Bagnólia Araújo da Silva

Pharmacological studies of ethanolic extracts of Maytenus rigida Mart (Celastraceae) in animal models

The crude ethanol extract (EEOH) of the bark of Maytenus rigida Mart (Celastraceae) a plant used in Brazil herbal traditional medicine, was tested for anti-inflammatory, antiulcer and antidiarrhoeal activities in animal models. No acute toxicological sign was observed in animals treated with the highest dose (5000 mg/kg, p.o. or 2000 mg/kg i.p.) of EEOH. The extract doses of 250, 500 or 750 mg/kg revealed a significant inhibitory effect (P < 0,01) in carrageenin-induced rat paw oedema and exhibited ulcer-protective properties against ethanol-induced ulceration in rats. An anti-diarrhoeal activity (P < 0.01) was also observed in castor-oil-induced diarrhoeal in mice. The intestinal transit was significantly (P < 0.01) reduced, however the pretreatment did not reduce the weight of intestinal contents. These results support the popular applications of Maytenus rigida for the treatment of inflammation, ulcer and diarrhoea in Brazil herbal traditional medicine.

Effect of the activity of the Brazilian polyherbal formulation: Eucalyptus globulus Labill, Peltodon radicans Pohl and Schinus terebinthifolius Radd in inflammatory models

The Brazilian polyherbal formulation (BPF) is composed by dyes of Eucalyptus globulus Labill, Peltodon radicans Pohl and Schinus terebinthifolius Raddi in alcohol at 13.3° GL. The formulation is popularly used in Paraiba state, Brazil since 1889 and it is used as an antiseptic and anti-inflammatory medicine. The aim of this study was to evaluate the anti-inflammatory property of the polyherbal formulation. For this purpose it was used the12-O-tetradecanoylphorbol 13-acetate (TPA) and capsaicin-induced mouse ear edema and the carrageenan-induced rat paw edema. The BPF at dose of 26 mL/Kg inhibited both 12-O-tetradecanoylphorbol 13-acetate (TPA) and capsaicin-induced ear edema by 49% (p < 0.05) and 24% (p < 0.01) respectively. Preliminary results on carrageenan-induced rat paw edema demonstrated that oral administration also inhibited the paw edema by approximately 29%. The results demonstrate that the Brazilian polyherbal formulation has anti-inflammatory activity and the better dose was the one used by the population.

Central antinociceptive effect of a hydroalcoholic extract of Dioclea grandiflora seeds in rodents

The acute treatment of rats and mice with a hydroalcoholic extract from the seeds of Dioclea grandiflora (EHDg) at doses of 250 and 500 mg/kg, by intraperitoneal or oral administration, produced a significant antinociceptive effect in the tail flick and hot plate tests, an effect which was inhibited by naloxone. EHDg given to mice daily for 30 days at a dose of 500 mg/kg, did not cause any observable toxic effect nor any alteration in the pattern of antinociceptive response by the tail immersion test during the course of this treatment. These results suggest that EHDg has a central antinociceptive action devoid of tolerance effect typical of opioid drugs.

Negative inotropic and chronotropic effects on the guinea pig atrium of extracts obtained from Averrhoa carambola L. leaves

It has been reported that star fruit can lead to a fatal outcome in uremic patients. The intoxication syndrome consists of hiccups, mental confusion, dizziness, and vomiting. On the other hand, folk medicine uses teas and infusions of carambola leaves to treat headache, vomiting, cough, insomnia, and diabetes. This motivated us to determine if Averrhoa carambola can act on the contractility and automaticity of the guinea pig heart. We measured the atrial isometric force in stimulated left atria and determined the chronotropic changes in spontaneously beating right atria. The carambola leaf extracts (1.5 mg/ml) abolished the contractile force in a concentration-dependent manner. Among the crude, methanolic, ethanolic, aqueous, and acetic extracts, the aqueous one was the most potent (EC50 = 520 +/- 94 microg/ml; flavonoids and tannins are the main constituents; Na+ and K+ contents in 1.0 mg/ml of aqueous extract were 0.12 +/- 0.016 and 1.19 +/- 0.15 mM, respectively). The aqueous extract abolished the positive Bowditch staircase phenomenon and reduced the inotropic response to CaCl2 (0.17-8.22 mM), events that are dependent on the cellular Ca2+ inward current. The adrenergic, muscarinic or opioid membrane receptors do not seem to participate in the mechanism of action of the cardioactive substance(s). In spontaneously beating atria, the aqueous extract promoted a negative chronotropic effect that was antagonized by 0.1 microM isoproterenol bitartrate. With this agonist, the EC50 of the aqueous extract increased from 133 +/- 58 to 650 +/- 100 microg/ml. These data regarding the effect of A. carambola on guinea pig atrial contractility and automaticity indicate an L-type Ca2+ channel blockade.

Malignant Hyperthermia: Clinical and Molecular Aspects

CONTENT Malignant hyperthermia (MH) is a potentially lethal pharmacogenetic disorder that affects genetically predisposed individuals. It manifests in susceptible individuals in response to exposure to Inhalant anesthetics, depolarizing muscle relaxants or extreme physical activity in hot environments. During exposure to these triggering agents, there is a rapid and sustained increase of myoplasmic calcium (Ca(2+)) concentration induced by hyperactivation of ryanodine receptor of skeletal muscle (RyR1), causing a profound change in Ca(2+) homeostasis, featuring a hypermetabolic state. RyR1, Ca(2+) release channels of sarcoplasmic reticulum, is the primary locus for MH susceptibility. Several mutations in the gene encoding the protein RyR1 have been identified; however, other genes may be involved. Actually, the standard method for diagnosing MH susceptibility is the muscle contracture test for exposure to halothane-caffeine (CHCT) and the only treatment is the use of dantrolene. However, with advances in molecular genetics, a full understanding of the disease etiology may be provided, favoring the development of an accurate diagnosis, less invasive, with DNA test, and also will provide the development of new therapeutic strategies for treatment of MH. Thus, this brief review aims to integrate molecular and clinical aspects of MH, gathering input for a better understanding of this channelopathy.

Spasmolytic Action of Diplotropin, a Furanoflavan from Diplotropis ferruginea Benth., Involves Calcium Blockade in Guinea-Pig Ileum

Diplotropis ferruginea Benth. (Fabaceae) is a tree popularly known in Northeastern Brazil as “sucupira-preta”. In the present work, the isolation, identification and pharmacological activity of a furanoflavan-type flavonoid (2,3-trans-3,4-trans)-3,4,5,8-tetramethoxy-(6,7,2”,3”)-furanoflavan, which received the trivial name diplotropin is reported. The structure was determined by means of spectroscopic techniques, especially EIMS and 1D and 2D NMR. Diplotropin (10−8 −3 · 10−4 M) inhibited the phasic contractions induced by both acetylcholine (IC50 = 4.6±0.8 · 10−5 M) and histamine (IC50 = 2.3±1.1 · 10−5 M) in guinea-pig ileum. Diplotropin relaxed the ileum pre-contracted with KCl (EC50 = 3.9±1.1 · 10−6 M), acetylcholine (EC50 = 3.7±1.6 · 10−6 M) and histamine (EC50 = 4.4±1.4 · 10−5 M) in a concentration-dependent manner. As the maintenance of tonic contraction induced by these contractile agents involves Ca2+ influx through voltage-dependent Ca2+ channels, it is suggestive that this relaxation may be due to the blockade of Ca2+ influx through those channels. This hypothesis was confirmed by the observation that diplotropin antagonized (pD’2 = 4.83±0.37) CaCl2 induced contractions in Ca2+-free depolarizing medium (IC50 = 1.5±0.8 · 10−5 M).

Spasmolytic Effect of Caulerpine Involves Blockade of Ca2+ Influx on Guinea Pig Ileum

In this work, we investigated the spasmolytic effect of caulerpine, a bisindole alkaloid isolated from marine algae of the Caulerpa genus, on guinea pig ileum. Our findings indicated that caulerpine inhibited phasic contractions induced by carbachol (IC50 = 7.0 ± 1.9 × 10−5 M), histamine (IC50 = 1.3 ± 0.3 × 10−4 M) and serotonin (IC50 = 8.0 ± 1.4 × 10−5 M) in a non-selective manner. Furthermore, caulerpine concentration-dependently inhibited serotonin-induced cumulative contractions (pD′2 = 4.48 ± 0.08), shifting the curves to the right with Emax reduction and slope of 2.44 ± 0.21, suggesting a noncompetitive antagonism pseudo-irreversible. The alkaloid also relaxed the ileum pre-contracted by KCl (EC50 = 9.0 ± 0.9 × 10−5 M) and carbachol (EC50 = 4.6 ± 0.7 × 10−5 M) in a concentration-dependent manner. This effect was probably due to inhibition of Ca2+ influx through voltage-gated calcium channels (CaV), since caulerpine slightly inhibited the CaCl2-induced contractions in depolarizing medium without Ca2+, shifting the curves to the right and with Emax reduction. According to these results, the spasmolytic effect of caulerpine on guinea pig ileum seems to involve inhibition of Ca2+ influx through CaV. However, other mechanisms are not discarded.

Spasmolytic action of the methanol extract and isojuripidine from Solanum asterophorum mart. (Solanaceae) leaves in Guinea-Pig Ileum

Abstract Solanum asterophorum Mart. (Solanaceae) is a shrub popularly known as “jurubeba-defogo” in the northeast of Brazil. In the present work, the methanol extract (SA-MeOH, 3-750 μg/mL) and isojuripidine (10-7 - 3 x 10-4 ᴍ), a steroidal alkaloid obtained from S. asterophorum Mart. leaves, inhibited phasic contractions induced by both 1 μᴍ histamine [IC50 = (225.8 ± 47.4) μg/mL and (3.5 ± 0.8) x 10-5 ᴍ] or 1μᴍ acetylcholine [IC50 = (112.5 ± 20.6) μg/mL and (2.3 ± 0.4) \ 10-5 ᴍ] in guinea-pig ileum, respectively. The extract and isojuripidine also relaxed the ileum (SA-MeOH, 1-750 μg/mL, and isojuripidine, 10-9 - 3 x 10-4 ᴍ) pre-contracted with 1 μᴍ histamine [EC50 = (101.1 ± 17.4) μg/mL and (1.2 ± 0.3) x 10-6 ᴍ] or 1 μm acetylcholine [EC50 = (136.8 ± 21.1) μg/mL and (1.9 ± 0.4) x 10-6 ᴍ] or 40 mᴍ KCl [EC50 = (149.4 d 19.5) μg/mL and (1.8 ± 0.7) x 10-6 ᴍ], respectively, in an equipotent and concentration-dependent manner. This effect is probably due to inhibition of calcium influx through voltage-operated calcium (Cav) channels. To confirm this hypothesis, we evaluated their effect on cumulative CaCl2 curves in depolarizing medium nominally without Ca2+. SA-MeOH (27, 243, 500, and 750 μg/mL) and isojuripidine (3 x 10-8, 10-6, 3 x 10-5, and 3 x 10-4 m) inhibited the contractions induced by CaCl2, in a concentrationdependent manner. The concentration-response curves to CaCl2, in the presence of SAMeOH and isojuripidine, were shifted downward in relation to a control curve in a nonparallel manner resulting in reduction of the maximum effect [Emax = (71.2 ± 9.2); (57.4 ± 9.2); (43.8 ± 3.4); (41.5 ± 2.4) and (90.6 ± 4.8); (74.7 ± 8.7); (66.4 ± 3.9); (31.3 ± 4.1)%, respectively]. SA-MeOH and isojuripidine present spasmolytic action in guinea-pig ileum due to a partially blockade of calcium influx through Cav channels.

Complete atrioventricular block on isolated guinea pig heart induced by an aqueous fraction obtained from Psidium guajava L. leaf

O presente trabalho visou estudar o efeito eletrocardiografico produzido pela fracao aquosa (AqF) obtida do extrato acetico das folhas de Psidium guajava L. em coracao isolado de cobaia. Os tracados eletrocardiograficos foram obtidos em coracoes batendo espontaneamente ou entao sob estimulacao eletrica. Os coracoes foram montados em uma sistema de perfusao do tipo Langendoff de fluxo constante. A AqF, usada em concentracoes menores que 20 mg/mL, nao alterou a frequencia espontânea do coracao (controle: 180 ± 9 bpm, teste: 182 ± 10 bpm; N = 3; p > 0,05). Todavia, concentracoes iguais ou maiores que 20 mg/mL produziram bloqueio atrioventricular completo (BAV). Este efeito, contudo, desapareceu prontamente quando se removeu a AqF do fluido de perfusao coronariana (N = 3 coracoes). O BAV promovido pela AqF se faz mediado pelos receptores muscarinicos porque o sulfato de atropina (1,5 mM) impediu o aparecimento deste efeito.

Inotropic effect of Citrus sinensis (L.) Osbeck leaf extracts on the guinea pig atrium

The objective of the present investigation was to determine the contractile effect of crude and acetone leaf extracts of Citrus sinensis (L.) Osb. on mammalian myocardium. Crude leaf extracts have been used in folk medicine to treat neurological disorders. Some flavonoids isolated from this plant presented a positive inotropic effect on myocardium. This motivated us to test the extracts on the atria of guinea pigs of both sexes (300-500 g) and surprisingly we observed inotropic depression instead of an increase in force. The maximum effect of the crude extract was 79.4 +/- 8.1% of the control force amplitude (N = 5 hearts, 10 trials, 27 +/- 0.1 degrees C, stimulus: 2 Hz, 400 V, 0.5 ms). The EC50 for crude, ethanol, acetic, aqueous, and acetone extracts was 300, 300, 600, 1000, and 140 microg/ml, respectively, with a Hill constant of 1.8, 2.0, 2.5, 2.0, and 1.4, respectively. Blockade of cholinergic, beta-adrenergic, or opioid membrane receptors with 1.5 microM atropine sulfate, 1 microM propranolol, and 10 microM naloxone, respectively, did not change the effect of the crude extract. The acetone extract abolished the Bowditch positive staircase phenomenon (N = 5 hearts, 10 trials, 27 +/- 0.1 degrees C), suggesting a possible reduction of the calcium inward current, and also promoted the so-called Woodworth phenomenon. The effect was concentration-dependent and indicated the existence of another inhibitory contractile mechanism such as the simultaneous activation of some of the membrane potassium channels reducing the myocardial action potential duration and further decreasing the cellular calcium entry.