Browsing by Author "Ascenso, JR"
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- A Diterpene with a Rearranged Jatrofane Skeleton and other Terpenes from Euphorbia portlandicaPublication . Madureira, AM; Ascenso, JR; Ferreira, MJU
- Complexation and transport of alkali and alkaline earth metal cations by p-tert-butyldihomooxacalix[4]arene tetraketone derivativesPublication . Marcos, PM; Felix, S; Ascenso, JR; Segurado, MAP; Mellah, B; Abidi, R; Hubscher-Bruder, V; Arnaud-Neu, EThe binding properties of three p-tert-butyldihomooxacalix[4]arene tetraketone derivatives (tert-butyl 2b, adamantyl 2c and phenyl 2d) in the cone conformation and one derivative (methyl 2a) in a partial cone conformation, towards alkali and alkaline earth metal cations have been established by extraction studies of metal picrates from water into dichloromethane, stability constant measurements in methanol and acetonitrile, and by H-1 NMR spectrometry. Transport experiments of metal picrates through a dichloromethane membrane were also performed. The results are compared to those obtained with closely-related calix[n]arene derivatives (n = 4 and 5) and discussed in terms of the substituents, size and conformational effects. Methylketone 2a is a poor binder for all the cations studied, due to its partial cone conformation. Ketones 2b, 2c and 2d show high extraction and complexation levels for the alkali cations, with similar profiles and preference for K+ and Na+ (plateau selectivity). Towards alkaline earth cations, these ketones show a strong peak selectivity for Ba2+ in extraction, but a plateau selectivity for Ca2+, Sr2+ and Ba2+ in complexation. The nature of the substituent attached to the ketone function has some influence on their binding properties, with phenylketone 2d being a slightly weaker binder than ketones 2b and 2c. H-1 NMR titrations confirm the formation of 1:1 complexes between the ketones and the cations studied, also indicating that they should be located inside the cavity defined by the phenoxy and carbonyl oxygen atoms. Ketones 2b, 2c and 2d show transport rates that do not follow, in general, the same trends observed in extraction and complexation.
- Complexation and transport of alkali and alkaline earth metal cations by p-tert-butyldihomooxacalix[4]arene tetraketone derivatives (vol 18, pg 2, 2006)Publication . Marcos, PM; Felix, S; Ascenso, JR; Segurado, MAP; Mellah, B; Abidi, R; Hubscher-Bruder, V; Arnaud-Neu, FThe binding properties of three p-tert-butyldihomoox-acalix[4]arene tetraketone derivatives (tert-butyl 2b, adamantyl 2c and phenyl 2d) in the cone conformation and one derivative (methyl 2a) in a partial cone conformation, towards alkali and alkaline earth metal cations have been established by extraction studies of metal picrates from water into dichloromethane, stability constant measurements in methanol and acetonitrile, and by H-1 NMR spectrometry. Transport experiments of metal picrates through a dichloromethane membrane were also performed. The results are compared to those obtained with closely-related calix[n]arene derivatives (n = 4 and 5) and discussed in terms of the substituents, size and conformational effects. Methylketone 2a is a poor binder for all the cations studied, due to its partial cone conformation. Ketones 2b, 2c and 2d show high extraction and complexation levels for the alkali cations, with similar profiles and preference for K+ and Na+ (plateau selectivity). Towards alkaline earth cations, these ketones show a strong peak selectivity for Ba2+ in extraction, but a plateau selectivity for Ca2+, Sr2+ and Ba2+ in complexation. The nature of the substituent attached to the ketone function has some influence on their binding properties, with phenylketone 2d being a slightly weaker binder than ketones 2b and 2c. 1H NMR titrations confirm the formation of 1:1 complexes between the ketones and the cations studied, also indicating that they should be located inside the cavity defined by the phenoxy and carbonyl oxygen atoms. Ketones 2b, 2c and 2d show transport rates that do not follow, in general, the same trends observed in extraction and complexation.
- Complexation and transport of alkali, alkaline earth, transition and heavy metal cations by p-tert-butyldihomooxacalix[4]arene tetra(diethyl)amidePublication . Marcos, PM; Felix, S; Ascenso, JR; Segurado, MAP; Pereira, JLC; Khazaeli-Parsa, P; Hubscher-Bruder, V; Arnaud-Neu, FThe binding properties of the tetra( diethyl) amide ( 2) derived from p-tert-butyldihomooxacalix[4]arene, in the cone conformation, towards alkali, alkaline earth, transition (Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+) and heavy (Ag+, Cd2+, Hg2+ and Pb2+) metal cations have been established by extraction studies of metal picrates from an aqueous solution into dichloromethane, transport experiments with the same salts through a dichloromethane membrane and stability constant measurements in methanol. Results concerning the calorimetric study of Na+ and K+ complexes in methanol are presented. The affinity of 2 for some cations (Na+, K+, Ba2+, Ag+ and Zn2+) has been investigated by H-1 NMR spectrometry, as well. The results are compared to those obtained with the analogous calix[4]arene tetraamide derivative 3. Amide 2 displays a preference for the alkali cations (mainly Na+ and K+) in contrast to amide 3 that prefers the alkaline earth cations. Ag+ and Cd2+ soft Lewis acids are also strongly bound by both amides. H-1 NMR titrations confirm the formation of 1: 1 complexes between 2 and all cations studied, also suggesting that they should be located inside the cavity defined by the phenoxy and carbonyl oxygen atoms. 2 shows transport rates that do not follow the same trends as the stability constants or extraction percentages; it can therefore be characterized as a selective receptor.
- Compostos Terpénicos Isolados de Euphorbia segetalisPublication . Madureira, AM; Valente, C; Palma, AC; Ascenso, JR; Ferreira, MJU
- Cycloartane triterpenes from Euphorbia tuckeyanaPublication . Ferreira, MJU; Pinto, FC; Ascenso, JRInvestigation of the acetone extract of the whole plant of Euphorbia tuckeyana afforded a new cycloartane-type triterpene named as cyclotucanol. Its structure was established as cycloartane-24-methylene-3beta,25-diol (1). The known cycloartane triterpenes cycloeucalenol (2), 3,8-hydroxy-cycloart-25-en-24-one (3), cycloart-25-ene-3beta,24-diol (4), 25,26,27-trisnor-3beta-hydroxycycloartan-24-al (5) and cycloart-23-ene-3beta,25-diol (6) were also isolated and identified.
- Euphopubescenol and euphopubescene, two new jatrophane polyesters, and lathyrane-type diterpenes from Euphorbia pubescensPublication . Valente, C; Pedro, M; Ascenso, JR; Abreu, PM; Nascimento, MSJ; Ferreira, MJUThe structures of euphopubescenol and euphopubescene, two new macrocyclic jatrophane diterpene polyesters, isolated from the whole dried plant of Euphorbia pubescens, were established as 5alpha,8alpha,15beta-triacetoxy-3alpha-benzoyloxy-4alpha-hydroxy-9,14-dioxo-13betaH-jatropha-6(17),11E-diene (1) and 3beta,7beta,8beta,9alpha,14alpha,15beta-hexa-acetoxy-2betaH-jatropha-5E,11E-diene (2) by 1D- and 2D-NMR (COSY, HMQC, HMBC and NOESY), IR, EI-MS and EI-FTICR-MS. Two known lathyrane derivatives, jolkinol A (3) and jolkinol A (4), whose C-13-NMR spectra were assigned, were also isolated. Compounds 1-3 have been evaluated for their ability to inhibit the in vitro growth of three human tumour cell lines representing different tumour types, MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer) and SF-268 (CNS cancer). They inhibited both MCF-7 and NCI-H460 cell lines, with GI(50) values ranging between 40.9 muM and 95.3 muM, but were found to be ineffective as growth inhibitors of the SF-268 cell line.
- Evaluation of the antiviral and antimicrobial activities of triterpenes isolated from Euphorbia segetalisPublication . Madureira, AM; Ascenso, JR; Valdeira, L; Duarte, A; Frade, JP; Freitas, G; Ferreira, MJUA phytochemical reinvestigation of the whole plant of Euphorbia segetalis yielded five tetracyclic triterpenes: 3 beta- hydroxy- cycloart- 25- en- 24- one ( 1), cycloart- 25- ene- 3 beta, 24- diol ( 2), cycloart- 23- ene- 3 beta, 25- diol ( 3), lanosta-7,9( 11), 24- trien- 3 beta- ol ( 4) and lanosta- 7,9( 11), 24( 31)- trien- 3 beta- ol ( 5). 3 beta- acetoxy- cycloart- 25- en- 24- one ( 1a) and glutinol ( 6), lupenone ( 7), dammaranodienol ( 9), cycloartenol acetate ( 10), 24- methylenecycloartanol acetate ( 11) and beta- sitosterol ( 12), isolated previously, were evaluated for their antiviral activities against Herpes simplex virus ( HSV) and African swine fever virus ( ASFV). Lupenone exhibited strong viral plaque inhibitory effect against HSV- 1 and HSV- 2. The in vitro antifungal and antibacterial activities of 1a, cycloart- 23- ene- 3 beta, 25- diol, 3- acetate ( 3a) and 6 - 12 were also investigated.
- Isoprenoid compounds from Euphorbia portlandica. X-ray structure of lupeportlandol, a new lupane triterpenePublication . Madureira, AM; Duarte, MT; Piedade, MFM; Ascenso, JR; Ferreira, MJUPhytochemical survey of the Me2CO extracts of the whole dried plant Euphorbia portlandica led to the isolation of a new pentacyclic triterpene alcohol, with the lupane skeleton, named lupeportlandol. Its structure was established as 3alpha-hydroxy-19alphaH-lup-20(29)-ene. The known pentacyclic triterpene glutinol and the steroid beta-sitostenone were also isolated. The characterization of the new compound and its acetylated derivative was based on spectroscopic methods and an Xray diffraction analysis. Lupeportlandol acetate was inactive in cytotoxicity assays in vitro against three human tumor cell lines: MCF-7 (breast cancer), NCI-H460 (non-small cell lung cancer) and SF-268 (CNS cancer).
- p-tert-butyldihomooxacalix[4]arene/p-tert-butylcalix[4]arenePublication . Marcos, PM; Ascenso, JR; Segurado, MAP; Pereira, JLCThe binding properties of two phenylketones ( 2a and 3a) and two ethylesters ( 2b and 3b) derived from p-tert-butyldihomooxacalix[4]arene or from p-tert-butylcalix[4]arene, in the cone conformation, towards transition (Ag+, Ni2+, Cu2+, Co2+, Zn2+, Fe2+ and Mn2+) and heavy (Cd2+, Hg2+ and Pb2+) metal cations have been determined by extraction studies with metal picrates and liquid membrane transport experiments with the same salts. The affinity of these ligands for Ag+ has also been investigated by H-1 NMR spectroscopy. Both ketones are better extractants than the esters, and show a strong preference for Ag+, while Cu2+ is the most extracted cation with the esters. H-1 NMR titrations with AgSO3CF3 indicate 1 : 1 complexes for all ligands, those with ketones are more stable, on the NMR time scale, than those with esters. Both esters are good carriers for Ag+, and 2b exhibits the highest transport rate (4.7 mumol h(-1)) found until now with dihomooxacalix[4]arene derivatives.