Ignacio Gracia

Supercritical fluid extraction of tocopherol concentrates from olive tree leaves

Olive tree leaves, a residue obtained during the harvest of olives for oil production were treated with supercritical carbon dioxide to analyze the possibility of obtaining tocopherol concentrates. Oil and tocopherol extraction rates were determined as a function of pressure (25–45 MPa), particle size (0.25–1.5 mm), solvent flow (0.5–1.5 SL/min) and temperature (313–333 K). Two optimal extraction conditions were determined, considering the maximum recovery or concentration criterion. Those conditions led to a highly valuable extract of 74.5 and 97.1% (w/w) tocopherol concentration, respectively. Results obtained were compared to hexane soxhlet extraction.

Thermal Degradation of Allicin in Garlic Extracts and Its Implication on the Inhibition of the in-Vitro Growth of Helicobacter pylori

Allicin, the main active principle related to Allium sativum chemistry, is considered to be responsible for the bacteriostatic properties of garlic. The work described here has demonstrated the direct implication of the allicin present in solvent‐free garlic extracts obtained with ethanol (ethanolic garlic extract, EGE) and acetone (acetonic garlic extract, AGE) in the inhibition of the in‐vitro growth of Helicobacter pylori ( Hp), the bacterium responsible for serious gastric diseases such as ulcers and even gastric cancer. The evolution of allicin concentration as a function of time and temperature has been the subject of a kinetic study. The reaction order, activation energy, and preexponential factor (in accordance with Arrhenius theory) have been determined for the decomposition process of allicin in these organic media. First‐order decomposition, an activation energy of 97.4 kJ/mol, and an Arrhenius preexponential factor of 8.9 × 1010 s−1 have been determined for allicin in EGE. For allicin in AGE the kinetic order determined was 1.5, the activation energy 184.5 kJ/mol, and the preexponential factor 3.1 × 1024 s−1 (mg/L)(−0.5). The presence or absence of allicin in these garlic products was found to be crucial for the inhibition of the in‐vitro growth of Hp, as demonstrated by microbiological analysis for AGE. A relationship has been identified between the effectiveness and durability of the anti‐ Hp properties shown by AGE and the allicin content of these products. The bacteriostatic properties were active for up to 10 months if the samples were maintained at 6 °C.

Supercritical carbon dioxide extraction of fatty and waxy material from rice bran

Waxy and fatty materials were removed from rice bran by supercritical carbon dioxide at pressures up to 28 MPa and temperatures between 40 and 70°C. The yields of the supercritical extraction were only 16–60% of those obtained by Soxhlet extraction with hexane. The highest yield was reached at the highest pressure and temperature used (28 MPa and 70°C), indicating that supercritical extraction of this lipid-bearing material could probably be improved at more severe extraction conditions. The supercritical extract obtained at operational conditions giving high yield was chromatographically characterized. Compared to the hexane extract, the supercritical extract was lighter in color and richer in wax content and long-chain fatty acids C20−C34. Triacontanol was the most abundant alcohol in both extracts. Tocopherol contents were similar.

Allyl-thiosulfinates, the bacteriostatic compounds of garlic against Helicobacter pylori

Allicin and allyl‐methyl plus methyl‐allyl thiosulfinate from acetonic garlic extracts (AGE) have been isolated by high‐performance liquid chromatography. These compounds have shown inhibition of the in vitro growth of Helicobacter pylori(Hp), the bacterium responsible for serious gastric diseases such as ulcers and even gastric cancer. A chromatographic method was optimized and used to isolate these thiosulfinates. The method developed has allowed the isolation of natural thiosulfinates extracted from garlic by organic solvents and is an easy and cheap methodology that avoids complex synthesis and purification procedures. The capacity and effectiveness of isolated natural thiosulfinates have been tested, and this has enabled the identification of the main compounds responsible for the bacteriostatic activity shown by AGE origin of these kinds of organosulfur compounds along with ethanolic garlic extracts (EGE). Additionally, microbiological analyses have suggested that these compounds show a synergic effect on the inhibition of the in vitro growth of Hp. The results described here facilitate the process of obtaining garlic extracts with optimal bacteriostatic properties. The product is obtained in a way that avoids expensive purification methods and will allow the design of live tests with the aim of investigating the potential for the use of these garlic derivatives in the treatment of patients with Hp infections.

Optimization of Allium sativum solvent extraction for the inhibition of in vitro growth of Helicobacter pylori

Helicobacter pylori (Hp) is the bacterium responsible for serious gastric diseases such as ulcers and cancer. The work described here involved the study of the inhibitory power of Allium sativum extracts against the in vitro growth of Hp(Hp ivg). We used purple garlic of the “Las Pedroñeras” variety for this study. The effects of two different extraction methods (Soxhlet, stirred tank extractor) and four solvents with different characteristics (water, acetone, ethanol, and hexane) were investigated in terms of the efficiency of the extraction process. Satisfactory results were obtained in most cases in the activity tests, indicating that different extracts gave rise to good inhibitory activity against Hp ivg. The extracts that showed the highest bacteriostatic activities were selected to evaluate the influence of the most important operation variables on the extraction yield: stirring speed, operation time, garlic conditioning, and garlic storage time. The best results were obtained using ethanol and acetone as solvents in a stirred tank. The inhibitory powers of these extracts were compared to those shown by some commercial antibiotics used in the medical treatment of Hp infections. The results of this study show that garlic extracts produce levels of inhibition similar to those of the commercial materials. These extracts were also tested against other common bacteria, and equally satisfactory results were obtained. The research described here represents an important starting point in the fight against and/or prevention of peptic ulcers, as well as other pathologies associated with Hp infections such us gastric cancer. The extracted material can be used by direct application and involves a simple and economical extraction procedure that avoids isolation or purification techniques.

Isolation of Rock Rose Essential Oil Using Supercritical CO2 Extraction

Supercritical carbon dioxide has been used as a solvent for the extraction of rock rose leaf (Cistus ladanifer L.). The aim of this work was to identify the best processing conditions to obtain rock rose essential oil. The operating variables were selected so that the only extracted compounds were essential oils and waxes (8–10 MPa and 30–60°C), avoiding the coextraction of high-molecular-weight compounds that do not contribute to fragance formation. Moreover, a two-stage separation procedure was used to separate the waxes from the essential oil. The supercritical extracts were characterized by gas chromatography (GC) to assess the presence of undesirable compounds and to obtain the detailed oil composition. The best oil was produced by extraction at 9 MPa and 40°C and fractionation of the product in two separators in series operating at P = 7 MPa, T = –10°C and at P = 2 MPa, T = 10°C, respectively. Organoleptic analysis confirmed the high quality of the product.

Study of Different Catalysts and Initiators in Bulk Copolymerization of d,l-Lactide and Glycolide

Poly(d,l-lactide-co-glycolide), PLGA, is a biodegradable polyester with many medical applications. In this article, several catalysts are studied as potential substitutes of the conventional catalyst, tin (II) 2-ethylhexanoate (known as tin octoate, SnOct2). Namely, different metal carboxylates have been examined, in order to study the influence of the metal counterion. Among them, most promising results have been obtained when using zinc (II) 2-ethylhexanoate (ZnOct2) followed by potassium (I) 2-ethylhexanoate. Furthermore, in the case of ZnOct2, the use of alcohols as initiators was examined in order to improve reaction rate and to study their effect on molecular weight distribution, polymer microstructure, and side reactions, such as transesterification reaction.

Potassium removal from water-methanol-polyol mixtures by ion exchange on Amberlite 252

Abstract Equilibrium isotherms for the uptake of potassium from polyol-water-methanol mixtures on Amberlite 252, a strong acid ion exchange resin, have been obtained in order to assess the possibility of using such a system to purify industrial polyether-polyols. The selectivity was very high. A two-step reaction scheme was proposed and equilibrium data were correlated by an equation derived according to the mass action law. Effective intraparticle diffusivities were obtained using a homogeneous model and the effects of the viscosity of the bulk solution and resin swelling on the exchange rate are discussed. A simple empirical equation correlating diffusivity with viscosity and resin swelling is suggested. Breakthrough curves were obtained under a wide range of conditions, being well correlated by the expression for breakthrough curves with rectangular isotherm. The proposed purification procedure is generally applicable to different polyol types, being economically and technically feasible.

Polystyrene Wastes: Threat or Opportunity?

The recycling of polystyrene (PS) wastes could be considered even economically feasible if, apart from the intrinsic environmental benefits, the wastes are transformed into high-added value products with enhanced properties. In this work, the development of an integral recycling process for polystyrene wastes by means of a new and cost-effective alternative to traditional plastic recycling techniques has been proposed. The methodology consists of the selective dissolution of the plastic wastes with suitable natural solvents (terpene oils) to get a volume reduction without degradation of the polymer chains. The employment of a natural solvent for the treatment of polystyrene wastes transforms the process in an environmentally friendly technology. High pressure CO2 is proposed to perform the solvent removal in order to avoid the formation of undesirable by-products and to improve the quality of the recycled plastic, since it acts as a physical foaming agent. The use of CO2 is very attractive because it makes the polymer–solvent separation easier, improves the mass transfer into the highly swelled polymer bulk and allows the tuning of the final properties of the recovered PS. A controlled foaming of the polystyrene–solvent mixtures can be easily carried out at moderate temperatures and pressures by exploiting the advantages that provide the recycling with a natural solvent, obtaining completely free of solvent PS foams. Adjusting the working conditions, the structure of the foams produced can be tailored enhancing the initial properties of the PS wastes.

Optimization of a High Pressure CO2 Antisolvent Process for the Recycling of Polystyrene Wastes

ABSTRACT The recycling of polystyrene wastes by precipitation from limonene solutions using CO2 as antisolvent is an alternative and original environmentally friendly route to recover high quality wastes. The most suitable working conditions to conduct the process are selected based on the accurate knowledge of the phase equilibrium for the ternary mixture. To maximize the recycling of polymeric wastes while the consumption of CO2 and limonene is minimized, high values of pressure (≥100 bar), low values of temperature (≤30°C) and moderated concentrations of polymer (≤0.4 g PS/ml limonene) are required. GRAPHICAL ABSTRACT