Genesys 150 uv spectrophotometer

To determine total phenolic compound content in raw propolis, ethanolic extracts of propolis, and nanoencapsulates, the Folin–Ciocalteu methodology [45 ] was used, for which a 0.25 N Folin solution (Merck, Darmstadt, Germany) and a 20% Na₂CO₃ solution (Spectrum, NB, Canada) were prepared; the calibration curve was generated using gallic acid (Merck, Darmstadt, Germany) at the concentrations of 5, 10, 20, 25, 30, and 35 mg/L.
Finally, 900 µL of a sample (previously extracted in a methanolic solution) were mixed with 150 µL of Na₂CO₃, 300 µL of Folin reagent, and 900 µL of ultrapure water. Then, readings were taken in a Genesys 150 UV spectrophotometer (Thermo Fisher Scientific, Waltham, MA, USA) at a wavelength of 755 nm. The results were expressed as mg of gallic acid equivalent (GAE) per g sample on a dry basis.

To determine flavonoids in raw propolis, ethanolic extracts of propolis, and nanoencapsulates [44 (link)], a calibration curve was previously generated with quercetin (Sigma Aldrich, St. Louis, MI, USA), using concentrations of 0.2, 0.4, 0.6, 0.8, 1, and 1.2 mg/mL; then, 90 µL of sample extract was mixed with 4.81 mL of 80% methanol and 0.1 mL of 5% AlCl₃ (Sigma Aldrich, St. Louis, MI, USA) in ethanolic solution and left to stand in the absence of light for 10 min. Finally, readings were completed in a Genesys 150 UV spectrophotometer (Thermo Fisher Scientific, Waltham, MA, USA) at a wavelength of 425 nm. Flavonoid content was expressed as mg quercetin per g of sample on a dry basis.