Browsing by Author "Pereira, Helena"
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- Bark-based biorefineries: anatomical and chemical characterization of the bark of endemic Quercus vulcanica of TurkeyPublication . Şen, Ali Umut; Simões, Rita; Yücedağ, Cengiz; Quilhó, Teresa; Sousa, Vicelina; Miranda, Isabel M.; Fernandes, Ângela; Pereira, HelenaThe detailed anatomical and chemical features of the bark from endemic Quercus vulcanica in Turkey are reported here for the first time and discussed in the perspective of integration into a bark-based biorefinery system. The bark of Q. vulcanica trees was collected and studied through observations using light and scanning electron microscopy, wet-chemical analysis, inorganic elemental and FTIR analyses, GC-MS determinations of lipophilic extractives and suberin monomers, as well as TBARS antioxidant activity of hydroethanolic extracts. The bark of Q. vulcanica comprises phloem and a rhytidome with thin periderms and a few cork layers. The ash content is high (16.4%), primarily consisting of calcium oxalate crystals. Extractives were present in a high amount (23.1%) of which 88% corresponded to hydrophilic extractives (10.3% ethanol, and 10.1% water solubles). The suberin content is low (3.7%), which aligns with the small proportion of cork in the bark rhytidome. The composition of suberin is characterized by similar proportions of alpha, omega-alkanoic diacids and omega-hydroxyalkanoic acids, with 18-hydroxy-9-octadecenoic acid (26% of monomers) and octadec-9-enedioic acid (20.6%) as the main monomers. The lignin content is 21.9%, and the monomeric composition of polysaccharides includes glucose, xylose, arabinose, galactose, rhamnose, and acetyl groups. The lipophilic extractives are mainly composed of terpenoids (72.2% of all compounds), with friedelin and friedelanol as the main compounds. Hydroethanolic extracts, obtained under mild conditions with a yield of 10.2%, exhibited antioxidant activity (TBARS assay, EC50 value of 55 mu g/mL). The overall chemical and structural properties of Q. vulcanica bark indicate promising potential for biorefineries.
- Bioactivities of Waste Cork and Phloem Fractions of Quercus cerris BarkPublication . Şen, Ali Umut; Almeida, Daiana; Silveira, Tayse F. F. da; Pires, Tânia C.S.P.; Añibarro-Ortega, Mikel; Mandim, Filipa; Barros, Lillian; Ferreira, Isabel C.F.R.; Pereira, Helena; Fernandes, ÂngelaRecently, more and more researchers have begun to consider using waste bark fractions to produce value-added biochemicals and materials, as well as for energy production. Extraction is often the first operation in biomass biorefineries. Here we obtained hydroethanolic extracts from waste cork and phloem fractions of Quercus cerris bark and analyzed them to determine their antioxidant, antimicrobial, and nitric oxide (NO) production inhibition properties and their hepatotoxicity. The antioxidant properties were investigated by ex vivo TBARSs as well as OxHLIA antioxidant assays, the antibacterial properties against Gram-positive and Gram-negative bacteria isolated from food and clinical sources, and antifungal properties against Aspergillus brasiliensis and A. fumigatus. The NO production inhibition activity was assessed in a lipopolysaccharide (LPS)-stimulated murine macrophage (RAW 264.7) cell line, and antiproliferative activities were determined against five different cell lines, including lung (NCI-H460), gastric (AGS), breast (MCF7), and colon (CaCo2) tumor cell lines, as well as a non-tumor cell line (PLP2). The hydroethanolic maceration of waste cork and phloem yielded 4.4% and 2.4% extracts, respectively. Gallic acid glucosides, phenolic acids, and ellagic acid were identified in both extracts. The waste cork and phloem extracts showed antioxidant, antimicrobial, antifungal, and antiproliferative properties but also showed hepatotoxicity in the case of waste cork. Both bark fractions varied in terms of their bioactivity, with waste cork extracts showing, in general, higher bioactivity than phloem extracts.
- Biochemical characterization and fuel properties of endemic taurus flowering ash (Fraxinus ornus subsp. cilicica) bark from TurkeyPublication . Şen, Ali Umut; Simões, Rita; Yücedağ, Cengiz; Miranda, Isabel M.; Fernandes, Ângela; Pereira, HelenaTaurus flowering ash (Fraxinus ornus subsp. cilicica) is an endemic tree species in Turkey. The bark of the species was characterized for summative chemical composition, the monomeric composition of polysaccharides, phenolic content, in vitro and ex vivo antioxidant properties of hydrophilic extracts, the composition of lipophilic extractives and suberin, and thermal degradation. The bark has an elevated ash content (17%), primarily composed of calcium, and a noteworthy extractive content (38.9%), predominantly of hydrophilic compounds. The antioxidant activity of the bark extracts is moderate, with an IC50 value of 40 g/mL and an EC50 value of 230 g/mL by DPPH and TBARS methods. The lipophilic extractives principally contain fatty acids and diterpenoids. The suberin content is low (1%) and composed primarily of !-hydroxy acids with 9,10,18 trihydroxyoctadecanoic acid as the major suberin monomer. The lignin content is low (9.8%), and polysaccharides represent 33%. The ignition temperature of the bark is 190 C, the burnout temperature is 653 C, and the activation energy in combustion is 29 kJ mol1. A biorefinery concept was developed considering the bark’s chemical and thermal characteristics to convert approximately 90% of the bark mass into valuable chemicals, extracts, functional materials, and additives.
- Evaluation of FT-Raman and FTIR-ATR spectroscopy for the quality evaluation of Lavandula spp. HoneyPublication . Anjos, Ofélia; Guiné, Raquel P.F.; Santos, António J.A.; Paula, Vanessa B.; Pereira, Helena; Estevinho, Leticia M.Monofloral Lavandula spp. honey is very appreciated by consumers due to its characteristic and pleasant aroma and flavor. Given the economic importance of this type of honey, it is important to develop a rapid and non-expensive methodology that allows certifying its quality. In this context, this study aimed to compare the applicability and accuracy of FTIR-ATR and FT-Raman techniques for the quality evaluation of Lavandula spp. honey. Calibration models, with PLS regression models, were obtained for both methodologies concerning the following parameters: total acidity, reducing sugars, hidroximetilfurfural (HMF), electrical conductivity, ash, proline content, diastase activity, apparent sucrose, total flavonoids, and total phenolic contents. The calibration models had high regression coefficients, r2 (FTIR-ATR: 0.965–0.996; FT-Raman: 0.983–0.999), high ratios of performance to deviation, RPD (FTIR-ATR: 5.4–15.7; FT-Raman: 7.6–53.7), and low root mean square errors (RMSEs; FTIR-ATR: 0.005–3.0; FT-Raman: 0.004–1.02). These results corroborate the potentiality of FTIR-ATR and FT-Raman for quality evaluation and evaluation of the chemical properties of Lavandula spp. honey even though FT-Raman technique provided more accurate models.
- Exploring the Bioactive Properties of Hydroethanolic Cork Extracts of Quercus cerris and Quercus suberPublication . Sen, Umut; Almeida, Daiana; Silveira, Tayse F. F. da; Pires, Tânia C.S.P.; Añibarro-Ortega, Mikel; Mandim, Filipa; Barros, Lillian; Ferreira, Isabel C.F.R.; Pereira, Helena; Fernandes, ÂngelaThe bioactive properties of underutilized corks such as Quercus cerris cork and planted Quercus suber cork in the Eastern Mediterranean are not well-known but are crucial in developing lignocellulosic biorefineries. To assess their biological potential, hydroethanolic cork extracts of Quercus cerris and Quercus suber were analyzed for phenolic composition, antioxidant, antiproliferative, antimicrobial activities, and hepatoxicity, as well as NO-production inhibition. Here, we show that a mild hydroethanolic extraction of Q. cerris and Q. suber corks yielded 3% phenolic extracts. The phenolic composition was similar in both cork extracts, with phenolic acids and ellagitannins as the primary compounds. The bioactivity of hydroethanolic cork extracts from Q. cerris surpassed that of Q. suber and showed effectiveness against all cancer cell lines tested. This first comprehensive study on the bioactivities of different corks involves detailed characterizations of phenolic compounds of cork extracts using UPLC-DAD-ESI/MSn, evaluations of the antioxidant properties with TBARS and OxHLIA methods, evaluation of antiproliferative activity against gastric (AGS), lung (NCI-H460), colon (CaCo2), and breast cancer (MCF7) cell lines, as well as evaluations of hepatotoxicity and NO-production inhibition. The findings from this study will help bolster the potential of using underutilized cork-rich barks as a valuable resource in bark-based biorefineries.
- Pine Nutshells and Their Biochars as Sources of Chemicals, Fuels, Activated Carbons, and Electrode MaterialsPublication . Şen, Ali Umut; Rodrigues, João F.G.; Almeida, Daiana; Fernandes, Ângela; Gonçalves, Margarida; Martins, Marta; Santos, Diogo M.F.; Pereira, HelenaPine nutshells (PNSs) are lignocellulosic waste materials with limited use in domestic heating. However, a biorefinery approach may be applied to fractionate PNSs and produce chemicals, materials, and improved solid fuels. In this study, we fractionated PNSs and produced antioxidant extracts, lignins, polysaccharides, chars, and activated carbons and analyzed their potential applications. Pyrolytic kinetic modeling as an alternative method to chemical fractionation was also tested. The results showed that the PNS contains low amounts of extracts with weak thiobarbituric acid reactive substances (TBARS) antioxidant properties, while its lignin content is remarkable (50.5%). Pyrolytic kinetic modeling was comparable to wet chemical analysis for estimating lignin yield. Moderate-temperature pyrolysis of the PNS resulted in a 23% char yield. The PNS chars showed improved fuel characteristics, retained 36% water, and leached 151 mg/L potassium into the water. The steam activation of PNS biochars at 750 ◦C resulted in oxygen-enriched activated carbons with specific surface areas up to 467 m2/g. The overall results indicate promising biochar applications of the PNS for soil amendment and supercapacitor uses.