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- Monitoring the modifications of Aloe vera by high performance liquid chromatographyPublication . Tojeira, Ana; Pereira, Rúben; Bártolo, Paulo; Mendes, Ausenda; Vaz, Daniela; Oliveira, Nelson SimõesAloe vera is a widely known and studied plant due to its therapeutic properties. The therapeutic properties exhibited by the Aloe vera exudates have been associated to the presence of certain compounds, such as, chromones, anthrones and anthraquinones. In this study, we have identified, and monitored by reversed phase high performance liquid chromatography (HPLC), six major compounds present in the Aloe vera exudates. The chromatographic profiles were followed in the course of time and at different wavelengths. This monitoring allowed us to verify the constitution and modifications of the samples, in order to identify the main changes responsible for the chemical degradation and loss of proprieties exhibited by the exudates over time.
- Nutrient‐efficient catfish‐based aquaponics for producing lamb's lettuce at two light intensitiesPublication . Sebastião, Fernando; Vaz, Daniela C.; Pires, Cristiana L; Cruz, Pedro F; Moreno, Maria João; Brito, Rui M M; Cotrim, Luís; Oliveira, Nelson; Costa, Ana; Fonseca, André; Rodrigues, Maria; Ispolnov, Kirill; Bernardino, Raul; Vieira, JuditeBACKGROUND: Aquaponic systems are sustainable processes of managing water and nutrients for food production. An innovate nutrient-efficient catfish-based (Clarias gariepinus) aquaponics system was implemented for producing two cultivars of two leafy vegetables largely consumed worldwide: lamb's lettuce (Valerianella locusta var. Favor and Valerianella locusta var. de Hollande) and arugula (Eruca vesicaria var. sativa and Eruca sativa). Different growing treatments (4 × 2 factorial design) were applied to plants of each cultivar, grown at two light intensities (120 and 400 ∼mol m−2 s −1). During growth, several morphological characteristics (root length, plant height, leaf number, foliage diameter and biggest leaf length) were measured. At harvest, plants were weighed and examined qualitatively in terms of greenness and health status. Additionally, leaf extracts were obtained and used to determine total phenolic contents, antioxidant capacities, and levels of cytotoxicity to Caco-2 intestinal model cells. RESULTS: After a 5-week growth period, both lamb's lettuce cultivars presented high levels of greenness and health status, at both light intensities, particularly the var. de Hollande that also showed higher average performance in terms of plant morphology. In turn, arugula cultivars showed lower levels of greenness and health status, especially the cultivar E. vesicaria var. sativa submitted to direct sunlight during growth. In addition, plant specimens submitted to higher levels of light intensity showed higher contents in antioxidants/polyphenols. Cultivars with a higher content in antioxidants/polyphenols led to higher Caco-2 cell viability. CONCLUSION: For successful industrial implementation of the aquaponics technology, different and optimized acclimatizing conditions must be applied to different plant species and cultivars. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
- Degradation of Oxytetracycline in Aqueous Solutions: Application of Homogeneous and Heterogeneous Advanced Oxidative ProcessesPublication . Giler-Molina, José Miguel; Zambrano-Intriago, Luis Angel; Quiroz-Fernández, Luis Santiago; Napoleão, Daniella Carla; Vieira, Judite dos Santos; Oliveira, Nelson Simões; Rodríguez-Díaz, Joan ManuelOxytetracycline is one of the antibiotics most frequently used in the Shrimp Industry during the control of bacterial diseases. These emerging pollutants, which appear in low concentrations, are persistent and alternative treatments and are required for their elimination. The degradation of oxytetracycline was evaluated in an aqueous solution by applying homogeneous (UV/H2O2 and photo-Fenton) and heterogeneous (UV/TiO2 /H2O2) advanced oxidative processes (AOPs). The studies were carried out using a bench reactor with short-wave ultraviolet lamps (UV-C). We quantified the extent to which the degradation of the drug had been efficient by employing highly efficient liquid chromatography (HPLC) and a PDA detector with a wavelength of 354 nm and a C18 column. The best results were obtained when applying the UV/H2O2 treatment, which attained a degradation of 97% under the initial conditions of a dose of 8 µL of H2O2 and 120 min of radiation. The pseudo-first order kinetic model proposed by Chan and Chu showed that the experimental results had an adequate fit, with values greater than R2 ≥ 0.95. Toxicity tests were applied to verify the effect of AOPs employed, when the drug was present in low concentrations. The test results demonstrated a decrease in the root growth of the species Lactuca sativa and Daucus carota.
- Adsorption Behavior and Mechanism of Oxytetracycline on Rice Husk Ash: Kinetics, Equilibrium, and Thermodynamics of the ProcessPublication . Andrade, Christhel A.; Zambrano-Intriago, Luis Angel; Oliveira, Nelson S.; Vieira, Judite S.; Quiroz-Fernández, Luis Santiago; Rodríguez-Díaz, Joan ManuelThe main objective of the present study is to determine the kinetics, thermodynamics, and adsorption mechanism of the oxytetracycline (OTC) on rice husk ash (RHA). The adsorbent was characterized by scanning electronic microscopy, Fourier transform infrared spectroscopy, and nitrogen physisorption. Batch studies were carried out to evaluate the influence of the adsorbent dose, initial concentration, contact time, temperature, and initial pH. RHA was characterized as having heterogeneous, fibrous, and porous particles, consisting predominantly of silica. The removal of OTC depends on the pH of the medium, which is favored at acid pH values. The kinetic data followed the Bangham model, which indicated an OTC diffusion in the pores of RHA, although this was not the only process, as demonstrated through the use of the Weber-Morris model (IPD model). The Sips isotherm best represents the experimental results of the equilibrium study. It was found that the adsorption process was spontaneous and endothermic. The highest adsorption capacity was found at a pH in the range of 4–6, when the OTC is in its zwitterion form and the surface of the RHA is positively charged, thus permitting electrostatic interactions and the formation of hydrogen bonds between the adsorbent and adsorbate molecules. These findings demonstrate the potential of rice husk ash to remove oxytetracycline from water.