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Beta(2)-receptor adrenergic agonists as clenbuterol and analogues are illegally used as growth promoters in cattle, in Europe, as well as in other countries. Following consumption of meat or liver, intoxication cases were described, and cardiovascular toxic effects (tachycardia, hypertension) were of clinical relevance. Therefore, we investigated whether heart rate increase induced by clenbuterol could depend upon stimulation of beta(1)- and/or beta(2)-adrenergic receptors, and in which ratio. We used in vitro guinea-pig atria, a model in which beta(1)-/beta(2)-receptors ratio is similar to that found in men. In our experiments both beta(1)- and beta(2)-receptors contributed to clenbuterol-induced heart rate increase, but with a different potency. The selective beta(2)-antagonist ICI-118,551 competitively antagonized responses to clenbuterol with high affinity (pA(2) 9.47+/-0.28, SchildSlope 0.98+/-0.20 not significantly different from unity, K(B) 0.34 nM). The selective beta(1)-antagonist atenolol antagonized clenbuterol with a relatively lower affinity (pA(2)=7.59+/-0.14), the SchildSlope=1.97+/-0.33 was significantly different from unity (P<0.05). Results show that clenbuterol stimulates guinea-pig heart rate by acting chiefly on beta(2)-adrenoceptor, although responses to clenbuterol apparently are mediated by an inter-play between both beta-adrenoceptors. Further experiments are necessary to understand which beta-adrenergic antagonists are of effectiveness to counteract cardiovascular effects in case of intoxication following clenbuterol, or other beta-adrenergic stimulants.

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Three new phenolic compounds, 1-galloyl-beta-D-glucopyranosyl-(1-->4)-beta-D-galactopyranoside (1), 2-methoxy-5-(1 '2 3'-trihydroxypropyl)-phenyl- 1-0-(6"-galloyl)-beta-D-glucopyranoside (2),and 2-methoxy-5-hydroxymethyl-phenyl-1-O-(6"-galloyl)-beta-D-glucopyranoside (3), together with the known compounds benzyl 6'-O-galloyl-beta-D-glucopyranoside (4), 1,6-di-O-galloyl-beta-D-glucopyranose (5), myrciaphenone B (6), kaempferol 3-0-(6"-galloyl)-beta-D-glucopyranoside (7), quercetin 3-0-(6"-galloyl)-beta-D-glucopyranoside (8), vomifoliol 9-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside, 2,3-dihydrobenzofuran-2-(4'-hydroxy-3'-methoxyphenyl)-3-alpha-L-rhamnopyranosyloxymethyl-7-methoxy-5-propanol, and benzyl-O-alpha-L-rhamnopyranosyl-(1-->6)-Beta-D-glucopyranoside were isolated from the leaves of Baseonema acuminatum P. Choux (Asclepiadaceae). Their structures were determined by 1D- and 2D-NMR spectroscopy and by ESI-MS analysis. The antimicrobial activity of all compounds was evaluated in vitro against bacteria (Staphylococcus aureus two strains, Bacillus cereus, Bacillus subtilis, Escherichia coli, Salmonella thyphimurium) and three strains of Candida albicans. The new compounds 2 and 3, together with the known compound 4, showed antifungal activity against two clinically isolated Candida albicans strains and against C. albicans ATCC 2091; MIC values were in the range of 25-100 microg/mL. Compound 5 was active against the two clinically isolated strains of C. albicans with MICs of 12.5 microg/mL and 25 microg/mL. Compounds 1, 6, 7, and 8 inhibited only one strain of C albicans at the maximum concentration used. None of the phenolic compounds tested was active against the bacteria studied.

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In the last years several plant-derived natural compounds have been screened for their anti-HIV activity in order to find lead compounds with novel structures or mechanisms of action. Among these, several triterpenoids have been found to exhibit an antiretroviral activity with different mechanisms of action. In this study the effect of two limonoids, limonin and nomilin, on the growth of human immunodeficiency virus-1 (HIV-1) in culture of human peripheral blood mononuclear cells (PBMC) and on monocytes/macrophages (M/M) is described. Limonin and nomilin were found to inhibit the HIV-1 replication in all cellular systems used. A dose-dependent inhibition of viral replication was observed in PBMC isolated from healthy donors and infected with HIV-1 strain after incubation with limonin and nomilin (EC (50) values: 60.0 microM and 52.2 microM, respectively). The two terpenoids inhibited at all concentrations studied the production of HIV-p24 antigen even when the PBMC employed were chronically infected (EC (50) values of 61.0 microM for limonin and 76.2 microM for nomilin). Moreover, these compounds inhibited the HIV-1 replication even in infected M/M. In this cellular system the inhibitory effect was significant at the concentrations of 20 microM, 40 microM and 80 microM starting from day 14 and reached the maximum effect after 18 days of incubation. As regards the mechanism of action, limonin and nomilin inhibit in vitro HIV-1 protease activity. In general, the results obtained point out a similar anti-HIV activity of limonin and nomilin indicating that this activity is not drastically influenced by the structural difference between the two compounds.

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Six diterpenes, including two new natural products, were isolated from the seeds of Cephalotaxus harringtonia. The new metabolites were characterised as 8 beta-hydroxy-9(11),13-abietadien-12-one and 5,6-didehydroferruginol, while the known compounds were identified as ferruginol, sugiol, 6,12-dihydroxyabieta-5,8,11,13-tetraen-7-one, and abieta-8,11,13-trien-7 beta-ol. These compounds were studied in vitro for their antimicrobial activity against clinically isolated bacteria and Candida strains. Ferruginol and 6,12-dihydroxyabieta-5,8,11,13-tetraen-7-one showed antimicrobial activity against Gram-positive bacteria. None of the six diterpenes was active against the Gram-negative organisms and yeasts tested.

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The muscle relaxing activity of the essential oil of Hyssopus officinalis L. (Lamiaceae) and some of its main components (isopinocamphone, limonene and beta-pinene) was studied on isolated preparations of guinea-pig and rabbit intestine. The essential oil and isopinocamphone inhibited the acetylcholine- and BaCl2-induced contractions in guinea-pig ileum in a concentration-dependent manner (IC50 42.4 microg/ml and 61.9 microg/ml to acetylcholine; 48.3 microg/ml and 70.4 microg/ml to BaCl2) whereas limonene or beta-pinene left tissue contraction unchanged. In guinea-pig ileum H. officinalis essential oil also blocked the contractions induced by CaCl2. In isolated rabbit jejunum the essential oil reduced the amplitude of spontaneous movements and decreased the basal tone; neither haemoglobin, methylene blue, N(omega)-nitro-L-arginine methyl ester (L-NAME) or propranolol blocked the myorelaxant effect.

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Oleanolic acid is a triterpenoid which is quite common in nature in the form either of free acid or in triterpenoid saponin glycosides. This study describes the effect of oleanolic acid on the growth of human immunodeficiency virus-1 (HIV-1) in cultures of human peripheral mononuclear cells (PBMC) and of monocyte/macrophages (M/M). Its inhibitory activity was also evaluated on PBMC obtained from HIV-1 infected patients. Results obtained show that oleanolic acid inhibits the HIV-1 replication in all the cellular systems used (EC50 values: 22.7 microM, 24.6 microM and 57.4 microM for in vitro infected PBMC, naturally infected PBMC and M/M, respectively). As regards the mechanism of action, oleanolic acid inhibits in vitro the HIV-1 protease activity.

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Neither quercetin (Q), nor 3-O-acylquercetines, up to 100 microg/mL, had any significant activity on selected gram-positive strains (Staphylococcus aureus, Bacillus subtilis, Listeria ivanovi, Listeria monocytogenes, Listeria serligeri), gram-negative strains (Escherichia coli, Shigella flexneri, Shigella sonnei, Salmonella enteritidis, Salmonella tiphymurium) and yeasts (Candida albicans and Candida glabrata). In addition, we confirmed the known anti-HIV activity of Q (80% inhibition at 40 microM), which might depend on the free hydroxyl in the C-3 position, as suggested by the lack of activity of the 3-O-acylquercetines. Finally, we described an interesting inhibitory activity on Candida rugosa lipase by Q (IC(16)=10(-4) M) and its esters (3-O-acylquercetines) which, in vivo, could play an important role against lipase producing microorganisms. In particular, 3-O-acyl-quercetines, being more active (IC(16)=10(-4)-10(-6) M) and more lipophilic, could be more effective than Q when applied to the skin or mucosae, and deserve to be studied further.

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