Pharmacological characterisation of the antihyperglycaemic properties of Tinospora crispa extract

The efficacy of Tinospora crispa (Menispermaceae) extract for the treatment of diabetes has previously been verified in animal models. In order to substantiate the antidiabetic effect, we characterised the antihyperglycaemic properties by studying its effect on intestinal glucose absorption and glucose uptake into adipocytes. We also performed experiments to characterise in more detail the mechanism of T. crispa-evoked insulin release by challenging it with insulin secretory antagonists viz. adrenaline, somatostatin, verapamil and nifedipine. In addition, we also performed experiments to determine the effect of the extract on cAMP content. The results clearly showed that the antihyperglycaemic effect is not due to interference with intestinal glucose uptake or uptake of the sugar into the peripheral cells. Rather, the antihyperglycaemic effect of T. crispa is probably due to stimulation of insulin release via modulation of β-cell Ca²⁺concentration. That the insulinotropic effect of T. crispa is physiological suggests that the extract contains compounds which could be purified for use in the treatment of type II diabetes.     

Korean red ginseng stimulates insulin release from isolated rat pancreatic islets

Ethnopharmacological relevance

Korean red ginseng (KRG), one of heat-processed Korean ginseng (Panax ginseng C.A. Meyer), has a long history as herbal remedy for antidiabetic effect.

Aim of the study

The effect and mechanism of KRG on stimulation of insulin release were investigated in isolated rat pancreatic islets.

Material and methods

Pancreatic islets isolated from rats were used to evaluate the insulinotropic action of KRG. The effect of Ca on the insulinotropic action of KRG was investigated.

Results

The aqueous ethanolic extract of KRG (AEE-KRG) (0.1–1.0 mg/ml) significantly evoked a stimulation of insulin release at 3.3 mM glucose compared to the control. Experiments at different glucose concentrations (8.4 and 16.7 mM) showed that AEE-KRG significantly stimulated on its own whereas it did not potentiate insulin secretion induced by glucose. The extracellular Ca²⁺-free condition, a L-type Ca²⁺ channel blocker and an ATP-sensitive K⁺ channel opener significantly inhibited insulin secretion evoked by AEE-KRG.

Conclusion

These findings suggest that KRG displays beneficial effects in the treatment of diabetes at least in part via the stimulation of insulin release in a glucose-independent manner.     

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.     

Induction of insulin secretion by an aqueous extract of Tabernanhte iboga Baill. (Apocynaceae) in rat pancreatic islets of Langerhans

The effect of an aqueous extract of Tabernanthe iboga (TBEt) was studied in the rat islets insulin secretion based on its use in traditional medicine for the treatment of diabetes. Rats islets were isolated by collagenase digestion. In insulin release experiments, the insulin content was determined by Enzyme-Link Immunosorbent Assay (ELISA). For experiments on ⁴⁵Ca²⁺ Uptake, the radioactive content was determined using a liquid scintillation analyzer. The extract (10⁻³ μg/ml-100 μg/ml) did not exert a significant increase of insulin secretion (p > 0.05) in the presence of 2.8 mM of glucose (a none stimulatory concentration). Whereas, in the presence of 11.1 mM of glucose (stimulatory concentration), TBEt augmented glucose-stimulated insulin secretion in a dose-dependent manner. Interestingly, the secretory effect of the extract was glucose-dependent (5.6-16.7 mM). Furthermore, the insulinotropic effect of TBEt (1 μg/ml) was significantly potentiated (p < 0.001) in K⁺-depolarised media as well as in the presence of 2.8 mM and 16.8 mM of glucose concentrations. In contrast, in the same conditions, TBEt failed to stimulate the high K⁺ medium-induced insulin release. The extract significantly amplified (p < 0.001 and p < 0.05) the insulin secretion induced by either IBMX or tolbutamide. Diazoxide, cobalt or calcium removal inhibited the insulinotropic effect of the extract. TBEt increased glucose-induced ⁴⁵Ca²⁺ uptake in rat islets. Overall, our findings suggest that Tabernanthe iboga contains water soluble insulinotropic compounds. The insulin secretion of TBEt's active principles might involve the closure of K⁺-ATP and the intensification of calcium influx through voltage-sensitive Ca²⁺ channels.     

Ferulic acid enhances insulin secretion by potentiating L-type Ca2+ channel activation

Objective: To investigate the effect of ferulic acid, a natural compound, on pancreatic beta cell viability,Ca²⁺ channels, and insulin secretion.Methods: We studied the effects of ferulic acid on rat insulinoma cell line viability using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide viability assay. The whole-cell patch-clamp technique and enzyme-linked immunosorbent assay were also used to examine the action of ferulic acid on Ca²⁺ channels and insulin se...     

Effects on rat uterine and aorta strip smooth muscle of Thymus leptophyllus extract

The diethylether extract from Thymus leptophyllus was found to be more active on uterine smooth muscle than on aorta strips. Rat uterus experiments with and without extracellular calcium, yielded similar IC₅₀ values. A non-specific mechanism for the relaxant activity can therefore be postulated. In rat aorta and in the presence of extracellular calcium the extract inhibited the contractile response induced by K⁺ depolarizing solution and had a less inhibitory effect on noradrenaline (NA) contraction. In a Ca²⁺-free solution the extract strongly reduced the Ca²⁺-release induced by NA, but it did not affect the transient contraction caused by caffeine (CAF).     

Endothelium‐Independent Vasorelaxation Effects of Sigesbeckia glabrescens (Makino) Makino on Isolated Rat Thoracic Aorta

The present study aimed to investigate the vasorelaxant effect of the methanol extract of Sigesbeckia glabrescens (Makino) Makino (MESG) on rat aortic rings and mechanism of action. MESG inhibited both noradrenaline bitartrate (NA)‐ and potassium chloride (KCl)‐induced contraction of endothelium‐intact aortic rings in a concentration‐dependent manner. Removal of the endothelium did not influence the effect of MESG on NA‐precontracted aortic rings. Pretreatment with MESG (250 µg/mL) inhibited calcium chloride‐induced vasocontraction of NA‐ or KCl‐precontracted endothelium‐denuded aortic rings. It also relaxed phorbol‐12‐myristate‐13‐acetate‐induced contraction of aortic rings in a concentration‐dependent manner. In addition, Bay K8644 (an L ‐type calcium channel opener) vasocontracted in MESG pretreated aortic rings. On the other hand, the inositol 1,4,5‐triphosphate receptor, the ryanodine receptor, the Rho‐kinase inhibitor (Y‐27632), a soluble guanylyl cyclase blocker (1‐H‐[1,2,4]‐oxadiazolo‐[4,3a]‐quinoxalin‐1‐one), and K⁺ channel blockers (glybenclamide, tetraethylammonium, and 4‐aminopyridine) did not affect the effect of MESG. These results suggested that the mechanism underlying the vasorelaxant effect of MESG is mediated by endothelium‐independent pathways. This specifically refers to blockade of the influx of extracellular Ca²⁺ via receptor‐operative Ca²⁺ channels and voltage‐dependent Ca²⁺ channels and inhibition of a protein kinase C‐mediated cellular pathway. Copyright © 2012 John Wiley & Sons, Ltd.     

Terpenoids Isolated from Psidium guajava Hexane Extract with Depressant Activity on Central Nervous System

A bioguided fractionation of the hexane extract obtained from Psidium guajava leaves led to the isolation of sesquiterpenes with depressant activities on the central nervous system. The results demonstrated that the already reported relaxant properties of Psidium guajava hexane extract are largely due to the presence of terpenes, especially caryophyllene-oxide and β-selinene, which were by far the largest single components and potentiated pentobarbital sleeping time and the latency of convulsions induced by leptazol in mice. Calcium concentration-response curves showed a rightward displacement when the active fraction was added to isolated guinea-pig ileum depolarized with K⁺ (60 mm ) and cumulative concentrations of CaCl₂, suggesting that caryophyllene-oxide, a known Ca²⁺ antagonist agent could be responsible for the blockade of extracellular Ca²⁺ observed with the active fraction.     

Musclide-A1: A novel Ca2+-dependent protein kinase activator derived from musk and its cardiotonic potentiating action in guinea-pig cardiac muscles

Musclide-A1 (6-methyl-2, 5-heptanediol 5-(hydrogen sulfate)) was isolated from musk, a dried secretion from the preputial follicle of musk deer, Moschus moschiferus Linn. Musclide (100 μg/mL), a water-soluble extract, and musclide-A1 (30 μg/mL) potentiated β-adrenergic cardiotonic action in guinea-pig papillary muscles. Musclide-A1 at 130 μM or 1,2-dioctanoylglycerol at 200 μM potentiated the positive inotropic action induced by the maximal concentration of isoproterenol (258 nM). The potentiation was suppressed by 3 nM staurosporine or 1 μM H-7, an inhibitor of Ca²⁺-dependent protein kinase. Musclide-A1 at 4 and 8 μM activated protein kinase C and other Ca²⁺-dependent protein kinase in ventricular muscles of guinea-pig. The activation of Ca²⁺-dependent protein kinase was completely suppressed by 3 nM saturosporine. The activity of musclide-A1 (4 μM) was comparable to that of 1,2-dioctanoylglycerol (4 μM, the optimum concentration to stimulate protein kinase C), and were inhibited completely by 30 nM staurosporine. These results indicate that one mechanism of cardiotonic potentiation induced by musk, may be in part due to the activation of protein kinase C and other Ca²⁺-dependent protein kinases.     

天钩降压胶囊对家兔主动脉血管条收缩反应的影响

目的:观察天钩降压胶囊对家兔主动脉条收缩反应的影响,探讨其降压作用机制.方法:将家兔离体主动脉条置于灌流肌槽中,记录天钩降压胶囊提取物对去甲肾上腺素(NE)、氯化钾(KCl)、氯化钙(CaCl2)诱导的主动脉条收缩作用的影响,以及对NE诱导的主动脉条细胞内钙及细胞外钙依赖性收缩反应的影响.结果:天钩降压胶囊1,3,5g·L-1剂量组均能使NE,CaCl2引起的主动脉条最大收缩反应降低(P＜0.01);对NE诱发主动脉条细胞内钙及细胞外钙依赖性收缩均有明显抑制(P＜0.01),对细胞外钙依赖性收缩的抑制作用更显著;对KCl引起的动脉条收缩反应无明显影响.结论:天钩降压胶囊可通过影响细胞内钙离子浓度促进血管平滑肌舒张从而发挥降压作用.其机制可能主要通过影响受体操纵的Ca2+通道(ROC),对电压依赖性Ca2+通道(PDC)作用不显著.对NE诱发主动脉条细胞外钙依赖性收缩的抑制作用优于对细胞内钙依赖性收缩的作用.     

Inhibitory effects of Cistus populifolius on contractile responses in the isolated rat duodenum

The medicinal plant Cistus populifolius L., shows an important dose-dependent spasmolytic activity. The ability of the Cistus extract to inhibit both acetylcholine (ACh) (3.4 × 10⁻⁸–6.8 × 10⁻⁵ M) and CaCl₂ (2 × 10⁻⁴–1.28 × 10⁻² M) -induced contractions and the relaxing effect on K⁺ (75 mM) -induced contractions may indicate a non-specific receptor antagonist. However, this action may be related to the influx of extracellular Ca²⁺. These antispasmodic effects are partly consistent with the use of C. populifolius in folk medicine for certain gastrointestinal disorders.     

Antidiabetic Effects of a Standardized Egyptian Rice Bran Extract

An extract was prepared from Egyptian stabilized rice bran and standardized to contain 2% γ‐oryzanol in addition to its content of other bioactives, notably tocotrienol and policosanol. The standardized extract was found to have a concentration‐dependent effect on insulin release in vitro, which, however, is not mediated by γ‐tocotrienol in rice bran (detected by HPLC) as could have been expected. Policosanol and γ‐oryzanol have insulinotropic effects. The in vitro data of rice bran directly translate into in vivo data of rats by using a glucose tolerance test (increase in plasma insulin). Tocotrienols are well known for their apoptotic effect on tumor cells; nevertheless, an attempt was made to study glucose uptake in HEP‐G2 cells, which needs to induce an insulin‐resistant state by TNF‐α. The Egyptian rice bran extract has an antidiabetic effect. γ‐Oryzanol, which is a possible precursor of the insulinotropic compound ferulic acid, is a candidate for this effect. Therefore, it is reasonable to assume that the prevalence of diabetes or at least a prediabetic (type 2) situation can be ameliorated by the investigated rice bran extract. The potential usefulness of the extract as a nutraceutical is currently undergoing more thorough investigations. Copyright © 2012 John Wiley & Sons, Ltd.     

Pycnogenol Cytotoxicity in Pancreatic INS‐1E β cells Induced by Calcium Dysregulation

Natural standardized flavonoid extract from the bark of Pinus pinaster, Pycnogenol (Pyc), was recently found to decrease intensively the activity of sarcoplasmic reticulum Ca²⁺‐ATPase of rabbit skeletal muscle (SERCA1). On the basis of this inhibitory effect in a cell‐free system and similarities of SERCA1 to its other isoforms, proapoptotic properties of Pyc may be expected in cellular systems. Pycnogenol (40–100 μg/mL) induced a concentration‐dependent decrease of the viability of pancreatic INS‐1E β cells associated with induction of apoptosis. In addition, intracellular Ca²⁺ level increase was found along with reduction of protein expression level of SERCA2b and impairment of insulin secretion by β cells. These facts indicate that Pyc may induce apoptosis by impairment of calcium homeostasis. Copyright © 2017 John Wiley & Sons, Ltd.     

Effect of Terminalia arjuna extract on KCl induced contractions in the rat vas deferens

Experiments were carried out to elucidate the effects of extracts from Terminalia arjuna on potassium chloride (160 mM) induced contraction in smooth muscle. The petroleum ether extract did not exhibit a response, whereas the preincubation of tissue with the alcoholic extract inhibited contraction. Experimental approaches, described here, lead to the speculation that T. arjuna may impart its action through the modulation of Ca²⁺ ions across the cellular membrane.     

白藜芦醇对大鼠离体胸主动脉环的舒张作用

目的:观察白藜芦醇(resveratrol,RVL)对大鼠离体胸主动脉血管的舒张作用并探讨其机制。方法:采用离体血管环灌流方法,观察RVL在含Ca²⁺或无Ca²⁺ Krebs液孵育条件下对去甲肾上腺素(NA)引起的血管平滑肌收缩的影响;同法观察RVL对30,80mmol·L^-1的KCl引起的血管平滑肌收缩的影响;RVL对NA引起的依赖于细胞内钙和细胞外钙收缩反应的影响,以及加入N-G-硝基-L-精氨酸(L-NNA)和优降糖后RVL舒张大鼠离体主动脉环效应的变化。结果:RVL呈浓度依赖性舒张NA引起的血管收缩;无Ca²⁺ 组RVL抑制NA所致血管平滑肌收缩效应大于含Ca²⁺ 组;RVL能够拮抗NA诱发的依内钙的收缩反应,而对外钙收缩无抑制。RVL对80,30mmol·L^-1 的KCl引起的血管平滑肌收缩均有抑制作用,且前者量效曲线明显上移。L-NNA使RVL舒血管效应降低(26.0±4.6)%;优降糖组的血管舒张受抑程度与对照组无显著差别(P>0.05)。结论:RVL可呈内皮依赖性舒张血管平滑肌,其作用机制可能与该药促进NO合成释放,开放钙激活的钾通道以及抑制血管平滑肌细胞外钙内流和内钙释放有关。     

灵芝多糖对小鼠腹腔巨噬细胞胞浆游离Ca2+浓度的影响

 目的:探讨灵芝多糖(GLP)对免疫细胞信号转导过程的影响?方法:采用激光扫描共聚焦显微镜(LSCM)技术,动态监测GLP均一体组分GLB₇对小鼠腹腔巨噬细胞(MΦ)胞浆游离Ca²⁺浓度([Ca²⁺]i)的影响?结果:GLB₇(20μg·ml^-1)引起小鼠腹腔MΦ中[Ca²⁺]i明显升高,升高值为(248±18)%(n=6);GLB₇引起小鼠腹腔MΦ外钙内流及MΦ内IP₃敏感和IP₃非敏感钙池释放Ca²⁺,[Ca²⁺]i升高值分别为(76±10)%,(58±10)%,(41±8)%(n=6);GLB₇对MΦ[Ca²⁺]i的影响与K⁺通道及其引起的膜电位变化无关?结论:MΦ是灵芝多糖作用的靶细胞;GLB₇引起MΦ中[Ca²⁺]i快速升高,可能是灵芝多糖产生作用的重要途径?     

20(S)‐ginsenoside Rg3, a neuroprotective agent,inhibits mitochondrial permeability transition pores in rat brain

Ginseng, the root of Panax ginseng C.A. Meyer (Araliaceae), is a well‐known traditional Chinese herbal medicine. Ginsenosides, which are triterpene derivatives that contain sugar moieties, are the main active ingredients of ginseng. 20(S)‐Ginsenoside Rg3, a triterpene glycoside which chemically belongs to the protopanaxadiol ginsenoside group, is effective in attenuating brain infarction after cerebral ischemia, but the detailed mechanism is not known. This study examined the effect of 20(S)‐ginsenoside Rg3 on mitochondrial permeability transition pore (MPTP) in the rat brain. 20(S)‐Ginsenoside Rg3 at 2–16 µm inhibited Ca²⁺‐ and H₂O₂‐induced swelling of mitochondria isolated from rat brains. The addition of Ca²⁺ generated reactive oxygen species (ROS) in isolated mitochondria. 20(S)‐Ginsenoside Rg3 (2–16 µm ) inhibited Ca²⁺ induced generation of ROS. At the same time, 20(S)‐ginsenoside Rg3 significantly improved mitochondrial energy metabolism, enhanced ATP levels and the respiratory control ratio. These results suggest that 20(S)‐ginsenoside Rg3 inhibits the opening of MPTP by free radical scavenging action in the brain, and this implies that inhibition of MPTP may contribute to the neuroprotective effect of 20(S)‐ginsenoside Rg3. Copyright © 2008 John Wiley & Sons, Ltd.     

胡颓子叶对豚鼠离体气管平滑肌收缩功能的影响

目的 研究胡颓子叶乙醇提取物正丁醇部位(胡颓子叶正丁醇部位)对正常及多种致痉剂诱导的豚鼠气管平滑肌收缩功能的影响.方法 制备豚鼠离体气管平滑肌螺旋条,在其正常状态下以及用乙酰胆碱、组胺、氯化钾、无钙下乙酰胆碱诱导细胞内钙释放和高钙下诱发细胞外钙内流条件下,观察胡颓子叶正丁醇部位对离体气管张力的影响.结果 胡颓子叶正丁醇部位对静息状态下的豚鼠离体气管平滑肌有明显的舒张作用,使乙酰胆碱和组胺的量效曲线发生明显右移,抑制加入高钾或高钙后引发细胞外钙内流导致的收缩.结论 胡颓子叶正丁醇部位能明显抑制正常状态及多种致痉剂诱发的豚鼠气管平滑肌收缩.     

艾灸“足三里”和干姜水提取液对正常大鼠胃能量代谢作用机制差异研究＊

目的 探讨艾灸“足三里”和干姜提取液对正常大鼠胃能量相关因子的影响，采用代谢组学技术探索其对能量代谢的作用机制及物质基础。方法 通过艾灸大鼠“足三里”穴位和灌胃干姜水提液，检测胃组织的能量相关因子、体质量、体温、血清生化指标等，评价艾灸和干姜对胃能量代谢的影响，并通过血清代谢组学探讨其作用机制。结果 艾灸足三里可显著升高胃组织Na⁺-K⁺-ATP酶、Ca²⁺-ATP酶、Ca²⁺-Mg²⁺-ATP酶、SDH活性。灌胃干姜提取液可显著升高Mg²⁺-ATP酶、Ca²⁺-Mg²⁺-ATP酶、SDH活性。两种方式显著降低大鼠体质量，且对肝肾功能没有显著的影响。艾灸足三里后发现5种差异代谢物，分别为N-乳酸酰亮氨酸、异亮氨酸、D-谷氨酰胺、2-花生四烯酸甘油磷酸胆碱、PC（202（11Z，14Z）/140）。给予干姜提取液后发现5种差异代谢物，分别为黄嘌呤、视黄酯、2-花生四烯酰甘油磷酸胆碱、花生四烯酸、3-羟胆酸。结论 艾灸足三里可通过调节氨基酸代谢、脂质代谢来调控胃的能量代谢，干姜提取液通过调节视黄醇代谢、嘌呤代谢、脂质代谢来调控胃的能量代谢。     

Antiplatelet activity of Phellinus baummii methanol extract is mediated by cyclic AMP elevation and inhibition of collagen-activated integrin-α(IIb) β₃ and MAP kinase

Phellinus baumii is a mushroom that has been used as folk medicine against various diseases and is reported to have antidiabetic, anticancer, antioxidant, antiinflammatory and antihypertensive activities. However, information on the effects of P. baumii extract in platelet function is limited. Therefore, the aim of this study was to examine the impact of a P. baumii methanol extract (PBME) on platelet activation and to investigate the mechanism behind its antiplatelet activity. PBME effects on agonist‐induced platelet aggregation, granule secretion, [Ca²⁺]_i mobilization, α_IIbβ₃ activation, cyclic AMP release and mitogen‐activated protein kinase (MAPK) phosphorylations were studied using rat platelets. PBME dose‐dependently inhibited collagen, thrombin and ADP‐induced platelet aggregation with an IC₅₀ of 51.0 ± 2.4, 54.0 ± 2.1 and 53.0 ± 4.3 μg/mL, respectively. Likewise, thrombin‐induced [Ca²⁺]_i and collagen‐activated ATP secretions were suppressed in PBME treated platelets. Aggregation and ATP secretion were also markedly attenuated by PBME alone or in combination with PP2 (Src inhibitor) and U‐73122 (PLC inhibitor) in collagen‐stimulated platelets. Besides, PBME treatment elevated basal cyclic AMP levels and inhibited collagen‐induced integrin‐α_IIbβ₃ activation. Moreover, PBME attenuated extracellular‐signal‐regulated protein kinase 2 (ERK2) and c‐Jun N‐terminal kinase 1 (JNK1) phosphorylations. Further PD98059 (ERK inhibitor) and SP60025 (JNK inhibitor) reduced collagen‐induced platelet aggregation and ATP secretion. In conclusion, the observed PBME antiplatelet activity may be mediated by activation of cyclic AMP and inhibition of ERK2 and JNK1 phosphorylations. Finally, these data suggest that PBME may have therapeutic potential for the treatment of cardiovascular diseases that involve aberrant platelet function. Copyright © 2011 John Wiley & Sons, Ltd.