Publications by authors named "Daniel Oliveira Freire"

Article Synopsis
  • * Key tests conducted included measuring dry extract, total phenolic content (TPC), and antioxidant activity, as well as determining minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) for bacterial strains.
  • * Results indicated that green propolis extracts had the highest TPC and antioxidant activity, with ethanol proving to be the most effective solvent, while stingless bee propolis displayed notable antimicrobial efficacy, particularly from specific regions in Brazil.
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This study presents an optimized microwave-assisted method for the green synthesis of silver nanoparticles (AgNPs) using a root extract obtained from DC. The influence of temperature, reagent concentration, and irradiation time was systematically investigated to enhance synthesis yield. Characterization techniques including XRD, UV-vis, FTIR, XPS, and zetametry were employed to confirm the successful formation of nanoparticles with a metallic silver core (∼17 nm) functionalized with organic molecules derived from the plant extract.

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We describe here a green method for the preparation of silver nanoparticles (AgNPs), by a microwave-assisted synthesis route using underbark extract, with antibacterial activity. After optimizing the synthesis parameters with a Box-Benhken designed experiment, samples were characterized by powder XRD, TEM, UV-Vis spectroscopy, FTIR and zetametry. Using the overall optimized conditions of synthesis - time of reaction 15 min at 200 °C and plant extract/AgNO volume ratio equal to 10% - highly crystalline ∼13.

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Envenomation by wasp stings is a public health preoccupation, and signals after stings have variable effects depending on the number of attacks and individual sensitivities. Even with the high rate of wasp sting cases, the study of phatophysiological effects of the envenomation is still very incipient. In this context, early and accurate assessment of this prognostic can aid in the reduction of the symptomatology and complete remission of the later symptoms.

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