COMPOSITION OF SUPERCRITICAL CARBON DIOXIDE EXTRACTS OF PITANGA (EUGENIA UNIFLORA L.) LEAVES

The leaves of the Pitanga bush (Eugenia uniflora L.) are considered to be effective against many diseases. Extracts from Pitanga leaves have been found to show pronounced anti-inflammatory action and to have antimicrobial and antifungal activities, among other properties. In this work, extracts from Pitanga leaves were obtained by hydrodistillation and by extraction with supercritical carbon dioxide (SC-CO(2)) at three conditions of temperature and pressure. In the SC-CO(2) extractions also were collected the components that are lost with the CO(2) in the exit of the system using Porapak-Q polymer trap. All extracts were analyzed by gas chromatography-mass spectrometry (GC-MS). Thirty-nine compounds were found in the extracts and twenty-six were identified. The main components identified in the extracts in decreasing quantitative order were: curzerene, germacrene B, C(15)H(20)O(2) and beta-elemene for hydrodistillation; C(15)H(20)O(2) and curzerene for SC-CO(2) extracts and 3-hexen-1-ol, curzerene, C(15)H(20)O(2), beta-elemene and germacrene B for SC-CO(2) extracts captured in Porapak-Q. PRACTICAL APPLICATIONS The natural extracts are a potential source of compounds possessing biological activities. They can be used in foods, pharmaceutics and cosmetics. Pitanga is an exotic fruit from Brazil and extracts from its leaves have been used against many diseases in Brazilian folk medicine. Supercritical extraction is an interesting process for the production of natural extracts because it is a clean process and the knowledge of composition of extracts is crucial for the identification of the probable active components.

Response surface analysis of extract yield and flavour intensity of Brazilian cherry (Eugenia uniflora L.) obtained by supercritical carbon dioxide extraction

This work evaluated the effect of pressure and temperature on yield and characteristic flavour intensity of Brazilian cherry (Eugenia uniflora L) extracts obtained by supercritical CO(2) using response surface analysis, which is a simple and efficient method for first inquiries. A complete central composite 2(2) factorial experimental design was applied using temperature (ranging from 40 to 60 degrees C) and pressure (from 150 to 250 bar) as independent variables. A second order model proved to be predictive (p <= 0.05) for the extract yield as affected by pressure and temperature, with better results being achieved at the central point (200 bar and 50 degrees C). For the flavour intensity, a first order model proved to be predictive (p <= 0.05) showing the influence of temperature. Greater characteristic flavour intensity in extracts was obtained for relatively high temperature (> 50 degrees C), Therefore, as far as Brazilian cherry is concerned, optimum conditions for achieving higher extract yield do not necessarily coincide to those for obtaining richer flavour intensity. Industrial relevance: Supercritical fluid extraction (SFE) is an emerging clean technology through which one may obtain extracts free from organic solvents. Extract yields from natural products for applications in food, pharmaceutical and cosmetic industries have been widely disseminated in the literature. Accordingly, two lines of research have industrial relevance, namely, (i) operational optimization studies for high SFE yields and (ii) investigation on important properties extracts are expected to present (so as to define their prospective industrial application). Specifically, this work studied the optimization of SFE process to obtain extracts from a tropical fruit showing high intensity of its characteristic flavour, aiming at promoting its application in natural aroma enrichment of processed foods. (C) 2008 Elsevier Ltd. All rights reserved.

Study of the carbon dioxide chemical fixation-activation by guanidines

Fixation of CO(2) is one of the most important priorities of the scientific community dedicated to reduce global warming. In this work, we propose new methods for the fixation of CO2 using the guanidine bases tetramethylguanidine (TMG) and 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]-pyrimidine (TBD). In order to understand the reactions occurring during the CO(2) fixation and release processes, we employed several experimental methods, including solution and solid-state NMR, FTIR, and coupled TGA-FTIR. Quantum mechanical NMR calculations were also carried out. Based on the results obtained, we concluded that CO(2) fixation with both TMG and TBD guanidines is a kinetically reversible process, and the corresponding fixation products have proved to be useful as transcarboxylating compounds. Afterward, CO(2) thermal releasing from this fixation product with TBD was found to be an interesting process for CO(2) capture and isolation purposes. (C) 2008 Elsevier Ltd. All rights reserved.

Hydrogen peroxide and supercritical carbon dioxide: a new bleaching stage for Eucalyptus kraft-O(2) pulps

Kraft pulp is currently bleached largely by the elemental chlorine free (ECF) technology with oxygen, chlorine dioxide, and hydrogen as active agents. This technology brought about significant environmental improvements in relation to standard processes based on chlorine gas and hypochlorite, but there is still need for further improvements. This study presents a novel environmentally friendly bleaching stage - the so-called `hydrogen peroxide in supercritical carbon dioxide`, P((SC-CO2)) - that can be adapted to current ECF bleaching processes, with preference in cases where hydrogen peroxide is already used. In this study, the P((SC-CO2)) stage was evaluated as a replacement to the last peroxide stage of the D(EP)DP bleaching sequence and to the first peroxide stage of the D(EP)DP sequence, for an oxygen delignified eucalypt kraft-O(2) pulp. The P((SC-CO2)) stage was run with 0.5% hydrogen peroxide, at 15% consistency, 70 degrees C, and 73 bar. The reaction time was 30 min. The performances of regular P stages and the new P((SC-CO2)) stage were compared. Promising results were observed with the DEP((SC-CO2))DP sequence; the P((SC-CO2)) decreased kappa number from 2.7 to 2.1, and the hexenuronic acid groups from 17.0 to 12.4 mmol kg(-1). The P((SC-CO2)) stage showed poor performance when applied in the D(EP)DP((SC-CO2)) sequence. It is concluded that the process presents potential but requires further optimization to improve selectivity and efficiency.

Carbon dioxide reforming of ethanol over Ni/Y(2)O(3)-ZrO(2) catalysts

Supported nickel catalysts of composition Ni/Y(2)O(3)-ZrO(2) were synthesized in one step by the polymerization method and compared with a nickel catalyst prepared by wet impregnation. Stronger interactions were observed in the formed catalysts between NiO species and the oxygen vacancies of the Y(2)O(3)-ZrO(2) in the catalysts made by polymerization, and these were attributed to less agglomeration of the NiO during the synthesis of the catalysts in one step. The dry reforming of ethanol was catalyzed with a maximum CO(2) conversion of 61% on the 5NiYZ catalyst at 800 degrees C, representing a better response than for the catalyst of the same composition prepared by wet impregnation. (C) 2009 Published by Elsevier B.V.