Beta-carotene isomer composition of sub- and supercritical carbon dioxide extracts. Antioxidant activity measurement.
ABSTRACT In the present work sub- and supercritical extraction conditions using carbon dioxide were studied in order to obtain extracts with different compositions from the green microalgae Dunaliella salina. Different compositions of beta-carotene isomers were identified in the extracts by using HPLC-DAD. Also, antioxidant activity of the extracts was measured using a TEAC assay. An experimental design was applied considering two factors, extraction pressure and temperature, in a wide range of values, trying to maximize the extraction yield. Higher yields were obtained at high pressures and low temperatures, that is, at higher CO2 densities. Attempts were made to correlate the antioxidant activity of the extracts with their chemical composition by means of principal component analysis. A certain relationship was found between their antioxidant activity and the isomeric composition of beta-carotenes. As a result, an original equation is proposed to predict the antioxidant activity of extracts from D. salina in terms of the ratio 9-cis-beta-carotene/all-trans-beta-carotene, the concentration of alpha-carotene, and, especially, the concentration of 9-cis-beta-carotene.
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ABSTRACT: Marine ecosystems cover more than 70% of the globe’s surface. These habitats are occupied by a great diversity of marine organisms that produce highly structural diverse metabolites as a defense mechanism. In the last decades, these metabolites have been extracted and isolated in order to test them in different bioassays and assess their potential to fight human diseases. Since traditional extraction techniques are both solvent- and time-consuming, this review emphasizes alternative extraction techniques, such as supercritical fluid extraction, pressurized solvent extraction, microwave-assisted extraction, ultrasound-assisted extraction, pulsed electric field-assisted extraction, enzyme-assisted extraction, and extraction with switchable solvents and ionic liquids, applied in the search for marine compounds. Only studies published in the 21st century are considered.Marine Drugs 05/2015; 13(5):3182-3230. DOI:10.3390/md13053182 · 3.51 Impact Factor
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ABSTRACT: The simultaneous analysis of fat- and water-soluble vitamins from foods is a difficult task considering the wide range of chemical structures involved. In this work, a new procedure based on a sequential extraction and analysis of both types of vitamins is presented. The procedure couples several simple extraction steps to LC-MS/MS and LC-DAD in order to quantify the free vitamins contents in fresh-cut vegetables before and after a 10-days storage period. The developed method allows the correct quantification of vitamins C, B(1), B(2), B(3), B(5), B(6), B(9), E and provitamin A in ready-to-eat green leafy vegetable products including green lettuce, ruby red lettuce, watercress, swiss chard, lamb's lettuce, spearmint, spinach, wild rocket, pea leaves, mizuna, garden cress and red mustard. Using this optimized methodology, low LOQs were attained for the analyzed vitamins in less than 100min, including extraction and vitamin analysis using 2 optimized procedures; good repeatability and linearity was achieved for all vitamins studied, while recoveries ranged from 83% to 105%. The most abundant free vitamins found in leafy vegetable products were vitamin C, provitamin A and vitamin E. The richest sample on vitamin C and provitamin A was pea leaves (154mg/g fresh weight and 14.4mg/100g fresh weight, respectively), whereas lamb's lettuce was the vegetable with the highest content on vitamin E (3.1mg/100g fresh weight). Generally, some losses of vitamins were detected after storage, although the behavior of each vitamin varied strongly among samples.Journal of Chromatography A 05/2012; 1261:179-88. DOI:10.1016/j.chroma.2012.04.067 · 4.26 Impact Factor
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ABSTRACT: In this work we investigate the effect of cis isomerizations and conformational changes on the antioxidant activity of β-carotene, one of the most important pigments in nature. The electrodonating (ω(-)) and electroaccepting (ω(+)) powers of the most relevant isomers of β-carotene are first evaluated in polar and nonpolar solvents using density functional theory (DFT), and these quantities are then used to establish an antioxidant scale of the isomers. The electrodonating power, which is directly related to the antioxidant activity, is shown to provide a very good correlation with the experimental data. Next, we compute the intermediate twisted structures of the β-carotene isomers generated by partial rotation of every single bond in the polyenic chain. The electrodonating and electroaccepting powers are evaluated for each of these intermediate structures along with their maximum absorption wavelengths, which are computed using time-dependent DFT (TD-DFT). The trends observed for both the electrodonating power and the maximum absorption wavelength can be rationalized in terms of the effective conjugated chain length of the structure resulting from single bond rotations. The results obtained are used to analyze the conformational distribution of β-carotene in the well-resolved photosystem I (PS-I) of purple cyanobacteria. It is then shown that the isomers present in this photosystem are those having the lowest calculated relative energies and that those with enhanced antioxidant activity are preferentially located in the inner core of the protein complex.The Journal of Physical Chemistry A 03/2012; 116(13):3498-506. DOI:10.1021/jp301485k · 2.78 Impact Factor