Browsing by Author "Miranda, Isabel M."
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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.
- 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.
- Development of cross-resistance by Aspergillus fumigatus to clinical azoles following exposure to prochloraz, an agricultural azolePublication . Faria-Ramos, Isabel; Farinha, Sofia; Neves-Maia, João; Tavares, Pedro Ribeiro; Miranda, Isabel M.; Estevinho, Leticia M.; Pina-Vaz, Cidália; Rodrigues, Acácio G.Background: The purpose of this study was to unveil whether azole antifungals used in agriculture, similar to the clinical azoles used in humans, can evoke resistance among relevant human pathogens like Aspergillus fumigatus, an ubiquitous agent in nature. Additionally, cross-resistance with clinical azoles was investigated. Antifungal susceptibility testing of environmental and clinical isolates of A. fumigatus was performed according to the CLSI M38-A2 protocol. In vitro induction assays were conducted involving daily incubation of susceptible A. fumigatus isolates, at 35°C and 180 rpm, in fresh GYEP broth medium supplemented with Prochloraz (PCZ), a potent agricultural antifungal, for a period of 30 days. Minimal inhibitory concentrations (MIC) of PCZ and clinical azoles were monitored every ten days. In order to assess the stability of the developed MIC, the strains were afterwards sub-cultured for an additional 30 days in the absence of antifungal. Along the in vitro induction process, microscopic and macroscopic cultural observations were registered. Results: MIC of PCZ increased 256 times after the initial exposure; cross-resistance to all tested clinical azoles was observed. The new MIC value of agricultural and of clinical azoles maintained stable in the absence of the selective PCZ pressure. PCZ exposure was also associated to morphological colony changes: macroscopically the colonies became mostly white, losing the typical pigmentation; microscopic examination revealed the absence of conidiation. Conclusions: PCZ exposure induced Aspergillus fumigatus morphological changes and an evident increase of MIC value to PCZ as well as the development of cross-resistance with posaconazole, itraconazole and voriconazole.
- Environmental azole fungicide, prochloraz, can induce cross-resistance to medical triazoles in Candida glabrataPublication . Faria-Ramos, Isabel; Tavares, Pedro Ribeiro; Farinha, Sofia; Neves-Maia, João; Miranda, Isabel M.; Silva, Raquel M.; Estevinho, Leticia M.; Pina-Vaz, Cidália; Rodrigues, Acácio G.Acquisition of azole resistance by clinically relevant yeasts in nature may result in a significant, yet undetermined, impact in human health. The main goal of this study was to assess the development of cross-resistance between agricultural and clinical azoles by Candida spp. An in vitro induction assay was performed, for a period of 90 days, with prochloraz (PCZ) - an agricultural antifungal. Afterward, the induced molecular resistance mechanisms were unveiled. MIC value of PCZ increased significantly in all Candida spp. isolates. However, only C. glabrata developed cross-resistance to fluconazole and posaconazole. The increased MIC values were stable. Candida glabrata azole resistance acquisition triggered by PCZ exposure involved the upregulation of the ATP binding cassette multidrug transporter genes and the transcription factor, PDR1. Single mutation previously implicated in azole resistance was found in PDR1 while ERG11 showed several synonymous single nucleotide polymorphisms. These results might explain why C. glabrata is so commonly less susceptible to clinical azoles, suggesting that its exposure to agricultural azole antifungals may be associated to the emergence of cross-resistance. Such studies forward potential explanations for the worldwide increasing clinical prevalence of C. glabrata and the associated worse prognosis of an infection by this species.