Alberto S. Pereira

Federal University of Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil

Are you Alberto S. Pereira?

Claim your profile

Publications (8)12.3 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Acetone and ethanol extracts of two Bulgarian propolis samples (Bur and Lov) were investigated by high temperature high resolution gas chromatography coupled to mass spectrometry (HT-HRGC-MS), and their activity against Trypanosoma cruzi was evaluated. The ethanol extracts--Et-Bur and Et-Lov--showed similar composition, with a high content of flavonoids, and strong inhibitory activity against T. cruzi proliferative epimastigotes, which were more susceptible than trypomastigotes. In the presence of blood, the activity of Et-Bur or Et-Lov against trypomastigotes was similar to that of the standard drug, crystal violet. Both extracts also showed similar and significant activity against Staphylococcus aureus and Candida albicans, while being inactive against Escherichia coli. The acetone extract, Ket-Bur, was more active than Et-Bur against both forms of T. cruzi.
    Journal of Ethnopharmacology 11/2003; 88(2-3):189-93. · 2.76 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Electron impact mass spectra were measured by high temperature high resolution gas chromatography-mass spectrometry (HT-HRGC-MS) for three homologous series of high molecular weight compounds present in the Amazonian plants Marupá (Simaruba amara) and Brazil nut (Bertholettia excelsa). Based on their mass spectra, the compounds were identified as three wax ester series of alpha-tocopherol (vitamin E), beta-tocopherol and phytol (2,6,10,14-tetramethylhexadec-14-en-16-ol). The interpretations are supported by high resolution mass spectrometry and GC retention indices of authentic standards.
    Phytochemistry 12/2002; 61(6):711-9. · 3.05 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: High temperature high resolution gas chromatography coupled to mass spectrometry (HT-HRGC-MS) isa powerful analytical tool. In this work we applied this technique to the study of crude extracts of propolis collected near the city of Uberlândia-Minas Gerais State. Eucalyptus trees and native plants from "cerrado" (savannah) were the material sources disposable for the Apis mellifera bees. A lot of known propolis constituents were identified, however, several high molecular weight compounds including lupeol alkanoates were identified for first time in propolis.
    Zeitschrift fur Naturforschung C 01/2002; 57(7-8):721-6. · 0.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: High-temperature high-resolution gas chromatography (HTGC) is an established technique for the separation of complex mixtures of high molecular weight (HMW) compounds which do not elute when analyzed on conventional GC columns. The combination of this technique with mass spectrometry (i.e., HTGC−MS) is not so common and application to aerosols is novel. The HTGC and HTGC−MS analyses of smoke samples taken by particle filtration from combustion of different species of plants provided the characterization of various classes of HMW compounds reported to occur for the first time in emissions from biomass burning. Among these components are a series of wax esters (long chain alcohols esterified with long chain fatty acids) with up to 58 carbon numbers, aliphatic hydrocarbons (C15−C40; Cmax = C31; odd predominance), triglycerides, long chain methyl ketones (up to 37 carbons; Cmax = C33; odd predominance), alkanols (up to 40 carbons; Cmax = C32; even predominance), and a series of triterpenyl fatty acid esters (e.g., α- and β-amyryl stearate) which have been characterized as novel natural products. Long chain fatty acids with more than 32 carbon numbers are not present in the smoke samples analyzed. The HMW compounds in smoke samples from the burning of plants from Amazonia indicate the input of directly volatilized natural products in the original plants during their combustion. However, the major organic compounds extracted from smoke consist of a series of lower molecular weight polar components, which are not natural products but the result of the thermal breakdown of cellulose and lignin. In contrast, the HMW natural products may be suitable tracers for specific sources of vegetation combustion because they are emitted as particles without thermal alteration in the smoke and can thus be related directly to the original plant material.
    Environmental Science & Technology - ENVIRON SCI TECHNOL. 05/1999; 33(14).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Crude ethanol extracts of leaves of Croton (Euphorbiaceae) species (C. hemiargyreus var. gymnodiscus, C. hemiargyreus var. hemiargyreus and C. echinocarpus) were analysed using on-column injection high temperature gas chromatography coupled with mass spectrometry. Several isoquinoline alkaloids were identified, including isocorydine, corydine, glaucine and laurelliptine as the principal constituents. The cold on-column technique proved to be appropriate for injection of these compounds. The technique is shown to be a valuable tool and an alternative technique to classical phytochemical procedures permitting the fast analysis of alkaloid mixtures without the need for (extensive) fractionation and derivatisation. Copyright © 1999 John Wiley & Sons, Ltd.
    Phytochemical Analysis 01/1999; 10(5):254-258. · 2.48 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A custom-made glass capillary column coated with OV-1701-OH (88% methyl, 7% cyanopropyl, 5% phenylpolysiloxane) was used to analyze smoke samples from biomass combustion of different species of plants collected in the Amazon forest. CS2 was used as solvent in order to enhance the dissolution and analysis of the heavier molecular weight components. The performance of the column was monitored during the experiments and a moderate increase in activity was observed after taking the column to high analytical temperatures (390°C). Trennzahl values typically dropped 20–30% from 1.7/m to the average of 1.35/m. In general, the performance of the custom-made column was satisfactory and comparable to the commercial high temperature columns. The high temperature high resolution GC and GC-MS analyses revealed the presence of a number of high molecular weight components reported to occur in smoke aerosols for the first time. These components consisted of series of wax esters (long chain alcohols esterified with long chain fatty acids) with up to 58 carbon numbers, aliphatic hydrocarbons, triglycerides, triterpenyl esters (e.g. α- and β-amyryl stearate). Although other types of compounds were also detected, their complete structure elucidation solely by electron impact MS was not adequate and other techniques will be required.
    Journal of High Resolution Chromatography 12/1998; 21(2):87 - 93.
  • Hrc-journal of High Resolution Chromatography - HRC-J HIGH RES CHROMATOGR. 01/1998; 21(9):513-518.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A series of high molecular mass pentacyclic terpenoid wax esters in smoke from biomass combustion were characterized by high-temperature, high-resolution gas chromatography–mass spectrometry. Based on their mass spectra, they are interpreted as being a series of triterpenyl fatty acid esters (e.g. α- and β- amyryl palmitate). The carbon chain length of the fatty acids ranges from 5 to 20. This interpretation is supported by retention indeces, molecular ions and typical fragments of pentacyclic triterpenoids. Essentially, the mass spectra are simple and composed of the molecular ion, M-CH3, M-fatty acid and fragments characteristic of the esterified triterpenoid moieties. © 1997 John Wiley & Sons, Ltd.
    Biological Mass Spectrometry 01/1997; 32(12):1356-1361. · 3.41 Impact Factor