Biomedical subjects

Elena Ibañez

Publications and source records attributed to Elena Ibañez.

7 recordsLinked to original sources

PubMed2006

Selective recovery of tagatose from mixtures with galactose by direct extraction with supercritical CO2 and different cosolvents.

A selective fractionation method of carbohydrate mixtures of galactose/tagatose, using supercritical CO(2) and isopropanol as cosolvent, has been evaluated. Optimization was carried out using a central composite face design and considering as factors the extraction pressure (from 100 to 300 bar), the extraction temperature (from 60 to 100 degrees C), and the modifier flow rate (from 0.2 to 0.4 mL/min, which corresponded to a total cosolvent percentage ranging from 4 to 18% vol). The responses evaluated were the amount (milligrams) of tagatose and galactose extracted and their recoveries (percent). The statistical analysis of the results provided mathematical models for each response variable. The corresponding parameters were estimated by multiple linear regression, and high determination coefficients (>0.96) were obtained. The optimum conditions of the extraction process to get the maximum recovery of tagatose (37%) were 300 bar, 60 degrees C, and 0.4 mL/min of cosolvent. The predicted value was 24.37 mg of tagatose, whereas the experimental value was 26.34 mg, which is a 7% error from the predicted value. Cosolvent polarity effects on tagatose extraction from mixtures of galactose/tagatose were also studied using different alcohols and their mixtures with water. Although a remarkable increase of the amount of total carbohydrate extracted with polarity was found, selective extraction of tagatose decreased with increase of polarity of assayed cosolvents. To improve the recovery of extracted tagatose, additional experiments outside the experimental domain were carried out (300 bar, 80 degrees C, and 0.6 mL/min of isopropanol); recoveries >75% of tagatose with purity >90% were obtained.

Carbon Dioxide↗

PubMed2005

Characterization via liquid chromatography coupled to diode array detector and tandem mass spectrometry of supercritical fluid antioxidant extracts of Spirulina platensis microalga.

Spirulina platensis microalga has been extracted on a pilot scale plant using supercritical fluid extraction (SFE) under various extraction conditions. The extraction yield and the antioxidant activity of the extracts were evaluated in order to select those extracts with both the highest antioxidant capacity and a good extraction yield. These extracts were characterized using LC coupled to diode array detection (DAD) and LC coupled to mass spectrometry (MS) with two different interfaces, atmospheric pressure chemical ionization (APCI) and electrospray (ESI) which allowed us to perform tandem MS by using an ion trap analyzer. The best extraction conditions were as follows: CO2 with 10% of modifier (ethanol) as extraction solvent, 55 degrees C (extraction temperature) and 220 bar (extraction pressure). Fractionation was achieved by cascade depressurization providing two extracts with different activity and chemical composition. Several compounds have been identified in the extracts, corresponding to different carotenoids previously identified in Spirulina platensis microalga along with chlorophyll a and some degradation products. Also, the structure of some phenolic compounds could be tentatively identified. The antioxidant activity of the extracts could be attributed to some of the above mentioned compounds.

Antioxidants↗

PubMed2004

Separation of rosemary antioxidant compounds by supercritical fluid chromatography on coated packed capillary columns.

Antioxidant compounds in rosemary extracts obtained by supercritical fluid extraction (SFE) were separated by supercritical fluid chromatography (SFC) on packed capillary columns. The columns contained silica particles coated with SE-54 (5% phenyl, 95% methyl silicone) and Carbowax 20 M [poly(ethylene glycol)]. The use of coated packed capillary columns allowed the separation of polar compounds by SFC with neat CO2. The SFC conditions were selected on the basis of previous work. High pressures (up to 370 atm; 1 atm = 10,325 Pa) and moderate temperatures (up to 100 degrees C) were used to separate the compounds responsible for the antioxidant activity such as carnosic acid and camosol while lower pressures were sufficient to separate the compounds of the essential oil.

Abietanes↗

PubMed2004

Tocopherol measurement in edible products of vegetable origin.

Since natural antioxidants present increasing interest for food industry due to their beneficial effect on health, new potential sources have been screened among edible aromatic plants and a microalgae, Spirulina platensis. The determination was performed after optimising a previously validated method, because important differences have been found among values described in literature for tocopherol content in products of vegetable origin. Values obtained ranged from 3.42 mg alpha-tocopherol/100 g of dill to 132.2 mg/100 g of fresh bay and from 0.14 mg gamma-tocopherol/100 g of spearmint to 3.45 mg/100 g of parsley. In all cases results were calculated from fresh leaves. Preliminary experiments were developed with bay (Laurus nobilis) plant to devise the supercritical fluid extraction of tocopherols, generating environmentally friendly processes to selectively extract fractions enriched with antioxidant compounds while removing fractions corresponding to essential oils, that is, those that correspond to the characteristic aroma of the plants. Another striking result has been the tocopherol content in the microalgae, 1.3 mg alpha-tocopherol/100 g of dried commercial spirulina, which do not justify the supposed source of antioxidant vitamins. Results suggest the need of more reliable determinations of tocopherols in vegetable sources to be included in databases.

Chromatography, Supercritical Fluid↗

PubMed2003

Subcritical water extraction of antioxidant compounds from rosemary plants.

Subcritical water extraction at several temperatures ranging from 25 to 200 degrees C has been studied to selectively extract antioxidant compounds from rosemary leaves. An exhaustive characterization of the fractions obtained using subcritical water at different temperatures has been carried out by LC-MS, and the antioxidant activities of the extracts have been measured by a free radical method (DPPH). Results indicate high selectivity of the subcritical water toward the most active compounds of rosemary such as carnosol, rosmanol, carnosic acid, methyl carnosate, and some flavonoids such as cirsimaritin and genkwanin. The antioxidant activity of the fractions obtained by extraction at different water temperatures was very high, with values around 11.3 microg/mL, comparable to those achieved by SFE of rosemary leaves. A study of the effect of the temperature on the extraction efficiency of the most typical rosemary antioxidant compounds has been performed.

Abietanes↗

PubMed2002

Analysis of antioxidants from orange juice obtained by countercurrent supercritical fluid extraction, using micellar electrokinetic chromatography and reverse-phase liquid chromatography.

Antioxidants from orange juice were determined by the combined use of countercurrent supercritical fluid extraction (CC-SFE) prior to reverse-phase liquic chromatography (RP-LC) or micellar electrokinetic chromatography (MEKC). The separation of antioxidants found in the SFE fractions was achieved by using a new MEKC method and a published LC procedure, both using diode array detection. The characterization of the different antioxidants was further done by LC-mass spectrometry. Advantages and drawbacks of LC and MEKC for analyzing the antioxidants found in the different orange extracts are discussed. Although LC yields higher peak area and slightly better reproducibility than MEKC, the latter technique provides information about the CC-SFE extracts in analysis times 7 times faster than by LC. This analysis advantage can be used for the quick adjustment of CC-SFE conditions, thus providing a fast way to obtain orange fractions of specific composition.

Antioxidants↗

PubMed2002

Truffle aroma analysis by headspace solid phase microextraction.

An experimental design has been used to optimize the extraction of volatile compounds from summer truffle aroma (Tuber aestivum) by using headspace solid phase microextraction. The extracted compounds have been analyzed by gas chromatography with a flame ionization detector and by gas chromatography-mass spectrometry (GC-MS). In an attempt to develop an objective method to fully characterize truffle aroma, a fiber of medium polarity (for flavors) was used to avoid discrimination toward very nonpolar and polar volatile compounds. To optimize the extraction conditions, a response surface experimental design was applied considering three factors such as extraction temperature, equilibrium time, and extraction time. From the statistical analysis of the experimental design, it was possible to determine that the most important factor influencing the abundance of aroma compounds was the extraction temperature. Optimal extraction temperature was established at approximately 50 degrees C. By using GC-MS, it was possible to identify 37 compounds, most of them previously described as responsible for truffle aroma.

Ascomycota↗