C. Mantell

Semi-batch extraction of anthocyanins from red grape pomace in packed beds: experimental results and process modelling

A semi-batch extraction process of anthocyanins was studied in a packed bed. Methanol was used as solvent and the raw material studied consisted of skins of the tempranillo grape, which was obtained from the pomace from red wine vinification. The results show large diffusional effects due to strong control from the mass transfer. The best results were obtained using a high temperature and a high flow rate. A penetration model is proposed in terms of a bed of spherical particles. The model provides a value for the diffusion coefficient of the solute within the solid matrix. It can be seen that the adjustment of the model is satisfactory and that it is able to predict, to a reasonable extent, the yield of the extraction process.

Measurement of the diffusion coefficient of a model food dye (malvidin 3,5-diglucoside) in a high pressure CO2+methanol system by the chromatographic peak-broadening technique

Abstract The accurate determination of the diffusion coefficients of solutes in supercritical solvents is a prerequisite for the modeling and design of extraction processes. At present, reported data on the diffusion of polar solutes in the system CO 2 +methanol at high pressure is scarce. In the work described here, malvidin 3,5-diglucoside was chosen as a representative example of anthocyanin compounds (natural food dyes). The diffusion coefficient of this compound was determined using a chromatographic peak-broadening technique. The effect of the amount of methanol in the solvent has been analyzed and the results show that a decrease in the diffusion coefficient occurs as the amount of methanol increases. This behavior has been attributed to the formation of solute–methanol clusters. Finally, the results obtained have also been correlated with temperature, solvent density and viscosity, with the best fit found in the correlation with density.

Green Extraction of Antioxidants from Different Varieties of Red Grape Pomace

The extraction yield, phenolic content, anthocyanin content and antioxidant activity of extracts from different varieties of red grapes, Cabernet Sauvignon, Merlot, Petit Verdot, Syrah, Tempranillo and Tintilla, using pressurized green solvents have been analyzed. Two techniques were studied and compared: supercritical fluid extraction (SFE) with CO2 + 20% ethanol and pressurized liquid extraction (PLE) with either ethanol, water or an ethanol/water mixture as the extraction solvents. The Petit Verdot variety allowed the highest global and phenolic yield, and antioxidant activity. The best conditios for PLE obtained from the experimental design and kinetic study were 50% ethanol/water as the pressurized solvent at 90 bar, 120 °C, a flow rate of 5 g/min and, an extraction time of 90 min. A statistical analysis of variance has been performed and it was found that temperature is the only variable that has a statistical influence on the extraction yield. The antioxidant activity levels of the extracts are very promising and they are similar to those obtained with the antioxidant tocopherol.

Effect of the pre-treatment of the samples on the natural substances extraction from Helianthus annuus L. using supercritical carbon dioxide.

The extraction of bioactive compounds from sunflowers (Helianthus annuus L.) with supercritical carbon dioxide has been studied. The samples were treated in four different ways and the effects of two factors (pressure and temperature) were investigated at 100, 500 bar and 35, 50 degrees C. The best yields were obtained using a high temperature and a high pressure (50 degrees C and 500 bar). The dry samples produced better extraction yields than the moist samples. The bioactivities of the extracts were compared for the samples treated in different ways. The best activity profiles were obtained for the moist samples extracted at 35 degrees C and 500 bar.

Kinetics and Mathematical Modeling of Anthocyanin Extraction with Carbon Dioxide and Methanol at High Pressure

In this work, the kinetics of the high‐pressure extraction (HPE) of anthocyanins from red grape pomace using a packed bed was studied. The solvent used was carbon dioxide modified with methanol as a cosolvent. A penetration model was developed that due to the laminate form of the grape skin particles, was based on the application of the mass balance to an infinite planar particle. The model was completed with a study of the soaking time of the process and this concludes with an empirical equation describing the behavior of this variable vs pressure, temperature, solvent flow rate, and cosolvent percentage. The fit of the model is satisfactory and it is able to predict in a reasonable way the extraction yield of the process. Finally, the model provides a value for the internal diffusion coefficient and this allows an analysis of the influence of the different variables in the extraction process.

Estimation of the diffusion coefficient of a model food dye (malvidin 3,5-diglucoside) in a high pressure CO2+methanol system

Abstract Experimental data for the diffusion coefficient of malvidin 3,5-diglucoside in carbon dioxide and methanol as cosolvent at high pressure are compared with the values estimated by predictive equations. Those equations studied are based on the Stokes–Einstein theory and the rough-hard-sphere theory. The values predicted using these equations are, in general, higher than experimental values and these differences become more marked as the percentage of methanol in the solvent system is increased. The best fit was obtained with the Wilke–Chang, Scheibel, Hayduck–Minhas, and Dymond equations when the cosolvent is present at 5%. Correlation of the experimental data with the Stokes–Einstein equation allows to estimate the diffusing solute radii. The increase in these radii with the percentage of cosolvent is related to the formation of solute/methanol clusters. Finally, modifications of the different equations from the Stokes–Einstein model and the rough-hard-sphere theory are proposed.

Isolation of Bioactive Compounds from Sunflower Leaves (Helianthus annuus L.) Extracted with Supercritical Carbon Dioxide

The work described herein is a continuation of our initial studies on the supercritical fluid extraction (SFE) with CO2 of bioactive substances from Helianthus annuus L. var. Arianna. The selected SFE extract showed high activity in the wheat coleoptile bioassay, in Petri dish phytotoxicity bioassays, and in the hydroponic culture of tomato seeds. Chromatographic fractionations of the extracts and a spectroscopic analysis of the isolated compounds showed 52 substances belonging to 10 different chemical classes, which were mainly sesquiterpene lactones, diterpenes, and flavonoids. Heliannuol M (31), helivypolides K and L (36, 37), and helieudesmanolide B (38) are described for the first time in the literature. Metabolites have been tested in the etiolated wheat coleoptile bioassay with good results in a noteworthy effect on germination. The most active compounds were also tested on tomato seeds, heliannuol A (30) and leptocarpin (45) being the most active, with values similar to those of the commercial herbicide.

SFE kinetics of bioactive compounds from Helianthus annuus L.

The kinetics of the supercritical fluid extraction of bioactive compounds from sunflower using CO(2) as solvent were studied in order to establish an efficient method for this extraction. The influence of time of extraction at different solvent flow rates was investigated. The extraction pressure and temperature were optimized in previous studies and these values used were 400 bar and 50 degrees C. The extraction yields and the bioactivity levels of the extracts were also analysed. The results indicate that the most appropriate extraction time is between 120 and 180 min depending on the solvent flow and the pretreatment of the sample. The dried sample extracted at 40 g/min, the congealed sample extracted at the same flow and 180 min, and the dried sample extracted at 25 g/min for 120 min showed the best activity profiles. The extractions were carried out in a pilot plant with an extraction vessel with a capacity of 2 L.

Mango leaf extract improves central pathology and cognitive impairment in a type 2 diabetes mouse model.

Epidemiological studies reveal that metabolic disorders, and specifically type 2 diabetes (T2D), are relevant risk factors to develop Alzheimers disease (AD) and vascular dementia (VaD), the most common causes of dementia. AD patients are in a tremendous need of new therapeutic options because of the limited success of available treatments. Natural polyphenols, and concretely Mangifera indica Linn extract (MGF), have been reported to have antiinflammatory, antioxidant and antidiabetic activities. The role of MGF in central complications associated with T2D, after long‐term treatment of db/db mice with MGF was analyzed. Metabolic parameters (body weight, glucose and insulin levels) as well as central complications including brain atrophy, inflammatory processes, spontaneous bleeding, tau phosphorylation and cognitive function in db/db mice treated with MGF for 22 weeks were assessed. MGF limits body weight gain in obese db/db mice. Insulin and C‐peptide levels, indicative of pancreatic function, were longer maintained in MGF‐treated animals. MGF reduced central inflammation by lowering microglia burden, both in the cortex and the hippocampus. Likewise, central spontaneous bleeding was significantly reduced in db/db mice. Cortical and hippocampal atrophy was reduced in db/db mice and tau hyperphosphorylation was lower after MGF treatment, resulting in partial recovery of learning and memory disabilities. Altogether, the data suggested that MGF treatment may provide a useful tool to target different aspects of AD and VaD pathology, and could lead to more effective clinical therapies for the prevention of metabolic related central complications associated with AD and VaD.

Supercritical CO2 extraction of PAHs on spiked soil: co-solvent effect and solvent regeneration by ozonization.

The supercritical CO(2) extraction of four PAHs (acenaphthene, phenanthrene, anthracene and fluoranthene) from an artificially contaminated soil has been investigated. The effect of temperature (40-60 degrees C), pressure (300-500 bar) and extraction time (90-150 min) has been assessed by conducting a Box-Behnken experimental design. The results suggest the existence of perturbation variables other than the aforementioned controlled variables leading to a significant dispersion of extraction recoveries. With the exception of anthracene, an optimum in temperature (50 degrees C) is envisaged when extracting the PAHs. Analogously, with the exception of anthracene (positive effect), pressure does not have a significant influence. The recovery yield increases as extraction time is increased to a value of 120 min. No further improvement is experienced thereafter. If a co-solvent is used (H(2)O(2) aqueous solution) a beneficial effect can be noticed. Hydrogen peroxide concentration did exert no significant influence in the process. Methanol used to collect the extracted PAHs could be regenerated by gaseous ozone and reused in several consecutive runs.