Isolation of a neuromuscular junctional blocking agent from Cleistanthus collinus plant leaf extract

A potent neuromuscular junctional blocking agent was isolated from chloroform extracts of poisonous Cleistanthus collinus leaf by a combined chromatographic—cholinesterase inhibition technique. An amorphous yellowish green extract was eluted from paper or micro thin layer chromatographic plates. This compound caused a 93% fade on nerve evoked muscle tension and a 95% decrement in nerve evoked muscle action potentials and least change in muscle evoked muscle action potentials and tension in a rat phrenic nerve—diaphragm preparation, suggesting the presence of a potent pharmacologically active ingredient causing neuromuscular blockade which is irreversible.     

Effects of stembark and leaf extracts of Bridelia ferruginea on skeletal muscle

The ethanolic extracts of the leaves and stembark of Bridelia ferruginea were separately investigated for their effects on skeletal muscle using the phrenic nerve-hemidiaphragm muscle preparation from rats. The bark extract inhibited twitch tension induced by direct electrical stimulation (muscle) (MS) but not indirect electrical stimulation (nerve) (NS) of the diaphragm. It inhibited tetanus tension to both nerve (TNS) and muscle stimulation (TMS), had no effect on K⁺-induced contracture and reduced the minimal fusion frequency (MFF). The leaf extract had no effect on twitch tension to NS and MS or K⁺-induced contracture but increased tetanus tension to TNS or TMS as well as MFF. These findings suggest that the bark extract does not affect influx of extracellular Ca²⁺ but inhibits the intracellular mobilization of Ca²⁺. The leaf extract also had no effect on influx of extracellular Ca²⁺ but most likely facilitated the intracellular mobilization of Ca²⁺. Thus, the intracellular action of the bark extract is opposite to that of the leaf extract.     

Pharmacological effects of Synclisia scabrida alkaloid B on some isolated muscle preparations

Alkaloid B reversibly blocked the responses of rat diaphragm to electrically induced stimulations via the phrenic nerve. The alkaloid had no effect on the responses of the diaphragm elicited by direct electrical stimulation. The responses of frog rectus abdominis muscle to acetylcholine were inhibited by alkaloid B.Alkaloid B reversibly antagonised the responses of rabbit duodenum to exogenously applied acetylcholine. The contractile effect of oxytocin on rat uterus was specifically inhibited by alkaloid B. The effects of alkaloid B on isolated muscle preparations were concentration-dependent. However, the effect of dopamine and noradrenaline on rat vas deferens was not altered by alkaloid B.     

The neuromuscular blockade produced by pure alkaloid,mitragynine and methanol extract of kratom leaves (Mitragyna speciosa Korth.)

Aim of the study

The effects of pure alkaloid, mitragynine and a methanolic extract of kratom leaves were investigated on neuromuscular junction and compound nerve action potential.

Materials and methods

Wistar rats were killed by cervical dislocation and decapitated. The phrenic nerve–hemidiaphragms, hemidiaphragms and sciatic nerve were isolated.

Results

Kratom methanolic extract present at 0.1–1 mg/mL and mitragynine (0.0156 mg/mL) decreased the muscle twitch on the isolated phrenic nerve–hemidiaphragm and hemidiaphragm preparation. Muscle relaxation caused by kratom extract (1 mg/mL) was greater than the effect of mitragynine. Pancuronium and succinylcholine potentiated the effect of kratom extract. It also had a direct relaxation effect on the hemidiaphragm muscle. The muscle relaxation caused by kratom extract was not antagonized by neostigmine, tetraethylammonium and calcium chloride. High concentrations of kratom extract (10–40 mg/mL) and mitragynine (2 mg/mL) blocked the nerve conduction, amplitude and duration of compound nerve action potential.

Conclusions

The mechanism of action of kratom extract might not act as a competitive antagonist of acetylcholine yet its dominant effect was at the neuromuscular junction and not at the skeletal muscle or somatic nerve.     

Some neuromuscular effects of the crude extracts of the leaves of Abrus precatorius

Some neuromuscular effects of the crude extracts of the leaves of Abrus precatorius were investigated using isolated toad rectus abdominis and rat phrenic nerve-diaphragm muscle preparations as well as young chicks. The ethanol extract of the leaves inhibited acetylcholine-induced contractions of both toad rectus abdominis and rat phrenic nerve-diaphragm muscle preparations. The effects were concentration-dependent and reversible. The extract also caused flaccid paralysis when injected intravenously into young chicks. The ethanol extract had no effect on direct electrical stimulation of rat diaphragm. The inhibitory effect of the ethanol extract on the rat phrenic nerve-diaphragm preparation was potentiated in the presence of reduced calcium ions, elevated magnesium ions, or reduced potassium ions. Thus, the ethanol extract showed a similarity to d-tubocurarine in respect of the pattern of neuromuscular blockade. Both the petroleum ether and the water (cold and hot) extracts had no observable effects on the skeletal muscles used in this project. Apparently, the poisonous neuronal component of the leaves of Abrus precatorius resides mainly in the ethanol extract.     

The skeletal muscle relaxant action of Portulaca oleracea: role of potassium ions

An aqueous extract of the stems and leaves of Portulaca oleracea abolishes the twitch contraction of the directly stimulated rat hemidiaphragm preparation. The effects of the extract mimic qualitatively the action of potassium oxalate — a known constituent of Portulaca oleracea — on the diaphragm. Removal of K⁺ ions from the methanol extract by passing it through a cation exchange resin reduced the inhibitory effect of the extract. There was a positive correlation between the concentration of K⁺ ions in the extract and the effects of potassium chloride of similar molarity. It is concluded that the K⁺ ion content of Portulaca oleracea is at least partly responsible for the relaxant effect observed on the isolated rat diaphragm.     

Effects of extracts of Portulaca oleracea on skeletal muscle in vitro

Extracts of Portulaca oleracea inhibited twitch tension due to direct (MS) and indirect electrical stimulation via the phrenic nerve (NS) of the rat hemidiaphragm muscle. The rank order of potency was dialysable extract greater than or equal to methanol extract greater than diethylether extract, although all exhibited equal efficacy. The non-dialysable extract did not inhibit twitch tension due to MS or NS. The dialysable, methanol and diethylether extracts inhibited tetanus tension, and attenuated the area under the K+- and caffeine-induced contracture. The contracture induced by nicotinic agonists and K+ on the rectus abdominis muscle was significantly inhibited by these extracts.     

Pharmacological effects of Eugenia punicifolia (Myrtaceae) in cholinergic nicotinic neurotransmission

The effects of the aqueous crude extract (5%) of Eugenia punicifolia on cholinergic nicotinic neurotransmission were investigated. Actions of aqueous crude extract over the inhibitory effect of the cholinergic nicotinic antagonists gallamine or pancuronium, on contractions induced by electrical stimulation of phrenic nerve of rat diaphragm, were studied. Tissues were mounted as for isotonic contractions and stimulation was delivered at submaximal voltage. Addition of Eugenia punicifolia did not alter the amplitude of twitch contraction. Gallamine (IC(50): 28.8+/-0.51 microM) or pancuronium (IC(50): 3.16+/-0.11 microM) completely inhibited twitch contractions. After the maximum effect of the antagonists was achieved, addition of the aqueous crude extract (0.5-1.0 mL) totally recovered the responses to electrical stimulation. Neostigmine, a reversible acethylcholinesterase inhibitor, partially recovered responses (49.70+/-6.90% at 1 microM). In another series of experiments, previous incubation of the extract (0.5 mL) shifted to the right inhibitory concentration-response curves for the antagonists gallamine (IC(50) before E. punicifolia: 35.8+/-1.61 microM; IC(50), after E. punicifolia: 2.24+/-0.04 mM) and pancuronium (IC(50), before E. punicifolia: 3.55+/-0.13 microM; IC(50), after E. punicifolia: 0.39+/-0.01 mM). Our results show that the aqueous extract of E. punicifolia recovered the action of competitive nicotinic antagonists at the neuromuscular junction. A receptor-mediated mechanism or the possibilities of interactions of the extract with the enzyme acethylcholinesterase, however, remain to be investigated.     

Cardiovascular effects in rodents of the methanolic extract of the stem bark of Khaya senegalensis A. Juss

The methanolic bark extract of Khaya senegalensis was investigated for its effects on the cardiovascular system. The extract increased the blood pressure of chloralose anaesthetized rats. The increase in rate and force of contraction of isolated, spontaneous rabbit atria evoked by the extract were dose dependent and less pronounced than those produced by isoprenaline. The chronotropic effects of the extract and isoprenaline were antagonized by propranolol which also abolished the ionotropic effect of the extract and antagonized isoprenaline-induced inotrophy. The vasoconstrictor effect of the extract observed with isolated spiral strips of rabbit aorta was dose dependent, less potent than noradrenaline and was abolished by prazosin. These findings indicate that the hypertensive effect of the methanolic bark extract of K. senegalensis is partly due to the stimulation of β-receptors and α-adrenoceptors.     

Skeletal muscle relaxant properties of the aqueous extract of Portulaca oleracea

The skeletal muscle relaxant properties of an aqueous extract of Portulaca oleracea were examined on the twitch and tetanus tension evoked by electrical stimulation using the rat phrenic nerve-hemidiaphragm and frog sciatic nerve-sartorius muscle preparations and on contractures induced by nicotinic agonists using the rat rectus abdominis muscle preparation. The extract (5-50 X 10(-4) g/ml) produced a dose-dependent initial enhancement, followed by a longer lasting depression of twitch tension as induced by indirect electrical stimulation (NS) as well as direct stimulation (MS) of the diaphragm and sartorius muscle preparations. The augmentation of twitch amplitude (MS) produced by the extract was not significantly antagonised or potentiated by d-tubocurarine (5-50 X 10(-8) M) or physostigmine (5-50 X 10(-8) M) at concentrations which blocked or potentiated NS-induced twitch contractions. Furthermore, tetrodotoxin (5 X 10(-7) g/ml) alone or in combination with d-tubocurarine did not significantly attenuate extract-induced augmentation of twitch contractions to MS. In addition, the depression of twitch tension due to NS was not antagonised by physostigmine but was reversed and/or abolished by Ca2+ (2-5 X 10(-3) M) or potassium thiocyanate (1 X 10(-3) M). Contractures induced by K+ (80 mM) or by tetanic stimulation (20-60 Hz) were significantly reduced by the extract whereas, contracture induced by caffeine (2.5-6.0 mM) was not affected. Ca2+-free Tyrode's solution and EDTA (1.25 X 10(-3) g/ml) potentiated extract-induced depression of twitch tension to MS. On the rectus abdominis, contractures induced by nicotinic agonists (acetylcholine, 3-500 X 10(-7) M; carbachol, 5-500 X 10(-7) M and nicotine, 5-500 X 10(-8) M) were significantly attenuated and/or abolished by the extract (5-10 X 10(-3) g/ml). These observations indicate that the aqueous extract possesses unique skeletal muscle relaxant properties which do not appear to involve interference with cholinoceptor mechanism(s). It appears that the mechanism of action of the extract may involve interference with Ca2+ mobilization in skeletal muscle.     

人参皂甙对大鼠输精管和肛尾肌中α受体效应的影响

人参皂甙(G,10~(-4)g/ml)对离体大鼠输精管(RVD)的正常张力无影响,但能增强电场刺激引起的RVD收缩效应,对抗可乐定(Clo)抑制和育亨宾(Yoh)增强电场刺激引起的RVD收缩。G使苯福林(Phe)对RVD和肛尾肌(RAM)α_1受体作用的量效曲线右移。上述结果进一步支持G在突触前后膜α受体水平上可能均起着调谐剂(modulator)样作用的观点。     

A pharmacological study of two bisbenzylisoquinoline alkaloids, thalistyline and obamegine

Thalistyline, a monoquaternary bisbenzylisoquinoline alkaloid isolated from Thalictrum sp. inhibited respiration in anesthetized dogs. Thalistyline is about one-fourth as potent as d-tubocurarine in blocking neuromuscular transmission in the rat hemidiaphragm preparation. The pharmacological mechanism of action of the alkaloid is similar to that of d-tubocurarine. Obamegine did not exhibit curare-like activity. On the isolated rabbit aorta, contractions induced by an alpha-adrenoreceptor agonist, phenylephrine, were antagonized by both alkaloids. Increasing concentrations of thalistyline produced parallel shifts to the right in the dose-response curves of phenylephrine. The pA2 value for the competitive pharmacological antagonism was 6.33. Obamegine also antagonized the effects of phenylephrine on the aorta, line and obamegine lowered blood pressure in normotensive dogs. The effect was transient. Repeated injections of the alkaloids resulted in tachyphylaxis to blood pressure lowering effects. Although alkaloids exhibited alpha adrenergic blockade in the vascular preparation, the mechanism for the hypotensive effect remains to be established.     

Pharmacological studies on siculine syrup. II: effects on smooth,skeletal and cardiovascular muscle preparations

Earlier pharmacological screening showed that siculine syrup (a traditional herbal remedy purported to be useful in the prevention and treatment of sickle cell pain – crises, due to sickle cell anaemia – SCA) had antisickling and analgesic activities as well as antimicrobial and diuretic effects. SCA is an important haemoglobinopathy in Africa and many other communities/countries worldwide, with relatively high morbidity and mortality. The present study was to determine the effects of the extract on various isolated muscle preparations – smooth, skeletal and cardiovascular. Siculine (4–20 µg/mL), like acetylcholine (40–400 µg/mL), contracted the isolated rat uterus concentration dependently. Similar effects were observed with the guinea‐pig ileum and rabbit jejunum (2–20 µg/mL). In contrast to these effects, the direct (muscle) and indirect (nerve) stimulations of rat phrenic nerve–diaphragm were relaxed by siculine (4 and 8 µg/mL) and d ‐tubocurarine (0.8 µg/mL). Siculine also concentration‐dependently decreased both the rate and force of contraction of guinea‐pig atria and rabbit heart and also resulted in a fall in cat blood pressure in a manner similar to those of acetylcholine. The possible therapeutic and/or toxicological consequences of these effects including the hypotensive activity is noteworthy since siculine syrup is used by the local population for the prevention and treatment of sickle cell pain crises. Copyright © 2008 John Wiley & Sons, Ltd.     

吴茱萸氯仿提取物对胃排空的影响

目的：研究吴茱萸氟仿提取物(Evo)对胃肠动力的影响并初步探讨其作用机制。方法：吴茱萸以乙醇热回流，并以氟仿萃取，其主要有成分为生物碱。以胃残留率为指标，考察Evo对正常小鼠及胃排空亢进模型小鼠胃残留率的影响，并观察其对离体肠管收缩的作用。结果：Evo抑制正常小鼠、利血平化小鼠胃排空。对抗新斯的明、胃复安所致的胃排空亢进，协同阿托品胃排空抑制作用，抑制乙酰胆碱及氟化钡所致肠平滑收缩运动。结论：Evo具有抑制胃排空，缓解胃肠平滑肌痉挛的作用，其机制作用可能是其对M胆碱能受体的直接拮抗作用。     

Comparison of the skeletal muscle relaxant properties of Portulaca oleracea extracts with dantrolene sodium and methoxyverapamil

The effects of aqueous (AEE), dialysable (DIF) and methanol (MEE) extracts of Portulaca oleracea stems and leaves were compared with those of dantrolene sodium and methoxyverapamil (D-600) with respect to inhibition of twitch tension on the rat phrenic nerve-hemidiaphragm and with respect to contracture induced by nicotinic agonists on the frog rectus abdominis preparations. The extracts, dantrolene and D-600 inhibited twitch tension due to indirect electrical stimulation via the phrenic nerve (NS) on hemidiaphragm muscle, whereas the extracts and dantrolene inhibited, in addition, twitch amplitude due to direct muscle stimulation (MS). The extracts, dantrolene and D-600 also attenuated K+- and caffeine-induced contractures with the extracts and D-600 also reducing the time taken for the K+-induced contracture to fall to basal tension. In addition, the tetanic tension due to NS and MS was attenuated with only the extracts and dantrolene reducing the twitch/tetanus ratio (MS). There was a non-significant but consistent tendency for mutual potentiation between the extracts and dantrolene with respect to their inhibitory effect on twitch amplitude (MS) resulting in a shift to the left of the concentration-response curves to the extracts or dantrolene. This was not evident with the extracts and D-600 or dantrolene and D-600. Simultaneous addition of the extracts and dantrolene resulted in an increase in the rate of twitch tension inhibition and a decrease in the time to maximum relaxation of twitch amplitude (MS). The extracts and D-600 proved more effective in attenuating nicotinic agonist (acetylcholine, carbachol and nicotine)-induced contractures on the rectus abdominis muscle than dantrolene. From these observations, it appears that the Portulaca oleracea extracts mimic, in part, the effect of D-600 and dantrolene on the rat hemidiaphragm and frog rectus abdominis muscles; therefore, the muscle relaxant properties of the extracts may be due, in part, to inhibition of trans-membrane Ca influx, interference with the Ca-induced Ca release process and/or inhibition of the release of intracellular Ca from stores in the sarcoplasmic reticulum.     

Mechanisms of Vasorelaxation Induced by Hexahydrocurcuminin Isolated Rat Thoracic Aorta

This study was designed to examine the vasorelaxant effects of hexahydrocurcumin (HHC), one of the major natural metabolites of curcumin from Curcuma longa, on rat isolated aortic rings, and the underlying mechanisms. Isometric tension of the aortic rings was recorded using organ bath system. HHC (1 nM to 1 mM) relaxed the endothelium‐intact aortic rings pre‐contracted with PE and KCl in a concentration‐dependent manner. Removal of the endothelium did not alter the effect of HHC‐induced relaxation. In Ca²⁺‐free Krebs solution, HHC significantly inhibited the CaCl₂‐induced contraction in high K⁺ depolarized rings and suppressed the transient contraction induced by PE and caffeine in a concentration‐dependent manner. HHC was also observed to relax phobal‐12‐myristate‐13‐acetate (PMA), an activator of protein kinase C (PKC), precontracted aortic rings in a concentration‐dependent manner with EC₅₀ values equivalent to 93.36 ± 1.03 μM. In addition, pre‐incubation with propranolol (a β‐adrenergic receptor blocker) significantly attenuated the HHC‐induced vasorelaxation. These results suggest that the vasorelaxant effect of HHC is mediated by the endothelium‐independent pathway, probably because of the inhibition of extracellular Ca²⁺ influx through voltage‐operated Ca²⁺ channels and receptor‐operated Ca²⁺ channels, the inhibition of Ca²⁺mobilization from intracellular stores, as well as inhibition of PKC‐mediated Ca²⁺‐independent contraction. Moreover, HHC produces vasorelaxant effects probably by stimulating the β‐adrenergic receptor. Copyright © 2015 John Wiley & Sons, Ltd.     

Effects of an aqueous extract of Terminalia arjuna on isolated rat atria and thoracic aorta

Terminalia arjuna (Combretaceae) is used traditionally in ayurveda, to treat a variety of cardiovascular disorders. The aims of this study were to characterize the positive inotropic effect of the aqueous extract of T. arjuna bark in isolated paced rat left atria and to study its effects on a vascular smooth muscle preparation, the rat thoracic aorta. The crude and semipurified aqueous extracts produced a positive inotropic effect of rat atria and the maximum contraction was comparable to that produced by isoprenaline. The positive inotropic effect of the extract was completely blocked by a β-adrenoceptor blocker, propranolol, and an uptake-1 blocker, cocaine. In precontracted aorta, the aqueous extract produced a contraction followed by relaxation. Propranolol did not block the relaxant effect of the aqueous extract. It is concluded that the positive inotropic effect of the aqueous extract was mediated via an action on β₁-adrenoceptors and was likely to be due to the release of noradrenaline from the sympathetic nerve endings. The vasorelaxant effect of the extract, however, was not mediated via an action on β₂ adrenoceptor.     

Inhibitory effect of Pruni Cortex extract and its component,octacosyl ferulate,on tumour promotion by 12-O-tetradecanoylphorbol-13-acetate in two-stage carcinogenesis in mouse skin

The methanol extract of Pruni Cortex inhibited tumour promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA) in 7,12-dimethylbenz[a]anthracene (DMBA)-initiated mice. The active component was isolated from the methanol extract of Pruni Cortex. The active compound was characterized as octacosyl ferulate by physical and chemical analysis. Octacosyl ferulate markedly inhibited the inflammatory activity induced by TPA in mice. The 50% inhibitory dose of octacosyl ferulate is 0.7 mg/ear on TPA-induced inflammation. Furthermore, octacosyl ferulate suppressed markedly the tumour-promoting effect of TPA on skin tumour formation following initiation with DMBA. Since protein kinase C (PK-C) was shown to be an intracellular target of TPA, effects of octacosyl ferulate on the activity of this enzyme were investigated. Octacosyl ferulate also inhibited the phosphorylation of histon III-S by PK-C in a concentration dependent manner. © 1998 John Wiley & Sons, Ltd.     

藏药1号水提液对大鼠离体胸主动脉条收缩作用的影响

目的：通过观察藏药1号水提液对大鼠离体胸动脉条收缩作用的影响研究其降压机制。方法：观察藏药1号水提液(6mg／mL)和维拉帕米(Ver0.013mg／mL)对高K^ 液引起的主动脉条收缩的时效影响，对KCl，NE及CaCl2引起的大鼠主动脉条收缩的量效曲线的影响，以及对NE引起的依赖于细胞内钙及细胞外钙的收缩的影响。结果：藏药1号水提液抑制高K^ 液引起的主动脉收缩；且可使KCl、NE及CaCl2引起的大鼠主动脉条收缩的量效曲线非平行右移，最大效应降低，呈非竞争性拮抗作用：与维拉帕米相似，对NE引起的依赖于细胞内钙及细胞外钙的收缩均有抑制作用。结论：提示藏药1号的降压机制与钙离子通道拮抗剂一致。     

Investigation of the antispasmodic potential of Hibiscus sabdariffa calyces

Addition of an aqueous extract of Hibiscus sabdariffa calyces (2.5 ml/bath approximately 125 mg of starting crude material) inhibited the tone of various isolated muscle preparations (rabbit aortic strip, rhythmically contracting rat uterus, guinea-pig tracheal chain and rat diaphragm). Other muscles were stimulated (quiescent rat uterus and frog rectus abdominis). Intravenous injection of the extract to anaesthetized cats lowered the blood pressure in a dose-response manner. The inhibitory effects were resistant to a number of standard receptor blockers but the hypotensive influence was partially blocked by atropine and the tonic effects on rat uterus were partially reduced by hydrocortisone and indomethacin.