Pilar Puebla

Assessment of the antihypertensive and vasodilator effects of ethanolic extracts of some Colombian medicinal plants

The antihypertensive and vasodilator effects of ethanolic extracts prepared from Calea glomerata Klatt, Croton schiedeanus Schlecht, Curatella americana L., Lippia alba (Mill)n N.E.Br. and Lupinus amandus, which are medicinal plants used in Colombian folk medicine for the treatment of hypertension, were assayed both in SHR and Wistar rats and in rat isolated aortic rings. At a dose of 20 mg/kg, intravenous bolus administration of the ethanolic extracts, from C. schiedeanus, C. americana and L. amandus showed significant antihypertensive activity in SHR, C. schiedeanus being the most active. C. schiedeanus elicited dose-dependent decreases in mean arterial pressure and heart rate (5-100 mg/kg, i.v.) in SHR but 200 mg/kg administered orally did not show any significant effects, even after 3 h of observation. In intact rat aortic rings, ethanolic extracts from C. schiedeanus and Calea glomerata relaxed the contractions induced by KCl (80 mM) and phenylephrine (10(-6) M) in a concentration-dependent manner (10(-6)-3x10(-4) g/ml), with IC(50) of 6.5x10(-5) (7.3-5.8) g/ml and 7.1x10(-5) (7.9-6.4) g/ml, respectively. Bioguided phytochemical fractionation of the ethanolic extract from C. schiedeanus was started. More than one active principle seems to be present, flavonoids and terpenoids compounds were detected.

Terpenoids from leaves of Juniperus thurifera

Abstract Nineteen diterpenoids of the labdane, pimarane and abietane skeletons and four known sesquiterpenoids were isolated from Juniperus thurifera leaves. Thirteen of these diterpenoids are described for the first time as natural products. Their structures were elucidated principally by NMR techniques and chemical transformations.

Quercetin 3,7-dimethyl ether: a vasorelaxant flavonoid isolated from Croton schiedeanus Schlecht.

The vasorelaxant profile of quercetin 3,7‐dimethyl ether, a flavonoid isolated from Croton schiedeanus Schlecht (Euphorbiaceae), was assessed in aortic rings isolated from Wistar rats. To gain insight into its structure‐activity relationship, we compared this substance with quercetin 3,4′,7‐ trimethyl ether (ayanin), another flavonoid isolated from this plant, quercetin 3,3′,4′,7‐tetramethyl ether, a flavonoid synthesized by us, and quercetin. In addition we examined the interaction of quercetin 3,7‐dimethyl ether with the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway. According to their pEC50 values (concentration producing a 50% inhibition of the maximal contractile response) to phenylephrine‐induced precontraction in rat isolated aorta, the potency order was quercetin 3,7‐dimethyl ether > quercetin > quercetin 3,4′,7‐trimethyl ether > quercetin 3,3′,4′,7‐tetramethyl ether (4.70 ± 0.18; 3.96 ± 0.07; 3.64 ± 0.02; 3.11 ± 0.16). The relaxant effect of quercetin 3,7‐dimethyl ether was significantly decreased by the removal of endothelium as well as by methylene blue, an inhibitor of guanylyl cyclase, and by NG‐nitro‐L‐arginine methyl ester hydrochloride (L‐NAME), an NO‐synthase inhibitor. Therefore, quercetin 3,7‐dimethyl ether has a NO/cGMP pathway‐related profile, with increased vasorelaxant activity due to hydroxylation at positions 3 and 4 of the B ring. In addition, methylation at positions 3 and 7 with respect to quercetin of the C and A rings, respectively, seems to further enhance the vasorelaxant activity of quercetin 3,7‐dimethyl ether.

Endowing Indole-Based Tubulin Inhibitors with an Anchor for Derivatization: Highly Potent 3‑Substituted Indolephenstatins and Indoleisocombretastatins

Colchicine site ligands with indole B rings are potent tubulin polymerization inhibitors. Structural modifications at the indole 3-position of 1-methyl-5-indolyl-based isocombretastatins (1,1-diarylethenes) and phenstatins endowed them with anchors for further derivatization and resulted in highly potent compounds. The substituted derivatives displayed potent cytotoxicity against several human cancer cell lines due to tubulin inhibition, as shown by cell cycle analysis, confocal microscopy, and tubulin polymerization inhibitory activity studies and promoted cell killing mediated by caspase-3 activation. Binding at the colchicine site was confirmed by means of fluorescence measurements of MTC displacement. Molecular modeling suggests that the tropolone-binding region of the colchicine site of tubulin can adapt to hosting small polar substituents. Isocombretastatins accepted substitutions better than phenstatins, and the highest potencies were achieved for the cyano and hydroxyiminomethyl substituents, with TPI values in the submicromolar range and cytotoxicities in the subnanomolar range. A 3,4,5-trimethoxyphenyl ring usually afforded more potent derivatives than a 2,3,4-trimethoxyphenyl ring.

Lignans from Juniperus thurifera

Abstract The isolation and identification of two new natural lignans, (-)epi-podorhizol and deoxypicropodophyllotoxin, and 12 known lignans from a hexane extract of Juniperus thurifera is described.

Chemical constituents of the bark of Dipteryx alata vogel, an active species against Bothrops jararacussu venom.

The effect of four sub-extracts prepared from the lyophilized hydroalcoholic bark of Dipteryx alata (Leguminosae-Papilionoideae) dissolved in a methanol-water (80:20) mixture through a liquid-liquid partition procedure has been investigated against the neuromuscular blockade of the venom of the snake Bothrops jararacussu. The active CH2Cl2 sub-extract has been extensively analyzed for its chemical constituents, resulting in the isolation of four lupane-type triterpenoids: lupeol (1), lupenone (2), 28-hydroxylup-20(29)-en-3-one (3), betulin (4), nine isoflavonoids: 8-O-methylretusin (5), 7-hydroxy-5,6,4’-trimethoxyisoflavone (6), afrormosin (8), 7-hydroxy-8,3’,4’-trimethoxyisoflavone (9), 7,3’-dihydroxy-8,4’-dimethoxyisoflavone (10), odoratin (11), 7,8,3’-trihydroxy-4’-methoxyisoflavone (13), 7,8,3’-trihydroxy-6,4’-dimethoxyisoflavone (15), dipteryxin (17), one chalcone: isoliquiritigenin (7), one aurone: sulfuretin (14) and three phenolic compounds: vanillic acid (12), vanillin (16), and protocatechuic acid (18). Their chemical structures were elucidated on the basis of spectroscopic analysis, including HRMS, 1D- and 2D-NMR techniques.

Neo-clerodane diterpenoids from Croton schiedeanus

Two new neo-clerodane type furano diterpenoids were isolated from the aerial part of Croton schiedeanus, besides the clerodane diterpenes cis- and trans-dehydrocrotonin, previously isolated from other species of Croton. Structural elucidation was achieved on basis of extensive NMR experiments, including X-ray diffraction analysis and molecular mechanics calculations. The previously known flavonoids ayanin and quercetin-3,7-dimethyl ether were also obtained from the extract of this plant.

Thuriferic acid. A novel lignan type from juniperus thurifera l

Abstract The isolation and structural determination of a novel type of lignan, thuriferic acid, obtained from the hexane extract of the leaves of Juniperus thurifera L (Cupressaceae) are described. Its structure was confirmed by synthesis and the signals of its 1H and 13C NMR spectra were assigned unequivocally by two-dimensional techniques.

Antihypertensive effect of some oxazolo[3,2-a]pyridines, thiazolo[3,2-a]pyridines and pyrido[2,1-b]oxazines in conscious spontaneously hypertensive rats

The antihypertensive activity of eighteen oxazolo[3,2‐a]pyridine, fhiazolo[3,2‐a]pyridine and pyrido[2,1‐b]oxazine derivatives has been evaluated in conscious spontaneously hypertensive rats (SHRs), and compared with that of nifedipine, used as reference.

Synthesis and pharmacological activities of some pyrido[2,1-b]oxazines

Abstract A novel kind of fused heterocyclic compounds, with the pyrido[2,1- b ]oxazine ring have been prepared and tested for their pharmacologic properties. Some of them have shown long-term antihypertensive-bradycardic effects as well as anti-inflammatory, spasmolytic and other effects.