Supercritical Impregnation of PETG with Olea europaea Leaf Extract: Influence of Operational Parameters on Expansion Degree, Antioxidant and Mechanical Properties.

PETG (poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate)) is an amorphous copolymer, biocompatible, recyclable, and versatile. Nowadays, it is being actively researched for biomedical applications. However, proposals of PETG as a platform for the loading of bioactive compounds from natural extract are scarce, as well as the effect of the supercritical impregnation on this polymer. In this work, the supercritical impregnation of PETG filaments with Olea europaea leaf extract was investigated, evaluating the effect of pressure (100-400 bar), temperature (35-55 °C), and depressurization rate (5-50 bar min-1) on the expansion degree, antioxidant activity, and mechanical properties of the resulting filaments. PETG expansion degree ranged from ~3 to 120%, with antioxidant loading ranging from 2.28 to 17.96 g per 100 g of polymer, corresponding to oxidation inhibition values of 7.65 and 66.55%, respectively. The temperature and the binary interaction between pressure and depressurization rate most affected these properties. The mechanical properties of PETG filaments depended greatly on process variables. Tensile strength values were similar or lower than the untreated filaments. Young's modulus and elongation at break values decreased below ~1000 MPa and ~10%, respectively, after the scCO2 treatment and impregnation. The extent of this decrease depended on the supercritical operational parameters. Therefore, filaments with higher antioxidant activity and different expansion degrees and mechanical properties were obtained by adjusting the supercritical processing conditions.

Extraction of Bioactive Compounds from Prestonia mollis Leaves and Their Impregnation into Polylactic Acid Using High-Pressure Technologies: Potential for Biomedical Application.

Enhanced solvent extraction (ESE) and pressurized liquid extraction (PLE) have been used for the first time to obtain antioxidant compounds from Prestonia mollis leaves. The effects of pressure (100-250 bar), temperature (55-75 °C) and the composition of the extraction solvent (ethanol, water and hydroalcoholic mixtures) were evaluated according to multilevel factorial designs. PLE provided the largest extraction yields compared to ESE, as well as a greater impact of the operating conditions studied. The highest total phenolic content was obtained when using a hydroalcoholic mixture (CO2/ethanol/water 50/25/25) through ESE at 100 bar and 75 °C. The antioxidant capacity of this extract is related to higher concentration levels of the identified flavonoids: Quercetin 3-O-xylosyl-rutinoside, Kaempferol 3-(2G-apiosylrobinobioside) and Kaempferol 4'-glucoside 7-rhamnoside. This extract was tested for the supercritical impregnation of polylactic acid (PLA), which is a polymer widely used in the biomedical industry. The influence of pressure (100-400 bar), temperature (35-55 °C), amount of extract (3-6 mL) and impregnation time (1-2 h) have been evaluated. The best results were obtained by impregnating 3 mL of extract at 100 bar and 55 °C for 2 h, achieving 10% inhibition with DPPH methods. The extract presented a potentially suitable impregnation of PLA for biomedical applications.

Use of Winemaking By-Products for the Functionalization of Polylactic Acid for Biomedical Applications.

The addition of naturally active compounds to implantable polymers is an efficient strategy against inflammation issues that might lead to rejection, while promoting controlled re-endothelialization of the tissues. This work proposes the use of winemaking by-products with high active properties of biomedical interest to obtain bioactive PLA by using supercritical technologies. First, two red grape pomace extracts, obtained by high-pressure extraction with supercritical CO2 and cosolvents (either ethanol or water-ethanol), have been studied. Second, two impregnation methods have been studied with both extracts, traditional supercritical CO2-assisted impregnation (SSI) and a novel pressurized soaking method (PSI). The amount of extract impregnated as well as the bioactivity levels achieved-i.e., antioxidant, antimicrobial, and anti-inflammatory properties- have been determined for each extract and impregnation method at different pressure and temperature conditions. Both extracts obtained had good antioxidant, anti-inflammatory, and antibacterial capacities, especially the hydroethanolic one (0.50 ± 0.03 mg TE/g versus 0.24 ± 0.03 mg TE/g, respectively). Regarding impregnated filaments, impregnation loadings depended especially on the extract and P/T conditions, providing up to 8% (extract mass/polymer mass) of impregnation. The antioxidant capacity increased noteworthily by using the ethanolic extract by PSI, with values near 100 µg TE/g PLA.

Structural Modification of Polymers Functionalized with Mango Leaf Extract by Supercritical Impregnation: Approaching of Further Food and Biomedical Applications.

Identifying new polymers from natural resources that can be effectively functionalized can have a substantial impact on biomedical devices and food preservation fields. Some of these polymers would be made of biodegradable, renewable and compostable materials, and present the kind of porosity required to effectively carry active compounds that confer on them the desired properties for their intended applications. Some natural extracts, such as mango leaf extract, have been proven to have high levels of antioxidant, antimicrobial or anti-inflammatory properties, making them good candidates for controlled-release applications. This work intends to investigate the supercritical impregnation of different types of polymers (ABS, PETG, TPU, PC and PCL) with mango leaf extract. The influence of temperature and pressure on the polymers' structure (swelling and foaming processes) and their different behaviors have been analyzed. Thus, TPU and PC experience minimal structural modifications, while PETG, PCL and ABS, on the other hand, suffer quite significant structural changes. TPU and PETG were selected as the representative polymers for each one of these behaviors to delve into mango leaf extract impregnation processes. The bioactive capacity of the extract is present in either impregnated polymer, with 25.7% antioxidant activity by TPU processed at 35 °C and 100 bar and 32.9% antioxidant activity by PETG impregnated at 75 °C and 400 bar.

Screening of the Supercritical Impregnation of Olea europaea Leaves Extract into Filaments of Thermoplastic Polyurethane (TPU) and Polylactic Acid (PLA) Intended for Biomedical Applications.

The leaves of Olea europaea as agricultural waste represent a convenient source of antioxidants. In combination with supercritical CO2 (scCO2), assisted impregnation is an interesting strategy for the preparation of biomedical devices with specific bioactivity. For this purpose, 3D-printable filaments of thermoplastic polyurethane (TPU) and polylactic acid (PLA) were employed for the supercritical impregnation of ethanolic olive leaves extract (OLE) for biomedical application. The extraction of OLE was performed using pressurized liquids. The effect of pressure (100-400 bar), temperature (35-55 °C), and the polymer type on the OLE impregnation and the swelling degree were studied including a morphological analysis and the measurement of the final antioxidant activity. All the studied variables as well as their interactions showed significant effects on the OLE loading. Higher temperatures favored the OLE loading while the pressure presented opposite effects at values higher than 250 bar. Thus, the highest OLE loadings were achieved at 250 bar and 55 °C for both polymers. However, TPU showed c.a. 4 times higher OLE loading and antioxidant activity in comparison with PLA at the optimal conditions. To the best of our knowledge, this is the first report using TPU for the supercritical impregnation of a natural extract with bioactivity.

Pro-Angiogenic Effects of Natural Antioxidants Extracted from Mango Leaf, Olive Leaf and Red Grape Pomace over Endothelial Colony-Forming Cells.

Cardiovascular diseases remain the leading cause of death worldwide, mainly triggered by the formation of atherosclerotic plaques that reduce blood flow. Angiogenic cell therapy based on endothelial colony forming cells (ECFCs) constitutes a promising alternative to promote vascular revascularization; however, under the oxidative environment that prevails in ischemic areas, these cells become impaired. Thus, it is necessary to investigate strategies to enhance their regenerative properties. Antioxidant substances, such as polyphenols, have been shown to be useful for this purpose. In the current study we evaluated the potential of mango leaves, olive leaves and red grape pomace extracts, rich in polyphenols, to promote ECFC reparative effects. For this, aqueous and ethanolic extracts of the aforementioned raw materials were obtained by pressurized liquid extraction (PLE). After evaluating the polyphenol content and the antioxidant activity, in vitro assays were carried out, and we found that ethanolic extracts at low concentrations improved angiogenic capacities of ECFCs and reduced proliferation, apoptosis, and the inflammatory response of these cells. Overall, mango leaves ethanolic extract provided the most promising results, but all three extracts ameliorated the functionality of ECFCs.

Application of Citrus By-Products in the Production of Active Food Packaging.

Some citrus by-products such as orange peel contains valuable compounds that could be recovered and restored into the food chain. In this study, an efficient valorization of orange peel has been investigated using green extraction, fractionation, and impregnation techniques. The first step included its extraction using CO2 and ethanol under different pressure (200-400 bar) and temperature (35-55 °C) conditions. The extracts obtained at 300 bar and 45 °C showed strong antioxidant with moderate antimicrobial activity. Then, the extract was subjected to a sequential fractionation process. The fraction obtained at 300 bar, 45 °C, and using 32% ethanol showed the strongest antioxidant and antimicrobial activity with a high extraction yield. Finally, the potential of the two best extracts (obtained at 400 bar and 45 °C before any fractionation and the fractions obtained at 300 bar, 45 °C using 32% ethanol) was determined by conducting an impregnation process to obtain an antioxidant food-grade rigid plastic that would preserve fresh food. The percentage of cosolvent (1 and 2% ethanol), the impregnation time (1 and 3 h), the pressure (200 and 400 bar), and the temperature (35 and 55 °C) were evaluated as variables of this process. The impregnated plastic showed good antioxidant and antimicrobial activities.

Health-Promoting Properties of Borage Seed Oil Fractionated by Supercritical Carbon Dioxide Extraction.

Borage (Borago officinalis L.) seed oil is an important source of γ-linolenic acid, which is normally used as a treatment against different pathologies. Since the fractionation of this interesting seed oil has many environmental, economic and biological benefits, two borage fractionation techniques after extraction with CO2 under supercritical conditions have been studied: precipitation in two cyclone separators and countercurrent extraction column. Both techniques have successfully collected free fatty acids in one fraction: (i) two separators set up in series obtained the highest concentration of free fatty acids in separator 2 at 90 bar/40 °C; (ii) when countercurrent extraction column was used, the acidity index of the raffinate stream was independent from the operating conditions (2.6 ± 0.5%). Furthermore, the composition of the fatty acids, as well as their antioxidant and cytotoxic activities, were determined. The profile of the fatty acids obtained by either of these two methods remained unaltered, so that the crude oil exhibited improved antioxidant and cytotoxic properties. All the extracts obtained in the two cyclone separators at the same pressure/temperature conditions displayed high tumouricidal activity against HL 60 promyelocytic leukaemia cells, even if the extracts at 50% concentration from separator 2 presented a lower inhibitory activity (IC50). The extracts from separator 2 at 90 bar/40 °C exhibited the highest anti-proliferative activity at low doses (IC50 of 0.3 µL/mL for the trypan blue exclusion test). To reach the lethal dose-IC50-with the product obtained through countercurrent column fractionation, a concentration of 2 µL/mL of crude borage oil raffinate was required.

Potential Use of Annona Genus Plants Leaf Extracts to Produce Bioactive Transdermal Patches by Supercritical Solvent Impregnation.

The objective of the present work was to develop a bioactive transdermal patch functionalized with Annona leaf extracts (ALE) by means of supercritical impregnation technique. The potential of six different Annona leaf extracts (ALE) obtained with the enhanced solvent system formed by carbon dioxide + ethanol/acetone was evaluated taking into account the antioxidant activity, total phenol composition and global extraction yields. For the impregnation of ALE, two drug supporting systems were tested: hydrocolloid sodium carboxymethyl cellulose (NaCMC) and polyester dressings (PD). The effect of the impregnation conditions, including pressure (P), temperature (T), percent of co-solvent (ethanol) and ALE/polymer mass ratio, was determined with regard to the loading and the functional activity of the impregnated samples. The optimal impregnation conditions of ALE were established at 55 °C and 300 bar which led to obtained transdermal patches with antioxidant and antimicrobial capacity. In order to understand the behavior of the process, the homogeneity of the samples in the vessels was also evaluated. The best results were obtained at higher proportions of co-solvent in the system.

Supercritical Impregnation of Ketoprofen into Polylactic Acid for Biomedical Application: Analysis and Modeling of the Release Kinetic.

Ketoprofen (KET) is an anti-inflammatory drug often used in medicine due to its analgesic and antipyretic effects. If it is administered in a controlled form by means of different dosing devices, it acts throughout the patient's recovery period improving its efficacy. This study intends to support the use of supercritical solvent impregnation (SSI) as an efficient technique to develop polylactic acid (PLA) functionalized with ketoprofen, for use as controlled drug release devices. For this purpose, firstly, the influence of different SSI variables on the desirable swelling of the polymer structure, while avoiding their foaming, were evaluated. Then, the resulting ketoprofen loading was evaluated under different pressure/temperature conditions. It was generally found that as pressure and temperature are higher, the drug impregnation loads also increase. The maximum impregnation loads (at about 9% KET/PLA) were obtained at 200 bar and 75 °C. In vitro drug release tests of the impregnated compound were also carried out, and it was found that drug release profiles were also dependent on the specific pressure and temperature conditions used for the impregnation of each polymer filament.

Application of a Natural Antioxidant from Grape Pomace Extract in the Development of Bioactive Jute Fibers for Food Packaging.

There is an increasing demand for the use of new food packaging materials. In this study, natural jute fibers impregnated with a Petit Verdot Red Grape Pomace Extract (RGPE) was proposed as a new active food packaging material. Pressurized Liquid Extraction (PLE) and Enhanced Solvent Extraction (ESE) techniques were employed to obtain the bioactive RGPE. Afterward the supercritical solvent impregnation conditions to obtain RGPE-natural jute fibers were studied, by varying pressure, modifier percentage and dried RGPE mass. PLE technique offered the highest bioactive extract at 20 MPa, 55 °C, 1 h residence time using C2H5OH:H2O (1:1 v/v), providing an EC50 of 3.35 ± 0.25 and antibacterial capacity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa (MIC of 12.0, 1.5 and 4.0 mg/mL RGPE respectively). The natural jute fibers impregnated with 3 mL of that RGPE (90 mg/mL) at 50 MPa and 55 °C generated the most efficient packing material with regards to its food preservation potential.

Mass Transfer and Optical Properties of Active PET/PP Food-Grade Films Impregnated with Olive Leaf Extract.

A supercritical solvent impregnation (SSI) technique was employed to incorporate, by batch- and semicontinuous-modes, bioactive olive leaf extract (OLE) into a food-grade multilayer polyethylene terephthalate/polypropylene (PET/PP) film for active food packaging applications. The inclusion of OLE in the polymer surfaces significantly modified the colour properties of the film. A correlation of 87.06% between the CIELAB colour parameters and the amount of the OLE impregnated in the film was obtained which suggests that colour determination can be used as a rapid, non-destructive technique to estimate the OLE loading in the impregnated matrices. The UV barrier and water permeability properties of the films were not significantly modified by the incorporation of OLE. The migration of OLE into a 50% (v/v) ethanol food simulant demonstrated faster release of OLE from the PP surface than from the PET surface which may be due to the different interactions between OLE and each polymer.

Comparative study of submerged and surface culture acetification process for orange vinegar.

BACKGROUND: The two main acetification methodologies generally employed in the production of vinegar (surface and submerged cultures) were studied and compared for the production of orange vinegar. Polyphenols (UPLC/DAD) and volatiles compounds (SBSE-GC/MS) were considered as the main variables in the comparative study. Sensory characteristics of the obtained vinegars were also evaluated. RESULTS: Seventeen polyphenols and 24 volatile compounds were determined in the samples during both acetification processes. For phenolic compounds, analysis of variance showed significant higher concentrations when surface culture acetification was employed. However, for the majority of volatile compounds higher contents were observed for submerged culture acetification process, and it was also reflected in the sensory analysis, presenting higher scores for the different descriptors. Multivariate statistical analysis such as principal component analysis demonstrated the possibility of discriminating the samples regarding the type of acetification process. Polyphenols such as apigenin derivative or ferulic acid and volatile compounds such as 4-vinylguaiacol, decanoic acid, nootkatone, trans-geraniol, ß-citronellol or α-terpineol, among others, were those compounds that contributed more to the discrimination of the samples. CONCLUSION: The acetification process employed in the production of orange vinegar has been demonstrated to be very significant for the final characteristics of the vinegar obtained. So it must be carefully controlled to obtain high quality products. © 2017 Society of Chemical Industry.

Chemical and sensory characteristics of orange based vinegar.

Several experiments were conducted to developed orange based vinegar by surface culture. The addition of sugar (sucrose and concentrated must) and the presence/absence of peel in the raw material (squeezed juice, peeled orange, non-peeled orange plus squeezed juice) have been studied during the development of the final product. Polyphenolic and volatile characterization and sensory analysis have also been carried out. The polyphenolic and volatile content of the resulting wines and vinegars showed significant differences depending upon the raw material used. In general, the complexity of the polyphenolic and volatile profiles increased for experiments in which orange peel was included in the raw material. Sensory analysis revealed significant differences between the samples in respect of both sugar addition and raw material. The vinegars using sugar, peeled orange and non-peeled orange plus squeezed juice raw materials, had more preference and keeping in view relative efficiency of the process, vinegar made from the peeled orange material was considered to be best.