplatelet activities in Viscum cruciatum mediated through cholinergic and calcium channel antagonist activities along with the blockade of adrenergic and ADP receptors, respectively, which explains its medicinal use in gut motility and inflammatory disorders