*2.2. Propolis Extracts*

The samples of propolis were grounded individually in a marble mortar at room temperature. To start the extraction process, 100 mL of ethanol (Scharlab, Spain) were added to 14 g of each pulverized propolis sample. The mixtures were left for 48 h under magnetic stirring at room temperature and in the absence of light. After 48 h, the mixtures were filtered and transferred to round bottom flasks to evaporate the ethanol using a rotary evaporation system at 45 ◦C. To ensure the complete evaporation, the round bottom flasks were kept in a vacuum oven for 24 h at 35 ◦C.

The propolis extracts were labelled as Propolis Extract 1 (PE1), Propolis Extract 2 (PE2), and Propolis Extract 3 (PE3) and were frozen at −20 ◦C until they were used.

#### *2.3. Mixtures of Honey with Propolis*

Each propolis extract was added in a concentration of 0.3% (w/w) and 0.5% (w/w) to the Honey 1 (the one that presented the best results), according to the previously published work dealing with the evaluation of the bioactive properties of honey with propolis [1]. The mixtures were prepared by weighting the corresponding amounts of honey and propolis and mixing them to complete 100 g of each mixture. To guarantee the complete homogenization, all mixtures were subjected to mechanical stirring, after which they were stored at −20 ◦C until further use.

The mixtures were identified as Honey 1 followed by the corresponding Propolis Extract and percentage added resulting in Honey 1-Propolis Extract 1 (H1PE1), Honey 1-Propolis Extract 2 (H1PE2) and Honey 1-Propolis Extract 3 (H1PE3) at 0.3% or 0.5%.

#### *2.4. Fourier-Transform Infrared Spectroscopy (FTIR)*

FTIR was used to obtain spectra of the samples of honey, propolis and propolis extracts. These spectra were obtained with 64 scans and a 4 cm<sup>−</sup><sup>1</sup> resolution, between 4000 and 600 cm<sup>−</sup><sup>1</sup> using a Nicolet iS10 smart iTRBasic (Thermo Fisher Scientific, Waltham, MA, USA) model.
